Electric motor testing-is it good or not?

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Old 09-28-08, 11:20 AM
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Electric motor testing-is it good or not?

Hello all,
First time posting. I have about three old machines (welding and air compressor) and I hate to throw them out without knowing for sure if they are bad. I have what seems to be issues with the motor(s). Can anyonoe explain how I can test motors to findout what is good or bad on them? When a company wants to "bench test" a motor in the 2-3 hp range -what do they do and can I do it myself at home? I have a multimeter and am learning how to use it. I am very handy and have built almost all of my own things I have ever needed from new or recycled parts. I knwo I can fgiure this out I just need direction. these motors have two capacitors by the way on the housing and can I test these with a Multimeter?

thanks,
Ryan
 
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Old 09-28-08, 12:18 PM
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They would test to make sure it is not a dead short, and no conduction to the enclosture.

They would then probably do a live test, by connecting the required power to it, and checking amps flowinth through it, possibly imposing a load on it.
 
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Old 09-28-08, 08:41 PM
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thanks for the reply. Is there any good info out there on the net that has the exact process of doing this stuff with home tools like a multimeter?

Lets look at one of the problems: I put a garage sale motor on my older sears air compresor (motor looks brand new and matches everything the old motor has) and put power to it ahead of time and it spun just fine. Then I connected the belt and my air compressor starts and only fills up to 20 psi and then the motor seems to strain to the point where it cannot go anymore and will blow the circuit. I have checked the wiring four times. these things are not complicated to wire so that is not the issue. It is wired and used on 110.

Thanks,
Ry
 
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Old 09-28-08, 09:00 PM
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Sound like you have one of the winding or coil[s] are open many single phase motor can be wired dual voltage however.,,
Some are not but all the motor do have multi set of coils so one of the winding get open you will loose the perfromace pretty fast depending on the type of motor itself.

if this compressor is actally a dual voltage it may be little easier to pinpoint if you have bad coil or not.

If that the case I have a trick up the sleeve for this let me know if that motor is confirmed a dual voltage then we can go from there other wise I may have a other trick I can do.

Merci,Marc
 
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Old 09-29-08, 08:46 PM
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yes this motor can be wired for 220 or 110. is there any good info out there on what a normal motor should look like on the inside and how to test individual components?

Thank you for all the help you are giving me.

Ryan
 
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Old 09-29-08, 09:55 PM
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Normally with good windings in the motor they should not show any burnt mark on them at all but if you did see one " ring " of burnt mark that useally tell that one coil is burnted out.

But you can able ohm it depending on the numbers of connections of motot itself


Typically you will see it numbered or both colour and numbered leads on the motor

1 ,2 is one set of coil
3,4 is other set of coil
{ both useally are run coil type }

8,5 is starting coil that is used breifly during start up. { pretty good percentage of single phase motor will have a starting capaitor so if you going do this part make sure you short out the capaitor with screwdriver otherwise you will be in nasty suprised of shock .,, yeah they can hold a bit of juice}

but there is other set you may run into this

1,2
3,4 those are main run winding

7,8 run capaitor winding
5,6 start capaitor winding


So you can run the ohmmeter if you are famiaur with it

ring it out on 1 and 2 first then do 3 and 4 both set should read the same if they read the diffrent then a good chance one of the coils are shot.

As I describing above this part that is the main useage of motor coils and also before you start work on this make sure you make a note of connections on the motor itself so it will really save yourself alot of headaches down the road.

Merci,Marc
 
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