Testing of H.T. motor

Hello pranayshah,

Off-Line:

1. Insulation test, using a 1,000 Volt Megger or Insulation tester - dependent on motor size, for at least a minute, between each winding and the case or earth.
2. Insulation test, using a 1,000 Volt Megger or Insulation tester - between windings, for at least a minute, between each winding and the other two.
3. Winding resistance test: Each winding, using a low-ohms or Kelvin Bridge Test instrument.

On-Line:

1. Graphically record the current/time curve, and make a permanent record - Polaroid type film or Digital camera adaptor is good for that.
   
2. Record motor no-loadspeed
3. Record motor full-loadspeed

Mechanical:

1. Check bearings, use vibration meter, or stethoscope to ascertain a bearing due to fail.
2. Regrease bearings, ensure you do not overfill, because that causes grease turbulence, and overheating of the bearing.
3. Check couplings
4. Check mounting plates, slides, bolts for proper working of all.

Records:

1. Ensure all plant and equipment has a "Plant Number", on a permanent plate attached in a visible place on the motor/gearbox/machine part etc.
   
2. Record all readings against that "Plant Number".
3. Ensure Serial Numbers are properly checked against earlier records.
4. Write up all tests,check for discrepancies, from the series for the item, taken and recorded before.

Go home, put your feet up, have a nice cup of tea, you earned one....

Everything is listed and described perfectly except that Megger should be 2500V = 2.5 kV

Thank you southern123,

In my day we had only 3 Test Voltages for Meggers, all of which were the hand-cranked models:

• 500 VDC - Metal case version - for everyday Insulation Tests
  
• 1,000 VDC - Wooden box Lab version
  
• 5,000 VDC - Wooden box Lab version

500 VDC was used for wiring & machines up to 1.1kV - 1 minute each Test.

1,000 VDC for wiring & machines up to 3.3kV - 1 minute each Test.

5,000 VDC for busbars & machines up to 13.6kV - 5 minutes each Test - and that after over 15 minutes per winding to charge up and meter to remain steady, for Powerhouse Alternator winding Tests.

We used to take it in turn, as the wrists of the cranker would usually weaken, after 20 minutes per winding.

It was easier for me, as I grew up on a farm where we hand-milked cows, and another of my duties was to use the hand-cranked separator, so I could wind a Megger crank without weakening.

For higher Test Voltages we used the Hipot High Voltage Testing Apparatus, up to 80kVDC.

Higher that that, we used special transformer/rectifier units, with Variac Input, up to 750kVDC Test Voltage.

Perhaps over the years, or in your jurisdiction, Testing Standards have changed.

There was no 2,500 Volt Megger, in my day.

With the modern Test Instruments, Testing is far simpler, that's for sure, set up, press a button, wait for result.

Cheers....

If it is at manufacturers works then all routine test as per IEC or BS or if in Indaia as per IS to be carried out.At site normally IR value no load running ,Direction of rotation (Some HT motors have fans which are unidirectional)are important.

Please refer to I.S 325 it has specified routine test to be carried out for electric Motors.You need to have test lab for carrying out such test or approach motor mfr. in your area who is supposed to have such testing equipments. It consists of tests such as insulation test , H.V test, Load test with Dynomometer I.S has given format for conduction such tests. Suresh. Sharma

Dynamometr for 3.3 kV motor?

It should have more than 100 kW rating power