isolate the avr unit,and,then,check,the ,phases,w.r.t. earth,and,make sure,that,the generator,is in dead condition,i,e,,it is not running.
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A good number on a megger test should be around 2 megohms.
Megger tests are important because the test makes sure that your electrical insulation is safe and operating as intended. Megger tests are performed using a Meg-ohmmeter.
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It is the terminal on the megger that the ground cable connect to when testing a device to ground.
Strictly-speaking, this instrument is called a 'megohm meter', but is widely-known as a 'megger' which is the trade name of the company that manufactures the instrument.
The megger is used to find insulation resistance in any equipement. It will generate around 10kVA power to test.
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DC
If a megger test fails you have a short between the two wires or the wire to ground that you are testing. This short circuit has to be repaired before the equipment is placed back into service.
The time duration for a megger test is as long as it takes to turn the handle of the megger about five times. Voltage is generated on the first turn and if there is an insulation breakdown on the device being tested it will show instantaneously. If the megger is an electronic megger hold the generate button down for about three seconds.
To test a motor, use a megger (megohm meter) to test the insulation of the internal motor windings. Select a voltage to apply to the motor using an output from the megger that is higher that the operating voltage that the motor operates on.