Tom Bishop, P.E. Forum Moderator 17 Posts
Re: How do you correctly test the motor after repairing or overhauling?22 July 2009 at 1:29pm
There are reliable acceptance tests that should be part of a company's repair specification. The simplest is to document the no-load amperage (NLA) of the electric motor operating at rated voltage. A rule of thumb is that most motors should draw approximately 1/3 of the rated full load current (FLA). There are exceptions -- motors that have very low running speeds, and 2-pole motors (3600 rpm on 60 Hz systems, or 3000 rpm on 50 Hz). Since most electric motors are 4-poles (1800 rpm at 60 Hz, or 1500 rpm at 50 Hz), this quick check offers a reasonable confirmation that nothing is drastically wrong.
More stringent tests cost more, but are justifiable for critical applications and locations where installation is difficult. Some service centers have a dynamometer, and can simulate the actual load conditions.
How do you correctly test the motor after repairing or overhauling? Is there any fixed procedure for taking measurement value? When testing without load, everything is OK. But when I put the load/taking online with rotating equipment (example: pump), it becomes trip overload. Why did this happen?
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