Basic Megger Use

[Stanley36]

Good day all.

I was wondering how you actually go about using a megger to test the quality of insulation of a motor, I understand why you would do the test. If you were to test it at the motor starter and you have isolated the circuit would you need to disconnect the wires going to the motor from the contactor or overload first?

Also would you need to disconnect the motor links (on a 6 terminal DOL motor) to carry out phase to phase resistance tests.

Any other Noddy information about this would be much appreciated .

Many thanks

 

[telectrix]

if it's the motor you're testing, then isolate, diss feed at motor, remove links, then test phase-phase and each phase to E.

 

[PEG]

You would be wise to know the type and layout of the particular motor,to eliminate false readings due to suppressors,capacitors,thermal and centrifugal switches,etc.

You may get a result which shows an issue,but whether that is a failed winding,or just an chaffed link wire,could be the difference between an expensive strip-out...or a simple hours' repair.

Fully understanding the internal connections and function,can allow you to individualize your tests,for example,knowing where and how a centrifugal switch is wired,will enable three tests to be applied to that item,all be it with a little help, on one :blush5: