Air Compressor Problem - Motor Stalls
in [Repair]
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From: GregS on 19 Mar 2010 16:19 In article <q6e7q5daqoilfbm0c7aarr47lcv3stka6k(a)4ax.com>, PlainBill47(a)yahoo.com wrote: >On Thu, 18 Mar 2010 15:58:38 -0500, "David" <someone(a)somewhere.com> >wrote: > >> >> >><PlainBill47(a)yahoo.com> wrote in message >>news:vrs4q59ejbb3o71mmtejt53subrukq6vg1(a)4ax.com... >>> On Thu, 04 Mar 2010 05:13:31 GMT, hatespam(a)invalid.invalid >>> (Sparks >>> Fergusson) wrote: >>> After reading all the posts, several things stand out. >>> The most >>> significant: There is no excessive current draw when the >>> motor stalls. >>> By all the laws of physics, that is flat out impossible. >>> There are >>> two explanations (well, three, but I'm assuming you aren't >>> making this >>> up). The first is slippage at the belt, motor pulley, or >>> rotor. >>> Given the knowledge you have exhibited, I say that can't >>> be the >>> problem; it's pretty hard to miss the fact that the motor >>> is spinning >>> but the belt is slipping. >>> >>> That leads to only one conclusion: The actual voltage to >>> the windings >>> is dropping. Possible causes are a bad thernal overload >>> protector, >>> bad run capacitor (some motors hide the starting capacitor >>> inside, >>> while the run capacitor is in a cupola on the side), or a >>> corroded >>> terminal so only one of the paired windings is used. >>> >>> All of these possible causes result in a lot of heat >>> generated at >>> one small point EXCEPT the single winding and the bad run >>> capacitor. >>> The single winding explanation is unlikely because it >>> would not >>> deteriorate gradually. That leaves the bad run capacitor. >>> >>> PlainBill >> >>There is one more possible cause: Some or all of the >>windings on the rotor that are supposed to be shorted are >>open. An induction motor works because windings on the rotor >>are shorted to induce the field needed to turn the rotor. >> >>David >> >I've never seen that, but it is definitely a possibility and would >also explain the symtoms. > >PlainBill With all the talk, I would have liked to hear the final answer to the story. Is the compressor working yet. Its been a long time. greg
From: Sparks Fergusson on 20 Mar 2010 00:34 zekfrivo(a)zekfrivolous.com (GregS) wrote: >With all the talk, I would have liked to hear the final answer to >the story. Is the compressor working yet. Its >been a long time. Um...can I phone a friend? :-) Ok, here's the status. I have disassembled the motor. I have found the following: * The windings appear to all be in good shape. I don't see anything obviously open or burned. * The bearing surfaces are all in good shape. * The contacts of the centrifugal switch are badly carbonized. I will clean those up before reassembly. * I have ordered a replacement start capacitor. I don't have a capacitor tester, but for $5, why not just replace it, eh? * The thermal overload tests OK (dead short,) but I can't easily test it under load. * The rotor showed no evidence of hitting the stator and appeared undamaged. I will clean all the connections before reassembly, although all looked fairly good already. I'll also measure to make sure I have good continuity through all the windings. Hopefully, that should get things going again. Thanks to everyone for their help and suggestions. I'll post another update when I get it all back together. Thanks!
From: PeterD on 20 Mar 2010 09:15
On Sat, 20 Mar 2010 04:34:46 GMT, hatespam(a)invalid.invalid (Sparks Fergusson) wrote: >zekfrivo(a)zekfrivolous.com (GregS) wrote: > >>With all the talk, I would have liked to hear the final answer to >>the story. Is the compressor working yet. Its >>been a long time. > >Um...can I phone a friend? :-) > >Ok, here's the status. I have disassembled the motor. I have found the >following: > >* The windings appear to all be in good shape. I don't see anything >obviously open or burned. > >* The bearing surfaces are all in good shape. > >* The contacts of the centrifugal switch are badly carbonized. I will >clean those up before reassembly. > >* I have ordered a replacement start capacitor. I don't have a >capacitor tester, but for $5, why not just replace it, eh? > >* The thermal overload tests OK (dead short,) but I can't easily test >it under load. > >* The rotor showed no evidence of hitting the stator and appeared >undamaged. > >I will clean all the connections before reassembly, although all >looked fairly good already. I'll also measure to make sure I have good >continuity through all the windings. Hopefully, that should get things >going again. Thanks to everyone for their help and suggestions. > >I'll post another update when I get it all back together. > >Thanks! Sounds good, please give more updates as you go along. Maybe it was the start switch contacts that you mention. |