What is a good megohm reading for a 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.
What should a 480 volt motor Meg?
Our minimum meg readings are 1.5 megs for 480 volt motors at 1000 volt meg. (That would be 1.5 million ohms to ground resistance.) 1.5 to 20 is fair. 20 to 50 is good.
Can you meg a motor?
Depending on the insulation class of the motor, a good motor could measure well into Tera Ohms or 1,000,000,000,000 ohms! This is an insulation test of motor windings, commonly referred to as megging, to megger, or to meg a motor. Using a megohmmeter properly will test any motor insulation.
What does a Megger reading between phases show?
On a good motor, a megger reading between phases will show a short. Another test we might do is called a Polarization Index test. It is like taking a 10 minute megger reading.
When to Megger a motor phase to phase?
I always megger a 3 phase 480V motor phase to ground, but I am wondering if meggering phase to phase can tell me something about the state of the winding insulation as well, and what kind of a reading I would be looking for considering the windings are “shorted” together.
How to test and check single phase electric motors?
Earth Continuity and Resistance Test With a multimeter, measure the resistance between motor frame (body) and earth. A good motor should read less than 0.5 ohms. Any value greater 0.5 ohms indicate trouble with the motor.
What should the Megger reading be for a good motor?
Also we use a fluke digital megger, and generally look for a reading of >500M on a good motor, but is there a general rule of thumb to use as far as how low the reading can go before a motor is actually considered bad???? Thank you for any knowledge you can share! Click to expand…