Testing a pm dc motor

180 vdc, 1 hp, pm motor.
with dmm what should be the first tests? motor is in a difficult location to examine visually so i'd like to start with electrical evaluation.
it measures 1.2 ohms between the 2 armature leads.
thanks.
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Paul Conners prodded the keyboard with:

If it isn't turning, then check that it has actually got voltage applied to it. You have to consider both the motor and controller !
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On Thu, 5 Mar 2015 23:37:00 -0800, Paul Conners

Can you spin the shaft and see how much voltage it generates?
Ohm it to ground, too.
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John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
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Perhaps if we knew in what way the motor was acting up we could better suggest a course of diagnostics. Like does it make any noise, does it turn slowly or not at all, is it popping the breaker, etc.
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On Thu, 5 Mar 2015, Paul Conners wrote:

The faq, http://www.repairfaq.org has some words about the testing of DC motors, though I'm not sure where.
I think Sam did write something about checking CD player motors, and I'm sure he gave tips on figuring out whether it was good or bad.
Michael
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snipped-for-privacy@gUSmail.com says...

those kind of motors tend to have mechanical issues..
Bearings is common which causes a tight turning shaft and may cause the armature to move around on the brushes.
Also, a bearing could be completely blown out and the motor will still make attempts to turn if the brushes are still making contact.
Another issue is the PM's some times fall off, lose their bond to the outer shell and come in contact with the rotor.
Then you get the occasion of weak magnets due from too many hours of running hot, which causes more Arm current and lack of torque but with higher RPM abilities.
Now and then, the armature windings may short to each other but not to ground. Most of the time megger meters will not reveal this defect but usually signs of over heated wire is a good bet.
Also, if you manually spin the motor it can act as a generator..
Disconnect the leads to the motor and see if it turns freely, if so then you most likely do not have mechanical issue.. Now connect the ARM leads together from the motor and see if you get heavy drag (Dynamic Braking) due to energy being generated and short via the A1 and A2 leads. If you do get a got drag on it, chances are it's of.
When checking the brushes via the DMM, you need to turn the motor very slowly so that you can account for all the armature bars, you may have a set of scorched brushes.
Jamie
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Motor out of the equipment. Turning armature slowly, the resistance reading between the armature leads varies from a low of 2.3 to high of 10; most are around 6-7 ohms. Resistance of each lead to motor frame is minimum 150K up to over 1 meg.
What's normal for such a motor?
Thanks.
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Open it up and see if it has discolored windings. Does it smell burned? It would seem to me that the resistance readings indicate compromised winding insulation.
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