Air Compressor Problem - Motor Stalls
in [Repair]
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From: PeterD on 6 Mar 2010 20:02 On Sat, 06 Mar 2010 09:09:57 -0500, Alan Douglas <alan_douglasat(a)verizon.net> wrote: >>>Assuming it's a 120V/240V motor connected for 120, can you check to >>>see if both run windings are actually connected? Perhaps a nut is >>>working loose on the terminal plate inside the motor. >> >>Hmm, you might have something, there! This motor is probably 15+ years >>old, and has never had anything done to it. Could corrosion and/or >>loose connections account for the lack of power? I can certainly try >>cleaning and tightening anything I can get to. > >None of the other suggestions I've read, fit the symptoms. First >would be low voltage to the motor under load, but you've already >checked that. The starting capacitor is out of the circuit when the >motor is up to speed. There's nothing left in circuit but the two run >windings, wired in parallel. > >Alan And all those replies ignore the fact the unloader is operating (at a wrong, low pressure) which certainly doesn't point an evil finger at the motor at all...
From: Alan Douglas on 7 Mar 2010 08:00 >And all those replies ignore the fact the unloader is operating (at a >wrong, low pressure) which certainly doesn't point an evil finger at >the motor at all... > Hmmm, yes, I think that wasn't in the original post so I missed it. That would account for gradual deterioration too. Alan
From: Andy on 7 Mar 2010 08:36 On Mar 5, 5:44 pm, hates...(a)invalid.invalid (Sparks Fergusson) wrote: > Meat Plow wrote: > >What kind of motor is this? I didn't see you mention that. A 1/3 horse > >induction motor should not draw 1.5 amps with no load. > > It's some sort of GE induction motor. I have the model number, but I > can't find anything about it on the GE website or Google. > > What sort of problems would high no-load amp draw suggest? Motors don't generally fade away; they usually burn up. I don't see how a motor would become weaker, especially an induction motor. There are no parts to wear out other than the stator winding, which doesn't fail gracefully. If it fails there will be an unmistakable stinky cloud of white smoke. You probably have a thermal overload on the motor, and that's what trips when the motor appears to stall. Based on what I have read here, this is what I would check first. 1. Check the thermal overload. Remove it from the circuit, and find a way to load it up with a known current until it trips. It should trip after some time at 1.15 times the nameplate current. It generally takes a long time, like several minutes, at that current. This will be around 2x the motor FLA. If the overload trips before you reach 1.15x, then the overload is bad. I hope this helps. 2.
From: malua mada! on 7 Mar 2010 12:20 On Mar 4, 11:35 am, hates...(a)invalid.invalid (Sparks Fergusson) wrote: > Bennett Price <bjpr...(a)cal.berkeley.edu> wrote: > >> Thanks! > >Do you know for sure that your gauge is correct? Maybe the compressor > >and pressure switch are fine. > > Well, it's been working for a long time, but over the past few months > has been exhibiting the stalling issue. > > I guess the guage could be wrong, but I kind of know what 120psi > "feels like" and it's not getting up to what it used to, either by the > guage or by feel. I'd verify the gauge anyway.
From: Sparks Fergusson on 7 Mar 2010 13:16
Alan Douglas <alan_douglasat(a)verizon.net> wrote: >>And all those replies ignore the fact the unloader is operating (at a >>wrong, low pressure) which certainly doesn't point an evil finger at >>the motor at all... >> > >Hmmm, yes, I think that wasn't in the original post so I missed it. >That would account for gradual deterioration too. The unloader is functioning properly, as far as I can tell. It's a combination check valve/unloader. So, when the check valve is open, it allows the high pressure air into the tank. When the check valve closes, it vents the pump side to atmosphere. So, then the motor stalls, the check valve closes and the unloader part releases the pressure. When the presssure falls sufficiently, the motor restarts and the cycle continues. |