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.