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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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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. |
#2
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Testing a pm dc motor
On Friday, 6 March 2015 07:37:11 UTC, Paul Conners wrote:
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. That's the problem trying to measure motors. If it's ok it's always going to read low ohms, but maybe it should read 3.2ohms (eg) and has shorted turns (eg), how would you ever know? If on the other hand it measured K ohms it would be faulty. An insulation test from windings to armature would be more appropriate. If that's ok give it a spin (I mean apply power). |
#3
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
Paul Conners prodded the keyboard with:
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. 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 ! -- Best Regards: Baron. |
#4
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
On Thu, 5 Mar 2015 23:37:00 -0800, Paul Conners
wrote: 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. Can you spin the shaft and see how much voltage it generates? Ohm it to ground, too. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com |
#5
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
On Thu, 5 Mar 2015 23:37:00 -0800, Paul Conners
wrote: 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. 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. |
#6
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
On Thu, 5 Mar 2015, Paul Conners wrote:
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. 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 |
#7
Posted to sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
On Fri, 06 Mar 2015 14:50:23 -0500, Michael Black wrote:
On Thu, 5 Mar 2015, Paul Conners wrote: 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. 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 Not likely that his info is pertinent for 180 volt motors of that size, when his info is for miniature DC motors. The motor types likely differ as well. |
#8
Posted to sci.electronics.repair
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Testing a pm dc motor
"Allan" wrote in message ... On Friday, 6 March 2015 07:37:11 UTC, Paul Conners wrote: 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. That's the problem trying to measure motors. If it's ok it's always going to read low ohms, but maybe it should read 3.2ohms (eg) and has shorted turns (eg), how would you ever know? If on the other hand it measured K ohms it would be faulty. An insulation test from windings to armature would be more appropriate. If that's ok give it a spin (I mean apply power). +++++++++++++++++++++++++++++++++= The resistance sounds too low. Can you rotate the armature and re measure at a different point? A 180 volt DC 1 hp motor should require around 5 amps or less at full load. I would expect somewhere around 40-50 ohms when running under full load. But as others have said, you want to check from the armature to frame ground. Any resistance might be bad. Regards |
#9
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
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#10
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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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. 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. |
#11
Posted to alt.engineering.electrical,sci.electronics.design,sci.electronics.misc,sci.electronics.repair
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Testing a pm dc motor
"Paul Conners" wrote in message ... 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. 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. 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. |
#12
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Testing a pm dc motor
On Sun, 08 Mar 2015 22:20:50 -0800, Paul Conners wrote:
Motor out of the equipment. ... Now you can wind a bit of string round the shaft and pull it to see if it generates any DC output! Of course if there's another motor you can link it to with a bit of hose or similar (as a flexible coupling; no water!), so much the better. Mike. |
#13
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Testing a pm dc motor
Now you can wind a bit of string round the shaft and pull it to see if it
generates any DC output! Of course if there's another motor you can link it to with a bit of hose or similar (as a flexible coupling; no water!), so much the better. Mike. Will check or DC output. Ah, now that you mention it, this equipment experienced a flood which probably submerged the motor fully for 48 hours (late last year). Not operated when submerged (!) but probably some moisture still in it when first operated after the flood. (2 other equipment suffered damage: a VFD and a contactor burnt out.) Thanks. |
#14
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Testing a pm dc motor
Will check or DC output.
Will check *for* DC output... |
#15
Posted to sci.electronics.repair
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Testing a pm dc motor
"Paul Conners" wrote in message ... Now you can wind a bit of string round the shaft and pull it to see if it generates any DC output! Of course if there's another motor you can link it to with a bit of hose or similar (as a flexible coupling; no water!), so much the better. Mike. Will check or DC output. Ah, now that you mention it, this equipment experienced a flood which probably submerged the motor fully for 48 hours (late last year). Not operated when submerged (!) but probably some moisture still in it when first operated after the flood. (2 other equipment suffered damage: a VFD and a contactor burnt out.) Thanks. That is something that should have been noted up front. You have a bad motor. |
#16
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Testing a pm dc motor
That is something that should have been noted up front. You have a bad motor.
Something killed the motor but didn't affect the measurements discussed here? What could that be? |
#17
Posted to sci.electronics.repair
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Testing a pm dc motor
That is something that should have been noted up front. You have a bad motor.
Something killed the motor but didn't affect the measurements discussed here? What could that be? |
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