The megger tester uses a high voltage, generally in the 1000 to 10,000 volt range to identify insulation leakage in motor coils and adjacent wiring. By following a basic setup you can test a DC motor using this high voltage testing device.
What is the acceptable megger reading for a DC motor?
A general rule-of-thumb is 10 Megohm or more.
This is how the test works: DC voltage of 500 or 1000 V is applied between the windings and the ground of the motor.
How do you test a DC motor?
Check to make sure the DC motor’s rotor can turn with no impediments. Switch the voltmeter to “Ohms“. Attach one end of the red lead wires to the DC motor and run the DC motor’s red wire to the battery. Attach the clip of the black lead wire to the DC motor and run the black motor wire to the battery.
Can you megger a motor?
A megger is used to check the insulation resistance of the electrical equipment. So we can use a megger to test a motor, generator winding, cable, etc. A megger tests a wire by applying a high voltage DC to it for a certain time period so that the insulation quality can be determined.
Why DC is used in megger?
Insulation tests, known as megger tests, are carried out using DC because AC introduces reactance, mainly capacitive (AC resistance), into the readings. The high voltage DC, usually twice the operating voltage, will break down any defective resistance in the insulation.
How many ohms does a DC motor have?
You should receive an immediate reading in ohms of approximately 10 to 100 ohms on the meter. This wide range takes into account for the carbon brush connection to the rotor windings. Rotate the motor shaft very slowly in either direction.
What is a bad megger reading?
What is a bad Megger reading? If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes.
What should be the Megger value of motor?
Insulation resistance should be approximately one megohm for each 1,000 volts of operating voltage, with a minimum value of one megohm. For example, a motor rated at 2,400 volts should have a minimum insulation resistance of 2.4 megohms.