general orientation of manufacturing unit and overview of motor testing

7/29/2019 General Orientation of Manufacturing Unit and Overview of Motor Testing

1/23

M a r a t h o n E l e c t r i cM o t o r s I n d i a L i m i t e d

P a h a r p u r W o r k s

5 8 T a r a t a l a R o a d

9 1 3 3 2 4 6 9 5 5 6 0 / 6 1 / 6 5

9 1 3 3 2 4 6 9 8 5 3 0 / 5 3 6 9

6 / 1 / 2 0 1 2

Summary:

An Industrial Summer Training Report of

things learnt during Orientation program; and

an overview of the different tests carried out

on a motor to meet Indian Standards.

General

Orientation ofManufacturing

Unit and Overview

of Motor Testing


2/23

2

Details

Document: Industrial Summer Training Report on General Orientation of

Manufacturing Unit and Overview of Motor Testing required for Indian Standard

Certification.

Company: Marathon Electric Motors India Limited

Paharpur Works58 Taratala Road

Kolkata - 700024 (West Bengal)

Guided By: Mr. Rajiv RanjanGeneral Manager (Design, LT Motors)

&

Mr. Subal Chatterjee

Manager in-Charge, Testing Dept.

Submitted By: Rishabh Dassani

B.Tech, Electronics & Electrical Engineering (2nd

yr)

School of Electronics Engineering

Kalinga Institute of Industrial Technology (KIIT) University

Bhubaneswar - 751024 (Odisha)

Submitted To: Dr. Saranjit Singh, Dean, (T&P)

Kalinga Institute of Industrial Technology (KIIT) University

Bhubaneswar 751024 (Odisha)


3/23

3

Acknowledgement

This project report has been made possible due to the kind hands of support extended by a

number of people and I would like to thank the following who helped directly or indirectly.

First, to Mr. Saranjit Singh, Dean (T&P), for giving permission to undergo training at an

organization of my choice.

Secondly, to Mr. Riten Chatterjee, General Manager (HR), Paharpur Works for referring my

application and making it possible to undergo training here.

Third, Mr. Rajiv Ranjan, General Manager (Design, LT Motors), Paharpur Works for being In-

Charge of my project here.

Fourth, to entire staff of Motor Testing Department for the Immense patience kept while

showing me around and help extended towards me in garnering knowledge for further

assistance in my career.

Fifth, to Mr. Basudeb Dutta, Assistant Manager (HR), for assisting me in whatever way possible.

Most importantly, to all the Managers in- Charge of the various Units of the Manufacturing

Plant and all the working staff who were mostly ready to lend a helping hand.

Rishabh Dassani

B.Tech (2nd Year)

Electronics & Electrical Engineering

School of Electronics

KIIT University


4/23

4

Company Profile

Marathon Electric Motors India Limited (MEMIL) is part of the Regal Beloit family of

companies. Regal Beloit Corporation is a leading manufacturer of electrical and mechanical

motion control and power generation products serving markets throughout the world. Regal

Beloit has its headquarters at Beloit, Wisconsin, and has manufacturing, sales, and service

facilities throughout North America and in Mexico, Europe and Asia.

From electric motors and generators to gear reducers, and electronic switchgears, Regal

Beloit's products are often concealed within, but essential to the function of much of the

equipment powering the world. Regal Beloit products can be found in home furnaces, pumps,

elevators, conveyors, x-ray machines, office equipment, power stations and thousands of other

places of critical uses. Regal Beloit's strength is in its market diversity as it serves an expansivearray of markets from heavy industry to high technology. Markets include Heating Ventilating

and Air Conditioning (HVAC), food processing, medical, material handling, petrochemical,

construction, manufacturing, agriculture and mining, to name a few. Few companies can match

Regal Beloits abilities to adapt and modify products to required specifications and deliver

consistent quality, at a fair price and a time dictated by the customer.

Regal Beloit's ongoing success can be attributed, in part, to an aggressive acquisition program,

which has become a company hallmark. 2004 saw two major motor acquisitions from General

Electric (GE), which effectively doubled the size ofRegal Beloit. In 2007, the Company acquired

Morrill Motors, a leading manufacturer of fractional horsepower motors for commercial

refrigeration and freezer markets. With the acquisition of Fasco and Jakel that same year, Regal

Beloit expanded into blower systems for the HVAC market. Alstoms motor and fan business in

India was then purchased, taking another step towards the execution of the Companys

globalization initiative. The Company now has over 17,000 employees and 54 manufacturing

and service/distribution facilities throughout the United States and in Canada, Mexico, Europe,

Asia and Australia.

Since 1913, Marathon Electrics name has been recognized for engineering excellence, custom

designed products and an extensive product line industrial quality motors. Available in allpopular enclosures from 1/12 HP through 800 HP and in a variety of mounting configurations,

Marathon Electrics unique design provide more ways in which to add accessories, such as

blowers, brakes and encoders, to motors than anyone else in the motor business.

State of-the-art lab facilities are equipped and staffed with the finest resources available to

ensure successful utilization of products. Since 1913, Marathon Electric has beendedicated


5/23

5

providing customers with quality products for targeted applications. Located in Wausau,

Wisconsin, the company is composed of two strategic product lines: motors and generators.

Marathon Electric Motors:

Delivers efficient mechanical power solutions using AC electric motors up to 1250 HP.

Marathon Electric Generators:

Offers power generation for the 21st century with a wide selection of generators for standby

and continuous power.

Proven top performers in every respect, Marathon Electric Motors India Limited, Paharpur

Works, is essentially a supplier of export goods to well known MNCs and national giants

including the likes of Hitachi, Danfos, ABB and BHEL amongst others. The manufacturing unit

here in Paharpur, produces a wide variety of LT Induction Motors in the frame size of 63mm to

355mm, within a power rating of 80W to 250kW, and various fans of Industrial, Centrifugal,

Axial Flow and Man Cooler Types.


6/23

6

ELECTRIC MOTORS

An Electric motor is an electrical machine which converts electrical energy into mechanical energy usingFaradays Laws.

1.1 PRINCIPLE OF OPERATION

Current carrying conductor placed in a magnetic field, experiences amechanical force whose

direction is given by Flemings Left-hand rule and whose magnitude is given by

(Figure A. Block Diagram of functioning of Motor)

1.2 AC MOTOR

INTRODUCTION

An AC motor is an electric motor that is driven by an alternating current. It consists of two basic

parts, an outside stationary stator having coils supplied with alternating current to produce a

rotating magnetic field, and an inside rotor attached to the output shaft that is given a torque

by the rotating field.

1.2.1 Types of AC motor(depending on the type of rotor used):1.2.1.1 Synchronous motor

This rotates exactly at the supply frequency or a sub-multiple of the supply frequency. The

magnetic field on the rotor is either generated by current delivered through slip rings or by

a permanent magnet.

1.2.1.2. Induction motor

This rotates slightly slower than the supply frequency. The magnetic field on the rotor of this

motor is created by the current due to the induced emf.

1.2.2 HISTORY

In 1882, Serbian inventor Nicola Tesla identified the rotating magnetic induction field principle

and pioneered the use of this rotating and inducting electromagnetic field force to generate

torque in rotating machines. He exploited this principle in the design of a poly-phase induction

motor in 1883. In 1885, Galileo Ferraris independently researched the concept. In 1888, Ferraris

published his research in a paper to the Royal Academy of Sciences in Turin.

Electrical

Energy Input

Motor

System

Mechanical

Energy Output


7/23

7

Introduction ofTesla's motor from 1888 onwards initiated what is sometimes referred to as the

Second Industrial Revolution, making possible both the efficient generation and long distance

distribution of electrical energy using the alternating current transmission system, also of

Tesla's invention (1888). Before widespread use ofTesla's principle of poly-phase induction for

rotating machines, all motors operated by continually passing a conductor through a stationary

magnetic field (as in homo-polar motor). Initially Tesla suggested that the commutators from amachine could be removed and the device could operate on a rotary field of electromagnetic

force. Professor Poeschel, his teacher, stated that would be akin to building a Perpetual motion

machine. This was because Teslas teacher had only understood one half ofTesla's ideas.

Professor Poeschel had realized that the induced rotating Magnetic field would start the rotor

of the motor spinning, but he did not see that the counter electromotive force generated would

gradually bring the machine to a stop. Tesla later obtained U.S. Patent # 416,194.

Michail Osipovich & Dolivo-Dobrovolsky later invented a three-phase "cage-rotor" in 1890. This

type of motor is now used for the vast majority of commercial applications.

1.3 INDUCTION MOTORS

Most AC motors are induction motors. Induction motors are favored due to their ruggedness

and simplicity. In fact, 90% of industrial motors are induction motors. Induction motors are the

workhorses of industry and motors up to about 500 kW (670 hp) in output are produced in

highly standardized frame sizes,

making them nearly completely interchangeable between manufacturers (although European

and North American standard dimensions are different). Very large induction motors are

capable of tens of megawatts of output, for pipeline compressors, wind-tunnel drives,

and overland conveyor systems.

1.3.1 PRINCIPLE OF OPERATION

Based on rotating magnetic induction field principle, the rotating and inducting electromagneticfield force generates torque in rotating machines. Conversion of electrical power into

mechanical power takes place in the rotating part of the motor. InInduction motors rotor

receive electric power by induction in exactly the same way as the secondary of a 2-winding

transformer receives its power from the primary. That is why such motors are known induction

motors. One means of creating a rotating magnetic field is to rotate a permanent magnet. If the

moving magnetic lines of flux cut a conductive disk, it will follow the motion of the magnet. The

lines of flux cutting the conductor will induce a voltage, and consequent current flow, in the

conductive disk. This current flow creates an electromagnet whose polarity opposes the motion

of the permanent magnet according to Lenzs Law.

Lenz's Law: The polarity of the electromagnet is such that it pulls against

the permanent magnet. The disk follows with a little less speed than the permanent magnet.

Nicola Tesla conceived the basic principles of the poly-phase induction motor in 1883, and had

a half horsepower (400 watts) model by 1888. Tesla sold the manufacturing rights to

George Westinghouse for $65,000. Most large (> 1 hp or 1 kW) industrial motors arepoly-phase

induction motors. Large industrial motors are mostly 3- phase motors.


8/23

8

General Orientation

The general orientation program spanned over a period of 2 weeks was as:

2.1 ENVIRONMENT, HEALTH AND SAFETY: Conducted under Mr. Amal Mukhopadhyay.

This department though not directly concerned with motors from a students perspective, is

given a lot of importance by the company as proved by its, Policy, and effort.

Governed by the Factory Act of India, all companies are under the judicial obligation to met out

certain safety measures for its workers, and disposal of waste, and Marathon Electric Motors

are no different. Only they consider it also to be their ethical binding to look after the

immediate, work and surrounding environment to which the plant is exposed.

The ensuring of maintenance of environment is done by ensuring proper disposal of waste to

the designated locations, by filtering out air pollutants, and by introducing an effluent

treatment plant so as to be able to reuse the water being thrown out such that water

consumption is reduced drastically. Everyday 22,000 lts of water is reused, and the demand is

for just a meagre 4,000 lts extra.

Now, it is identified that RISK=HAZARD times EXPOSURE to HAZARD. Now, the HAZARDS cannot

be removed, like electricity, and Volatile Organic Compounds, Fire etc so the only way to reduce

the risk would be to limit the exposure, and hence PPE or Personal Protective Equipments are

made compulsory, and all workers are to wear it.

The National Safety Day, on 4 th March, is celebrated every year with mock fire drills, and poster

making competitions to raise awareness amongst the workers.

A number of steps have been taken to limit accidents and it is reflected in the fact that as of

June, 2012 there hasnt been an accident for over 500 days.

2.2 MAINTENANCE: Conducted under Mr. Prasant Banerjee

The Maintenance department of the manufacturing plant is a prized asset for the company.

They are the caretakers of every nook and corner and solely responsible for the clockwork like

precision and working of the entire plant, along with skilled workers who know their jobs. The

plant being functional since 1930s, under many a different company, has a few prizedmachinery and they are nearly 70 years old yet functioning properly.

Most of these machines are tweaked and modified to improve their efficiency and working

capabilities by the Maintenance dept. The team also performed some spectacular self repairing

projects in a couple of parts of the plant which reduced the cost of repair by more than 300%

The maintenance team meticulously focuses on Response Time, Proper Planning, Rigorous hard

work and Preventive Measures and Action.


9/23

9

2.3 MACHINE SHOP: Conducted under Mr. Subrata Koley

The machine shop makes some of the motor parts that are not bought from third party dealers

or vendors. The formation or rather transformation of raw cylindrical shaped rods into shafts,

by undergoing numerous turning operations are carried out here. There are automatic

machines for quicker work, and manually operated machines for higher precision.

Shells of cast iron material are bought from outside, and given the trademark touch here in the

plant by the use of vertical and horizontal turning machines which are mostly automated for

higher efficiency. The stator shells undergo first operation and second operations, in the same

machine and then loaded into another machine for third and final operation.

The brackets or end shields are also perfected her using vertical and horizontal turning

machines. The stator core and rotor cores are either made in the die-casting department or

bought from outside depending upon their convenience.

The polishing, and finer grooving and many such intricate detailing operations are carried out

by manually operated machines.

The automated machines run on a software program called FARROW and FANUC.

Most of the productions of completed motor parts are finished here.

2.4 DIE-CASTING DEPARTMENT: Conducted under Mr. Partha Pratim Das

The die-cast department has a small foundry of its own for the making of small to medium sized

shields, stator shells and stator and rotor cores. The department uses a one-of-a-kind 750 ton

press machine imported from South Africa and is the only such specimen in India. There are a

450 ton and 250 ton such smaller press machines for die-casting.

The rotor cores made are of two types: squirrel cage and slip ring type. The squirrel cage rotor

core is made by stacking fine sheets of laminations and then heating them and adding molten

aluminium to fuse and form a solid conducting rotor. The filling of air gaps can be done in three

procedures:

Gravity Control: this method requires poring of molten metal and waiting for it to settledown and remove air pockets under the effect of gravity. Very poor method.

Pressure Control: this method requires pressurizing the molten metal into the gaps andis a slightly better method than above.

Centrifugal Control: this method puts the cylindrical stack on a plate which rotates oncethe molten metal is poured into it. This centrifugal process is the best cause it pushes

the molten metal into the smallest of gaps and cracks.

Using the above methods, the squirrel cage rotors are made with implanted shafts.

2.5 WINDING AND VARNISHING DEPARTMENT: Conducted under Mr. Ranjan Mandal

The winding department has to install winding in two different parts of the motor, the stator

core and the rotor core.


10/23

10

2.5.1 STATOR:

The stator is wound with pairs of coils corresponding to the phases of electrical energy

available. The 2-phase induction motor stator above has 2- pairs of coils, one pair for each of

the two phases of AC. The individual coils of a pair are connected in series and correspond to

the opposite poles of an electromagnet. That is, one coil corresponds to a N-pole, the other to

a S-pole until the phase of AC changes polarity. The other pair of coils is oriented 90 in space

to the first pair. This pair of coils is connected to AC shifted in time by 90 in the case of a 2-

phase motor. In Tesla's time, the source of the two phases of AC was a 2-phase alternator. For

the stators which has salient, obvious protruding poles, as used on Tesla's early induction

motor, is used to this day for sub-fractional horsepower motors (


11/23

11

General check points for insulation are proper checking of stack heights, diameter and

other mechanical dimensions of stator core, besides insertion of slot paper should be uniform

and of equal height with no shifting down from its original position.

2.5.1.2. WINDING

(Figure C. Stator with (a) 2- and (b) 3- windings)

The coils are wound on an external fixture, and then worked into the slots. Insulation wedged

between the coil periphery and the slot protects against abrasion.

In (Figure B), the windings for both a two-phase motor and a three- phase motor have been installed in

the stator slots. The coils are woundon an external fixture, and then worked intothe slots. Actual

stator windings are more complex than the single windings per pole in (Figure B). Comparing

the 2- motor to Tesla's 2- motor with salient poles, the number of coils is the same. In actual

large motors, a pole winding, is divided into identical coils inserted into many smaller slots than

above. This group is called a phase belt. The distributed coils of the phase belt cancel some of

the odd harmonics, producing a more sinusoidal magnetic field distribution across the pole. The

slots at the edge of the pole may have fewer turns than the other slots. Edge slots may contain

windings from two phases. That is, the phase belts overlap.

2.5.3. INSERTION

Wound coils are inserted into the stator slots at insertion machines along with the wedge

paper for insulation of coil periphery from stator laminations and adjoining cells. A great care istaken for proper insertion of wedge paper into the slots.

2.5.4. FORMING

The best winding and insertion still doesn't make the perfect stator. Forming process is another

focal point in the production process. Processes carried at this stage are such as expanding

lamellas, to final forming of I.D., O.D. and heights of the winding head, scratch wire detection.


12/23

12

After this lead or cables connection are made to the field. Winding and insulation tapes are

applied according to the specifications as per E.I. chart.

2.5.5. LACING

Lacing or knotting is done at the machine for finally tightening the all the loose wires of coil

winding. The end turns are laced with a "diamond" stitch pattern. Both sides are laced at thesame time and a real knot is being tied at the end. After this process the wound stator looks

like in figure and then thefinal process is carried out on field where final inspection is done for

visually detecting and removing the defects on account of following:

Loose wires/wiring, Lacing or knotting problem.

Wedge paper problem, shifted down wedge paper.

Slot paper.

Cables or connecting lead length and proper application of insulation tape.

Without marking. This is the most critical and important stage of passing line from the pointof view of quality control. At this stage the responsibility lies wholly on operator as there is no

intervention of machinery and the defects have to be detected visually and removed manually.

2.5.6. COMPUTERIZED WINDING TEST DESCRIPTION

Computerized winding tester is the most comprehensive quality control methodfor in-plant

testing process industries. It is extremely effective as a diagnostic tool to evaluate and detect

any windings fault that may exist. It can be used to detect the following in the windings:

turn to turn short circuits

Coil to coil short circuits

Phase to phase short circuits

reverse coil connections

Open coils

Grounded coils

Defective insulation

The following tests are performed by the computerized winding tester:

Resistance test:

The Resistance test is performed on the Main and Auxiliary windings. All the resistance

measurements are corrected to the ambient temperature (25 C) using the temperature

sensors. It checks wrong turn count, poor connections, mislabeled leads, and incorrect wire

size.


13/23

13

Insulation resistance test: The IR or megohm test checks the strength of the insulation.

AC Hi-Pot test: The AC hi-pot test detects if there is a breakdown to ground or between

windings which would otherwise go undetected using average current

measurement techniques. This measures the resistive portion of the leakage current, ratherthan the total current.

Surge test: The high voltage surge test checks for insulation problems between turns, coils,

and phases of the winding. Surge tests can also detect other faults which change the

inductance of a winding such as reversed coils. The surge test also has the ability to detect

corona caused by weak insulation in addition to actual insulation breakdown.

Rotation test: The rotation direction test determines the rotation of the stator whether it is

clockwise or anti-clockwise. This test uses the Hall-effect type sensors.

To manufacturers this means that the faulty windings can be isolated and repaired at every

stage of manufacturing thus, ensuring quality and saving in material and labour costs.

(Figure D. Manual Surge Comparison tester, Courtesy: Ample Machines)

2.5.7. VARNISHING

Finally the Wound stator i.e. the field after being properly checked goes for varnish plant

where penetrating coat of good insulating varnishes are applied on windings to protect them

from action of vibration, heat, water, oil, dirt and acid fume would soon cause a complete


14/23

14

failure of field or rotor circuits. Without a coating of insulating varnish, slot papers would soon

become brittle and crack or soggy from moisture and the enamel covering of wires would chip

and flake. When properly applied and treated, insulating varnish provides a solid film

protective covering.

The varnish here is done manually for the large stator and rotor windings, while the help of an

auto varnishing plant is present in the premises for the varnishing of small rotor and statorwindings. Loading onto the auto varnishing plant (here the entry and exit point for the stator

and rotor cores are the same, done using hangers) and unloading takes about 4-5 hours. At

both loading and unloading stations thorough inspection of fields is done to detect visually for:

Loose wires or wiring in green fields (at loading station)

Wedge paper problem.

Loose wires or wiring in varnished fields (at unloading station)

Without marking.

Knotting/lacing problem.

Lead cut/unequal length/terminal damage. From the point of view of quality control the

inspection made at varnish stations for defect is most crucial, since the varnished fields are

passed on for assembly line and if rejection is made on basis of above problems during

any stage of assembly line results in wastage of resources, manpower and time.

2.5.2. ROTOR

The rotor consists of a shaft, a steel laminated rotor, and an embedded Copper or aluminium

squirrel cage, as compared to a DC motor armature, there is no commutator. This eliminates

the brushes, arcing, sparking, graphite dust, brush adjustment and replacement, and re-

machining of the commutator. They are of two types as follows:2.3.2.1. Squirrel-cage Rotor:

Almost 90% of induction motors employ this type of rotors because of simple and rugged

construction and almost indestructible. The rotor consists of a cylindrical laminated core with

parallel slots for carrying the rotor conductors, which are not wires but consists of heavy copper

bars. One bar is placed in each slot; rather the bars are inserted from the end where semi-

closed slots are used. The rotor bars are brazed or electrically welded or bolted to two heavy

and stout short-circuiting end-rings.

The squirrel cage conductors may be skewed, twisted, with respect to the shaft. The

misalignment with the stator slots reduces torque pulsations.2.5.2.2. Phase-wound Rotor:

Motors employing this type of rotors are called wound motors or Slip-ring motors. This type

of rotor is provided with 3-phase, doublelayer, distributed winding consisting of coil as used

in alternators. The rotor is wound for as many poles as the no. of stator poles and is always

wound 3-phase even when the stator is wound two-phase.


15/23

15

2.6. MOTOR ASSEMBLY: Conducted under Mr. Sanjib Majumdar & Mr. Sujit Bhattacharya

The finished products reaching this segment of the plant are the stator shells & cores, rotor

cores, shafts and the brackets. The stator shell and core are pressed together by first heating

the shell so as to expand it, and then inserting the core and then pressed using a hydraulic

press machine. The rotor and shaft too are pressed together but using just the machine with

force applicable to a maximum of 200 tons.

After the pressing operation is complete, sphigoting is done on the shell for fixing of brackets.

Then after the last final adjustments in the form of fine cutting and grooving, the assembly line

workers collect each of a stator, rotor, brackets and terminal box. First the rotor is placed

inside of stator, and the fit is snug. Then the bearings are attached to the shaft and one of the

brackets. The other bracket is also similiarly attached. Then they are bolted together before the

terminal box is set up. The assembled product is then sent off to the paint shop where a basic

primer is put on in case the consumer wants to apply paint of their own accord, or the motors

are painted according to the demand, or company code. E.g. Motors for Hitachi are painted

black, while those for Danfos are painted military green. The name tags or plates are put on

once the paint dries up, mentioning the batch code, product no, power rating, current rating,voltage rating frequency and speed of rotation or rpm.

2.7. FAN ASSEMBLY: Conducted under Mr. Partha Pratim Das

Apart from the LT Induction Motors, the plant also manufactures fans of the types:

Industrial Fans Centrifugal Fans Axial Flow Fans, and Man Cooler Fans.

This department deals with cooler fans. They have blade sizes of 12, 15, 18 and 24.

The specifications are followed according to the Indian Standard 2312.

Application wise there are two types of cooler fans: Transformer cooling, as sold to ABB, BHEL

etc. and Chilling purpose, as sold to Hitachi, DANFOS. The fan as a whole again has two parts:

the motor and the impeller. Both of these are made in the plant. The flow chart of formation

of an impeller from the sheets of steel it arrives in is as:


16/23

16

(Figure E. Diagram showing process of formation of impeller)

2.7.1. PROCESS OF FORMATION OF IMPALER:

i. Shearing: The sheet metal is cut into smaller rectangular pieces.ii. Blanking: The outline of the blade is given to the pieces.iii. Forming: The pieces are further bent so as to shape up like a blade.iv. Drilling & Riveting: Done using a machine which does both together, the

machine is the only of its kind in Asia!

v. Pressing: The blades are taken together into the required no mentionedby design to form the impeller and pressed together with the help of nuts.

vi. Pretreatment: The impellers are taken in baskets and dipped in tanks ofchemicals. The process is better explained below.

vii. Balancing: All rotating devices are made to undergo balance tests, andweights are added as in where required to balance, and the machineaiding workers is an automated one.

viii. Painting: The finished impellers are sent off to be painted as required.After these processes are done, the impellers are sent to the assembly line to be put together

with the motor to form a fan.

2.8. QUALITY CONTROL/ASSURANCE: Conducted by Mr. Sukanto Roy.

Quality directly transcends into goodwill of the company in the market. So, a stringent quality

control and assurance department looks after all the tests that a motor undergoes from

production line till packaging. When a motor is tested only before packaging, many production

line faults may be noticed and fixing them requires dismantling and reconstruction, which is

unnecessarily cost increasing for the company. Hence, to reduce the cost of production,

optimal usage of raw materials and resources along with skilled management of goods, is

required.

The way forward, is to conduct tests of the parts during transit, between major stations.

Sheet(rawmaterial)

Shearing

Blanking Forming

Drilling &Rivetting

Pressing Pretreatment

Balancing

Painting


17/23

17

The standards for quality are predetermined by the ISO or International Organization for

Standardizations 9000 series. The standards of quantity are pre-specified by Indian Standards.

The aim of the QC/A is to keep the tested outputs to a half of the permissible half. That way,

there is a scope of provided for some error.

The raw materials taken from trusted sources are also sent for testing in 3rd

party laboratory, sothat they can be tested for quality.

Most of the tests carried out are mechanical in nature, and beyond scope of the report.

Special mention: PRETREATMENT FOR FAN BLADES:

The blades are dipped in 10 different tanks according to requirement. The tanks have:

The Aluminium materials follow the order: 1 > 2 > 8 > 9 > 10.

The Mild Steel materials follow the order: 1 > 2 > 3&4 > 5 > 7 > 10.

The above order signifies the drums into which the blades are put into.

1

I:PhoscleanP:Degreasing

2

I:RunningWaterP: Rinsing

3 & 4

I:Rustokit 161P:Pickling

5

I:Cold Running

WaterP:Rinsing

6

I:Phoschem Z

P:Anti-rustcoating

7

I:Cold Running

WaterP:Rinsing

8

I:Rustokit 176P:ChemicalEtching

9

I:Running WaterP:Rinsing

10

I:PhosbondP:Permanent acidparticle removal


18/23

18

General Overview of Motor

Testing3.1 CLASSIFICATION OF TESTS

According to the IS 325:1996, the tests on a LT Induction Motor are of two types:

Routine tests: The test on completion issues a certificate which means that the motorhas been run and found to be electrically and mechanically sound and in working order

in all particulars.

Type tests: The test on completion issues a certificate on a motor identical in essentialdetails with the all the motors in its batch (of maximum 20 quantity) along with the

routine test certificate for individual motors.

3.1.1 The ROUTINE TEST consists of:

Insulation Resistance test Measurement of winding resistance test No Load test Locked rotor test

Reduced voltage running up test (die-cast) HV test

3.1.2 The TYPE TEST consists of:

All Routine tests Full load test Torque test Vibration test Noise test

3.1.1.1 INSULATION RESISTANCE test and HIGH VOLTAGE test:

The test is conducted on isolated motors. The motor is kept on the ground and two connections

from a machine capable of generating 3kV potential difference are attached to the motors, one

to the windings and another to the body. The Megger, a resistance measuring device which

measures in M, is used between the ends of windings.


19/23

19

The aim is to check for the short connection, if any, between body and winding, which can lead

to disastrous consequences.

Ideally the result should be an insulation resistance of the order of 2.5M and open circuit

between body and windings.

3.1.1.2. Measurement of WINDING RESISTANCE test:

National Electrical Manufacturers Association (NEMA), has defined temperature rise of motor,

which effectively helps in checking whether a motor is working within accepted temperature

limits or not, in NEMA standard MG 1-1998.

Temperature rise has been defined as, the increase in temperature above ambient

temperature, i.e. the temperature of the cooling medium of the motor.

The test is conducted by measuring the lead-to-lead resistance (RC) in cold condition, i.e.

room temperature (TC). The temperature of the air gap of the motor is also noted. The motor is

then run at rated voltage till the air gap temperature stabilizes(TH). Once done, the resistance isagain checked (RH). The following formula is then used to calculate the acceptable temperature

rise (Th) :

Th= [(RH/ RC)x(K+ TC)]-K

Where K= 234.5 for copper (temp co-eff)

The aim is to find out the temperature till which the motor air gap heats up.

Ideally the result is aimed at half of the average of permitted range.

3.1.1.3 NO LOAD Test:

This is one of the most basic tests. Balanced voltages are applied to the stator terminals at the

rated frequency with rotor uncoupled from any mechanical load. Current, voltage and power

are measured at the motor input. The losses in the no-load test are all due to core-losses,

winding losses, windage and friction.

The aim is to find out the losses of the motor, using data from the readings of power, current

on input side, and speed of the motor.


20/23

20

(Figure F. Block Diagram of No-Load Test of Induction Motor)

3.1.1.4 BLOCKED ROTOR Test:

This is another basic test. The rotor is blocked to prevent rotation and balanced voltages are

applied to the stator terminals at a frequency of 25% of rated frequency at a voltage where the

rated current is achieved. Current, voltage and power are measured at motor input.

The aim is to find the breakaway torque, input current and power. In order to determine the

values at rated voltage, at least three test points of voltage versus current, watts and

sometimes torque are taken to as a high voltage as possible and then extrapolated to rated

voltage on log-lo9g graph paper to establish the desired values.

(Figure G. Block diagram of Locked Rotor Test of Induction Motor)

3.1.1.5. RUN-UP Test for Die-Cast Rotor

The test is applied to squirrel cage motors. The test is made to check the ability of the motor to

run upto its rated speed at no load. The motor upto 37kW is supplied with a reduced voltage of

of rated voltage for each direction of rotation. For motors above 37kW, the pre-mentioned

READINGS: Input current,

power and speed are

measured to calculate the

losses.

READINGS: The input current

and power are recorded

using 2-WATTMETER

method.


21/23

21

value or lesser is used, but the direction is as specified and not any random direction.

The aim is to find out the least voltage required to run the motor at rated speed.

3.1.2.1. FULL LOAD Test

Motor is initially run at full load till the constant temperature is attained in the air gap of the

motor. The above test is done simultaneously along with the temperature rise test and winding

resistance test on the same motor. So when the hot winding resistance is measured, along with

that the speed is measured using tachometer, or its variants. The speed obtained in rpm is

subtracted from the synchronous speed and difference is divided by the same to obtain slip.

The test is then repeated for 1/4th

, 1/2th

& 3/4th

load. Speed is measured for all conditions.

The aim is to calculate the efficiency , power factor cosine and slip. Slip is calculated byusing the slip formula:

The efficiency is calculated by dividing output by input. The torque measured is used to find out

the output power using the formula:

The last equation is for efficiency calculation. Weights scales are used to determine the torque.

3.1.2.2. TORQUE Test:

The rotor is locked and jammed, and run at rated voltage. Then the force exerted by the shaft is

measured by use of weight scale.

The aim is to ensure the torque developed is within the specified range.

3.1.2.3. NOISE and VIBRATION Test:

The motor while being run at various voltages is checked with a vibration meter for vibration in

the three axes of the motor so as to check if it is within permissible limits.

The aim is to make sure that the shaftdoesnt come under mechanical stress and lead to faulty

results from the motor.


22/23

22

3.1.2.4. SATURATION Test:

This test is performed to determine the windage, friction and core losses in a motor. The

saturation curve is taken with the motor running without any load. The test is usually

performed after half an hour or more after the no-load test to ensure input values have

stabilized.

At rated frequency, the line voltage on the motor is varied in steps from 125% of rated voltage

down till further voltage reduction brings about disproportionate increase in current. Voltage,

current, power and winding temperatures are recorded at each step.

To segregate the losses, power input minus the stator I2R loss is plotted versus voltage, and the

curve extended to zero voltage.

An entire graph is likewise used to determine the saturation test.


23/23

BIBLIOGRAPHY

1. A Textbook of Electrical Technology Vol 2 - B. L. Theraja.2. Three Phase Induction Motors- Specifications (5th Revision) - Bureau of IndianStandards.

3. Understanding Complete Tests Performed on Induction Motor-William R. Finley.4. Understanding Motor Temperature Rise Limits-Tom Bishop5. Bureau of Energy Efficiency Code : ELECTRIC MOTOR.

________________________

Project In-charge signature

general orientation of manufacturing unit and overview of motor testing

Documents