pltcm project at tata steel
DESCRIPTION
vocational project at tata steel electrical maintainanceTRANSCRIPT
PROJECT TITLE
STUDY OF NEW AC DRIVE
SYSTEM AT PLTCM CRM
Under Guidance: - Mr. ARGHYA DEB
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ACKNOWLEDGEMENT
With a great pleasure we would like to express our deep sense of gratitude to Mr. Ajit Kar, Chief, and MEG; Mr.Arghay Deb, Head, MEG
And to our guide and training co-coordinator Mr. Nirbhay Kumar Gupta, Sr. Technologist, MEG, TATA Steel Limited, For their valuable instructions, guidance and illuminating criticism throughout our projectWithout their involvement and supervision we could not have been able to complete this project.
We would like to express our sincere thanks to Mr. K. Paswan, Sr. Manager, and PH-4;Mr. V.G. Rao, Consultant, MEG; Mr. O.P. Gupta, MEG and so many others countless people of TATA Steel Limited, Jamshedpur for helping us in our project during our entire internshipWe would also like to thank Dr. Mandal Training and Placement
Last but not the least we would like to thank all of our friends and the employees of Maintenance Expert Group for their sincere co-operation and help throughout our training. Thanks to everybody and to almighty for giving us this opportunity in our lifetime.
NAME: VIDYA KUMARI
UNIV.ROLL NO.: JSDPRFELTNKSOJUL1100776
REFE NO: VT20131799
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CERTIFICATEThis is to certify that the project report entitled
“STUDY OF NEW AC DRIVE SYSTEMS”, PLTCM CRM
Being submitted by Ms. VIDYA KUMARI, JAGDISH Institute of Industrial Technology, Bhubaneswar to TATA Steel, as a part of summer training course of DIPLOMA in Electronics curriculum is a bonafide record of work carried out by them under my supervision and guidance. The sincerity and sense of dedication shown by them during the project is commendable.
Mr. ARGHYA DEBHEADMaintenance Expert GroupTATA Steel LimitedJamshedpurDate:
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CONTENTS
COMPANY PROFILE PAGE NO.
Tata Steel 5-7
-MAINTENANCE EXPERT GROUP 10
ELECTRONICS DEVIVE 11-12
A.C. MOTOR 19
Types 19
INDUCTION MOTOR
Construction 23
Working principle 24
Testing and Inspection parameter 24
OBSERVATION OF MOTORS 25
CONCLUSION 25
BIBLIOGRAPHY 31
THANKING YOU 35
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INTRODUCTION TO TATA STEEL
Tata Steel Limited
Type PublicTraded as NSE: TATASTEEL, BSE: 500470 (BSE SENSEX Constituent)Industry SteelFounded 1907Founder(s) Dorabji TataHeadquarters Mumbai, Maharashtra, India
Area served Worldwide
Key people CYRUS PALLONJI MISTRY (Chairman)HEMANT M. NERULKAR (Managing Director)
Products Steel, flat steel products, long steel products, wire products, plates
Tata Iron and Steel Company was established by Dorabji Tata on August 26, 1907, As part of his father Jamshedji's Tata Group. By 1939 it operated the largest steel plant in the British Empire.
The company launched a major modernization and expansion program in 1951. Later, the program was upgraded to 2 MTPA project. In 1990, it started expansion plan and established its subsidiary Tata Inc. in New York. The company changed its name from TISCO to TATA Steel in 2005.
Tata Iron and Steel Company was established by Dorabji Tata on August 26, 1907, As part of his father Jamshedji's Tata Group. By 1939 it operated the largest steel plant in the British Empire.
The company launched a major modernization and expansion program in 1951. Later, the program was upgraded to 2 MTPA project. In 1990, it started expansion plan and established its subsidiary Tata Inc. in New York. The company changed its name from TISCO to TATA Steel in2005.
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PLANS OF PROJECT
WEEK-1 Visit of electronics repair LAB, LDC Study of document.
WEEK-2 STUDY OF DOCUMENT AT AC DRIVE
WEEK-3 VISIT ON ELECTRICAL &AC REPAIR SHOP AND PROJECT WORK
WEEK-4 PROJECT WORK
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ELECTRONICS DEVICE
RESISTORA resister may be defining as an electronic component which is manufactured with a specified amount of resistance. Resistor is controls the flow of electric current.
RECTIFIERA rectifier is a circuit which is used to convert AC voltage in to the pulsating DC voltage .A rectifier circuit usage one or more diode.
DIODEIt has two terminal cathode (+) and anode (-).
TRANSISTORA semiconductor device consisting of a two p-n junction formed by sand witching either p-type or n-type semiconductor between a pair of opposites type is known as a Transistor.
THYRISTORTHYRISTOR is a generic term for a semiconductor device which has four semiconductor layers and operates as a switch, having stable ON and OFF.
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ELECTRICAL REPAIR SHOP
Defective electrical motors come here for repair and rectification and overhauling It is Asia second biggest electrical repair shop. ELECTRICAL REPAIR SHOP is one of the most important sections of the M.E.D. (Electrical) departments. The job of Electrical Repair Shop is to repair various kinds of electrical motors, main coolers changing sets and manufacturing panels for cranes .The ERS is divided into several sections for work efficiency
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ERS various sections are as follows:
1. Motor receiving section
2. Opening section
AC motor opening
DC motor opening
3. Motor washing area
4. Bearing section
5. Stripping section
6. Winding section
AC winding area
DC winding area
Heavy winding area
7. VPI (Vacuum Pressure impregnation) section
8. Assembly part
AC assembly area
DC assembly area
Heavy assembly area
9. Final testing Area
10. Final fitting Area
11. Motor Testing Area
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AC MOTOR
With the almost universal adoption of A.C. system of distribution of electrical energy for light
and power,
The field of application of A.C. motors has widened considerably during recent years.
TYPES OF AC MOTORS:
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INDUCTION MOTOR
Three phase induction motor is the most popular type of a.c. motor. It is very commonly used for
industrial drives since it is cheap, robust, efficient and reliable. It has good speed regulation and
high starting torque. It requires little maintenance. It has a reasonable overload capacity.
CONSTRUCTION:
A 3-Φ induction motor essentially consists of two parts: the stator and the rotor.
The stator is the stationary part of the motor’s electromagnetic circuit. The stator core is made up
of many thin metal sheets, called laminations. Laminations are
used to reduce energy loses that would result if a solid core were
used. Coils of insulated wire are inserted into slots of the stator
core. When stator windings supplied with 3-Φ currents, produce a
magnetic flux which revolves at constant speed & induces an
E.M.F. in the rotor by mutual induction.
Rotor is the rotating part and made up of thin laminations of the
same material as stator.
Squirrel-cage rotor: Motors employing this type of rotor are knows as squirrel-cage induction
motors. Almost 90 percent of induction motors are squirrel-cage
type. The rotor consists of a cylindrical laminated core with
parallel slots but little skewed for carrying the rotor conductor.
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Phase- wound or wound rotor: Motors employing this type of rotor are variously known as
phase wound motors or slip-ring motors. This type of rotor is provided with 3-Φ, double layer,
distributed winding consisting of coils as used in alternators.
Working principle of Induction
Motor
When three phase supply is given to three
phase stator winding, a rotating magnetic field
is produced. Due to rotating magnetic field,
the flux passes through the air gap between
rotor and stator, sweeps past the rotor surface and so cuts the rotor conductor. Hence according
to Faraday’s law of electromagnetic induction, there would be a induced current circulating in
the closed rotor conductors. The amount of induced current is proportional to the rate of change
of flux linkage with respect to time. Again this rate of change of flux linkage is proportional to
the relative speed between rotor and rotating magnetic field. As per Lenz law the rotor will try to
reduce the every cause of producing current in it. Hence the rotor rotates and tries to achieve the
speed of rotating magnetic field to reduce the relative speed between rotor and rotating magnetic
field.
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TESTING & INSPECTION PARAMETER OF A.C. MOTOR
STATOR:
If the stator is ok in IR test then:
Step1: BTS: - In BTS (Balance test of stator) the stator is checked for
whether the three phases of the winding are drawing same amount or not.
Step2: Impregnation in Hot Box. Here the stator is inserted into hot box after
varnishing so that moisture and dust are removed.
Step3: storage
ROTOR:
If it is a squirrel cage rotor then it is send to Bearing Removing and checking and if it is a Slip
Ring Rotor first it undergoes IR Test then it is moved to Bearing Removing and checking
From there it is send for Washing .Then if machining is required then it is send to machining
section and then only Slip Ring is send for BTR.
If BTR result is ok
Step 1: Bearing fitting
Step 2: Storage ok Rotor
Assembly:-Both the Rotor and Stator are assembled for no load test in the Test
Bed.
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Test in Test Bed: -Here the motor is tested as per the SOP.
MEGGER TEST:Checking of insulation resistance of motor is done this method.
Check MEGGER test leads are proper insulated.
Use 1000V MEGGER for IR test.
Rotate the MEGGER handle slowly & increases the speed to the slip speed
and note IR.
Insulation resistance is to be measured between phases and also between
phases and ground of stator and rotor winding (in case slip-ring motor).
After meggering discharge the stator/rotor winding by reversing MEGGER
terminal.
Minimum acceptable IR value is as follows:
Voltage rating of M/C Minimum acceptable value
Up to 450V 5.0 MΏ
3KV-11KV 100 MΏ
BLOCKED ROTOR TEST:
Apply voltage slowly (by regulating the regulator) to the motor so as to
inject rated full load current.
During increasing the voltage watch the reaction of the person holding
the shaft .Whether the person facing any difficulties to hold or not .If
any reaction noticed –Immediately bring the regulator to zero position.
If full load current cannot be injected then inject half of full load current
and note the voltage applied.
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Acceptable limit of locked rotor test voltage at full load current is 1/8 to
1/4 of rated voltage of motor.
OPEN CIRCUIT TEST ( FOR SLIP-RING MOTOR ):
Apply full stator voltage slowly to the stator terminal and measure
the rotor voltage (phase to phase) at rotor terminal keeping rotor
winding open. Rotor voltage should be equal to rated voltage.
Note down stator magnetising current, rotor voltage and stator
voltage.
RUN (NO-LOAD) TEST:
The rated voltage at rated frequency is applied to stator slowly (by
regulating the regulator) to run the motor.
Run the motor for half an hour at rated voltage, rated frequency.
Note down current reading from ammeter.
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All 3 phase current should be balanced
Acceptable range of no load current as follows:
Type Allowable range General purpose motors 20% to 50% of rated current
High torque motors like Withdrawal & Mudgun motors
60% of rated current
In case of slip-ring motor after doing open circuit test short the rotor and
run the motor as squirrel cage motor as above.
Following reading are taken in run test:
No-load current
No-load speed
Vibration at bearing, body & foundation of body.
Temperature at bearing, shaft, body etc.
Bearing condition by SPM meter.
Sound using stethoscope.
Sparking in case of slip-ring motor
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TEMPERATURE MEASUREMENT:
Take temperature reading of bearing, shaft & body by temperature gun .
Maximum acceptable value of temperature after half an hour is as follows:
Location Maximum acceptable temperatureSurface temp. of bearing housing 75°C
Body temp. class B motor 55°C
Body temp. class F motor 70°C
Body temp. class H motor 90°C
VIBRATION TEST:
Put vibration probe gently on motor driving and no driving end bearing
housing.Body and foundation base in horizontal, vertical & axial direction
and take the reading.
Maximum acceptable value of vibration as follows:
SL. No
shaft height(mm) 56<H≤132 132<H≤225 225<H≤400 H>400
1 Range of speed 500 to 1500 >1500-3000 500 to 1500 >1500-3000 500 to 1500 >1500 - 3000 500-1500 >1500-3000
2 N(normal) 1.8 1.8 1.8 2.8 2.8 4.5 2.8 4.5
3 R(reduced) 0.71 0.71 0.71 1.12 1.8 2.8 - -
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4 S(special) 0.45 0.45 0.45 0.71 1.12 1.8 - -
SOUND CHECKING:
Put the probe of stethoscope on bearing housing and body and observe any
unsual sound(humming, metallic, etc.) is coming or not.
BEARING CONDITION:
Connect the SPM probe to the instrument(shock pulse tester) and enter the
bearing data in the instrument.
Put the SPM probe on the bearing housing at an angle 45° to the load zone.
SPEED CHECKING:
Hold the Tachometer correctly and measure the speed of the motor.
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AC DRIVES
AC drives provide a very efficient and direct method of controlling the speed of the most rugged and reliable of prime movers, the squirrel cage motor. AC drives provide many economic and performance advantages in a wide variety of adjustable speed drive applications.The following are some of the benefits provided:
1. High efficiency and low operating cost.2. Minimal motor maintenance.3. Controlled linear acceleration and deceleration provide soft.4. Starting and stopping and smooth speed changes.5. Multiple motor operations are easily accomplished.6. Current limit provides for quick and accurate torque control.7. Adjustable speed operation can be accomplished with existing AC motors.8. Improved speed regulation can be accomplished by slip compensation.9. AC motors are available in a wide variety of mechanical configurations.10. Flexibility of machine design due to the light weight and compact size of AC motors.11. IR compensation provides high starting torque easily and economically.12. AC motors are available in enclosures suitable for hazardous or corrosive environments.13. Fewer spare motors are required since the same motor can be used for both adjustable speed and constant speed operations.14. Cutler-Hammer rugged and reliable designs ensure minimum downtime expense.15. High speed operation can be economically accomplished using extended frequency operation.16. Reverse operation is accomplished electronically without the need for a reversing starter.
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ADJUSTABLE FREQUENCY AC DRIVE SYSTEM
INTRODUCTION
An adjustable frequency AC drive system consists of an ordinary three-phase induction motor, an adjustable frequency drive to control the speed of the motor and an operator's control station.
The most common motor used with an AF drive system is a standard NEMA design B squirrel cage induction motor, rated for 230 or 460 volt, 3-phase, 60 Hz operation. The adjustable frequency controller is a solid-state power conversion unit. It receives 240 or 480 volt, 3-phase,60 Hz power and converts it to a variable frequency supply which can be sleeplessly adjusted between 0 and 60 Hz. The controller also adjusts the output voltage in proportion to the frequency to provide a nominally constant ratio of voltage to frequency as required by the characteristics of the motor. The operator's station provides the operator with the necessary controls for starting and stopping the motor and varying the motor speed. These functions can also be performed by a wide variety of automatic control systems. There are several classifications of adjustable frequency AC drives. Some common types of drives are VariableVoltage Input (VVI) sometimes called Six Step drives, current source input (CSI), pulse width modulated (PWM) drives, Sensor less Vector drives, Field Oriented drives and Closed LoopVector drives.
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PRINCIPLES OF ADJUSTABLE FREQUENCY MOTOR OPERATION
The operating speed of an AC induction motor can be determined by the frequency of the applied power and the number of poles created by the stator windings. Synchronous speed is the speed of the magnetic field created in the stator windings. It is given by:
N = 120f /PWhere:n = speed in RPMf = operating frequencyP = number of polesWhen the frequency is changed, the voltage must also be changed, based on the formula for reactance and Ohm’s Law.XL = 2πfLWhere L = inductanceXL = reactanceV = voltageIm = magnetizing currentIm = V/XL
Combining the above equations yields:Im = (V/f). (1/2πfL)For steady-state operation, constant volts per hertz ratio must be maintained. This is equal to the motor rated voltage divided by the rated frequency.For the magnetizing current to remain constant, the V/f ratio, or the volts per hertz ratio, must remain constant. Therefore, the voltage must increase and decrease as the frequency increases and decreases.
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INDUCTION MOTOR SPEED CONTROL
Standard induction motors (NEMA design B) have approximately 3% slip at full load.If the drive only controls the output frequency, the motor speed will deviate from the set speed due to slip. For many fan and pump applications, precise speed control is not needed
CONCLUSION
Motors failure can lead to even higher cost in terms of lost production and efficiency. Industrial
companies need effective motor management strategies to minimize overall motor cost.
The maintenance practices that encompassed “excellent” reliability of motors are:
• Visual inspections
• Insulation resistance
• Cleaning
• Lubrication and/or filters
• Vibration analysis
• Bearing check/inspection
• Temperature checking
• Air gap checks
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• Alignment
• Check/change brushes, as applicable.
* The use of continuous-monitoring systems (i.e., temperature and vibration) and the
application of technologies and maintenance practices that will avoid or detect electrical
and mechanical faults
*The result is about a two-thirds reduction in failure rate and a significant decrease in
production downtime.
*Proper shaft alignment can prolong the life and improve the efficiency of motors and
other integral equipment.
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