spring update cd, may 2001 torque production with ac drives & motors: understanding the...

Spring Update CD, May 2001

TORQUE PRODUCTION WITHTORQUE PRODUCTION WITHAC DRIVES & MOTORS:AC DRIVES & MOTORS:Understanding the technologyUnderstanding the technology

TORQUE PRODUCTION WITHTORQUE PRODUCTION WITHAC DRIVES & MOTORS:AC DRIVES & MOTORS:Understanding the technologyUnderstanding the technology

Developed by,Rockwell Automation Drives BusinessReliance Electric

Developed by,Rockwell Automation Drives BusinessReliance Electric


After 25 years of AC Drive After 25 years of AC Drive acceptance, drive manufacturers acceptance, drive manufacturers offer the industry many types of offer the industry many types of control methods.control methods.

We’ll review some motor & drive We’ll review some motor & drive basics and then discuss the basics and then discuss the technologies offered in AC Drives technologies offered in AC Drives along with the selection process.along with the selection process.

Presentation AbstractPresentation AbstractPresentation AbstractPresentation Abstract


REVIEWING MOTOR REVIEWING MOTOR FUNDAMENTALSFUNDAMENTALS

AC & DC Motor BasicsAC & DC Motor BasicsAC & DC Motor BasicsAC & DC Motor Basics


Motor nameplate HP is achieved at Base RPM:Motor nameplate HP is achieved at Base RPM:

HP = Torque * Speed / 5252HP = Torque * Speed / 5252Torque

RPMBase Speed

100%

Horsep

ower

Constant Constant Torque RangeTorque Range

Constant Horsepower Constant Horsepower RangeRange

Motor BasicsMotor BasicsMotor BasicsMotor Basics

Nameplate HP is only Nameplate HP is only achieved at base achieved at base speed, NOT BEFORE!speed, NOT BEFORE!

Nameplate HP is only Nameplate HP is only achieved at base achieved at base speed, NOT BEFORE!speed, NOT BEFORE!


3 phase stator winding circuit w/ connections T1, T2 & T33 phase stator winding circuit w/ connections T1, T2 & T33 phase stator winding circuit w/ connections T1, T2 & T33 phase stator winding circuit w/ connections T1, T2 & T3

Motor Basics - AC Motor ConstructionMotor Basics - AC Motor ConstructionMotor Basics - AC Motor ConstructionMotor Basics - AC Motor Construction

Motor Frame Motor Frame AssemblyAssembly

Motor Frame Motor Frame AssemblyAssembly

Rotor & ShaftRotor & ShaftAssemblyAssembly

Rotor & ShaftRotor & ShaftAssemblyAssembly

Stator Winding Stator Winding AssemblyAssembly

Stator Winding Stator Winding AssemblyAssembly


Rotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction Motor

Motor RPM is equal to:

120 * Frequency

# Motor Poles

2 Pole Motor2 Pole Motor2 Pole Motor2 Pole Motor

Note that Frequency Note that Frequency is the only variable to is the only variable to

affect motor speedaffect motor speed

Note that Frequency Note that Frequency is the only variable to is the only variable to

affect motor speedaffect motor speed

Motor Basics - AC Motor OperationMotor Basics - AC Motor OperationMotor Basics - AC Motor OperationMotor Basics - AC Motor Operation


Armature Armature AssemblyAssembly

Armature Armature AssemblyAssembly

Distinct Armature & Field Circuits are mechanically separatedDistinct Armature & Field Circuits are mechanically separatedDistinct Armature & Field Circuits are mechanically separatedDistinct Armature & Field Circuits are mechanically separated

NOTE: The Armature & Field NOTE: The Armature & Field Circuits are mechanically Circuits are mechanically

fixed at 90° at all timesfixed at 90° at all times

NOTE: The Armature & Field NOTE: The Armature & Field Circuits are mechanically Circuits are mechanically

fixed at 90° at all timesfixed at 90° at all times

Field Poles Field Poles AssembliesAssemblies

Field Poles Field Poles AssembliesAssemblies

Commutator & Commutator & Brush AssemblyBrush Assembly

Commutator & Commutator & Brush AssemblyBrush Assembly

Motor Basics - DC Motor ConstructionMotor Basics - DC Motor ConstructionMotor Basics - DC Motor ConstructionMotor Basics - DC Motor Construction


Rotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction MotorRotating Magnetic Field of a 2 Pole AC Induction Motor

Motor RPM is equal to:

Both Armature Terminal Both Armature Terminal Voltage & Field Strength Voltage & Field Strength affect DC Motor speedaffect DC Motor speed

Both Armature Terminal Both Armature Terminal Voltage & Field Strength Voltage & Field Strength affect DC Motor speedaffect DC Motor speed

Simple ModelSimple ModelSimple ModelSimple Model

Voltage - ( Voltage Drop )

Field Flux

Arm

SSSS NNNNVV

To create motor torque To create motor torque at the shaft, we increase at the shaft, we increase

Armature CurrentArmature Current

To create motor torque To create motor torque at the shaft, we increase at the shaft, we increase

Armature CurrentArmature Current

Motor Basic - DC Motor OperationMotor Basic - DC Motor OperationMotor Basic - DC Motor OperationMotor Basic - DC Motor Operation


Key Points of UnderstandingKey Points of Understanding

Mechanical differences must be overcome mathematicallyMechanical differences must be overcome mathematicallyMechanical differences must be overcome mathematicallyMechanical differences must be overcome mathematically

• AC Induction Motors have one circuit to connectAC Induction Motors have one circuit to connect

• Connection to T1, T2 & T3 for the statorConnection to T1, T2 & T3 for the stator

• DC Motors have 2 separate circuits to connectDC Motors have 2 separate circuits to connect

• Connection to F1 & F2 for the FieldConnection to F1 & F2 for the Field

• Connection to A1 & A2 for the ArmatureConnection to A1 & A2 for the Armature

• To make AC Motors perform like DC Motors To make AC Motors perform like DC Motors

• Treat the AC motor like a 2 circuit machineTreat the AC motor like a 2 circuit machine

Motor Basics - AC & DC SummaryMotor Basics - AC & DC SummaryMotor Basics - AC & DC SummaryMotor Basics - AC & DC Summary


PWM AC DRIVE PWM AC DRIVE FUNDAMENTALSFUNDAMENTALS

AC Drive BasicsAC Drive BasicsAC Drive BasicsAC Drive Basics


• Diode rectifier converts AC line voltage to fixed voltage DC.• DC voltage is filtered to reduce current ripple from rectification.• Inverter changes fixed voltage DC to adjustable PWM AC voltage.

• Diode rectifier converts AC line voltage to fixed voltage DC.• DC voltage is filtered to reduce current ripple from rectification.• Inverter changes fixed voltage DC to adjustable PWM AC voltage.

MotorMotorAC LineAC Line

IGBTIGBTInverterInverter

Diode Diode RectifierRectifier

DC BusDC BusFilterFilter

Drive Basics - PWM AC Drive ConstructionDrive Basics - PWM AC Drive ConstructionDrive Basics - PWM AC Drive ConstructionDrive Basics - PWM AC Drive Construction


PWM waveform is a series of repetitive PWM waveform is a series of repetitive Voltage pulsesVoltage pulsesPWM waveform is a series of repetitive PWM waveform is a series of repetitive Voltage pulsesVoltage pulses

1

3

+ DC Bus+ DC Bus

- DC Bus- DC Bus

VVLLLL @ Drive @ Drive

500 Volts / Div.500 Volts / Div.

Phase CurrentPhase Current10 Amps / Div.10 Amps / Div.

M2.00s Ch1 1.18V

AC Drive Basics - PWM AC WaveformsAC Drive Basics - PWM AC WaveformsAC Drive Basics - PWM AC WaveformsAC Drive Basics - PWM AC Waveforms


Motor speed is controlled by ramping Voltage & FrequencyMotor speed is controlled by ramping Voltage & FrequencyMotor speed is controlled by ramping Voltage & FrequencyMotor speed is controlled by ramping Voltage & Frequency

OutputOutputFrequencyFrequencyBase FrequencyBase Frequency

6060

Output Output VoltageVoltage

Hz30

460460

230

115

15 90

Ratio @ 460VAC

= 7.67 V/Hz

0

Operation at Base SpeedOperation at Base Speed

AC Drive Basics - V/Hz OperationAC Drive Basics - V/Hz OperationAC Drive Basics - V/Hz OperationAC Drive Basics - V/Hz Operation

At 100% of the motor’s base speed, the V/Hz ratio is At 100% of the motor’s base speed, the V/Hz ratio is determined: HP = 100% of motor nameplatedetermined: HP = 100% of motor nameplate


At 50% of base speed, Voltage & Frequency decrease by 1/2At 50% of base speed, Voltage & Frequency decrease by 1/2At 50% of base speed, Voltage & Frequency decrease by 1/2At 50% of base speed, Voltage & Frequency decrease by 1/2


60


Hz3030

460

230230

115

15 90

Ratio @ 460VAC

= 7.67 V/Hz

0


At 50% of the motor’s base speed, the V/Hz ratio is At 50% of the motor’s base speed, the V/Hz ratio is maintained: HP = 50% of motor nameplatemaintained: HP = 50% of motor nameplate

Operation at 50% Base SpeedOperation at 50% Base Speed


At 25% of the motor’s base speed, the V/Hz ratio is At 25% of the motor’s base speed, the V/Hz ratio is maintained: HP = 25% of motor nameplatemaintained: HP = 25% of motor nameplate


60


Hz30

460

230

115115

1515 90

Ratio @ 460VAC

= 7.67 V/Hz

0

At 25% base speed, Voltage & Frequency decreases by 3/4’sAt 25% base speed, Voltage & Frequency decreases by 3/4’sAt 25% base speed, Voltage & Frequency decreases by 3/4’sAt 25% base speed, Voltage & Frequency decreases by 3/4’s


Operation at 25% Base SpeedOperation at 25% Base Speed


To increase starting torque, V/Hz Drives use Voltage To increase starting torque, V/Hz Drives use Voltage Boost to over-flux the motor to increase starting torqueBoost to over-flux the motor to increase starting torque

Offsetting the voltage ratio increases motor starting torqueOffsetting the voltage ratio increases motor starting torqueOffsetting the voltage ratio increases motor starting torqueOffsetting the voltage ratio increases motor starting torque


60


Hz30

460

248

138

15 90

Ratio @ 460VAC

= 7.67 V/Hz +

% BOOST

0Voltage Voltage BoostBoost



Voltage Boost over prolonged operating Voltage Boost over prolonged operating periods may result in overheating of the periods may result in overheating of the motor’s insulation system and result in motor’s insulation system and result in damage or premature failure.damage or premature failure.

Unable to perform like DC, the industry looks to Vector ControlUnable to perform like DC, the industry looks to Vector ControlUnable to perform like DC, the industry looks to Vector ControlUnable to perform like DC, the industry looks to Vector Control

CAUTION: Motor Insulation Life is decreased by 50% for every 10C above the insulation’s temperature capacity

CAUTION: Motor Insulation Life is decreased by 50% for every 10C above the insulation’s temperature capacity



If we can de-couple and Regulate If we can de-couple and Regulate Current, the Current, the component that creates torque at the motorcomponent that creates torque at the motor, we , we can regulate motor torque, not just motor speed!can regulate motor torque, not just motor speed!

Current Regulation allows Torque ControlCurrent Regulation allows Torque ControlCurrent Regulation allows Torque ControlCurrent Regulation allows Torque Control

This is the premise for Vector Control

This is the premise for Vector Control

AC Drive Basics - Vector OperationAC Drive Basics - Vector OperationAC Drive Basics - Vector OperationAC Drive Basics - Vector Operation


AC VECTOR DRIVE AC VECTOR DRIVE FUNDAMENTALSFUNDAMENTALS

AC Drive BasicsAC Drive BasicsAC Drive BasicsAC Drive Basics


• Motor Magnetizing CurrentMotor Magnetizing Current

• Motor Full Load AmpsMotor Full Load Amps

• Motor VoltageMotor Voltage

• Motor Base FrequencyMotor Base Frequency

• Motor Base (Slip) RPMMotor Base (Slip) RPM

• Motor HorsepowerMotor Horsepower

Correct Motor Data is the most important factor for successCorrect Motor Data is the most important factor for successCorrect Motor Data is the most important factor for successCorrect Motor Data is the most important factor for success

AC Drive Basics - Motor ModelingAC Drive Basics - Motor ModelingAC Drive Basics - Motor ModelingAC Drive Basics - Motor Modeling

AC Drive Parameters create a “Motor Model” AC Drive Parameters create a “Motor Model” based on data entered in the drive parametersbased on data entered in the drive parameters


Magnetizing Current is the current required to excite the Magnetizing Current is the current required to excite the motor laminations and copper winding w/o doing work. motor laminations and copper winding w/o doing work.

• Magnetizing Current is: NO LOAD AMP draw less Magnetizing Current is: NO LOAD AMP draw less friction and windage friction and windage

• Establishes the motor’s FluxEstablishes the motor’s Flux

• (FLA - Mag. Amps) = 100% Torque Current(FLA - Mag. Amps) = 100% Torque Current

Wrong data will reduce motor torque productionWrong data will reduce motor torque production

Magnetizing Current will range from 35% to 50% of FLA valueMagnetizing Current will range from 35% to 50% of FLA valueMagnetizing Current will range from 35% to 50% of FLA valueMagnetizing Current will range from 35% to 50% of FLA value


AC Drive Parameters: “Magnetizing Current”AC Drive Parameters: “Magnetizing Current”


Torque is produced, as well as regulated even at “0” RPMTorque is produced, as well as regulated even at “0” RPM

Magnetizing Current is the equivalent of Field CurrentMagnetizing Current is the equivalent of Field CurrentMagnetizing Current is the equivalent of Field CurrentMagnetizing Current is the equivalent of Field Current

Magnetizing Current = Motor No Load Amps Magnetizing Current = Motor No Load Amps

““a fixed value from “0” RPM to Motor Base RPM”a fixed value from “0” RPM to Motor Base RPM”

Magnetizing Current = Motor No Load Amps Magnetizing Current = Motor No Load Amps

““a fixed value from “0” RPM to Motor Base RPM”a fixed value from “0” RPM to Motor Base RPM”


Torque Current

Magnetizing Current

100%

90


The motor FLA value The motor FLA value maymay set the scaling for: set the scaling for:

• Motor OverloadMotor Overload

• Drive OverloadDrive Overload

• Torque Current AvailableTorque Current Available

• (FLA * %OL) - Mag. Amps = Max. Available Torque Current(FLA * %OL) - Mag. Amps = Max. Available Torque Current

Wrong data affects available torque current and may Wrong data affects available torque current and may allow damage to the motor.allow damage to the motor.

Since every Vector algorithm is unique, check w/ manufacturerSince every Vector algorithm is unique, check w/ manufacturerSince every Vector algorithm is unique, check w/ manufacturerSince every Vector algorithm is unique, check w/ manufacturer


AC Drive Parameters: “Full Load Amps”AC Drive Parameters: “Full Load Amps”


Voltage & Base Hz values Voltage & Base Hz values willwill::

• Establish the motor V/Hz ratio for the drive outputEstablish the motor V/Hz ratio for the drive output

Wrong data will cause motor heating and possibly Wrong data will cause motor heating and possibly reduce motor torque as well as shorten insulation life.reduce motor torque as well as shorten insulation life.

Needed to assure proper motor operation w/o over-heatingNeeded to assure proper motor operation w/o over-heatingNeeded to assure proper motor operation w/o over-heatingNeeded to assure proper motor operation w/o over-heating


AC Drive Parameters: “Voltage & Base Hz”AC Drive Parameters: “Voltage & Base Hz”


Base Hz & RPM values Base Hz & RPM values willwill set the scaling for: set the scaling for:

• Calculation of motor slipCalculation of motor slip

• Identifies expected motor RPM at FrequencyIdentifies expected motor RPM at Frequency

• Allows for speed error detection & correctionAllows for speed error detection & correction

• Establishing the point of field weakeningEstablishing the point of field weakening

Wrong data here can cause excessive current drawWrong data here can cause excessive current draw

AC Drives regulate speed based upon motor slip AC Drives regulate speed based upon motor slip AC Drives regulate speed based upon motor slip AC Drives regulate speed based upon motor slip


AC Drive Parameters: “Base HZ & RPM”AC Drive Parameters: “Base HZ & RPM”


The Horsepower value The Horsepower value maymay be used to: be used to:

• Estimate the expected motor impedanceEstimate the expected motor impedance

• Estimate the expected motor inductanceEstimate the expected motor inductance

• Calculate the torque loop gainsCalculate the torque loop gains

Wrong data here can cause poor speed and torque Wrong data here can cause poor speed and torque regulationregulation

Horsepower information gets us “in the Ballpark”Horsepower information gets us “in the Ballpark”Horsepower information gets us “in the Ballpark”Horsepower information gets us “in the Ballpark”


AC Drive Parameters: “Horsepower”AC Drive Parameters: “Horsepower”


Flux Vector Drives act very much like DC DrivesFlux Vector Drives act very much like DC Drives

Field WeakeningField Weakening occurs whenever we exceed Motor Base RPM occurs whenever we exceed Motor Base RPM Field WeakeningField Weakening occurs whenever we exceed Motor Base RPM occurs whenever we exceed Motor Base RPM

Magnetizing Current is decreased above Motor Base RPMMagnetizing Current is decreased above Motor Base RPMMagnetizing Current is decreased above Motor Base RPMMagnetizing Current is decreased above Motor Base RPM


Torque Current

Magnetizing Current

100%

90

Torque Current

Magnetizing Current

100%

9090


Torque at the motor shaft based upon loadTorque at the motor shaft based upon load

Torque Current increases or decreases dependent upon loadTorque Current increases or decreases dependent upon loadTorque Current increases or decreases dependent upon loadTorque Current increases or decreases dependent upon load

Torque Current = Motor Load at the Shaft Torque Current = Motor Load at the Shaft

““a variable value” during speed regulated operationsa variable value” during speed regulated operations

Torque Current = Motor Load at the Shaft Torque Current = Motor Load at the Shaft

““a variable value” during speed regulated operationsa variable value” during speed regulated operations


Torque Current

Magnetizing Current

100%

90

Torque Current

Magnetizing Current

10%90


Torque at the motor shaft based upon “Torque Reference”Torque at the motor shaft based upon “Torque Reference”

Torque Current can be commanded as a reference valueTorque Current can be commanded as a reference valueTorque Current can be commanded as a reference valueTorque Current can be commanded as a reference value

Torque Current = Reference setting Torque Current = Reference setting

““a fixed value” during torque regulated operationsa fixed value” during torque regulated operations

Torque Current = Reference setting Torque Current = Reference setting

““a fixed value” during torque regulated operationsa fixed value” during torque regulated operations


Torque Current

Magnetizing Current

100%

90

Torque Current

Magnetizing Current

10%90


Torque production suffers if 90° is not maintainedTorque production suffers if 90° is not maintained

Motor torque is optimized ONLY when 90Motor torque is optimized ONLY when 90 is maintained is maintainedMotor torque is optimized ONLY when 90Motor torque is optimized ONLY when 90 is maintained is maintained

Improper tuning, incorrect motor parameters, problems Improper tuning, incorrect motor parameters, problems with motor speed feedback or undersized drive with motor speed feedback or undersized drive applications will result in poor load (torque) regulation.applications will result in poor load (torque) regulation.

Improper tuning, incorrect motor parameters, problems Improper tuning, incorrect motor parameters, problems with motor speed feedback or undersized drive with motor speed feedback or undersized drive applications will result in poor load (torque) regulation.applications will result in poor load (torque) regulation.


Torque Current

Magnetizing Current

100%

90

Optimized Optimized Torque Torque ProductionProduction

Torque Current

Magnetizing Current

?

Poor Torque Poor Torque Production & Production & RegulationRegulation

ie: Impact Loadie: Impact Load


Load Type: Forward Speed & Reverse TorqueLoad Type: Forward Speed & Reverse Torque

Time to find motor rpm & position is limited by inertia & speedTime to find motor rpm & position is limited by inertia & speedTime to find motor rpm & position is limited by inertia & speedTime to find motor rpm & position is limited by inertia & speed

How a load becomes applied How a load becomes applied to the drive system can be to the drive system can be critical to system success.critical to system success.

A load where there is Forward A load where there is Forward Velocity & Reverse Torque is Velocity & Reverse Torque is the most difficult load to the most difficult load to handle. handle.

How a load becomes applied How a load becomes applied to the drive system can be to the drive system can be critical to system success.critical to system success.

A load where there is Forward A load where there is Forward Velocity & Reverse Torque is Velocity & Reverse Torque is the most difficult load to the most difficult load to handle. handle.


?

If the Nip Rolls are engaged during If the Nip Rolls are engaged during web travel, a condition with web travel, a condition with forward velocity and reverse forward velocity and reverse torque can occur.torque can occur.

Use either V/Hz or a closed loop Use either V/Hz or a closed loop system if inertia or speed is high.system if inertia or speed is high.

If the Nip Rolls are engaged during If the Nip Rolls are engaged during web travel, a condition with web travel, a condition with forward velocity and reverse forward velocity and reverse torque can occur.torque can occur.

Use either V/Hz or a closed loop Use either V/Hz or a closed loop system if inertia or speed is high.system if inertia or speed is high.


Motor Current is = Vector Sum of Torque & MagnetizingMotor Current is = Vector Sum of Torque & Magnetizing

This is where the term This is where the term VECTOR DRIVEVECTOR DRIVE is derived is derivedThis is where the term This is where the term VECTOR DRIVEVECTOR DRIVE is derived is derived

Motor Current is what’s measured with a clamp-on meterMotor Current is what’s measured with a clamp-on meterMotor Current is what’s measured with a clamp-on meterMotor Current is what’s measured with a clamp-on meter


100%

Magnetizing Current

Torque Current

Magnetizing Current

100%

Motor Current

90

Torque Current

Motor Current

90

A² + B² = C²A² + B² = C²A² + B² = C²A² + B² = C²


Flux Vector Drives regulate current & torque using rotor Flux Vector Drives regulate current & torque using rotor speed & position to optimize torque at the motor shaft speed & position to optimize torque at the motor shaft along w/ current feedback from the motor.along w/ current feedback from the motor.

Encoders provide rotor speed & position information Encoders provide rotor speed & position information Encoders provide rotor speed & position information Encoders provide rotor speed & position information

L1L2

L3

Current Feedback

Motor

EMicro P

AC Drive Basics - Flux Vector OperationAC Drive Basics - Flux Vector OperationAC Drive Basics - Flux Vector OperationAC Drive Basics - Flux Vector Operation


As motor temperature reaches nominal operating values, As motor temperature reaches nominal operating values, torque linearity and accuracy improves in FVC operationtorque linearity and accuracy improves in FVC operation

Torque accuracy of

5% or better !

AC Drive Basics - Rotor Temperature & TorqueAC Drive Basics - Rotor Temperature & TorqueAC Drive Basics - Rotor Temperature & TorqueAC Drive Basics - Rotor Temperature & Torque

% Torque

Inch - Lbs

-800

-600

-400

-200

0

200

400

600

-200 -150 -100 -50 0 50 100 150 200 30 deg

80 deg

Ideal Value

HOT Motor

COLD Motor


Field Oriented Control uses the same basic technology as Field Oriented Control uses the same basic technology as Flux Vector Control, but adds Voltage Feedback to Flux Vector Control, but adds Voltage Feedback to optimize / adapt to changes in motor temperature.optimize / adapt to changes in motor temperature.

The drive continuously adapts to motor temperature changeThe drive continuously adapts to motor temperature changeThe drive continuously adapts to motor temperature changeThe drive continuously adapts to motor temperature change

L1L2

L3

Voltage Feedback

Motor

EMicro P

AC Drive Basics - Field Oriented ControlAC Drive Basics - Field Oriented ControlAC Drive Basics - Field Oriented ControlAC Drive Basics - Field Oriented Control


Key Points of UnderstandingKey Points of Understanding

Motor information, measured or programmed is key to successMotor information, measured or programmed is key to successMotor information, measured or programmed is key to successMotor information, measured or programmed is key to success

• Errors in Encoder Feedback affect the Micro-ProcessorErrors in Encoder Feedback affect the Micro-Processor

• Speed instability will occur Speed instability will occur

• Encoder Feedback Signals must be NOISE FREEEncoder Feedback Signals must be NOISE FREE

• Select an appropriate encoder for Vector Motor useSelect an appropriate encoder for Vector Motor use

• Proper grounding is very importantProper grounding is very important

• Motor Data programmed in the drive must be accurateMotor Data programmed in the drive must be accurate

AC Drive Basics - SummaryAC Drive Basics - SummaryAC Drive Basics - SummaryAC Drive Basics - Summary


• Those with a Those with a V/Hz CoreV/Hz Core

All Sensorless Vector Drives are All Sensorless Vector Drives are NOTNOT the same! the same!All Sensorless Vector Drives are All Sensorless Vector Drives are NOTNOT the same! the same!

There are actually 2 types of drives advertised as There are actually 2 types of drives advertised as Sensorless Vector;Sensorless Vector;

• Those with a Those with a Vector CoreVector Core

AC Drive Basics - Sensorless Vector OperationAC Drive Basics - Sensorless Vector OperationAC Drive Basics - Sensorless Vector OperationAC Drive Basics - Sensorless Vector Operation


SVC with SVC with V/Hz Core TechnologyV/Hz Core Technology

V/Hz Core SVC Drives can operate multiple motorsV/Hz Core SVC Drives can operate multiple motorsV/Hz Core SVC Drives can operate multiple motorsV/Hz Core SVC Drives can operate multiple motors

• Use sophisticated “Current Limiting” algorithms to Use sophisticated “Current Limiting” algorithms to improve constant torque & starting torque operationimprove constant torque & starting torque operation

• Typically needs less motor information for setup adding Typically needs less motor information for setup adding some simplicitysome simplicity

• Can operate multiple motors from one driveCan operate multiple motors from one drive

• ONLY regulates V/Hz output, clamps CURRENTONLY regulates V/Hz output, clamps CURRENT

• Can only operate as a Speed Regulator, NOT TORQUECan only operate as a Speed Regulator, NOT TORQUE



SVC with SVC with Vector Core TechnologyVector Core Technology

Vector Core SVC Drives can operate only one motor at a timeVector Core SVC Drives can operate only one motor at a timeVector Core SVC Drives can operate only one motor at a timeVector Core SVC Drives can operate only one motor at a time

• De-couples Torque & Magnetizing Currents to maintain 90 alignment

• Typically needs more motor information for setup adding some complexity

• Can operate only one motor per drive due to the information required to regulate current

• Regulates SPEED and Regulates TORQUE



SVC Drives w/ a Vector Core SVC Drives w/ a Vector Core estimatesestimates rotor speed & rotor speed & positionposition

A “Speed Estimator” calculates rotor speed & positionA “Speed Estimator” calculates rotor speed & positionA “Speed Estimator” calculates rotor speed & positionA “Speed Estimator” calculates rotor speed & position

L1L2

L3 Motor

Current Sensors

Micro P

( FVC + Speed Estimator )



POSITIONPOSITIONPOSITIONPOSITION SPEEDSPEEDSPEEDSPEED TORQUETORQUETORQUETORQUE MOTORMOTOR

Position Reference Position Reference is optional in most is optional in most Vector Controls, Vector Controls, internal in someinternal in some

Speed Reference is Speed Reference is typical of how we typical of how we control motor control motor operationoperation

Torque Reference can made Torque Reference can made directly, bypassing the speed directly, bypassing the speed loop as a reference for loop as a reference for applications such as Winders & applications such as Winders & Test StandsTest Stands

There are 3 Basic Control Loops in High Performance There are 3 Basic Control Loops in High Performance Drives:Drives:

Bandwidth ratio between loops ranges from 3:1 to 10:1Bandwidth ratio between loops ranges from 3:1 to 10:1Bandwidth ratio between loops ranges from 3:1 to 10:1Bandwidth ratio between loops ranges from 3:1 to 10:1

1,000 rad/sec100 rad/sec10 rad/sec

AC Drive Basics - Control LoopsAC Drive Basics - Control LoopsAC Drive Basics - Control LoopsAC Drive Basics - Control Loops


SpeedReference

FluxFluxCommandCommand

TorqueCommand Gate

Signals

AC Line

CurrentFeedback

Rotor Speed& Position

++

--Torque Torque LoopLoop

SpeedSpeedLoopLoop

FieldFieldControllerController

PWMPWMInverterInverter

SpeedSpeedFeedbackFeedback

ACMotor

E

Typical Regulator Control Diagram for FVCTypical Regulator Control Diagram for FVC

AC Drive Basics - Regulator DiagramAC Drive Basics - Regulator DiagramAC Drive Basics - Regulator DiagramAC Drive Basics - Regulator Diagram


INVERTERINVERTERDUTYDUTYMOTORSMOTORS

AC Motor Basics - Inverter DutyAC Motor Basics - Inverter DutyAC Motor Basics - Inverter DutyAC Motor Basics - Inverter Duty


Some motor frames are sized so Some motor frames are sized so that just the surface area is suitable that just the surface area is suitable to dissipate motor heat w/o the need to dissipate motor heat w/o the need

of a fan or blowerof a fan or blower

Some motor frames are sized so Some motor frames are sized so that just the surface area is suitable that just the surface area is suitable to dissipate motor heat w/o the need to dissipate motor heat w/o the need

of a fan or blowerof a fan or blower

Blowers may be added to Blowers may be added to motors to allow operation at motors to allow operation at low speed including “0” RPM low speed including “0” RPM with 100% Torque continuouswith 100% Torque continuous

Blowers may be added to Blowers may be added to motors to allow operation at motors to allow operation at low speed including “0” RPM low speed including “0” RPM with 100% Torque continuouswith 100% Torque continuous



Types of AC Motors

Definite purpose “laminated frame” Definite purpose “laminated frame” designs provide higher power designs provide higher power densities & improved torque to densities & improved torque to inertia performance.inertia performance.

Definite purpose “laminated frame” Definite purpose “laminated frame” designs provide higher power designs provide higher power densities & improved torque to densities & improved torque to inertia performance.inertia performance.

T-Frame Construction Motors allow T-Frame Construction Motors allow commonality in footprint & shaft commonality in footprint & shaft height.height.

T-Frame Construction Motors allow T-Frame Construction Motors allow commonality in footprint & shaft commonality in footprint & shaft height.height.


Match Motor type to meet your needs!


Rotor Designs Vary by motor type:

Definite purpose “single squirrel Definite purpose “single squirrel cage” rotor design for Variable cage” rotor design for Variable Frequency Drive useFrequency Drive use

Standard Industrial AC Motor “double Standard Industrial AC Motor “double squirrel cage” Rotor Design for squirrel cage” Rotor Design for improved across the line starting improved across the line starting torque.torque.


Rotor design affects torque production!

Rotor design affects torque production!


Equivalent Circuit Diagram of an AC Induction MotorEquivalent Circuit Diagram of an AC Induction Motor

Resistance Stator

Inductance Stator

Inductance Rotor

Resistance Rotor

Inductance Magnetizing

AC InputVoltage

-

+

Current

Working

AC Motor Basics - Equivalent Circuit DiagramAC Motor Basics - Equivalent Circuit DiagramAC Motor Basics - Equivalent Circuit DiagramAC Motor Basics - Equivalent Circuit Diagram

Rotor heating affects torque production!


Peak Torque capacity is dependent upon the motor BDT %Peak Torque capacity is dependent upon the motor BDT %Peak Torque capacity is dependent upon the motor BDT %Peak Torque capacity is dependent upon the motor BDT %

AC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating Region

NEMA Design ‘B” MotorNEMA Design ‘B” Motor

Full Load Torque

Breakdown TorqueRule of Thumb:Rule of Thumb:

Approximately 80% of BDT Approximately 80% of BDT (ft-lbs) is usable for PEAK (ft-lbs) is usable for PEAK Torque needs when current Torque needs when current is available.is available.

Therefore, current Therefore, current headroom from the drive headroom from the drive can improve recovery from can improve recovery from sudden load changes.sudden load changes.

Rule of Thumb:Rule of Thumb:

Approximately 80% of BDT Approximately 80% of BDT (ft-lbs) is usable for PEAK (ft-lbs) is usable for PEAK Torque needs when current Torque needs when current is available.is available.

Therefore, current Therefore, current headroom from the drive headroom from the drive can improve recovery from can improve recovery from sudden load changes.sudden load changes.


Breakdown Torque identifies Peak Torque capabilities Breakdown Torque identifies Peak Torque capabilities Breakdown Torque identifies Peak Torque capabilities Breakdown Torque identifies Peak Torque capabilities

AC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating RegionAC Motor Basics - Drive Operating Region

NEMA Design “B” Motors vary in Breakdown Torque capacityNEMA Design “B” Motors vary in Breakdown Torque capacity


Inverter Duty Motors operate at 1/10th Base RPMInverter Duty Motors operate at 1/10th Base RPMInverter Duty Motors operate at 1/10th Base RPMInverter Duty Motors operate at 1/10th Base RPM

Speed / Torque Curve of an AC Drive & Inverter Duty MotorSpeed / Torque Curve of an AC Drive & Inverter Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Acceptable Regionfor Continuous Operation

AC Motor Basics - Operating RangeAC Motor Basics - Operating RangeAC Motor Basics - Operating RangeAC Motor Basics - Operating Range


CHp Operation above Base RPM is typically limited to 150%CHp Operation above Base RPM is typically limited to 150%CHp Operation above Base RPM is typically limited to 150%CHp Operation above Base RPM is typically limited to 150%

Speed / Torque Curve of an AC Drive & Inverter Duty MotorSpeed / Torque Curve of an AC Drive & Inverter Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Torque above base RPM =

100%% Above Base RPM



Vector Duty Motors operate at “0” RPM w/ 100% Torque Cont.Vector Duty Motors operate at “0” RPM w/ 100% Torque Cont.Vector Duty Motors operate at “0” RPM w/ 100% Torque Cont.Vector Duty Motors operate at “0” RPM w/ 100% Torque Cont.

Speed / Torque Curve of a Vector Drive & Vector Duty MotorSpeed / Torque Curve of a Vector Drive & Vector Duty Motor

% TORQUE

0

10

20

30

40

50

60

70

80

90

100

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

HZ

Acceptable Regionfor Continuous Operation



Some Vector Duty Motors can provide CHp ( 2 * Base RPM )Some Vector Duty Motors can provide CHp ( 2 * Base RPM )Some Vector Duty Motors can provide CHp ( 2 * Base RPM )Some Vector Duty Motors can provide CHp ( 2 * Base RPM )

Speed / Torque Curve of a Vector Drive & Vector Duty MotorSpeed / Torque Curve of a Vector Drive & Vector Duty Motor

HZ

% TORQUE

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90

TorqueTorque

TorqueTorque

0

10

20

30

40

50

60

70

80

90

100

96 102 108 114 120

Vector Duty Motors may haveCHP Ranges of

2 * Base Speed or moredepending on their design


Special motor & drive Special motor & drive designs can allow designs can allow operation up to 8 * operation up to 8 *

Base RPMBase RPM

Special motor & drive Special motor & drive designs can allow designs can allow operation up to 8 * operation up to 8 *

Base RPMBase RPM


COMPARINGCOMPARINGAC DRIVE AC DRIVE PERFORMANCEPERFORMANCE

AC Drive PerformanceAC Drive PerformanceAC Drive PerformanceAC Drive Performance


Control SelectionControl SelectionControl SelectionControl Selection

• FVC operation is best since the position and velocity of the FVC operation is best since the position and velocity of the rotor is known and restarting is immediate.rotor is known and restarting is immediate.

• V/Hz being a soft speed regulator is very forgiving for V/Hz being a soft speed regulator is very forgiving for restarting into loads with high inertia.restarting into loads with high inertia.

• SVC may be more difficult to implement due to limitations by SVC may be more difficult to implement due to limitations by manufacturer. Processor & algorithm dependent.manufacturer. Processor & algorithm dependent.

• FVC operation is best since the position and velocity of the FVC operation is best since the position and velocity of the rotor is known and restarting is immediate.rotor is known and restarting is immediate.

• V/Hz being a soft speed regulator is very forgiving for V/Hz being a soft speed regulator is very forgiving for restarting into loads with high inertia.restarting into loads with high inertia.

• SVC may be more difficult to implement due to limitations by SVC may be more difficult to implement due to limitations by manufacturer. Processor & algorithm dependent.manufacturer. Processor & algorithm dependent.


• V/Hz operation inheriently controls multiple motors. V/Hz operation inheriently controls multiple motors.

• SVC or FVC operation with multiple motors is only possible SVC or FVC operation with multiple motors is only possible when motor shafts are mechanically locked together and when motor shafts are mechanically locked together and assumptions are made about “total” motor current values.assumptions are made about “total” motor current values.

• V/Hz operation inheriently controls multiple motors. V/Hz operation inheriently controls multiple motors.

• SVC or FVC operation with multiple motors is only possible SVC or FVC operation with multiple motors is only possible when motor shafts are mechanically locked together and when motor shafts are mechanically locked together and assumptions are made about “total” motor current values.assumptions are made about “total” motor current values.



• V/Hz is typically good for up to 10:1 Constant Torque. V/Hz is typically good for up to 10:1 Constant Torque.

• SVC is typically good for up to 40:1 Constant Torque.SVC is typically good for up to 40:1 Constant Torque.

• FVC is typically good for up to 1,000:1 which includes FVC is typically good for up to 1,000:1 which includes continuous operation at Zero Speed.continuous operation at Zero Speed.

• V/Hz is typically good for up to 10:1 Constant Torque. V/Hz is typically good for up to 10:1 Constant Torque.

• SVC is typically good for up to 40:1 Constant Torque.SVC is typically good for up to 40:1 Constant Torque.

• FVC is typically good for up to 1,000:1 which includes FVC is typically good for up to 1,000:1 which includes continuous operation at Zero Speed.continuous operation at Zero Speed.



• V/Hz has no quantifiable response time or bandwidth. V/Hz has no quantifiable response time or bandwidth.

• Typical SVC specifications may state 100 Radians/second.Typical SVC specifications may state 100 Radians/second.

• Typical FVC specifications may state 1,000 Radian/second.Typical FVC specifications may state 1,000 Radian/second.

• V/Hz has no quantifiable response time or bandwidth. V/Hz has no quantifiable response time or bandwidth.

• Typical SVC specifications may state 100 Radians/second.Typical SVC specifications may state 100 Radians/second.

• Typical FVC specifications may state 1,000 Radian/second.Typical FVC specifications may state 1,000 Radian/second.



Both AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to consider

Feature Flux Vector - benefits DC Drive - limitations

Power Factor 92% to 96% at all speeds &loads

88% to 33% dependent onspeed & load

Torque Production 1,000 radian/sec 300 radian/sec

Operation at Stall Closed Loop Flux Vector atStall continuous

DC operation at Stall limited bybrushes & commutator

Motor Cost AC Motor cost is lessexpensive due to simplicity

DC Motor cost is higher due tolabor complexity & parts

High SpeedApplications

Lower rotor mass allowshigh speed operation

Mechanically limited in speeddue to construction

Drive SelectionDrive SelectionDrive SelectionDrive Selection


Both AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to considerBoth AC & DC Drives have specific areas of merit to consider

Feature Flux Vector - limitations DC Drive - benefits

Line Regeneration 60% to 100% premium overdrive cost to do

5% to 25% premium over drivecost to do

Motor Lead Length Limitation of lead length – canaffect operation & reliability

No concerns of lead lengthother than voltage drop

Drive Only Cost More expensive due tocontroller complexity

Less expensive due tocontroller simplicity

Shock LoadApplications

Less inertia at motor requiresmore tuning and setup time

Armature inertia helps todampen shock loads

Drive SelectionDrive SelectionDrive SelectionDrive Selection


PerformanceFeatures

DC Drivew/ Encoder

DC Drivew/ Tach

DC Drivew/o Fdbk

FluxVector

SensorlessVector

OperatingSpeed Range

0 RPM toBase RPM

90 RPM toBase RPM

90 RPM toBase RPM

0 RPM toBase RPM

45 RPM toBase RPM

CT SpeedRegulationw/o loadchange

1,000 : 10.01%

70 : 11.0%

20 : 13.0%

1,000 : 10.01%

40 : 10.5%

CT SpeedRegulationw/ 100% loadchange

100 : 10.05%

30 : 13.0%

10 : 15.0%

100 : 10.05%

20 : 11.0%

Digital DC Drives & AC Vector Drives performance similarlyDigital DC Drives & AC Vector Drives performance similarlyDigital DC Drives & AC Vector Drives performance similarlyDigital DC Drives & AC Vector Drives performance similarly

Drive Selection - Speed RangeDrive Selection - Speed RangeDrive Selection - Speed RangeDrive Selection - Speed Range


Any Questions?

Thank You!Thank You!Thank You!Thank You!

spring update cd, may 2001 torque production with ac drives & motors: understanding the...

Documents

motor torque

ac motors

motor poles

dc voltage

motor drive basics

ac line voltage

ac drives motors

ac induction motors