hb959202000 (j) a30 excitation controller

Brush Electrical Machines Ltd.PO Box 18, Loughborough, Leicestershire, LE11 1HJ, England

Telephone: +44 (1509) 611511 Telefax: +44 (1509) 610440E-Mail: [email protected] Web Site: http://www.fki-et.com/bem

Instruction ManualPRISMIC A30 EXCITATION CONTROLLER

Manual No: HB959202000

Document No: TP00000021 Issue: JDate: 30 May 2003

PRISMIC A30 Excitation Controller

Manual No: HB959202000 Issue: J Date: 30 May 2003 Page: 2 of 126

HB959202000 (J) A30 Excitation Controller.doc Brush Electrical Machines Ltd. 2003

CONTENTS1 INTRODUCTION TO MANUAL ................................................................................................................. 4

1.1 General................................................................................................................................................ 41.2 How To Use The Manual .................................................................................................................... 41.3 Copies ................................................................................................................................................. 41.4 Feedback............................................................................................................................................. 51.5 Service & Spares................................................................................................................................. 51.6 Contact Address.................................................................................................................................. 51.7 Health & Safety At Work Act (1974).................................................................................................... 51.8 Protection And Monitoring Devices ..................................................................................................... 6

2 EUROPEAN DIRECTIVES ........................................................................................................................ 73 INTRODUCTION........................................................................................................................................ 84 RATINGS ................................................................................................................................................... 95 FEATURES .............................................................................................................................................. 106 SPECIFICATION...................................................................................................................................... 12

6.1 A30-CON Card .................................................................................................................................. 126.2 A30-MON Card.................................................................................................................................. 186.3 Standby Control Card........................................................................................................................ 216.4 Utilities Card ...................................................................................................................................... 246.5 A30-RACK1 Mainframe..................................................................................................................... 26

7 HARDWARE DESCRIPTION .................................................................................................................. 287.1 A30-CON Card .................................................................................................................................. 287.2 A30-MON Card.................................................................................................................................. 347.3 Standby Control Card........................................................................................................................ 367.4 Utilities Card ...................................................................................................................................... 407.5 A30-RACK1 Mainframe..................................................................................................................... 41

8 SOFTWARE DESCRIPTION ................................................................................................................... 448.1 A30-CON Card .................................................................................................................................. 448.2 A30-MON Card.................................................................................................................................. 47

9 INSTALLATION AND MECHANICAL DETAILS, CARD FITTING AND REMOVAL............................. 489.1 Installation ......................................................................................................................................... 489.2 Ventilation.......................................................................................................................................... 489.3 Wiring To The A30 Excitation Controller ........................................................................................... 489.4 Wiring To The Plug............................................................................................................................ 499.5 Safety ................................................................................................................................................ 509.6 Mechanical Details ............................................................................................................................ 509.7 Card Fitting and Removal ................................................................................................................. 51

10 COMMISSIONING................................................................................................................................ 5210.1 EMC Installation And Operation Guidelines...................................................................................... 5210.2 Pre-Commissioning Checks.............................................................................................................. 5310.3 Check Operation Of DC Contactors, Switches And Indications With Machine At Standstill ............ 5310.4 Check Standby Control ..................................................................................................................... 5510.5 Check A30-CON And A30-MON Settings......................................................................................... 5610.6 Check Display Of Measured Parameters On The A30-CON And A30-MON Card .......................... 5710.7 Check Null Balance Indication When In Standby.............................................................................. 5710.8 Set-up Stability In Main Channel....................................................................................................... 5710.9 Check The Voltage Range Of The A30-CON Card .......................................................................... 5810.10 Check Soft Start............................................................................................................................. 5910.11 Check For Smooth Changeover From Standby To Main Channel................................................ 5910.12 Check/Set-Up Over Excitation Limiters And Monitors................................................................... 5910.13 Over Voltage And Over Flux Monitors........................................................................................... 6010.14 Set/Check The Under Voltage Monitor Level ................................................................................ 6110.15 Check Parallel Operation............................................................................................................... 6110.16 Check Under Excitation Limiter ..................................................................................................... 6210.17 Check Under Excitation Monitor .................................................................................................... 6210.18 Check Power Factor Control (If Applicable) .................................................................................. 6210.19 Check VAr Control (If Applicable).................................................................................................. 6310.20 Check The VAr Shed (If Applicable).............................................................................................. 6310.21 Check Parallel Operation In Standby Line Voltage Control .......................................................... 63




10.22 Static Interrogation ........................................................................................................................ 6411 USING THE WINDOWS HMI COMMISSIONING SOFTWARE........................................................... 65

11.1 Setup Of the A30 Using An Alternative Power Supply...................................................................... 6511.2 PC Software Installation.................................................................................................................... 6511.3 Running the HMI Application............................................................................................................. 6511.4 Exiting the HMI Application ............................................................................................................... 6611.5 HMI Functions ................................................................................................................................... 6611.6 A30-CON Card HMI Displays Available........................................................................................ 6711.7 Logfile................................................................................................................................................ 6811.8 Saving Presets And Registers .......................................................................................................... 6811.9 Passwords......................................................................................................................................... 6811.10 Using The A30-CON HMI Displays ............................................................................................... 6911.11 A30-MON Card - HMI Displays Available...................................................................................... 7611.12 Using The A30-MON HMI Displays ............................................................................................... 77

12 USING THE SCADA COMMUNICATIONS PORT .............................................................................. 8212.1 Protocol Data..................................................................................................................................... 8212.2 Physical Connections........................................................................................................................ 8212.3 Data Available ................................................................................................................................... 82

13 TRANSDUCER CALIBRATION PROCEDURE................................................................................... 8313.1 Line Voltage Calibration On The A30-CON Card ............................................................................. 8313.2 Field Current Calibration On The A30-CON Card............................................................................. 8313.3 Line Current Calibration On The A30-CON Card.............................................................................. 8313.4 Temperature Transducer Calibration on the A30-CON Card............................................................ 8313.5 Line Voltage Calibration on the A30-MON Card ............................................................................... 8413.6 Field Current Calibration on the A30-MON Card .............................................................................. 8413.7 Line Current Calibration on the A30-MON Card ............................................................................... 8413.8 Temperature Transducer Calibration on the A30-MON Card ........................................................... 84

14 STEP RESPONSE TESTING............................................................................................................... 8514.1 Step Response.................................................................................................................................. 8514.2 Step Response on Open Circuit........................................................................................................ 8514.3 Stabilising Adjustment. ...................................................................................................................... 8514.4 UEL Stabilising .................................................................................................................................. 86

15 OPERATING PROCEDURES AND MAINTENANCE ......................................................................... 8715.1 Operating Procedures ....................................................................................................................... 8715.2 Maintenance...................................................................................................................................... 88

16 FAULT FINDING .................................................................................................................................. 8916.1 General Information........................................................................................................................... 8916.2 Precautions ....................................................................................................................................... 8916.3 Procedure.......................................................................................................................................... 8916.4 Fault Finding Tables.......................................................................................................................... 91

17 APPENDIX A - CONNECTIONS CHARTS........................................................................................ 10618 APPENDIX B - CARD LINK DESCRIPTIONS................................................................................... 11919 APPENDIX C - HOLDING REGISTERS FOR SCADA...................................................................... 12220 APPENDIX D - RECOMMENDED SPARES...................................................................................... 12521 APPENDIX E - DRAWINGS............................................................................................................... 126




1 INTRODUCTION TO MANUAL

1.1 General

The purpose of this manual is to provide information and advice on supplied equipment.

Warning symbols used in the manual are as follows:

Mandatory Notice - Instruction to be followed.

Danger, General - Caution to be exercised. Appropriate safety measures to betaken.Danger, Electricity - Caution to be exercised. Appropriate safety measures to betaken.Danger, Harmful or Irritating - Caution to be exercised. Appropriate safety measuresto be taken.

Information is given for guidance only and we do not accept any responsibility for the mannerin which the information is used, nor the consequences thereof.

The design and manufacture of equipment is subject to constant review and as a result theinformation provided herein may vary from that manufactured.

Verbal or written modifications to the information contained herein have no legal status unlessconfirmed in writing by the Technical Director or his nominated deputy.

The manual, and any amendments, should be maintained for the lifetime of the equipment.

It is important that any persons responsible for equipment installation,commissioning, operation and maintenance are provided with access to thismanual.

1.2 How To Use The Manual

It is recommended that prior to undertaking any installation, commissioning, operation ormaintenance activities on the equipment, this manual and any associated documentationshould be read in their entirety in order to gain an understanding of system operation.

The manual is written as a 'stand-alone' document, but should be read in conjunction with anyreferenced or associated documentation.

All pages and topic headings are numbered for easy reference. Cross-reference(s) toassociated paragraphs and documentation is included where appropriate. When referencingparticular paragraphs in communications, it is important to specify the Manual Number andthe Issue Reference.

Referenced drawings are attached as additional (unnumbered) pages.

1.3 Copies

Additional copies of the latest available version of manuals are available from our ServiceDepartment at the contact address given hereafter. A nominal charge may be made for thisservice.

The information provided remains the copyright of Brush Electrical Machines Ltd., and is notto be copied or disclosed to a third party without the written approval of the Technical Directorat the contact address given hereafter.




1.4 Feedback

We are constantly seeking to improve the quality and reliability of our products, and weactively encourage user feedback.

Any comments should be addressed to your usual representative, or to our ServiceDepartment at the contact address given hereafter.

1.5 Service & Spares

Quotations for Service and Spares can be obtained from our Service Department at thecontact address given hereafter.

Authorised users can also access spare parts information provided at the Web Site addressgiven hereafter.

1.6 Contact Address

Brush Electrical Machines Ltd.PO Box 18LoughboroughLeicestershireLE11 1HJEngland

Telephone:+44 (1509) 611511 (Switchboard)Telefax: +44 (1509) 612436 (Service Department)

E-Mail: [email protected]@bem.fki-et.com

Web Site: http://www.fki-et.com/bem

1.7 Health & Safety At Work Act (1974)

The information hereunder is supplied in accordance with Section 6 of the Health and Safetyat Work Act 1974 with respect to the duties of manufacturers, designers and installers inproviding health and safety information to Customers. The information advises of reasonablyforeseeable risks involved with the safe installation, commissioning, operation, maintenance,dismantling, cleaning or repair of products supplied by Brush Electrical Machines Ltd.

Every precaution should be taken to minimise risk. When acted upon, the followingprecautions should considerably minimise the possibility of hazardous incidents.

Delivery Checks: Check for damage sustained during transport. Damage to packing casesmust be investigated in the presence of an Insurance Surveyor.

Installation: Where installation is made by engineers other than Brush Electrical MachinesLtd. personnel, the equipment should be installed by suitably qualified personnel inaccordance with relevant legislation, regulations and accepted rules of the industry. Inparticular, the recommendations contained in the regulations with regard to the earthing(grounding) must be rigorously followed.




Electrical Installation:

IMPROPER USE OF ELECTRICAL EQUIPMENT IS HAZARDOUS.

It is important to be aware that control unit terminals and components maybe live to line and supply voltages.

Before working on a unit, switch off and isolate it and all other equipment withinthe confines of the same control cubicle. Check that all earth connections aresound.

WARNING: Suitable signs should be prominently displayed, particularly onswitches and isolators, and the necessary precautions taken to ensure that poweris not inadvertently switched on to the equipment whist work is in progress, or isnot yet completed.

Adjustment and fault finding on live equipment must be by qualified and authorised personnelonly, and should be in accordance with the following rules: Read the Instruction Manual. Use insulated meter probes. Use an insulated screwdriver for potentiometer adjustment where a knob is not provided. Wear non-conducting footwear. Do not attempt to modify wiring. Replace all protective covers, guards, etc. on completion.

Operation & Maintenance: Engineers responsible for operation and maintenance ofequipment should familiarise themselves with the information contained in this manual andwith the recommendations given in associated documentation. They should be familiar alsowith the relevant regulations in force. It is essential that all covers are in place and that all guards and/or safety fences to

protect any exposed surfaces and/or pits are fitted before the associated machine isstarted.

All adjustments to the associated machine must be carried out whilst the machine isstationary and isolated from all electrical supplies. Replace all covers and/or safety fencesbefore restarting the machine.

When maintenance is being carried out, suitable WARNING signs should be prominentlydisplayed and the necessary precautions taken to ensure power is not inadvertentlyswitched on to the equipment whilst work is in progress, or is not yet complete.

When power is restored to the equipment, personnel should not be allowed to work onauxiliary circuits, eg. heaters, current transformers etc.

1.8 Protection And Monitoring Devices

WARNING: It is essential that any protection or monitoring device for use withgenerators or ancillary equipment should be connected and operational at all timesunless specifically stated otherwise herein. It should not be assumed that allnecessary protection and monitoring devices are supplied as part of Brush ElectricalMachines Ltd. scope of supply.

Unless otherwise agreed, it is the responsibility of others to verify the correctoperation of all protection and monitoring equipment, whether supplied by BrushElectrical Machines Ltd. or not. It is necessary to provide a secure environment thatensures operator safety and limits potential damage to the generator and ancillaryequipment. If requested, Brush Electrical Machines Ltd. would be pleased toprovide advice on any specific protection application issues or concerns.




2 EUROPEAN DIRECTIVES




3 INTRODUCTION

The PRISMIC A30 Excitation Controller is designed to control the excitation of a brushless generator.Incorporating a wide range of features, the A30 is housed in a 19" rack assembly requiring only externalinstruments and control switches to provide the complete excitation system as shown in Figure 1.

For setup and commissioning of the A30 a PC is required. PC based software and two serialcommunications cables are provided.

A copy of the factory test record and factory setup data is provided with the A30 in the form of a BrushQC(T)48 document. When provided with a Brush generator, the A30 factory setup data will be matchedto the generator. The QC(T)48 document should be available when commissioning the A30.

Figure 1: A30 Excitation Controller Scheme




4 RATINGS

Max. continuous output current: 20A

Max. 10 second output current: 30A

Excitation supply voltage: Single phase 110Vac to 330Vac

Excitation supply frequency: 50Hz to 480Hz

Auxiliary dc Supply: 24Vdc or 110/125Vdc +15%, -20%

Nominal sensing voltage: 100V to 120V selectable in 5V steps

Voltage sensing phases: Three phase with single phase option

Voltage sensing input burden: Less than 3VA per phase

Nominal generator frequency: 50Hz or 60Hz

Current transformer input nominal: 5A or 1A selectable

Current transformer input burden: Less than 1VA

Max field voltage for forcing: 75% of single phase supply RMS voltage

Accuracy of control: 0.5%

Operating temperature range: 0C to +55C

Storage temperature range: -40C to +100C

Dimensions: Width 483mm, Height 266mm, Depth 400mm

Weight: 14.5kg




5 FEATURES

1) Complete System Housed In A Single 19 6U RackIncludes power semiconductor and control circuits, power supply transformers, contactors forexcitation changeover and field suppression and field suppression resistor.

2) Independent Main And Hot Standby Excitation ChannelsThe unit contains two power semiconductor circuits, one acting as a hot standby to the other. Eachcircuit is controlled by an independent control card with automatic following to enable smoothtransfer from one to the other.

Transfer to the standby system is initiated by a separate monitor module in the followingcircumstances: Voltage monitoring (over/under voltage on generator terminals) Excitation monitoring (over/under excitation with time delays) Over flux monitoring Control card failure

The settings for the monitor module are selected to enable the normal limiter settings to operatefirst. (See Figure 2)

Figure 2: Generator Capability Diagram3) PC Based Setup And Maintenance Software

The unit is provided with PC based setup and maintenance software and cable for connection to astandard PC 9 pin serial port. A PC is required to setup the A30.

4) Communication Port #1 For SCADA CommunicationsProvided to allow plant supervision computers to adjust setpoints and inspect generator andexcitation system data. Implemented using Modbus protocol.

5) Communication Port #2 For Set Up And MaintenanceProvided for connection to an RS232 port on a standard PC for commissioning.

6) Choice Of Setpoint Adjustment MethodEither external raise/lower contacts or SCADA communications may be used.

7) Line Voltage Control ModeIn Line Voltage Control Mode, line voltage is controlled to a constant adjustable setpoint. In thismode, parallel running capability is provided using quadrature current compensation (QCC) with anadjustable droop setting.

8) Power Factor Control ModeAvailable when parallel running.




9) VAr Control ModeAvailable when parallel running. Also incorporates VAr shed facility.

10) Soft Start FacilityAfter switching on excitation, line voltage is increased to the nominal level at an adjustable rate.

11) Fast Acting Field Current LimiterLimits excitation current to prevent excessive line current during power system faults.

12) Over Excitation LimiterUsing inverse time delay and temperature compensation if required, this facility is provided toprevent overheating of the generator rotor.

13) Under Excitation LimiterThis facility enables operation of the generator at maximum capability with a leading power factorbut avoiding the danger of the generator pole slipping.

14) Over Flux LimiterExcitation is controlled to ensure that generator line voltage is limited to a preset adjustablevoltage/frequency ratio to avoid over fluxing of the generator.

15) Selectable Standby System Control ModeThe standby system may be setup to operate in either Generator Voltage or Exciter Field CurrentControl Mode.

16) Rotating Diode Failure AlarmDetection of failed rotating diode or fuse is achieved by monitoring the ripple content of exciter fieldcurrent.

17) Adjustable Step ResponseThis facility enables an adjustable step increase in setpoint to be applied to evaluate the stabilitysettings of the excitation system. The PID parameters of the AVR may then be adjustedaccordingly. The rise time and overshoot values are recorded to help with commissioning. The stepreduction in setpoint may be used to evaluate the response of the underexcitation limiter.

18) Event RecorderA log of major events, such as limiter and monitor operations, and field suppression is maintainedwithin the unit. The events may be displayed using a PC connected to the commissioningcommunications port.




6 SPECIFICATION

6.1 A30-CON Card

Unless stated otherwise, all adjustments on this card are made using the HMI.

6.1.1 Voltage Control

1) Three Phase Or Single Phase SensingSelected by a link.

2) Accuracy0.5% of mean voltage.

3) Nominal Sensing VoltageSelectable from 100V to 120V in 5 volt increments.Frequency 50/60Hz 10%. Burden




6.1.3 Over-Flux Limiter

The ratio voltage/frequency is automatically limited to between 1.00 to 1.20 perunit, the level being adjustable in increments of 0.001 per unit. (1 per unit voltageis the nominal sensing voltage referred to in Section 6.1.1 Item 3)).

6.1.4 Soft Start

After switching on excitation, line voltage is slowly increased to the nominal level.Ramping rate is adjustable from 5V/s to 25V/s.

Excitation should only be switched on by energising the Excite input after theAVR Main Electronics Supply has been applied. This should be achieved using aspeed detector switch, external to the AVR, which should be set to switch at 80%rated speed.

6.1.5 Speed Detection

The AVR provides excitation build up when 85% rated speed is reached.Excitation is removed at 80% rated speed. Speed detection by the AVR uses PMGfrequency sensing. An external speed detector switch should also be fitted See6.1.4 above.

6.1.6 Power Factor Or Reactive Current (VAr) Control

1) PF/VAr Reference Adjustment RangePower Factor: 0.6 lag to 0.9 lead in increments of less than 0.001VAr: 100% rated VArs lagging to 50% rated VArs leading at

nominal volts in increments of 1%.

2) Method Of AdjustmentBy external raise/lower switches or relays on local panel. (Adjustment mayalso be made using the serial communications facility see Sections 6.1.15 and6.1.16)

3) Rate Of PF/VAr Reference AdjustmentFor PF control the range is adjustable from 1 to 20 seconds for 0.1PF.

For VAr control the range is adjustable from 50ms/% (20% rated VArs per sec)to 500 ms/%(2% rated VArs per sec)

4) AccuracyPower Factor Control: 1 at 100% rated current to 5 at 20% rated

current provided line current contains less then2% harmonics.

Reactive Current Control: 2% of rated line current provided line current isgreater than 10% rated and contains less than2% harmonics.




5) Automatic VAr SheddingIf the Power is reduced to zero while Power Factor Control is selected, the level ofVArs will automatically be reduced to a low level in order to maintain constantpower factor. Operation in this way will ensure that the Power Factor referenceremains unchanged when the set is shut down.

Operation of an external switch/relay will initiate automatic VAr shedding, and ifthis is invoked during the period that Power Factor control is also selected, VArshedding will occur irrespective of the power level. This is achieved by the PFcontroller reference being automatically set to unity. When this is done, the PF setpoint of unity is stored when the set is shut down and is the setting used on thenext start.

If VAr shedding is invoked during the period that PF Control is not selected, VArshedding operates by internally turning on the VAr controller with its VAr referenceto zero VArs. This means that when VAr shedding by this method, any previousVAr reference is changed to zero VArs, and this value is saved on shut down andrecovered on the next start. If it is required to retain a particular non-zero VArreference setting, the VAr controller should first be turned off, then selecting PFControl and VAr shedding simultaneously.

The rate of change of VAr or PF reference in response to a VAr sheddingcommand is determined by the programmed settings of the PF/VAr referenceadjustment rates referred to in 6.1.6 Item 3).

6) Selection Of PF/VAr ControlOperation of external switches or relays connected to the auxiliary dc supplywill initiate PF or VAr control. Internal dc supply isolation is provided. If PF orVAr controls are both selected together, PF control will result. (PF or VArcontrol may also be selected by the serial communications facility seeSections 6.1.15 and 6.1.16)

6.1.7 Over Excitation Limiter

1) Limiting LevelWithin range 2A to 25A in 0.01A increments.

2) Time DelayIntegrating time delay adjustable between 50 and 5000% seconds in 5%sincrements.

3) Increased SensitivityThe sensitivity can be increased by a factor of 4 to enable checking at 25% ofsetting during commissioning.

4) Temperature CompensationBy connecting a 100 platinum RTD located in the generator air intake to theAVR (no additional transducer required) the over excitation limiter setting canbe automatically adjusted according to temperature.

Compensation range: -10C to +55C

Compensation level: Adjustable from -0.2% to -1% per C rise in0.01% increments.

Compensation characteristic: Linear.




6.1.8 Under Excitation Limiter

1) Leading Reactive Current LimitThe limit at zero power and 100% volts is adjustable between 0.1A and 5.5Ain 0.01A increments. This covers the whole range for 1A and 5A CTs. The limitis automatically compensated in proportion to line voltage.

2) Limiting Level CurvatureThis is set by the external reactance control, which is adjustable between 0and 0.2 per unit in 0.01 per unit increments.

6.1.9 Fast Acting Field Current Limiter

1) RangeAdjustable from 2.5A to 30A in increments of 0.1A.

2) Time DelayLess than 0.05s.

3) Increased SensitivitySensitivity can be increased by a factor of 8 to enable checking at 12.5% ofnominal setting during commissioning.

6.1.10 Automatic Tracking of Standby Regulator

1) Standby FollowerWhen operating under Standby control and the sensing voltage is within thespecified range of the A30-CON card voltage reference, the reference of theA30-CON is automatically adjusted so that line voltage and VArs do notchange when voltage control is transferred from Standby to back to Auto.

If the A30-CON card has PF, VAr control or VAr shed selected when onStandby, they will not affect the automatic tracking but will become functionalwhen automatic control is selected.

2) Balance IndicationWhen in standby control, LED1 on the A30-CON card will flash while trackingis not achieved. When tracking is achieved, the LED will be continuouslyilluminated.

(Successful tracking is also indicated by the `high' or `low' LED indications onthe Standby regulator, and the external null balance meter (if fitted). NormallyLED 1 and LED 2 on the Standby card will alternate when balanced.Occasionally both LEDs will be off when balanced but if either LED is onpermanently, this indicates a fault).

3) Fail To Follow Alarm And Time DelayWhen operating in standby control, if the out of balance condition is presentfor a period greater than the Fail to Follow Alarm Time Delay an alarm isproduced by turning on LED6 on the A30-CON card and energising theLimiter Operating Relay on the Utilities card. The Fail to Follow Time delay isadjustable from 2 to 20 sec in increments of 1 sec.

6.1.11 Control Card LED Indications

LED 1 In Main control this LED has no function and will be turned off.In Standby control this LED will flash when Main has not matchedstandby.

It will be illuminated steadily when matching has been achieved.




LED 2 Watchdog dropout (program fails to cycle).

LED 3 Over excitation limiter operating.

LED 4 Under excitation limiter operating.

LED 5 PF control selected.

LED 6 In Main control this LED indicates Over Flux limiter operating.

In Standby control it indicates that Main has failed to match Standbywithin in a pre-set time.

LED 7 VAr shed selected.

LED 8 VAr control selected.

6.1.12 Control Card Output Signals

1) Limiter OperatingWhen Main channel control is selected a signal is provided to energise a relayon the Utilities card when either the over flux, over excitation or underexcitation limiter operates. When the standby channel is selected this signalindicates failure of the Main channel to match the standby channel within thespecified period.

2) Control Card Supervisory OutputA signal is provided to the A30-MON card in the event of a watchdog dropoutor failure of the 5V supply. This will cause the monitor to transfer to Standby.

6.1.13 Analogue Input Signal

The AVR can be configured to accept an analogue input such as a signal from apower system stabiliser (PSS). For this application Link 6A on the A30-CON cardmust be fitted.

Input impedance: 20K

Sensitivity: An input of 100mV will change the AVR reference byapproximately 2.5%

For details of connections to Brush power system stabilisers, please refer to therelevant PSS Instruction Manual.

An interface board A30-INT-PSS100, Part No 963135600, is available to provideeasy connection of a PSS with a 9Vdc output e.g. Basler PSS100. The interfaceboard connects directly to plug 1 at the back of the A30 rack. The wiring loom thenplugs into the interface board. The purpose of the interface board is to attenuatethe analogue input signal, on terminals 107 and 108, to a suitable level for theA30.




1k

47

8.6V

0.4V

9V

OutputTo A30

Con 1Con 2

Input FromPSS9V8

9

8

9 (A30 Terminal 108)

(A30 Terminal 107)

(Note: Pins 1 to 7 and Pins 10 to 16 are straight through)

Figure 3: A30-INT-PSS100 Interface Board ConnectionsWith an input of 9Vdc from the PSS the output to the A30 will be 0.4Vdc.Therefore 9Vdc from the PSS will equate to a change in the AVR reference ofapproximately 10%. Note: When a PSS is being used 107 is positive and 108negative.

An analogue input transducer is also provided on the A30. If this is to be used thenLink 6B should be fitted. This uses the same input terminals as the PSS input andtherefore they cannot both be used at the same time. The analogue inputtransducer is used with special control software, Part No 963113801, that controlsthe voltage reference depending on the analogue input see Section 8.1.7. Note:When using the analogue input transducer 107 is negative and 108 positive.

6.1.14 Output Voltage

The card produces firing pulses that are supplied to a half controlled full WaveBridge located in the mainframe. The maximum voltage that can be applied to thefield is approximately 75% of the PMG voltage at the input to the bridge.

6.1.15 Local Serial Communication Ports

A serial communication port (COM 2) is provided for transmitting and receivinginformation to or from the HMI for commissioning and maintenance.

6.1.16 Remote Serial Communications Facility.

1) Communications Protocol/Rate/Register AddressesModbus RTU, with the AVR acting as a slave with Modbus ID no 1.Communication Rate is 9600 baud, 8 data bits, no parity, 1 stop bit.Register Addresses and scaling factors are given in Appendix C - HoldingRegisters For SCADA.

2) Set Point Adjustment Via CommsIn order to adjust the set points via the HMI it is necessary for the Panel/HMIswitch to be set to HMI in which case the following set points are adjustablevia the communications link.

Note that unless Mode Selection via the HMI has been activated via thecomms link, the mode will remain selectable by hard wired signals a normal.




Note that the AVR will not allow a set point to be adjusted beyond thespecified range, and that following receipt of a new set point, the rate ofchange from the previous to the new set point will be according to the valuesset during commissioning.

Note also that for the Leading PF Reference to be used, the PF Ref Leadingmode must be selected.

Set Points available are: Voltage Reference VAr Reference PF Reference Lagging PF Reference Leading

3) Mode Selection Via CommsNote that unless Allow Mode Selection via the HMI has been activated via thecomms link, the mode will remain selectable by hard wired switch signals asnormal.

Note also that if Allow Mode Selection via the HMI has been activated, selectionof the mode by hard wired switch signals is inactive.

PF Reference Leading P F Control VAr Control VAr Shed Self Centre Voltage Reference Reset Monitors Allow mode selection Via Comms

4) Viewing Flags And Data Via CommsThe comms link can be used to provide digital and analogue data at the remoteterminal. The available data is given in Appendix C - Holding Registers ForSCADA

6.2 A30-MON Card

Unless stated otherwise all adjustments to this card are made using the HMI.

6.2.1 Over Voltage Monitor

1) Three Phase Or Single Phase SensingSelected by a link. (Selection must be same as that for the Under Voltage Monitor)

2) Accuracy 0.5% of mean voltage.

3) Trip LevelAdjustable between 100V and 140V in increments of 0.1V.

4) Time DelayAdjustable integrating time delay having a range of 10% seconds to 100%seconds in 1% second steps.

6.2.2 Over Flux Monitor

1) Measured QuantityRatio Line Voltage/Line Frequency




2) Trip LevelAdjustable between 1.00 and 1.25 per unit in increments of 0.001 per unit.

3) Time DelayAdjustable integrating time delay having a range of 10% seconds to 100%seconds in 1% second steps.

6.2.3 Under Voltage Monitor

1) Three Phase or Single Phase SensingSelected by a link. (selection must be same as Over Voltage Monitor)

2) Accuracy0.5% of mean voltage.

3) Trip LevelAdjustable between 70V and 120V in 0.1V increments.

4) Time DelayAdjustable integrating time delay having a range of 2%s to 25%s in 1%ssteps.

5) Under Frequency InhibitAt line frequency of less than 80% nominal the Under Voltage monitor isinhibited.

6) Over Flux Limiter InhibitThe under voltage monitor is inhibited if the flux limiter on the A30-CON Cardis operating.

7) Overcurrent InhibitThe under voltage monitor is inhibited if line current measured by the AVRexceeds 1.5 pu.

8) Soft Start InhibitThe under voltage monitor is inhibited during soft starting.

6.2.4 Over Excitation Monitor

1) Operating LevelAdjustable within range 2.5A to 35A in 0.01A steps.

2) Time DelayAdjustable integrating time delay having a range of 100%s to 5000%s in stepsof 5%s.

3) Increased SensitivitySensitivity can be increased by a factor of 4 to enable checking at 25% of thesetting during commissioning.

4) Temperature CompensationThe over excitation monitor is compensated for exciter input air temperatureby a signal from the RTD transducer located on the A30-CON card.

Compensation range: -10C to +55C

Compensation level: Adjustable from -0.2% to -1.0% per C rise in0.01% increments.

Compensation characteristic: Linear.




6.2.5 Under Excitation Monitor

1) Leading Reactive Current Tripping LevelThe tripping level at zero power and 100%V is adjustable between 0.1A and5.5A in 0.01A increments. This covers the whole range for 1A and 5A CTs.The trip level is automatically compensated in proportion to line voltage. Thisshould be set at least 10% greater than the under excitation limiter setting.

2) Tripping Level CurvatureThis is set by the `Xe' control and can be adjusted between 0 and 0.2 per unitin steps of 0.01 per unit. This should normally be set to the same value as thelimiter.

3) Time DelayA fixed time delay is included to prevent spurious tripping due to transients.This can be set between 1s and 10s in 0.1s increments.

6.2.6 A30-MON Card Indications

LED 1 SpareLED 2 Monitor watchdog dropout (program fails to cycle).LED 3 Over Excitation monitor tripped.LED 4 Under Excitation monitor tripped.LED 5 Over Voltage monitor tripped.LED 6 Under Voltage monitor tripped.LED 7 Over Flux monitor tripped.LED 8 Standby Power Supply Fault.LED 9 A30-CON watchdog dropout alarm.LED 10 Spare

6.2.7 A30-MON Card Output Signals

1) Monitor TripOne signal is provided to energise the monitor trip relay to select Standbycontrol when any of the following occur: Over Excitation monitor tripped Under Excitation monitor tripped Over Voltage monitor tripped Under Voltage monitor tripped Over Flux monitor tripped A30-CON watchdog alarm

2) Monitor Fault AlarmA signal is provided to energise the general alarm relay on the Utilities cardand prevent automatic selection of Standby control when any of the followingoccur: Monitor power supply failure Standby card power supply failure Monitor watchdog dropout alarm

6.2.8 Monitor Latch/Reset

When any of the monitors trip they remain latched until the fault is removed andthe reset pushbutton on the front of the card has been operated. Relay logic in theAVR prevents return to A30-CON card until monitors are reset.

6.2.9 Monitor Inhibit

Operation of the monitor can be inhibited if required by an external switch signal.The auxiliary dc supply is used and internal isolation is provided.




6.2.10 Local Serial Communication Port

A serial communication port (COM 2) is provided for transmitting and receivinginformation to or from the HMI for commissioning and maintenance.

6.2.11 Remote Serial Communications Facility.

Remote communication with the A30-CON card in the AVR is particularly usefulfor adjustment of settings, selection of operating modes, and acquisition of data fordisplay on a remote terminal via a serial link. Remote serial communication withthe A30-MON card is less useful and not available on the standard system.

6.3 Standby Control Card

6.3.1 Field Voltage Control

In this mode (which is selected by links), field voltage is controlled to a constantlevel. Two links - selected ranges of 0-100V and 0-200V are available. Themaximum field voltage is approximately 75% of the PMG supply voltage.

6.3.2 Line Voltage Control

In this mode (which is selected by links), single-phase line voltage is controlled toa constant adjustable level. 10% QCC is provided to facilitate stable paralleloperation. A 250mA fuse, FS3, protects the voltage sensing input.

1) Line Voltage Setting RangeSensing voltage adjustable from residual to 137.5V. VT burden




6.3.7 Automatic Follower

When the Main AVR channel is operating, the output of the Standby regulator iscontinuously adjusted to match that of the Main AVR, so that on transfer to theStandby regulator, there is minimal change in excitation. Note that the travel timeminimum to maximum introduces a time delay to the follower action.

After selection of Standby control, the set point remains constant unless adjustedby the operator. If line voltage control is selected, regular adjustment of the setpoint of the Standby regulator is unnecessary. This will prevent large variations ofmachine output voltage (or power factor if paralleled) as the load varies whichoccurs on manual regulators which control to a constant level of excitation.

6.3.8 Null Balance Indication

1) LocalTwo LED indicators are provided on the card which indicate `Manual High' and`Manual Low'. When the output of the Main and Standby control systems arematched, both LEDs are extinguished indicating balance between AVR andStandby, irrespective of whether Standby or Main is selected.

2) RemoteProvision is made for a 500-0-500 micro amp; centre-zero, null balance meterto indicate balance between Main and Standby irrespective of whetherStandby or Main control is selected.

6.3.9 Field Voltage Limiter

A field voltage limiter is included which is adjustable from 25V minimum to 200V or80% of the PMG supply voltage.

6.3.10 AVR Power Supply Monitor

A relay is energised in the event of failure of the A30-CON card power supply, itsoutput being used to initiate transfer to Standby control independently of the AVRmonitor relay which may be inoperative under a power supply failure situation.

6.3.11 Indications

LEDs provide the following indications: -

LED 1 Standby AVR lower than Main AVRLED 2 Standby AVR higher than Main AVRLED 3 Standby power supply healthyLED 4 A30-CON card power supply failureLED 5 Standby at minimumLED 6 Main AVR selected and excitation limiters off

6.3.12 Output Signals

1) Optically isolated signals to control and monitor boards to indicate Standbyhigh, low and power supply failed.

2) Normally open relay contact which closes on detecting A30-CON card powersupply failure. Used to initiate transfer to Standby control.

3) Signal for 500-0-500 micro amp analogue null balance meter.4) Standby at minimum. A volt-free, normally open contact wired to the rear plug

assembly. Rating as in 6.5.7.




6.3.13 Power Supply

The Standby board contains its own supply independent of the Main channel andMonitor. The power supply transformer primary is fused by FS1 and FS2(250mA). Link selected taps that cater for the following inputs, as seen in thefollowing table:

Links Selected Nominal Voltage Rating Over66-480Hz Range

Nominal Voltage Ratingat 50/60Hz

1, 3, 6 1, 5, 6 2, 3, 4

220 - 330V 165 - 250V 110 - 165V

250 10%187.5 10%125 10%

The unit is rated for 125% of the maximum for 1 minute to cater for over speedcondition.

6.3.14 Output Voltage

The card produces firing pulses that are supplied to a full wave, half-controlledbridge located in the mainframe. The maximum voltage that can be applied to thefield is approximately 75% of the PMG voltage at the input to the bridge.




6.4 Utilities Card

6.4.1 Power Supplies

The card produces the following fused power supplies:

Card Supply Fuse Value

A30-CON 15V 5% FS4 250mA

+5V 5% FS3 1A

A30-MON 15V 5% FS2 250mA

+5V 5% FS1 1A

Hand-held Terminal +9V 1V FS5 100mA

Note: The Hand-held Terminal Supply is not used on the A30 ExcitationController, and may not be fitted on later versions.

The +5V supplies are each fitted with over voltage protection.

The supplies are designed to operate in conjunction with the transformer mountedin the mainframe, connected to the Auxiliaries Board and will operate over thefollowing voltage/frequency range:

Auxiliaries Board VoltageLinks Selected

Nominal Voltage Rating66-480Hz

Nominal Voltage Ratingat 50/60Hz

1, 3, 6 1, 5, 6 2, 3, 4

220 - 330V 165 - 250V 110 - 165V

250 10%187.5 10%125 10%

The unit is rated for 125% of the maximum for 1 minute to cater for over speedcondition.

6.4.2 Diode Failure Relay

This unit detects exciter field current ripple and when this exceeds a pre-set limitlocal indication is given on the card and a relay is energised to give an outgoingsignal.

1) Normal Sensitivity (Link 1 & 2 Omitted)The relay will operate when the ripple exceeds 20% of the dc level.

2) Increased Sensitivity (Link 1 Fitted, 2 Omitted)The ripple to operate the relay is adjustable using RV1 from 20% to 12% ofthe dc level.

3) Reduced Sensitivity (Link 1 Omitted, 2 Fitted)The ripple to operate the relay is adjustable using RV1 from 20% to 40% ofthe dc level.

4) Test FacilityA front panel pushbutton (DFI Test) provides a means of testing the circuit.Approximately 2 seconds after pressing the button local indication is given andthe DF alarm relay is energised.




6.4.3 Relay Output Signals

The Utilities card contains relays described below having output signals that areaccessible on the rear plug assembly.

1) Contact RatingAll the relays on the Utilities card have the following rating:

Max switching Voltage 250V ac, 220V dcMax switching Current 2A ac, 2A dcMax switching Capacity 125VA, 60WMin permissible Load 10mV dc, 10A

2) Diode Failure Relay (RL1)A normally de-energised relay which energises when a diode failure isdetected. One volt-free changeover contact is provided.

3) Monitor Tripped Relay (RL3)A normally de-energised relay which is energised by a signal from the A30-MON card when any of the following fault conditions are detected unless thegeneral alarm relay RL4 is energised.

Over Voltage Under Voltage Over Excitation Under Excitation Over Flux monitor A30-CON card microprocessor fault

One volt-free changeover contact is accessible at the rear plug connections. Asecond changeover contact is internally wired to initiate transfer to Standby onmonitor operation.

4) Limiter Operating Relay (RL2)A normally de-energised relay that, in Main control, is energised by a signalfrom the A30-CON card when any of the following limiters operate: Over Excitation Under Excitation Over Flux

In Standby control this relay is energised whenever the Main channel hasfailed to match Standby in a specified time.

One volt-free changeover contact is accessible at the rear plug connections.One normally closed contact is internally wired to inhibit the auto follower onthe Standby control card on limiter operation.

5) General Alarm Relay (RL4)A normally de-energised relay that is energised by a signal from the A30-MONcard when any of the following fault conditions are detected: Loss of A30-MON power supply Loss of Standby regulator power supply A30-MON card microprocessor fault

One volt-free changeover contact is accessible at the rear plug connections.One normally closed contact is used to inhibit operation of the monitor-trippedrelay (RL3) in the event of the general alarm relay being energised.




6.4.4 Utilities Card LED Indications

LED 1 15V A30-CON supply healthyLED 2 15V A30-MON supply healthy

LED 3 5V A30-MON supply healthy LED 4 5V A30-CON supply healthy

LED 5 General alarm relay energisedLED 6 Monitor relay energised

LED 7 Diode failure relay energisedLED 8 Unused

6.5 A30-RACK1 Mainframe

6.5.1 Field Suppression Contactor (FSC)

This contactor is mechanically latched in the excite or tripped condition. Whentripped, the ac supply to the thyristor circuits is disconnected and the field currentdecays through the field suppression resistor.

6.5.2 Field Suppression Contactor Slave Relay (FSCS)

Indication of the state of FSC is given by a volt-free changeover contact on FSCSwired to the outgoing terminal block. See below for contact rating.

6.5.3 Excitation Changeover Contactor (ECC)

The contactor is mechanically latched in the `Main' or `Standby' condition to selectthe required power circuit.

6.5.4 Excitation Changeover Contactor Slave Relay (ECCS)

Indication of the state of ECC is given by a volt-free changeover contact on ECCSwired to the outgoing connections. See below for contact rating.

6.5.5 Power Supply Relay (PSR)

Indication of the presence of the dc auxiliary power supply is provided by volt-freechangeover contacts on this relay, which is energised when the auxiliary supply ispresent. See below for contact rating.

6.5.6 Fault Relay Slave (FRS)

Automatic changeover to Standby AVR occurs when FRS is energised byoperation of the monitor relay (RL3) on the Utilities card or operation of the A30-CON card power supply failure relay located on the Standby card. See below forcontact rating.

6.5.7 Relay Contact Ratings

The contact ratings of FSCS, ECCS, PSR and FRS are as follows: -

Maximum Switching Voltage 250V ac : 220V dcMaximum Switching Current 5A : 1A (resistive)Maximum Switching Capacity 1000VA : 50W




6.5.8 Fuses

The following fuses are located as shown:

On auxiliaries board accessible from front:

FS1 Auxiliary dc supply +ve (5A)FS2 Auxiliary dc supply -ve (5A)FS3 A30-CON/A30-MON supply (2A)FS4 A30-CON/A30-MON supply (2A)

In mainframe behind hinged door:

FS5 Main channel power circuit semiconductor fuse (20ET)FS6 Standby power circuit semiconductor fuse (20ET)

6.5.9 Power Circuit Rating

1) Input VoltageThe nominal voltage of the PMG must be within the range 110V to 330V.

The PMG voltage should not fall below 75% of the nominal when supplyingthe maximum field current required under fault conditions.

2) Output VoltageThe maximum voltage supplied to the exciter field will not be less than 75% ofthe (loaded) PMG voltage supplied to the AVR.

3) Maximum Output Current20A continuous30A 10 seconds.

4) Ambient Temperature (Standard Unit)Operating: 0C to +55CStorage: -40C to +65C

5) Principal Dimensions483mm wide x 266mm (6u) high x 400mm deep

6) Weight14.5kg approx. with plug in cards fitted.

6.5.10 Auxiliary Supply

Units can be supplied to operate from the following dc voltages:24V +15% -20%110/125V +15% - 20%




7 HARDWARE DESCRIPTION

7.1 A30-CON Card

The control card contains the microprocessor and its associated digital addressing circuitry,digital counter timer, signal conditioning circuitry, thyristor firing pulse isolation circuitry, digitalinput and output ports, and serial communication ports, see Figure 4.

This board carries a smaller mezzanine board, the A30-M188, which contains the majority ofthe microprocessor-allied components. A large proportion of these are contained in an FPGA(Field Programmable Gate Array IC4) which is configured on power up by boot ROM IC3.The EPROM (IC11-A) containing the working software is also on this board.

Figure 4: Block Diagram Of A30-CON Card




7.1.1 The Microprocessor And Its Associated Digital Circuitry

A 32MHz crystal (XTAL1) controls the Microprocessor (IC7) timing. It can be reseteither by the operation of the push button marked `Micro Reset' on the front panelor by the watchdog (1C1) whenever the software stops updating the watchdog.

The memory address circuits (IC6-A,IC8-A and IC9-A) produce a 17-bit address.128K of volatile RAM is fitted (IC10_A) and 8K of non-volatile memory EEPROM isfitted to store the commissioning and operator adjusted settings when the AVR isshutdown.

7.1.2 Serial Communication

Two serial RS232-C ports are available for local and remote communication.

A PC based HMI (Human-Machine Interface) can be connected to the localcommunication port via a `Comms' link to display and adjust contract settings.Provision is made for remote communication from a rear connector to enableadjustment of the settings and control modes via a SCADA link. This can also beused to display quantities measured by the control card.

7.1.3 Line Voltage Measurements

Figure 5: Voltage Sensing CircuitsFigure 5 shows the route between the sensing terminals and the control card.

Two transformers on the Utilities card (T1 and T2) isolate the three-phase linevoltage before this is supplied to the A30-CON card. The voltage is then rectifiedand buffered by IC3c to produce a smoothed dc voltage at TP9. Links 5A and 5Bare used to select the gain and smoothing according to whether single or threephase sensing is required.




The dc output voltage of IC3b is fed to a voltage to frequency converter (IC12)whose output frequency is proportional to the line voltage. This series of pulses isthen buffered and read into a counter timer, inside the FPGA on the A30-M188,over a fixed sampling period to provide a number which is proportional to linevoltage.

Typical voltage at TP9 is 4V - 6V dc at nominal line voltage.

7.1.4 Line Current Measurements

Figure 6: Line Current Sensing CircuitsThe line current signal is supplied to current transformer T3 and T4 on theBackboard.

The current sensing signal for the A30-CON card is produced across R2 (1Aprimary) or R1 (5A primary) connected across the output of T3. This ac voltage isfed to the A30-CON card where it is rectified and smoothed by IC3a and IC3cbefore being fed to voltage to frequency converter IC2 whose output frequency isproportional to line current.

Figure 6 shows the route between the current sensing terminals and the controlcard. The following shows typical voltage levels with 5A or 1A CT selections atrated or test levels of CT current.

Table 1: Typical Test Voltage Levels (With Respect To TP1)

CT LinkSelection

T3 PrimaryTest Current

AC Voltsat C1/1

DC Voltsat TP2

5A 1A 5A 5V 1.7V1A 1B 1A 4.7V 1.6V5A 1A 1A 1V 0.34V1A 1B 0.2A 0.94V 0.32V




7.1.5 Field Current Measurement Circuits

Figure 7: Field Current Measurement CircuitsThe field current is measured by two resistors R7 & R8 connected in series withthe exciter field, and mounted on the Backboard. The low voltage signal isamplified by IC1 on the Backboard and then fed to the A30-CON card.

The signal is then supplied to a voltage to frequency converter IC1 whose outputis proportional to exciter field current.

Figure 7 shows the circuitry used for exciter field current measurement. The dcvoltage on TP4, with respect to TP1, should be approximately 0.33 x the readingof the field current ammeter.




7.1.6 Ambient Temperature Measurement

Figure 8: Temperature Measurement Circuits

Ambient temperature is measured using a 100 platinum resistance temperaturedetector (RTD) normally placed in the generator cooling air inlet.

Any change in resistance of the RTD results in a change in the input signal toamplifier IC3d, whose output is connected to a voltage to frequency converter IC5to give a frequency signal which is related to RTD temperature.

Figure 8 shows the circuitry used for temperature measurement with typicalvoltage levels.

7.1.7 Thyristor Phase Reference And Firing Circuits

Figure 9: Phase Reference And Firing Circuits




The PMG voltage is isolated by transformer T2 on the auxiliaries board andsupplied to the A30-CON card where it is rectified by D11 & D12. The rectifiedsignal is compared to a negative signal and the difference amplified by IC7-D toproduce a narrow pulse at TP16 every zero crossing of the PMG voltage. Thissignal is used to reset a counter in the FPGA on the A30-M188.

A number calculated in the software (called DEMAND) is loaded into a countertimer every half cycle of the PMG voltage. Each time the PMG waveform passesthrough zero, the time begins to count, and when the counter reaches the numbercalled Demand the thyristor is fired via a pulse transformer.

When the firing pulse is produced the counter is reset and begins counting againon the next zero crossing of the PMG waveform.

7.1.8 Opto-Isolated Digital Inputs Of The A30-CON Card

Figure 10: Typical Arrangement Of Opto-Isolated Input SignalsExternal control panel inputs such as volts raise, volts lower, PF control, VAr shedetc are optically isolated from the A30 electronic circuitry. Each input is de-coupledto filter any transient spikes in the auxiliary dc supply. It can be used for 24/48V or110/125V dc supply, Link A being fitted for 24/48V supply, and Link B is fitted for110/125V supply.

When a dc signal of the correct level is applied to an input, a 5V-isolated signal isproduced at the output that is then applied to a digital input port of themicroprocessor.




7.2 A30-MON Card

7.2.1 Introduction

The A30-MON card contains the microprocessor and its associated digitaladdressing circuitry, digital counter timer, signal conditioning circuitry, digital inputand output ports, and serial communication ports. A Mezzanine Board, the A30-M188 carries the majority of the microprocessor components. This board isidentical to the one on the A30-CON card except for the software contained in theEPROM.

It is similar to the A30-CON card, except it does not have the thyristor firing circuitand the PMG voltage input. See Figure 11.

Figure 11: Block Diagram Of A30-MON Card

7.2.2 The Microprocessor And Its Associated Digital Circuitry

A 32MHz crystal (XTAL1) controls the Microprocessor (IC7) timing. It can be reseteither by the operation of the push button marked `Micro Reset' on the front panelor by the watchdog (1C1) whenever the software stops updating the watchdog.




The memory address circuits (IC6-A,IC8-A and IC9-A) produce a 17-bit address.128K of volatile RAM is fitted (IC10_A) and 8K of non-volatile memory EEPROM isfitted to store the commissioning and operator adjusted settings when the AVR isshut down.

7.2.3 Serial Communication

Two serial RS232-C ports are available for local and remote communication. AnHMI can be connected to the local communication port via a `Comms' link todisplay contract settings.

7.2.4 Line Voltage Measurements

Two transformers (T1 and T2) isolate the three-phase line voltage on the Utilitiescard before being supplied to the A30-MON card. The voltage is then rectified andbuffered by IC4d to produce a smooth dc voltage at TP4. Links 2A and 2B areused to select the gain and smoothing according to whether single or three phasesensing is required.

The dc output voltage of IC4d is fed to a voltage to frequency converter (IC3)whose output frequency is proportional to the line voltage. This series of pulses isthen buffered and read into a counter timer over a fixed sampling period to providea number which is proportional to line voltage.

Figure 5, Page 29 shows the route between the sensing terminals and the A30-MON card and typical voltage measurements with 110V sensing signal applied.

7.2.5 Line Current Measurement

The line current signal is supplied to current transformer T3 and T4 on theBackboard.

The current sensing signal for the A30-MON card is produced across R2 (1Aprimary) or R1 (5A primary) connected across the output of T3. This ac voltage isfed to the A30-MON card where it is rectified by IC10b and smoothed by IC10abefore being fed to voltage to frequency converter IC8 whose output frequency isproportional to line current.

Figure 6, Page 30 shows the route between the current sensing terminals and theA30-MON card with typical voltages and 5A or 1A flowing.

7.2.6 Field Current Measurement

The field current is measured by two resistors R7 & R8 connected in series withthe exciter field, and mounted on the Backboard. The low voltage signal isamplified by IC2 on the Backboard and then fed to the A30-MON.

The signal is then supplied to a voltage to frequency converter IC1 whose outputis proportional to exciter field current.

Figure 7, Page 31 shows the circuitry used for exciter field current measurement.The dc voltage on TP15, with respect to TP1, should be approximately 0.348 x thereading of the field current ammeter.

7.2.7 Ambient Temperature Measurement

Ambient temperature is measured using a 100 platinum resistance temperaturedetector (RTD) normally placed in the generator cooling air inlet.




An error proportional to the temperature change is produced by the A30-CON cardwhich is then supplied to the A30-MON, where it is amplified by IC10c whoseoutput is connected to a voltage to frequency converter IC7 to give a frequencysignal which is related to RTD temperature.

Figure 8, Page 32 shows the circuitry used for temperature measurement withtypical voltage levels.

7.2.8 Opto-Isolated Digital Inputs

External control panel inputs such as field suppression contactor and monitorinhibit etc. are optically isolated from the A30 Excitation Controller electroniccircuitry. Each input is de-coupled to filter any transient spikes in the auxiliary dcsupply. It can be used for 24/48V or 110V dc supply, Link A being fitted for 24/48Vsupply, and Link B is fitted for 110/125V supply.

When a dc signal of the correct level is applied to an input, a 5V-isolated signal isproduced at the isolator output that is then applied to a digital input port of themicroprocessor.

Figure 10, Page 33 shows the circuitry used.

7.3 Standby Control Card

7.3.1 Introduction

The Standby control card contains all the electronic circuitry to control the Standbypower circuit housed in the mainframe. It is designed to be independent of theUtilities, A30-CON and A30-MON cards.

7.3.2 Power Supply

The power supply is derived from the PMG voltage applied to the primary of T3 viaFS1 and FS2. Links are used to select the correct PMG voltage.

The 12V dc supplies are produced by VT1, VT2, Reg 1 and Reg 2 andassociated components. The supply is monitored by LED 3 to provide front ofpanel indications, and IC9d that provides an isolated signal to the A30-MON cardindicating the state of the Standby power supply.

Figure 12 shows the simplified circuitry associated with the Standby power supply.

Figure 12: Simplified Circuitry Associated With Standby Power Supply




7.3.3 Digital Reference

IC4, 3 and 1 form a 12 bit up down counter controlled by the raise/lower logicdescribed in 7.3.10.

The 12 outputs are connected to a network of resistors R1 to R24 to produce areference signal that is adjustable in 4096 steps. This signal is supplied to theinput of amplifier IC10a whose output provides the reference current for theStandby regulator to the input of IC15b.

The counter is limited to a maximum count when the 8 most significant bits reachlogic `1'. Under this condition the output of IC12 falls to logic `0' forcing the nextclock pulse to reduce the count.

Similarly, when the counter is in its `fully down' state the outputs will be at logic `0'and provide minimum reference current.

At Standby minimum Pin 6 of IC4 and Pin 7 of IC1 are both zero which causes theoutput of IC6c to fall to `0' and turn on FET 2 giving indication of Standby atminimum, whilst simultaneously removing further clock pulses via IC8a and IC8c.

7.3.4 Control Of Thyristor Firing

The thyristor in the Standby power circuit are phase controlled to provide therequired Standby output voltage. To control the instant of firing a triangularwaveform at TP4 that is synchronised to the PMG output voltage is compared to adc voltage at TP16.

When the voltage at TP4 exceeds that at TP16 the output of IC4d becomespositive and thyristor firing pulses are produced by oscillator IC16a and associatedcomponents. FET3 is pulsed on and transformer T2 supplies pulses to the gate ofthyristor SCR3 and SCR4.

7.3.5 Field Voltage Control

The output of the Standby regulator is fed to the Standby card terminal S2/11. It isthen attenuated, smoothed and supplied via LK14 to the input of an amplifier,where it is compared to the digital reference signal. The difference or error signalis amplified and then inverted by IC4b and IC4c to produce a signal at TP16 thatcontrols the firing angle.

If the output of the Standby regulator is higher than the reference, the voltage atTP16 becomes more positive and the firing angle is retarded.

7.3.6 Line Voltage Control

Line voltage is supplied to the Standby control card at S2/2 and S2/1. It is isolatedby T1 and rectified, attenuated and smoothed, and then supplied via LK15 to theinput of IC46 where it is compared to the digital reference signal. The error isamplified and then inverted to produce a signal at TP16 that controls the firingangle. A line current signal supplied at S1/1 and S1/3 provides a droopingvoltage/lagging VAr characteristic (QCC) LK12 is fitted for a 1A and LK13 is fittedfor 5A current sensing.

Figure 13 shows the simplified circuits associated with field voltage and linevoltage control.




Figure 13: Simplified Circuits Associated With Field Control And LineVoltage Control

7.3.7 Stabilising

The field voltage signal present at C32 is smoothed by R74, 78, 79 (asappropriate) and C21 and is then conditioned by IC11b and associatedcomponents and supplied to the input of the error amplifier via C25, RV2 and R71.RV1 provides adjustment of the quantity of stabilising signal provided and RV2provides adjustment of the phase shift. Links 25, 26 and 28 are set according tothe exciter field time constant (See Appendix B - Card Link Descriptions, LinkDescription 5).

7.3.8 Field Voltage Limiter

The output of the Standby regulator at S2/11 is attenuated, smoothed and thensupplied to the input of an amplifier, IC11a, where it is compared to a referencesignal.

If the attenuated field voltage exceeds the reference, the output of IC11a becomesnegative and the excitation is limited to that level by the signal flowing throughLK24, D5 and R83 to the input of IC15C. RV5 provides adjustment of the setting,and LK24 can be removed to inhibit the limiter if required.

7.3.9 Low Frequency Cut-Off

The line voltage signal at the input of DB1 is converted to a triangular waveform atTP22 whose height increases as frequency reduces.

When the frequency falls below a pre-set level set by RV3, the voltage at TP22causes the output of IC10c to switch positive which provides a signal to the 12 bitcounter to set its output to zero via D9 and LK7. Links 8 and 9 select the cut-offfrequency for 50/60Hz machines.

7.3.10 Raise/Lower Logic When Standby Control Selected

When Standby mode is selected, the auto follower mode is turned off since nosignal is applied to S1/5. To raise the digital reference, auxiliary dc should beconnected to S1/11, or PB2 on the card should be closed. Provided the counter isnot already at its upper limit, TP9 at the output of IC5a becomes positive andTP10 also becomes positive to gate the clock pulses (generated by IC5b andassociated components) to the counter.




Applying the dc supply to S1/9 or operating PB1 on the card lowers the digitalreference. In this case, TP9 is driven to a low level to make the clock pulsesreduce the counter setting.

When the raise or lower signals are removed the counter remains at its currentsetting.

7.3.11 Null Balance Detector

The null balance detector compares the instant at which the Main channel andStandby channel thyristor firing pulses occur and produces meter and LEDindications to show whether Standby is firing later than Main i.e. `STANDBY LOW',or earlier than Main i.e. `STANDBY HIGH'. Signals are also produced by the nullbalance detector to automatically match the firing angle of the Standby regulator tothat of the Main. This means that when Standby is selected from Main, it is set tothe correct level.

Conversely, when in Standby, control signals are produced by the null balancedetector, which are supplied to the A30-CON card to match the firing angle ofMain to that of Standby. By this means it is possible to run on Standby and checkautomatically that null balance can be obtained to indicate the state of the Mainchannel.

The null balance detector receives a firing pulse signal from the A30-CON card atS1/27, which is supplied, to IC14a. The firing pulse signal from the Standby pulsecircuit is supplied to IC14a and IC14b and are arranged to produce voltages atTP2 and TP3 which are equal when the firing angle of Main and Standby arebalanced.

Any difference in firing angle is amplified by IC13b whose output is driven positivewhen Main is higher than Standby and vice verse. The null balance meter is drivenfrom the output of IC13b through current limiting components.

IC13c and IC13d are voltage comparators arranged to produce raise and lowersignals to the auto follower, and also to give local LED indication of Standby highor low. Due to the fast response to the null balance measurement circuits,fluctuation of the null balance meter and Standby high/low LED's is normalparticularly when following an AVR channel.

7.3.12 Auto Follower

When operating in Main without any excitation limiters operating, internal relaylogic applies the dc auxiliary supply to S1/5 which turns on opto isolator IC9a anddrives the output of IC7a to logic 1. LED 6 on the Standby card is also turned on toindicate `Main Control' channel operation.

If the counter is not at the upper or lower limit, an `UP' or `DOWN' signal from thenull balance detector will set TP9 to level `1' to raise or `0' to lower, and driveTP10 to a logic `1' to gate the clock pulses to the counter.

The counter is adjusted and the reference changed which results in a change inthe voltage at TP16 and a subsequent change of Standby firing angle. By thismeans, the difference between Main and Standby firing angle is minimised.




7.3.13 Lower Limit And Standby At Minimum Indication

When the Standby reference is at minimum, Pin 6 of IC4 and Pin 7 of IC1 becomezero and the output of IC6c falls to zero preventing any further lower signals viaIC8a and IC8c. At the same time FET 2 is turned on, RL2 is energised, and LED 5turned on to give Standby at minimum indication.

7.3.14 Main AVR Power Supply Monitor

The Main channel 15V supply is applied to S1/19 and S1/21 and provides asignal to opto isolator IC12d. Loss of this supply causes RL1 and LED 4 to beturned on via FET 1. A contact on RL1 causes FRS in the mainframe to energiseand select the Standby system.

7.4 Utilities Card

7.4.1 Introduction

The Utilities card contains 15V and 5V-dc power supplies, and line voltagesensing transformers for the A30-CON and A30-MON cards. Relays associatedwith AVR logic, monitoring and indication facilities, together with the diode failuredetector are also included.

Figure 14 shows the circuitry that supplies the Utilities card with typical voltagelevels indicated. Allowance should be made when measuring transformer voltagesfor different PMG voltage levels to those shown.

Figure 14: Utilities Card Connections

7.4.2 5V DC Power Supplies

The PMG voltage on U1/5 and U1/9, supplied by the transformer T1 on theauxiliaries board, is rectified by the diode bridges (DB2 and DB4) and smoothedby C2 and C8. This unregulated dc voltage is then fed into a 5V dc regulator (IC1or IC3) and the 5V output supplied to A30-CON and A30-MON cards LED's 3 & 4provide indication that the 5V supply is energised. IC2 and IC4 monitor the 5V rail.If an over voltage condition occurs, thyristor 1 or 2 will be fired and cause fuseFS3 or FS1 to rupture.




7.4.3 15V DC Power Supplies

The transformer T1 on the auxiliaries board supplies the PMG voltage on U1/15,U1/17, U1/19 and U1/21. The diode bridges DB1 and DB3 rectify this AC voltage.The unregulated dc voltage is then fed into two zener diodes to produce 15V forthe A30-CON and the A30-MON cards. The transistor VT1 and VT2 provide aconstant current source for the 15V supplies. LED's 1 and 2 provide indicationthat the 15V supplies are energised.

7.4.4 HMI Power Supply

A +9Vdc power supply for a hand-held terminal. The dc voltage present at theoutput of DB4 is fused by FS5 (100mA) and regulated at 9V by VT3, Z11 andassociated components before being supplied to a socket on the front plate of theUtilities card.

Note: This feature is not used on the A30 Excitation Controller, and may not befitted on later versions.

7.4.5 Relays Associated With The AVR Logic And Indications

Input signals to the card include monitor trip at U2/18, general alarm at U2/24, andlimiter on at U2/20, are given by the A30-MON card and the A30-CON card. Logic0 at these terminals causes the corresponding FET3, FET5 or FET4 to turn on.This in turn gives a corresponding LED indication and energises relays thatprovide external indications.

7.4.6 Diode Failure Indication

Diode or fuse failure in the rotating assembly is detected by sensing ripple inducedin the exciter field current caused by unbalanced loading of the exciter output.

The voltage across R7 and R8 is amplified by IC2 on the Backboard and thensupplied to the diode failure circuit on the Utilities card.

Excessive ripple is detected by IC5b whose output is normally high and goes lowwhen ripple is detected. The output of IC5b is fed via D16 and R50 to IC5a whichturns on FET 2 after a time delay. FET2 turns on FET1 to energise the diodefailure relay RL1/1 and turn on LED 7 on the Utilities card.

The unit is supplied with fixed sensitivity but by fitting LK1, adjustable increasingsensitivity is provided as RV1 is turned clockwise. Fitting LK2 and rotating RV1clockwise can reduce the sensitivity.

7.5 A30-RACK1 Mainframe

Reference is made to the A30 Excitation Controller Circuit Diagram (See Appendix E -Drawings).

The mainframe is a 19", 6U rack. At the front, on the left, is a fixed panel. Next is a verticallyhinged panel and, at the right, is a printed circuit Backboard that carries four pairs of socketsfor the plug-in cards.

A printed circuit board (the Auxiliaries Board) is fixed towards the top of the left-hand sideplate. This board carries four fuses, which are accessible on the fixed front panel. At the rearof the board there are two, 16-way sockets. The board is also associated with the transformerthat provides the ac supply for the Main channel electronics power supply. The AuxiliariesBoard also contains four small, plug-in relays, PSR, FRS, ECCS and FSCS.

On the inside of the left-hand side plate, below the auxiliaries board, are mounted twocontactors, ECC and FSC and the field discharge resistor, FSR.

PRISMIC A30 Exci

hb959202000 (j) a30 excitation controller

Documents