58438009 major training ame bhel bhopal

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Acknowledgement

The extensive training program at BHARAT HEAVY ELECTRICALS LIMITED (BHEL),

Bhopal was a great opportunity and an exceptional learning experience for me. It is first hands on

experience and an exposure of practical world.

I got opportunity to work under the esteemed supervision of Mr. Baboo Sonwane, Sr. MGR

(AC Machines Engineering (AME) Department). It was great privilege for me to work under him.

I am thankful to him for his extremely patient gesture, to make training program fruitful for me

and for rendering every possible help to carry out this research project.

I offer my gratitude to the management and staff that have spent their precious time, expressed

keen interest and given continued encouragement throughout the study and enabled the successful

completion of my practical at BHEL, Bhopal.

I am indebted to my parents, teachers and friends who helped and encouraged me to work hard,

move ahead and inspired me with words. Their blessings made this work possible.

Prashant Mishra

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Contents

Acknowledgement...................................................................................................................................... 1

Company Overview:- ................................................................................................................................. 4

Bharat Heavy Electricals Limited (BHEL) .............................................................................................. 4

Product Profile ....................................................................................................................................... 5

Bharat Heavy Electricals Limited (BHEL), Bhopal ................................................................................. 9

Various Divisions at BHEL Bhopal .................................................................................................... 9

Product Profile of AC Machines (AME) Division......................................................................................... 12

Squirrel Cage Induction Motors ............................................................................................................ 13

Technical Features ............................................................................................................................ 13

Slip Ring Induction Motors ................................................................................................................... 14


Synchronous Motors ............................................................................................................................ 15


Synchronous Alternators ...................................................................................................................... 16


Variable Frequency Drive Motors ......................................................................................................... 16


Types of New H-Series Motors .............................................................................................................. 17

H-Compact Motors ........................................................................................................................... 17

H-Module Motors ............................................................................................................................. 18

H-Moflex Motors .............................................................................................................................. 19

Hazardous Area Requirements ......................................................................................................... 20

R-Series CACW Motor ....................................................................................................................... 21

Line-F Motors ................................................................................................................................... 21

Synchronous Motors ................................................................................................................................ 22

Parts ..................................................................................................................................................... 23

Principle of Operation .......................................................................................................................... 24

Starting methods .................................................................................................................................. 24

Uses ..................................................................................................................................................... 25

Advantages .......................................................................................................................................... 25

Induction Motors ..................................................................................................................................... 26

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Principle of Operation .......................................................................................................................... 26

Construction ......................................................................................................................................... 27

Bearings ................................................................................................................................................... 28

There are broadly two types of bearings employed: .................................................................................. 28

Rolling Element Bearing Sleeve Bearing ............................................................ 28

Testing of Motors ..................................................................................................................................... 29

Introduction ......................................................................................................................................... 29

1.0 Type of Tests ..................................................................................................................... 29

References ............................................................................................................................................... 35

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Company Overview:-

Bharat Heavy Electricals Limited (BHEL)

BHEL is the largest engineering and manufacturing enterprise in India in the energy-

related/infrastructure sector, today. BHEL was established more than 40 years ago, ushering in the

indigenous Heavy Electrical Equipment industry in India - a dream that has been more than

realized with a well-recognized track record of performance. The company has been earning

profits continuously since 1971-72 and paying dividends since 1976-77.

BHEL manufactures over 180 products under 30 major product groups and caters to core sectors

of the Indian Economy viz., Power Generation & Transmission, Industry, Transportation,

Renewable Energy, etc. The wide network of BHEL's 14 manufacturing divisions, four Power

Sector regional centers, over 100 project sites, eight service centers, 18 regional offices and one

subsidiary enables the Company to promptly serve its customers and provide them with suitable

products, systems and services -- efficiently and at competitive prices.

BHEL has acquired certifications to Quality Management Systems (ISO 9001), Environmental

Management Systems (ISO 14001) and Occupational Health & Safety Management Systems

(OHSAS 18001) and is also well on its journey towards Total Quality Management.

• BHEL has installed equipment for over 90,000 MW of power generation -- for Utilities,

Captive and Industrial users.

• Supplied over 2,25,000 MVA transformer capacity and other equipment operating in

Transmission & Distribution network up to 400 kV (AC & DC).

• Supplied over 25,000 Motors with Drive Control System to Power projects,

Petrochemicals, Refineries, Steel, Aluminum, Fertilizer, Cement plants, etc.

• Supplied Traction electrics and AC/DC locos to power over 12,000 kms Railway network.

• Supplied over one million Valves to Power Plants and other Industries.

BHEL's operations are organized around three business sectors, namely Power, Industry -

including Transmission, Transportation and Renewable Energy - and Overseas Business. This

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enables BHEL to have a strong customer orientation, to be sensitive to his needs and respond

quickly to the changes in the market.

BHEL's vision is to become a world-class engineering enterprise, committed to enhancing

stakeholder value. The company is striving to give shape to its aspirations and fulfill the

expectations of the country to become a global player.

The greatest strength of BHEL is its highly skilled and committed 42,600 employees. Every

employee is given an equal opportunity to develop himself and grow in his career. Continuous

training and retraining, career planning, a positive work culture and participative style of

management all these have engendered development of a committed and motivated workforce

setting new benchmarks in terms of productivity, quality and responsiveness

Product Profile

With an export presence in more than 60 countries, BHEL is truly India’s industrial ambassador to

the world. This list is intended as a general guide and does not represent all of BHEL's products

and systems.

Thermal Power Plants

• Steam turbines and generators of up to 500MW capacity for utility and combined-cycle

applications; capability to manufacture steam turbines with super critical steam cycle

parameters and matching generator up to 1000 MW unit size.

Gas based Power Plants

• Gas turbines of up to 260MW (ISO) rating.

• Gas turbine based co-generation and combined-cycle systems for industry and utility

applications.

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Hydro Power Plants

• Custom-built conventional hydro turbines of Kaplan, Francis and Pelton types with

matching generators, pump turbines with matching motor-generators. Mini/micro hydro

sets.

• Spherical, butterfly and rotary valves and auxiliaries for hydro station

DG Power Plants

• HSD, LDO, FO, LSHS, natural-gas/biogas based diesel power plants, unit rating up to

20MW and voltage up to 11kV, for emergency, peaking as well as base load operations on

turnkey basis.

Industrial Sets

• Industrial turbo-sets of ratings from 1.5 to 120MW.

• Gas turbines land matching generators ranging from 3 to 260MW (ISO) rating.

• Industrial stream turbines and gas turbines for drive applications and co-generation

applications.

Boilers and Auxiliaries

• Steam generators for utilities, ranging from 30 to 500MW capacity, using coal, lignite, oil,

natural gas or a combination of these fuels: capability to manufacture boilers with super

critical parameters up to 1000 MW unit size.

• Steam generators for industrial applications, ranging from 40 to 450t/hour capacity using

coal, natural gas, industrial gases, biomass, lignite, oil, bagasse or a combination of these

fuels.

• Pulverized fuel fired boilers.

• Stoker boilers.

• Pressure vessels.

Heat Exchangers and Pressure Vessels

• Air-cooled heat exchangers.

• Surface condensers.

• Steam jet air ejectors.

• LPG/propane storage bullets.

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• Feed water heaters.

Power Station Control Equipment

• Microprocessor-based distributed digital control systems.

• Sub-station controls with SCADA.

• Static excitation equipment/automatic voltage regulator.

• Electro-hydraulic governor control.

• Turbine supervisory system and control.

• Controls for electrostatic precipitators.

• Controls for HP/LP bypass valves.

Switchgears

• Switchgear of the various types for indoor and outdoor applications and voltage ratings up

to 400 kV.

• Minimum oil circuit breakers (66K – 132kV).

• SF6 circuit breakers (132 kV – 400 kV).

• Vacuum circuit breakers (3.3 kV – 33 kV).

• Gas insulated switchgears (36 kV).

Transformers

• Power transformers for voltage up to 400 kV.

• HVDC transformers and reactors up to + 500 kV rating.

• Series and shunt reactors of up to 400 kV rating.

• Current transformers up to 400 kV.

• Electro-magnetic voltage transformers up to 220 kV.

• Capacitor voltage transformers up to 400 kV.

• Special transformers: earthing; furnace; rectifier; electrostatic precipitator; freight loco and

AC EMU and traction transformers.

Insulators

• Disc/suspension insulators for AC/DC applications, ranging from 45 to 400 kn electro-

mechanical strength, for clean and pollute atmospheres.

• Pin insulators of up to 33 kV.

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• Hollow porcelains of up to 400 kV.

• Solid core insulators of 25 kV rating (both porcelain and hybrid) for railways.

• Disc insulators for 800 kV AC and HVDC transmission lines (BHEL is the first Indian

manufacturer to supply such insulators).

Capacitors

• Power capacitors for industrial and power systems of up to 250 kVAr rating for application

up to 400 kV, Coupling/CVT capacitors for voltages up to 400 kV.

• Low Tension Thyristor Switched Capacitors (LTTSC) for dynamic power factor

correction.

Energy Meters

• Single Phase, Poly Phase and Special-purpose electro-mechanical and electrical meters.

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Bharat Heavy Electricals Limited (BHEL), Bhopal

Heavy Electrical Plant, Bhopal is the mother plant of Bharat Heavy Electricals Limited, the largest

engineering and manufacturing enterprise in India in the energy-related and infrastructure sector,

today. With technical assistance from Associated Electricals (India) Ltd., a UK based company; it

came into existence on 29th of August, 1956. Pt. Jawaharlal Nehru, first Prime minister of India

dedicated this plant to the nation on 6th of November, 1960.

BHEL, Bhopal certified to ISO: 9001, ISO 14001 and OHSAS 18001, is moving towards

excellence by adopting TQM as per EFQM / CII model of Business Excellence. Heat Exchanger

Division is accredited with ASME ‘U’ Stamp. BHEL Bhopal has its own Laboratories for material

testing and instrument calibration which are accredited with ISO 17025 by NABL. The Hydro

Laboratory, Ultra High Voltage laboratory and Centre for Electric Transportation are the only

laboratory of it’s in this part of the world.

BHEL Bhopal's strength is its employees. The company continuously invests in Human Resources

and pays utmost attention to their needs. The plant's Township, well known for its greenery is

spread over an area of around 20 sq kms. and provides all facilities to the residents like, parks,

community halls, library, shopping centers, banks, post offices etc. Besides, free health services

are extended to all the employees through Kasturba Hospital and chain of dispensaries.

Various Divisions at BHEL Bhopal

• Industrial Machines

• Transportation Equipment

• Hydro Turbines and Generators

• Hydro Generators

• Heat Exchangers

• Excitation Control Equipment

• Steam Turbines

• Fabrication

• Coil & Insulation

• Casting

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• Stamping

• Tool & Gauge

• Transformer

• Switchgear

• On-Load Tap Changer

• Large Current Rectifiers

• Control & Relay Panels

• Hydro Power Plant

• Thermal Power Stations

• Works Engineering & Services

AC Machines EngineeringAC Machines Engineering (AME)

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Product Profile of AC Machines (AME) Division

AC Machines Division at BHEL, Bhopal manufactures wide range of electrical motors

satisfying customers’ requirements of motive power from all sectors like Steel, Cement,

Power Plant, Petrochemical, Refinery, Fertilizers, Irrigation etc.

The range of the motors vary KW wise from 140 KW to 20 MW, KV wise from 415V to

11 KV & enclosure wise TEFC, CACA, SPDP, CACW etc. They are designed for

various drives such as pump, compressor, fan, mill, conveyor, crusher, granulator etc.

The motors manufactured are of types squirrel cage induction motors, slip-ring induction

motors, synchronous motor and special motor.

Sailent features of the machines:-

• Highly reliable class ‘F’ (Thermally utilised to class 'B') micalastic insulation system.

• Low noise levels with means for further reduction.

• Vibro-stable frames and dynamically balanced rotors for minimal vibrations.

• Motor shipped completely assembled for quick and easy installation.

• Amply-sized terminal boxes for easy connection.

• Inductively brazed short circuit rings for enhanced reliability.

• Motors can be designed for special conditions and applications on request.

Squirrel Cage Induction Motors

Technical Features

Rating

(4Pole)

Upto

750KW

Voltage 415 –

Frequency 50Hz

Speed(rpm) 375 -

Method of cooling IC01,IC511,

IC611,IC616,

IC81W

Shaft Heights(mm) 355

Bearings Rolling/ Sleeve

Mounting IMB3,IMV10

Hazardous Area Ex’n’, Ex’e’, Ex’d’

Squirrel Cage Induction Motors

Upto

750KW

200- 800

KW

500-15000

KW

1000 V 3.3 – 11 KV 3.3 -13.8 KV

50Hz 50 & 60Hz 50 & 60Hz

- 3000 375 – 3600 250 – 3600

IC01,IC511,

IC611,IC616,

IC81W

IC01,IC511,

IC611,IC616,

IC81W

IC01,IC511,

IC611,IC616,

IC81W

355 – 710 355 – 710 630 – 1000

Rolling/ Sleeve Rolling/ Sleeve Rolling/Sleeve

IMB3,IMV10 IMB3,IMV10 IMB3,IMV10

Ex’n’, Ex’e’, Ex’d’ Ex’n’, Ex’e’, Ex’d’ Ex’n’, Ex’e’, Ex’p’

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15000

110000 -

25000KW

13.8 KV 6.0-13.8 KV

50 & 60Hz 50 & 60Hz

3600 500 – 3600

IC01,IC511,

IC611,IC616,

IC81W

C01,IC611,

IC81W

1000 1000–1120

Rolling/Sleeve Sleeve

IMB3,IMV10 IM7211

Horizontal

Ex’n’, Ex’e’, Ex’p’ Ex’n’,Ex’e’,

Ex’p’

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Slip Ring Induction Motors

Technical Features

Rating (4Pole) 200 - 1600KW 1500 - 6000KW 8500 - 15000KW

Voltage 3.3 – 11 KV 3.3 TO 13.8 KV 6.0 TO 13.8 KV

Frequency 50 & 60 HZ 50 & 60 HZ 50 & 60 HZ

Speed(rpm) 500 – 1800 500 – 1800 500 – 1800

Method of cooling IC01,IC511,

IC611,IC616,

IC81W

IC01,IC511,

IC611,IC616, IC81W

IC01,IC611,

IC81W

Shaft Heights(mm) 400 – 710 630 – 1000 1000 – 1120

Bearings Rolling/Sleeve Rolling/Sleeve Sleeve

Mounting IMB3,IMV10 IMB3 IM7211

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Synchronous Motors

Slow Speed Pressurized Synchronous Motor (1.2MW, 6.6KV)

Technical Features

Rating (4Pole) 2000 - 7000 KW 3700 -175000 KW

Voltage 2.0 TO 13.8 KV 6.0 TO 13.8 KV

Frequency 50 & 60 HZ 50 & 60 HZ

Speed(rpm) 1000 – 1800 333.3 – 1800

Method of cooling IC01,IC611,IC616,IC81W IC01,IC616,IC81W

Shaft Heights(mm) 630 – 900 1000 – 1180

Bearings Rolling/Sleeve Sleeve

Mounting IMB3 IM7211

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Synchronous Alternators

Technical Features

Rating (4Pole) 2000 - 9000 KVA 2500 - 30000 KVA

Voltage 415 TO 13800 V 415 – 13800 V


Speed(rpm) 500 – 1800 333 – 1500

Method of cooling IC01,IC611,IC616,IC81W IC01,IC616,IC81W

Shaft Heights(mm) 630 – 900 1000 – 1180



Variable Frequency Drive Motors

Technical Features

SYNCHRONOUS ASYNCHRONOUS

Rating (4 Pole) 1000-7000 KW 200-25000 KW

Voltage 415 V Onwards 415 V Onwards


Method of cooling IC01,IC611,IC616,

IC81W

IC01,IC616,IC81W

Shaft Heights(mm) 630 – 900 1000 – 1180



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On the basis of type of enclosure and cooling mechanism used, the motors are classified as under

for the design purposes-

Types of New H-Series Motors

The H-Series motors can be classified broadly into three major categories -

• H-Compact motors

• H-Module motors

• H-Moflex motors

The brief details of special features and technical particulars of these three major categories are as

follows -

H-Compact Motors

These are medium size motors with horizontal (lMB3) and vertical (lMV10) mountings and are

developed based on experience of rib-cooled low voltage motors. Special features of this series are

• Torsionally rigid, robust frame and endshield of cast iron with external and internal ribs for

optimum heat dissipation.

• Integrally cast mounting feet.

• State of art materials and design of external fans and fan cowls.

• Variable positioning of terminal boxes and their subsequent repositioning is possible.

The technical particulars of H-Compact motors are -

Ratings : 200 to 2500 kW

Voltages : 3.3 to 11 kY

Frequency / Speed : 50/60 Hz / 3000 to 500 rpm

Degree of protection : IP23 to IP55

Cooling : ICOl, IC411,

Shaft centre heights : 355,400,450,500 & 560 mm

Bearings : Rolling / Sleeve

H-Module Motors

These are medium and large size motors with horizontal (lMB3) and vertical (lMV

The design is based on the modular concept to adapt to various degree of protection and cooling

requirements. The mounting feet of these motors are variable in height and width which simplifies

adaptation to existing foundations. These motors

CACA, CACW with double / single bearing constructions.

The H-ModuIe motors have adapted the hybrid insulation technology of MICALASTIC materials

with vacuum pressure impregnation which ultimately results in less insulation thickness for the

same system voltages hence more space for copper in the slots. Thus kW

motors are very high in view of good quality insulation and better cooling systems. The technical

particulars of H-i\iIodule motors are

Ratings :

Voltages :

Frequency / Speed :

Degree of protection :

Cooling :

Shaft centre heights :

Bearings :

These are medium and large size motors with horizontal (lMB3) and vertical (lMV



adaptation to existing foundations. These motors are available in various enclosures like SPDP,

CACA, CACW with double / single bearing constructions.

ModuIe motors have adapted the hybrid insulation technology of MICALASTIC materials


same system voltages hence more space for copper in the slots. Thus kW to weight ratio of these


iIodule motors are -

1500 to 15000 kW

3.3 to 13.8 kV

50/60Hz , 3000 to 250 rpm

IP23. IP54 & IP55

IC01, IC611, IC616 & IC81W

630,710,800 & 900 mm

Rolling / Sleeve

H-Module CACA Motor

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These are medium and large size motors with horizontal (lMB3) and vertical (lMV10) mounting.



are available in various enclosures like SPDP,

ModuIe motors have adapted the hybrid insulation technology of MICALASTIC materials


to weight ratio of these


Module CACA Motor

H-Moflex Motors

These motors are an extension of other two series for higher outputs and are available in horizontal

mounting (B3 / D5) construction. These motors mounted on a solid, welded torsionally rigid base

frame, can be transpo11ed in fully assembled condition. The

dismantled without disassembly of wound statoL Once the top mounted cooler of these motors are

removed, the full core and winding assembly can be incepted. These motors are provided with

sleeve bearings mounted on separate ped

technical particulars of H-Moflex motors are as follows

Ratings :

Voltages :

Frequency / Speed :

Degree of protection :

Cooling :

Shaft centre heights :

Bearings :

H



frame, can be transpo11ed in fully assembled condition. The rotor of these motors can be



sleeve bearings mounted on separate pedestals with either ring oil or forced oil lubrication. The

Moflex motors are as follows -

10000 to 35000 kW

3.3 to 13.8 kV

50/60 Hz, 3000 to 500 rpm

IP23, IP54 & IP55

IC01, IC611 & IC81W

1000 & 1120 mm

Sleeve

H-Moflex CACW Horizontal Motor

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rotor of these motors can be



estals with either ring oil or forced oil lubrication. The

Hazardous Area Requirements

In order to prevent any explosion due to drive motors, various national &

have come out with stringent requirements

manufacture of the motors meant

basic principle behind the explosion protection includes the technique to prevent the simultaneous

occurrence of formation of explosive mixture and release

ignition. There are seven different types

• EX'i' : Intrinsic safety

• EX'd' : Flame proof enclosure

• EX'e' : Increased safety features

• EX'p' : Pressuriz

• EX'n' : Non sparking

In general, a certifying / approving au

the power to permit only the use of proper equipment & ensure the safe application of electrical

motors in hazardous areas.

equirements

In order to prevent any explosion due to drive motors, various national & international standards

have come out with stringent requirements for special features to be incorporated in design and

the motors meant for hazardous areas, and are termed as explosion protection. The


explosive mixture and release of energy in sufficient quantity to cau

ignition. There are seven different types of explosion protection:

Intrinsic safety

Flame proof enclosure

Increased safety features

Pressurized enclosure

Non sparking

In general, a certifying / approving authority is designated in various countries and entrusted with


Flame Proof Enclosure

Pressurized Enclosure

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international standards

special features to be incorporated in design and

hazardous areas, and are termed as explosion protection. The


energy in sufficient quantity to cause

thority is designated in various countries and entrusted with


Flame Proof Enclosure

Pressurized Enclosure

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R-Series CACW Motor

End Shield Mounted

Line-F Motors

Pedestal Mounted

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Synchronous Motors

A synchronous electric motor is an AC motor distinguished by a rotor spinning with coils passing

magnets at the same rate as the alternating current and resulting magnetic field which drives it.

Another way of saying this is that it has zero slip under usual operating conditions. They operate

synchronously with line frequency. It is a highly efficient means of converting ac energy to work.

It can operate at leading or unity power factor and thereby provide power-factor correction.

There are two major types of synchronous motors: non-excited and direct-current excited.

Non-excited motors are manufactured in reluctance and hysteresis designs, these motors employ a

self-starting circuit and require no external excitation supply.Reluctance designs have ratings that

range from sub-fractional to about 30 hp. Sub-fractional horsepower motors have low torque, and

are generally used for instrumentation applications. Moderate torque, integral horsepower motors

use squirrel- cage construction with toothed rotors. When used with an adjustable frequency power

supply, all motors in the drive system can be controlled at exactly the same speed. The power

supply frequency determines motor operating speed.

Cylindrical Rotor Synchronous Machine Salient Pole Synchronous Machine

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Hysteresis motors are manufactured in sub-fractional horsepower ratings, primarily as servomotors

and timing motors. More expensive than the reluctance type, hysteresis motors are used where

precise constant speed is required.

DC-excited motors — Made in sizes larger than 1 hp, these motors require direct current supplied

through slip rings for excitation. The direct current can be supplied from a separate source or from

a dc generator directly connected to the motor shaft

Slip rings and brushes are used to conduct current to the rotor. The rotor poles connect to each

other and move at the same speed - hence the name synchronous motor. Synchronous motors fall

under the category of synchronous machines which also includes the alternator (synchronous

generator). These machines are commonly used in analog electric clocks, timers and other devices

where correct time is required.

Parts

A synchronous motor is composed of the following parts:

• The stator is the outer shell of the motor, which carries the armature winding. This winding

is spatially distributed for poly-phase AC current. This armature creates a rotating magnetic

Wound Stator

Back to Index field inside the motor.

• The rotor is the rotating portion of the motor. it carries field winding, which may be

supplied by a DC source. On excitation, this field winding behaves as a permanent magnet.

• The slip rings in the rotor, to supply the DC to the field winding, in the case of DC excited

types

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Principle of Operation

The operation of a synchronous motor is simple to imagine. The armature winding, when excited

by a poly-phase (usually 3-phase) winding, creates a rotating magnetic field inside the motor. The

field winding, which acts as a permanent magnet, simply locks in with the rotating magnetic field

and rotates along with it. During operation, as the field locks in with the rotating magnetic field,

the motor is said to be in synchronization.

Once the motor is in operation, the speed of the motor is dependent only on the supply frequency.

When the motor load is increased beyond the break down load, the motor falls out of

synchronization i.e., the applied load is large enough to pull out the field winding from following

the rotating magnetic field. The motor immediately stalls after it falls out of synchronization.

Starting methods

Synchronous motors are not self-starting motors. This property is due to the inertia of the rotor.

When the power supply is switched on, the armature winding and field windings are excited.

Instantaneously, the armature winding creates a rotating magnetic field, which revolves at the

designated motor speed. The rotor, due to inertia, will not follow the revolving magnetic field. In

practice, the rotor should be rotated by some other means near to the motor's synchronous speed to

overcome the inertia. Once the rotor nears the synchronous speed, the field winding is excited, and

the motor pulls into synchronization.

The following techniques are employed to start a synchronous motor:

• A separate motor (called pony motor) is used to drive the rotor before it locks in into

synchronization.

• The field winding is shunted or induction motor like arrangements are made so that the

synchronous motor starts as an induction motor and locks in to synchronization once it

reaches speeds near its synchronous speed.

• Reducing the input electrical frequency to get the motor starting slowly, Variable-

frequency drives can be used here which have Rectifier-Inverter circuits or a Cyclo-

converter circuits.

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Uses

• Synchronous motors find applications in all industrial applications where constant speed is

necessary.

• Improving the power factor as Synchronous condensers.

• Electrical power plants almost always use synchronous generators because it is important

to keep the frequency constant at which the generator is connected.

• Low power applications include positioning machines, where high precision is required,

and robot actuators.

• Mains synchronous motors are used for electric clocks.

• Record player turntables

Advantages

Synchronous motors have the following advantages over non-synchronous motors:

• Speed is independent of the load, provided an adequate field current is applied.

• Accurate control in speed and position using open loop controls, eg. stepper motors.

• They will hold their position when a DC current is applied to both the stator and the rotor

windings.

• Their power factor can be adjusted to unity by using a proper field current relative to the

load. Also, a "capacitive" power factor, (current phase leads voltage phase), can be

obtained by increasing this current slightly, which can help achieve a better power factor

correction for the whole installation.

• Their construction allows for increased electrical efficiency when a low speed is required

(as in ball mills and similar apparatus).

• They run either at the synchronous speed else no speed is there.

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Induction Motors

An induction motor or asynchronous motor is a type of alternating current motor where power is

supplied to the rotor by means of electromagnetic induction.

An electric motor converts electrical power to mechanical power in its rotor (rotating part). There

are several ways to supply power to the rotor. An induction motor is sometimes called a rotating

transformer because the stator (stationary part) is essentially the primary side of the transformer

and the rotor (rotating part) is the secondary side. The primary side's current creates an

electromagnetic field which interacts with the secondary side's electromagnetic field to produce a

resultant torque, thereby transforming the electrical energy into mechanical energy. Induction

motors are widely used, especially polyphase induction motors, which are frequently used in

industrial drives.

Induction motors are now the preferred choice for industrial motors due to their rugged

construction, absence of brushes (which are required in most DC motors) and—thanks to modern

power electronics—the ability to control the speed of the motor.

Principle of Operation

A 3-phase power supply provides a rotating magnetic field in an induction motor.

The basic difference between an induction motor and a synchronous AC motor is that in the latter

a current is supplied into the rotor (usually DC) which in turn creates a (circular uniform) magnetic

field around the rotor. The rotating magnetic field of the stator will impose an electromagnetic

torque on the still magnetic field of the rotor causing it to move (about a shaft) and rotation of the

rotor is produced. It is called synchronous because at steady state the speed of the rotor is the same

as the speed of the rotating magnetic field in the stator.

By way of contrast, the induction motor does not have any direct supply onto the rotor; instead, a

secondary current is induced in the rotor. To achieve this, stator windings are arranged around the

rotor so that when energised with a polyphase supply they create a rotating magnetic field pattern

which sweeps past the rotor. This changing magnetic field pattern induces current in the rotor

conductors. These currents interact with the rotating magnetic field created by the stator and in

effect causes a rotational motion on the rotor.

27

However, for these currents to be induced, the speed of the physical rotor must be less than the

speed of the rotating magnetic field in the stator, or else the magnetic field will not be moving

relative to the rotor conductors and no currents will be induced. If by some chance this happens,

the rotor typically slows slightly until a current is re-induced and then the rotor continues as

before. This difference between the speed of the rotor and speed of the rotating magnetic field in

the stator is called slip. It is unitless and is the ratio between the relative speed of the magnetic

field as seen by the rotor (the slip speed) to the speed of the rotating stator field. Due to this an

induction motor is sometimes referred to as an asynchronous machine.

Construction

The stator consists of wound 'poles' that carry the supply current to induce a magnetic field that

penetrates the rotor. In a very simple motor, there would be a single projecting piece of the stator

(a salient pole) for each pole, with windings around it; in fact, to optimize the distribution of the

magnetic field, the windings are distributed in many slots located around the stator, but the

magnetic field still has the same number of north-south alternations. The number of 'poles' can

vary between motor types but the poles are always in pairs (i.e. 2, 4, 6, etc.).

There are three types of rotor:

• Squirrel-cage rotor

The most common rotor is a squirrel-cage rotor. It is made up of bars of either solid copper (most

common) or aluminum that span the length of the rotor, and those solid copper or aluminium strips

can be shorted or connected by a ring or some times not, i.e. the rotor can be closed or semiclosed

type. The rotor bars in squirrel-cage induction motors are not straight, but have some skew to

reduce noise and harmonics.

• Slip ring rotor

A slip ring rotor replaces the bars of the squirrel-cage rotor with windings that are connected to

slip rings. When these slip rings are shorted, the rotor behaves similarly to a squirrel-cage rotor;

they can also be connected to resistors to produce a high-resistance rotor circuit, which can be

beneficial in starting

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Bearings

There are broadly two types of bearings employed:

Rolling Element Bearing Sleeve Bearing

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Testing of Motors

Introduction

The motors manufactured are of types squirrel cage induction motors, slip-ring induction

motors, synchronous motor and special motor, such wide range of designs underscores

importance of testing. Each motor is tested to see that it meets the performance figures

given in the technical data sheet. For this, the test plant is equipped with all modern &

highly accurate instruments.

1.0 Type of Tests

The tests conducted on motors may be classified into routine test, type test & special

test.

1.1 ROUTINE TEST :

Routine tests are those tests which are conducted on all motors. They show in general

conformity of motors to design specification & reflect in general quality of

manufacturing. The tests are as follows :

• Measurement of resistance & IR value of St. winding and rotor winding (in case

of slip ring and synchronous motor).

• Mechanical Run. Motor is run at rated voltage & rated frequency. Measurement

of No load current, no load loss, stablilized bearing temperatures, vibration level,

shaft voltage.

LOCKED ROTOR TEST :

Measurement of line voltage, line current & power input. The test is conducted at rated

current.

POLARISATION INDIX TEST :

Polarization index is the ratio of IR value at 10 minute to IR value at 1 minute. PI value

2 is considered good for the insulation.

HV TEST :

This is conducted at (2U+1) KV & power frequency for 1 minute. Where U = rated

voltage in KV. IR value is measured before & after HV test.

2.0 TYPE TESTS :

These tests are conducted on one machine of a

are to establish design parameters such as efficiency, power factor, slip, starting current,

starting torque etc., all the tests covered under routine tests & some other tests which are

given listed below :

• No load saturation curve. The motor is run at no load and the applied voltage is

varied from 120% rated voltage to 40% rated voltage. At each point applied

voltage, current drawn & power input is measured.

• Determination of starting Current & torque in line with

• Temperature rise test

• Measurement of line voltage, line current, power input, power factor, slip at

100% load, 75% load & 50% load.

• Overload test at 160% for 15 seconds.

• Noise Measurement.

• Over speed test. The motor under test is run for 2 minutes

minute. Any abnormal sound is watched.

These tests are conducted on one machine of a rating. The purpose of carrying these tests



ad saturation curve. The motor is run at no load and the applied voltage is


voltage, current drawn & power input is measured.

Determination of starting Current & torque in line with JEC-37.

Measurement of line voltage, line current, power input, power factor, slip at

100% load, 75% load & 50% load.

Overload test at 160% for 15 seconds.

Over speed test. The motor under test is run for 2 minutes at 120% speed for 2

minute. Any abnormal sound is watched.

30

rating. The purpose of carrying these tests



ad saturation curve. The motor is run at no load and the applied voltage is


Measurement of line voltage, line current, power input, power factor, slip at

at 120% speed for 2

31

2.1 TEMPERATURE RISE TEST:

Temperature rise test is carried out by actually loading the motor so that rated loss occur

in the motor. Every half an hour measurement of RTD resistance is done till temperatures

of all parts of the motor stabilizes. Temperature stabilization is supposed to have

occurred if temperature rise in 1 hour does not exceed more by 2 Deg. C.

Loading of motor can be done by following methods.

i. Direct loading. By this tandem set of 2 DC motors each of capacity 650 KW

is used. Motors can be loaded by this method up to 1300 KW.

ii. Back to Back method. This method is used where motor of rating more than

1300 KW is to be loaded. For this two motors of identical rating is required.

One motor is loaded in the motor mode which is loaded by the other motor

which is loaded in the generator mode. The variation of loading is done by

varying the frequency.

iii. Mixed frequency method. This method is normally used when motor of

rating more than 1300 KW is to be loaded & no identical motor is available.

This method is also used in case of vertical motors where direct coupling with

the horizontal tandem set is not possible. In this the main supply of rated

voltage & 50 c/sec is superimposed with auxiliary frequency of approx 40 to

45 Hz and voltage of the order of 20% of the rated voltage. The

superimposition of the two frequencies sets up, series of beats, loading the

machine alternately in the motor or the generator mode. The auxiliary voltage

& frequency is so adjusted to set up rated current in the motor, thereby

loading the motor. By this method, the temperature rise is more than the

normal by approx 2 to 5 degree C.

32

2.2 CALCULATION OF EFFICIENCY :

One of the major objective of carrying out type test is determination of efficiency which

is one of chief concerns for customers in view of increasing power tariff. Our motors are

designed for high efficiency, which is borne out by test results as well. The efficiency is

determined by “ Summation of losses method”. The losses occurring in the motor are

determined by the load test & calculated as;

• Friction & windage loss ; This is taken from the No load Saturation Curve.

• Iron loss; This is taken from the No load Saturation Curve.

• Stator copper loss ; This is 3xIxIx r where I is the line current & r is the phase

resistance at 75 deg. C.

• Rotor copper loss ; This is sx Air gap power. Here power Air gap is (Input-

Stator copper loss-Iron Loss).

• Stray loss ; As per IS4728 this is taken as 0.5% of the output.

• Output = Input – summation of losses and Efficiency = Output / Input X 100.

2.3 NOISE MEASUREMENT :

Noise is ,measured at approx eight places around periphery of the motor at distance 1 m

from the motor in decibel in the audible spectrum in pressure. Then at the same

locations, background noise is measured after the motor has come to stand still. After

applying the corrections for the background noise average noise is calculated in line with

BS-4999 part 51.

2.4 TOLERANCES :

Tolerances in performance figures as per IS-325 are given as

i. Total losses 10%

ii. Power factor -1/6X(1-pf)

Min. 0.02 ; max. 0.07

iii. Starting current +20%

iv. St. torque -15% to +25%

v. Pull out torque -10%

33

2.5 DETERMINATION OF STARTING CURRENT & STARTING TORQUE

For our range of motors, it is not possible to start motor in the test bed direct on line.

Hence for determining the starting current & starting torque the methodology has been

adopted from JEC. This method is suitable for semi closed rotor slots which are the case

with our motors. In this locked rotor test is carried out at 100%, 150% & 200% rated

current. Applied voltage & power input is measured at 100% rated voltage & applied

voltage is measured at other currents.

1.0 SPECIAL TEST :

These are such tests which are not covered in the standards under routine or type sets but

are conducted if agreed between customer & manufacturer. Such tests for which facilities

are available in our test plant are:

• Water test for the second numeral of protection.

• tan Delta Tests: As no standard specifies limits in case of assembled motor, this

test is carried for customer’s reference only.

• Impulse Test: This test is carried out at coil stage only. For ground insulation it is

carried out at (4U+5) KV where U is the line voltage. The wave shape is of 1.2

micro secs/50 micro secs. For turn insulation, the wave shape is of 0.3 / 3.0 micro

seconds & the test voltage is 65% of the tests voltage in case of ground insulation.

4.0 INSTRUMENTION :

The measuring instruments used are of very high accuracy. The instruments used for

type tests are of 0.5% class and the instruments used for routine tests are of 1.0% class.

34

5.0 FACILITIES AVAILABLE :

Very modern facilities are available in our test plant. Some of them are listed below :

• one 10 MVA, MG set



• one 1750 MVA MG set

• one 650 KVA, MG set

• Digital instruments of high accuracy

• Power analyzer

• Resistance braking to facilitate fast stopping of motor, so that hot resistance can

be measured very fast.

• Modern instruments for measuring vibration & noise.

• Computer software in the design department for processing test data & generating

test certificates.

• 1 MVA, 60 Hz, generator for carrying out overspeed test.

Following facilities have been added:



• Replacement of resistance based control system with PLC backed, solid state

control system. Using these state of art facilities voltage & current can be

maintained at very constant level during testing.

• Hooking of all test plants to Design Department through local network.

35

References

• Electrical Machinery by P.S. Bhimbra.

• BHEL Website – www.bhel.com .

• BHEL, Bhopal Website – www.bhelbhopal.com .

• Website – www.wikipedia.org .

58438009 major training ame bhel bhopal

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