Is it my motor or Run / Start capacitor ?

I have a 5 hp 230 V AC motor on a 20 gal tank /air compressor.

When given to me by the past owner, he said it needs a new electric motor. Since I do not have a 240 line outlet in my home, as yet anyway. I plugged this 230 v AC motor into a 120 V ac outlet, just to see what it will do. Well what I got was the motor did indeed spin very fast, with out it being belted to drive the air compressor pump and all looked just fine, with out tripping the circuit breaker, then I belted it back to the compressor pump and started it up again, all seemd fine for about 2 / 3 min. then noticed the compressor slowing down a little at a time with every revolution it made, then it tripped the breaker. So even though the correct voltage was not supplied. Can my problem be a Run capacitor or the start capacitor , how do I test these two capacitors .Since the motor did indeed spin with out a load I hope it is just one of the two capacitors that is prcblem only. If it truly is the motor , does it pay to have it fixed (re-wound) or get a new one. this one has a pivot base. Any help appreciated.

Reply to
Mario G.
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On Sat, 26 Jun 2004 20:00:21 -0700, Mario G. put forth the notion that...

It was probably fine initially, but when you ran it at half its rated voltage and watched it slowly grind to a halt, you probably burned up the windings. Less voltage = more current = more heat = goodbye motor.

Reply to
Checkmate

The 240 volt motor is not going to be able to supply much torque on 120 volts. As the pump builds up pressure, the more load on the motor and it stalls. have the caps checked and feed it the correct voltage! John

Reply to
jriegle

Wrong! Here's another guy who thinks everything follows Ohm's law.

Most likely, when his motor, due to it being overwhelmed by the load and not being provided with the proper supply, stalled. This caused the impedance of the windings to go down very low. The motor windings then will draw lots of current and trip the breaker since it's basically a short-circuit at that point. Unless he left the motor in that condition for a long time or repeated the act, I doubt very much it would burn out the windings.

You should be able to visually see any such severe winding damage through the vent holes - and smell it for that matter. Check the caps and the CS switch before condemning the windings.

Reply to
Paul

Perhaps you can pickup the 240 volts from the main panel and rerun your test with the correct supply. If you don't know how to do that call an electrician. Odds are the windings are good if they don't smell bad from their trip to "overcurrent land"...You should be able to ring them out and get a reading of a couple of ohms or so, though, I don't know what the motor rating is and what "exactly" to expect. It would apparent, at least, that the windings were toast if they were open or high resistance and a reading of a fraction of an ohm might imply a short....There is no exactness here....just a quick test method. As far as testing the capacitors....I don't know how well you are equipped so your best bet would be to swap them out with a couple from surplus or just buy new ones. Sometimes surplus caps can be bad too....Try

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and type motor capacitor at the prompt and match the voltage and capacitance ratings. I bet you can find a couple for 5 or 6 bucks each. Good luck with your new toy....Ross

Reply to
Ross Mac

On Sun, 27 Jun 2004 14:27:20 GMT, Paul put forth the notion that...

...which is exactly what I just said.

Reply to
Checkmate

How does his statement "Less voltage = more current = more heat = goodbye motor." indicate he thinks everything follows Ohm's law?

Reply to
ehsjr

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