This is how the test works: DC voltage of 500 or 1000 V is applied between the windings and the ground of the motor. During the measurement and immediately afterwards, some of the terminals carry dangerous voltages and MUST NOT BE TOUCHED.
What is the acceptable Megger reading for a motor?
The rule may be stated: 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.
What should a motor read to ground?
Check all three wires singly T1,T2,T3 (all three phases) to the ground wire. Readings should be infinite. If its zero or reads any continuity at all, then a problem exists with either the motor or cable .
How do you test a motor to ground?
To test your motor for short to ground, you’ll need to set the multimeter to ohms and disconnect the motor from its power source. Then inspect each wire and look for infinite readings. Alternatively, if you get a reading of 0, you might have a cable issue.
What is considered a bad megger reading?
Turn on and read the meter. Anything reading between 2 megohms and 1000 megohms is usually considered a good reading, unless other problems have been noted. Anything less than 2 megohms indicates an insulation problem.
What is a bad reading on a megger?
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 does it mean when a motor goes to ground?
When a motor is “grounded“, the winding is shorted either to the laminated core or to the motor’s frame. The problem is usually found in a slot, where the slot insulation has broken down. Water is the most common cause of a grounded winding. A solid ground requires rewinding or replacing the motor.
How do I know if my electric motor is bad?
With a multimeter set to low ohms (usually 200), test between each winding terminal and the metal casing of the motor. If there is any reading on any of these then the motor is bad, do not use it. You may find that when it runs ungrounded that the casing becomes live at up to supply voltage.
How do you calculate the resistance of a motor?
You may calculate the resistance of your motor by measuring the consumed current and applied voltage. For any given resistance (in the motors it is basically the resistance of the coil) this formula explains that the current can be controlled by applied voltage.
What is the minimum insulation resistance of a motor?
It is recommended that the insulation resistance of the motor should at least be 1 MΩ1）, and for the voltage to ground of 200 V, I0r should be 200 μA or below.