We use a "megger" or "meg out" electrical wiring and equipment to see if it is shorted to ground in any way.
The megger uses much higher voltages to check resistance than a normal Volt-ohm meter.
Ideally, you want infinity resistance but I've installed 460 volt motors with 750 meg ohms resistance to ground and had no problem.
On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing.
Working voltages up to 240 volts should use the 300 range.
Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range.
As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.
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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
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.
megger are available in ac &dc
A megger device produces hundreds of volts in order to provide resistance values in the order of hundreds to thousands of megohm. The DC volts produced by a megger can and will harm humans.
Using a megger you check from either positive or nuetral to ground. The megger should read open (usually OL). It doesnt matter which connection you choose as long as one is ground. If the megger shows anything other than open the windings are bad.
By means of Megger Vidar or Vanguad VBT Series
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.
yes
It is the terminal on the megger that the ground cable connect to when testing a device to ground.
The megger is used to find insulation resistance in any equipement. It will generate around 10kVA power to test.
infinity
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.
The typical test equipment for this is a megger. The megger is connected to two conductors at a time to test the insulation between the two.
The Megger MFT 1552 is a combined electrical circuit tester which includes test features for Insulation testing, Earth loop impedance tests, RCD Testing and Continuity testing. It comes supplies with full Calibration Certificate.