MANUFACTURING OF LARGE ELECTRICAL MACHINE

AT BHEL BHOPAL

Presented by: Vaibhav SinghRoll no. 1301421101

Branch: EN‘13’S.R.M.S COLLEGE OF ENGINEERING AND TECHNOLOGY

Manufacturing of large electrical machine

• Foundry• Fabrication • Machining • Press• Coil insulation • Winding• Assembly• Testing

Foundry shop• Stator frame• Bay 1&2 non ferrous foundry• Bay 3 ferrous foundry• process:-

1. Pattern making2. Molding3. Metal melting4. Pouring5. Fettling

a) Knock outb) Shot blastc) Heat treatment

i. Annealingii. Normalizingiii. Stress removing

d) Rough machining

Pattern making

1. Thermacol(high density)2. Wooden(high density, laminated

permali wood)3. Aluminum

MouldingSilica sand+ phenol formaldehyde(20% of sand)+

cromide i.e. high temperature catalyst (15% of phenol)

Electric arc furnace(1500kva cost-9000rs/h)

Metal meltingInduction furnace

On load No load

Voltage (V) 1300 622

Current(A) 349.7

Power(Kw) 1010 203

Frequency(Hz) 229 226

pouring

fettling

• Fettling is the process which involves the removal of the cores, gates, runner, riser etc. all these are done by these process

a. Knock outb. Shot blastc. Heat treatment

Shot blast- • In this process we put the job

into a chamber and blasting the iron particle on the job for making the surface smooth and clear.

Heat treatmentAnnealing Normalizing Stress relieving

Soaking temperature

920±15˚C 920±15˚C 550-580˚C

Soaking time 4hrs. minimum (1inch/hr.)

4hrs. minimum (1inch/hr.)

4hrs. Minimum (1inch/hr.)

Cooling Inside the furnace

Outside the furnace

Inside the furnace

Fabrication shopshaft

fabrication

LEM

Rod and rib assembly

corner welding

summerge arc welding

DP test

stress relieving

shot blast

MPI test

paint

IMM

Rod and rib assembly

summerge arc welding

corner welding

DP TEST

Stress relieving

shot blast

MPI test

paint

Shaft fabrication

• LEM shaft

• IMM shaft

High tensile mild steel

Corner welding

Manually done to fix the rib on the rod. In v shaped

Submerged arc welding

• This welding is to provide the mechanical strength to joint of rib and rod. Firstly the shaft have to preheated up to 150˚C preheating temperature is depend on the type of welding. Aluminum, Pb(led), CaO is used as flux for the welding and for filling material mild steel coated with copper. Copper is used because it is a good conductor of heat and it’s also a rust proof material. This welding is done by the semi automatic machine.

Die penetration test:-

• The die penetration (DP) test is perform to found the defect of welding or forging on the surface of material. For this spread a die (liquid) on the surface of material and left it 15min on the joint of welding and for the forging left it on the surface for an hour because the hole or crack in case of forging is very small. After the time interval if there is any hole or crack is on the surface it make a red spot at defect. After punching at the defected part weld it again and repeat this process again.

• Stress remover • Shot blast:-In this process we put the job into a

chamber and blasting the iron practical on the job for making the smooth and clear.

• Magnetic particle inspection:- Magnetic particle inspection (MPI) is done for the inspection inside the surface up to 6mm. In MPI spread a liquid on the surface of the job and used two electrodes to make high current flow to the surface of the job. It make the black spot where the defect is. The current flow in this test is approx 250A. The liquid is made up of very small particle of iron and soap and water.

Paint :-

• At last the shaft of LEM paint and dispatch from this shop to other place. Painting is done for make the shaft rust proof and for look good.

FABRICATION OF THE STATOR FRAME

• In this section LEM’s &IMM’s stator frame is fabricate but some stator frame of IMM is made up in forging.

• The main parts of stator frame-• Rib • Rapper (cast iron sheet)• End stand (cast iron rod)• Buffel (pipe is inserted in the stator frame) this is

used for the cooling purpose of the motor but it is used only in IMM motor. Or it is not present in the stator frame of LEM.

MACHINE SHOP

• Machining is done to get the proper dimension of stator and rotor part. For this they use different machine & process

• Machines- • Lathe machine• Drill machine• Boring (horizontal and vertical)• Milling• Grinding

PRESS SHOP

• The core of LEM and IMM is made up of different sheets of CRNGO steel. In this shop the core of stator and rotor is made by stacking of different sheets all these are electrically insulated from each other to reduce the eddy current loss. The eddy current loss is depends on the thickness of the sheets.

• Thickness of individual sheet is approximate • 0.65mm for normal motor• 0.50mm for traction motor• 0.35mm for transformer

• In B.H.E.L Bhopal the core is made up in the range of 550mm to 2600mm internal diameter.

• For a small machine core diameter range from 550mm to 1250mm the sheets are in roll form which cuts in the required shape and size.

• For a large machine core diameter range from 1350mm to 2650mm the sheets are in segment form it’s directly sends to blanking section.

• The core is prepared by different process which are-Blanking

Notching (pressing)Blur removing

VarnishSpacer Stacking

Blanking:-

• Blanking is done only in stator core of machine after this the notching process will done

NOTCHING(PRESSING)

• In notching process they make slots and teeth in the sheet. In the stator core slots and teeth are inward direction & in rotor core the slots are in outward direction. There is manually and automatic (CNC) machine are there. 12.5 ton impact machine is the smallest manually operated notching machine.

• Different capacity of machine are installed in B.H.E.L Bhopal-

• 1. 16 ton 6 stations CNC machine• 2. 8 ton 8 stations CNC machine• 3. 16 ton segment manually machine (for large rotor

& stator)• 4. 250 ton segment • 5. 1600 ton segment (biggest machine in B.H.E.L

Bhopal this machine is able to make a slots on 8mm sheet)

• The tools of machine are Dia & punch, in nature these tools are very brittle and the material of the tool is high carbon steel.

Blur removing- Blur remover process is not compulsory this

is only done if blur is present in the sheet. If the blur is present sheets it can deform the shape of core or it remove to prevent the core form uneven height so the blur removing process is compulsory.

Varnishing :- Varnishing is done for insulation between

the sheets and is also provide the coating to the sheet for making it rust proof.

spacer It is clear by name that spacer is thing which is use to make a space between two or more than two things. In this shop they use a thin rectangular shape sheet which welded on the sheet of core vertically. Projection welding is used weld the spacer on plate.

Stacking

Stack means to arrange a number of things on the top of one another in a good order. So in stacking they arrange the sheets and make the core of rotor or stator segment, for the small machine core is made in this shop but for large machine it’s made in the LEM section. After stacking the consolidation is also important for consolidation they add a end ring, weld it and add a nut bolt to fix it. Spot welding is used to weld the few sheets together.

CIM shop

• 1. Conductor cutting and insulation removing:- This is the first step of coil making

they use a DGL (double glass laminated) copper to make the coil of hydro generator in this conductor copper is 99.99% pure and 0.01% is foreign material. Insulation is removed from the both end of conductor to connect the conductor to other conductor and make a coil.

• 2. Transposition:-In transposition they rotate the

conductor 360 to make the uniform electric flux only active part of winding is rotated. To make the conductor bars insulated from each insulations are provided by Epoxy treated glass cloth separator and gross over piece (nomex composite).

• 3. Stack consolidation/pressing:-In this process puts a conductor heated at temperature 160±10˚C for 1 hour after this cooling below 80˚C. For the heating purpose they use a water steam only the DGL side heated. After it again used some material for proper insulation materials are Mica paper putty & Propylene tape.

• 4. Bar forming:- To obtain the shape of coils/bars as per drawing different bench are used or because all the machine have different number of slots, number of poles, coil span etc. so all the bars are skewed at different angle and at different length so different bench are use to skewed the conductors.

Testing

• After all these process for coil making insulation providing testing is compulsory for check the insulation is proper or not for this they take two tests-i. Inturn test ii. High voltage test

WINDING

• Winding of a rotor and the stator are depends upon the design consideration of the machine or it depends on the work of the machine for an example if we want a machine for power generation we have to design a synchronous generation, which runs at constant speed but variable torque the speed of rotor is depends on the pole of generator and frequency of generated voltage.

In B.H.E.L Bhopal different rating of machine are made the range of that machines are

1. Squirrel cage induction motorsPower- 150Kw to 21Mw3.3Kv to 15KvDOL and VED fed2 pole to 36 pole3. Synchronous 500Kw to 25Mw3.3Kv to 15KvDOL and VED fed4pole to 30 pole

2.Slip ring induction motor150Kw to 10Mw3.3Kv to 15KvDOL and VED fed4 pole to 14 pole

4. Special design motors150Kw to 21Mw3.3Kv to 15Kv2pole to 36pole

So the winding are depend on the purpose and rating of the machine. Simplex winding are mainly two types

1. Closed winding 2. Open winding 1. Closed winding Closed winding is only used in D.C. machine and A.C.

commutator machine this winding is of two type first one is lap winding and the second one wave winding.

From any point of a winding after traversing the whole winding we reach at that point from we started means it’s a closed winding.

2. Open winding Open winding is used in A.C.

machine. There are two type of open winding –1 Lap winding 2 Wave winding• Lap winding is used for low voltage and high current

because in lap winding parallel path is equal to the number of pole.

• The wave winding is for the high voltage low current because in wave winding the number of parallel path is equal to two.

Assembly • For the assembly of the machine we take some step by step

process- • 1. End shield preparation – for sleeve bearing IBC mounty is

done.• For antifriction bearing, bearing housing is assemble on end

shield• 2. Air guide fixing on end shields or frame.• 3. Stator segment assemble and after this MTB (main

terminal box), NTB (neutral terminal box), RTD (resistance temperature detector), heater, heating box C.T. (current transformer), C.T. box are connected.

• 4. Air-inlet housing marking with stator to fix their position. After this they send it to the machine shop for drilling.

• 5. Rotor threading i.e. to put the rotor into stator of machine.

• 6. Both end shield assemble to the stator

• 7. Bearing box up assembly• 8. External fan and air inlet housing assembly, silencer

assembly all these are assemble to the stator.• After this motor sends to testing area and if all the test results

are under prescribe limit then motor send to the shipping area-

• In this few steps are also taken• 1. Rating plate mono and GLL name plate fitted on the stator.• 2. Shaft polish & key fitting is done.• 3. Motor painting is done.• 4. Silver paint is painted at earthed place. To increase the

conductivity of that part and check earthing symbols are at appropriate place.

• 5. Motor sends for packing after Q.C (quality control) inspection with green tag.

Finally the LEM will look like this

IMM will look like this