HELP, Electric Motor Guru's

[JimR]

HELP, Electric Motor Guru\'s

Today my 6.5 HP 220 volt 1PH. air compressor quit on me. The compressor tried to start up and blew the breaker. So I reset it and it blew again. The motor just made a loud hummmmm. I pulled the belt and the motor spins freely. It still just hums and blows the circuit breaker. It is a capaciter start motor with two capacitors mounted on top under a cover. One is white and the other is black. Both have 3 wires attached to them. Can anyone here tell me how to check these or the motor? TIA

 

[SPIKER]

Re: HELP, Electric Motor Guru\'s

Jim:

you more than likely do not have ability to check the caps but you MAY be able to check the motor it's slef. if you have a good meter (DOM or ANALOG will work)

measure all of the leads from lead to lead and to ground on the leads going INTo and OUT OF the motor. be carefull as some caps may hold a charge for a LONG TIME. three are meters made to check capasitors but they are rather expensive. some morot repair stores may have one and may check them for you right there call ahead and ask.


one other way to check is to remove the belt and see if the motor will run un-loaded by the compressor. also check to make sure the compressor motor still turns.

MarkM

 

[JimR]

Re: HELP, Electric Motor Guru\'s

Thanks for the info. The motor does not run unloaded. It just humms along and blows the breaker.

 

[v8dave]

Re: HELP, Electric Motor Guru\'s

As Spiker suggests check to see if the compressor turns freely. If it does then try replacing the capacitors (caps). They do go bad, usually cook out from the heat.

Surplus Center has both motor start and motor run caps for a cheap enough price to check by substitution. The microfarads (MFD) size is the easiest way for you to tell the difference between MS and MR caps. You most likely have motor start, MS, caps.

Check the caps that are on the motor now. If you can't get the exact voltage and MDF, you can safely go up in voltage, do not go down in voltage. You can go up in MFD, but try not to go over by more than ~50%. You can go under in MFD by 10% if necessary.

 

[JerryG]

Re: HELP, Electric Motor Guru\'s

<font color="blue">The microfarads (MFD) size is the easiest way for you to tell the difference between MS and MR caps. </font>
Which one is usually the largest?

 

[Junkman]

Re: HELP, Electric Motor Guru\'s

I can't offer any more than what has already been offered, but I can tell you that if you need to take it off and have it repaired, there is a company on Rt. 20 in Auburn, just past the Fair Plaza on the East bound side of the road that does motor repairs. I have used them in the past, but not recently, so I don't know how there prices are now. In the past, they were quite inexpensive... Junk..

Brown Alfred L Assoc Inc
Route 20
Auburn, MA 01501
Phone: (508) 754-5682

 

[TBAR]

Re: HELP, Electric Motor Guru\'s

Sounds like it is single phasing. Have you checked the voltage on both 110volt legs going to the motor???


TBAR

 

[_RaT_]

Re: HELP, Electric Motor Guru\'s

I have sometimes taken the belt off the motor, tried to see if it would start with no load. I have also been able to "push" start it by hand rotation with no load. If it will start and run fine under these situations, I usually find replacing a capacitor or two if that is the case to work.

 

[johnbilt]

Re: HELP, Electric Motor Guru\'s

Hi

An electric motor shop will have everything to check it out right. No guesses.

The humming indicates current is flowing to the motor and the breaker certainly verifies that. You could also have a shorted winding.

A cap can be checked by removing one lead and shorting to the other through a resistor. Don't short it directly as this creates a large energy dissipation and is harmful to the windings in the cap. After discharging, Put an ohm meter across the cap and verify it is not shorted. The resistance should rise steadily and then stabilize, indicating a charging cap voltage at the meter.

John

 

[v8dave]

Re: HELP, Electric Motor Guru\'s

Usually motor start caps are the larger capacity, 20 or so microfarads and on up. Physical size is not the measure.

But, I just looked at Surplus Center's caps and I see that is not the always the case. The motor run caps they have are in a more durable, metal, case than motor start. Motor start caps I've been familiar with (and the ones shown at supus center) are in a bakelite or hard plastic case.

I've used AC caps that look like Surplus Center's Motor Run caps as Motor Start caps. They were what I had at the time and I used them to diagnose the problem. But then, for safety reasons (to fit in the original space) I went and bought some correct size Motor Start caps and used them after trouble shooting with the bigger caps.

Look to see what you have, metal case or plastic case? Then select from the similar style capacitors.

 

[Gomez]

Re: HELP, Electric Motor Guru\'s

</font><font color="blue" class="small">( Sounds like it is single phasing.
)</font>

Well, it's a single phase motor. /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif

I agree with the suggestions given.

Sometimes motors hum because they don't know the words. (sorry) /forums/images/graemlins/tongue.gif

 

[JimR]

Re: HELP, Electric Motor Guru\'s

Junkman, I paid a visit to Auburn yesterday to have my capacitors checked out at Alfred Brown's. The people there are nice to deal with and checked them out for free. The capacitors checked out fine. They did mention to clean the two contacts on the rear motor plate. After cleaning the contacts on the motor it did start again. Sparks were flying out of the field windings and it finished burning up for good. I called Browns about rebuilding it and they said it wasn't worth it. A new one was almost $400.00 and of course not in stock. A search on E-bay brought up a distributer just north of Boston that sells electric motors and pumps. Today I picked up a Baldor 5HP 23 amp motor from them. The motor was rated 1 amp less than my old one. The price with a two piece pulley and tax was $297.45 out the door. This price also included a sleeved two piece pulley and the sales tax. One thing I can say about Baldor is that their motors are pretty strong. I could tell the difference right away with how fast my compressor was running. It makes me wonder if my old motor wasn't a lemon from the gitt-go. Maybe it has been dying a slow death for quite sometime? Anyway, the company was great to deal with and not too hard to find. Here is the website for all in the area to know if they need an electric motor for a reasonable price. They sold it to me for the price on E-bay. Here is their website www.weco-group.com
The name of the company is Williamson New England Electric Motor Service Corp. 111 Boston St. Everett, Ma. Check Ebay for prices before calling them. The price when I called was almost $80.00 higher than the E-bay price. They list on E-bay as seller weco-group. All I did was say that I saw the auctions on E-bay to get that price. Another Worcester based motor company quoted me a price of $450.00 to replace my 6hp Century motor. It was well worth the drive (100 miles round trip) to save over a $100.00 for a motor no one had in stock. They also take c.c.'s