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Message No. 14282, Started by rorschach on 07/15/04
 estimating HP of electric motor based on current draw. Guys, I got an electric motor in my shop that I'm trying to figure out what it is. It would appear to be a 240/480 3 phase motor, NEMA 215T frame. The nameplate is long gone and I have no history on the motor at all, I don't know what it came off of, where it has been, how it has been abused, nothing. The PLAN is to ohm the windings out and make sure nothing is open or shorted, hook it up and put a tach on it to determine the speed, and take current readings on each leg to verify that all three phases are pulling equal amounts of current. Now my question is this, can I estimate HP based on the current draw of the motor in a no-load state? or is there another way?
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Follow-up Messages (14)
 sadly, at this point the "internal temperatures" are pretty dang high, conn... No. 14345, Posted by rorschach on 07/27/04, 20:32 PST. OK, you've had lots of "answers" answering nothing. Regretfully, no load ... No. 14344, Posted by gbynum on 07/27/04, 20:14 PST. Don't you just love it when a plan comes together? No. 14301, Posted by rorschach on 07/20/04, 05:48 PST. Well that development makes things a little easier. All you need now is an... No. 14298, Posted by acroduster1 on 07/19/04, 16:15 PST. Acro, sadly, this method requires two things that are not readily available... No. 14296, Posted by rorschach on 07/19/04, 05:30 PST. I stand by my direct method. You need a heavy chunk of iron that's symmetr... No. 14293, Posted by acroduster1 on 07/16/04, 11:18 PST. No, it doesn't. That is the whole point of the post. the nameplate is long ... No. 14292, Posted by rorschach on 07/16/04, 05:35 PST. Doesn't this thing have any nameplate info? No. 14291, Posted by rolschwarz on 07/16/04, 04:44 PST. That is as I suspected, but rigging up a dyno test jig is outside the time ... No. 14290, Posted by rorschach on 07/16/04, 04:35 PST. In any case, I doubt running unloaded is any indication of the motor's capa... No. 14289, Posted by rolschwarz on 07/15/04, 20:02 PST. I think the no load current is more of an indication of the quality of the ... No. 14288, Posted by b1ueshift on 07/15/04, 19:41 PST. rolschwarz, maybe I wasn't clear, I knew I could calculate the power going ... No. 14287, Posted by rorschach on 07/15/04, 17:56 PST. OHM's LAW! for 3-phase, power = [voltage] x [current] x [sqrt(3)] Thi... No. 14285, Posted by rolschwarz on 07/15/04, 10:57 PST. The most direct way I can think of would be to attach a flywheel with a kno... No. 14283, Posted by acroduster1 on 07/15/04, 10:00 PST.