Best answer: What is a good reading when Megging 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 is a bad Megger reading on a motor?

The measurement of insulation resistance is carried out by means of a megohmmeter – high resistance range ohmmeter.



A general rule-of-thumb is 10 Megohm or more.

Insulation resistance value Insulation level
2 Megohm or less Bad
2-5 Megohm Critical
5-10 Megohm Abnormal
10-50 Megohm Good

What does Megging a motor tell you?

Megger testing measures resistance between the phase windings of the motor under test and ground. If there is an insulation breakdown, the resistance is negatively impacted and there is a departure between phases or between one measurement and a previous one and a determination of motor health is made.

What is a bad insulation resistance reading?

The purpose of the IR test is to check for damaged insulation, this can be mechanical damage or damage by heat, (overloaded cables), readings less than 2 Mohm indicate damaged insulation, readings of 2-50 Mohm are indicative of long circuit lengths, moisture and contamination and do not indicate the insulation quality, …

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Can a megger damage a motor?

Never use a megger if the motor windings are under a vacuum. … A high voltage for too long of a time may further weaken or fail motor windings and the winding insulation could be damaged by the testing procedure.

What could cause the insulation of a motor to fail?

Around 55% of insulating failures in motors occur due to overheating. Overheating can be caused by poor power quality, or a high temperature operating environment. For every 10oc that the temperature of a motor rises, the insulation life reduced by 50%.

What is the minimum insulation resistance of 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.

How do you test a motor to see if it is bad?

Start by completely disconnecting the spindle motor from all power sources. Check each wire, including T1, T2, T3 and the ground wire. If the reading is infinite, your motor should be fine. If you get a zero reading or any continuity reading, you have either a motor problem or a cable problem.

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