Single phase Capacitor start hoist Help me troubleshoot please 1

[bigmark1972]

I have a single phase 115v hoist

It will not start on it's own. If I spin it while holding the up or down button on the pendant it will run fine.

It also will run in either direction I start to spin it in, regardless if I am pressing the up or down button.

I checked all of the switch wiring and it is fine. I have replaced the starter capacitor also and this did not help.

I pulled the core out and checked for any burnt windings or shorts and everything looks and smells fine.

Any ideas on what could be wrong with, I would rather not buy a new hoist if this one could be fixed. Are these symptoms enough for anyone to have an idea of what the problem might be?

I do have good 120v of AC and like I said the pendant is working fine.

 

[itsmoked]

bigmark1972 have you checked the centrifical switch? It sounds like your probem. Especially after your other checks.

 

[jraef]

I agree, probably the speed switch. It could have been the capacitor but you already eliminated that. If you don't know what that is, it is a centrifugally operated switch, usually in under the bell housing of the non-drive end of the motor, that switches the cap in and out. It is N.C. feeding the cap at rest, and opens when the motor gets up to speed. If the switch is burned, broken or stuck open, no cap, therefore no start. They are simple to change out once you get the replacement.

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[ccjersey]

Either bad centrifugal (start) switch on the armature or an open start winding IF the capacitor you installed is good. Things that go wrong from most likely to least likely........Capacitor is most likely, followed by the switch, followed by the actual start winding in the stator and finally the centrifugal mechanism that actually operates the centrifugal switch.

You should hear the switch centrifugal mechanism click back closed as the motor coasts down to stop. It will make a slight rubbing noise usually as the motor stops. Once the motor stops, the capacitor and start winding are connected and an ohmeter attached to the motor leads (WITHOUT POWER) should deflect to very low resistance and then increase as the capacitor charges. If the capacitor only is checked, the reading will get a lot higher as it charges, but a quick check of the circuit is usually possible by reading the whole motor. An analog meter makes it easier to see this.

 

[itsmoked]

jraef didn't you have a picture of one laying around?

How is the direction imposed via the pendant? I know single phase has no inherent rotational vector so you must kick the motor in the direction desired.

Is there is one start winding or two?

What do you change?

 

[bigmark1972]

Thanks for all of the replies!

I looked at the centrifugal switch and there is nothing obviously wrong with it. I will verify that it is working with a voltmeter. It does throw itself out when I spin it in my lathe, I lubricated the pivots, etc.

 

[itsmoked]

Gotta check the contacts and wire connections to the C switch.

 

[aolalde]

Check with a clamp-on ampmeter that the starting winding is drawing the expected current and voltage drop at the capacitor and starting winding are correct.

 

[itsmoked]

Nice post A.

 

[ccjersey]

"""How is the direction imposed via the pendant? I know single phase has no inherent rotational vector so you must kick the motor in the direction desired.

Is there is one start winding or two?

What do you change?"""""

The change is to reverse the polarity of the start winding from the same as the main winding to the opposite of the main winding. So if the ends of the start winding are 5 and 8, switching the connections of 5 and 8 will reverse the motor.

 

[itsmoked]

Thank you ccjersey.

 

[edison123]

bigmark

Did you check the rotor ? May be rotor bars are cracked.

If it is a conical rotor, may be rotor position is not right.

 

[bigmark1972]

Thanks again for all of the input.

The centrifugal switch was broken, after checking it with an ohm meter it had been repaired incorrectly previously. There are two starter windings and both of them were getting power at once. I think they are still OK (not cooked) they do not smell and the windings look fine. I ordered a new switch I will get it in on Monday and repost if it works then.

Thanks,
Mark

 

[bigmark1972]

Well, I put in the new centrifugal switch and it is still not working. I can use it but the operator has to pull the chain to start the motor.

The starter windings must be burnt out, there is nothing else left as far as I can tell. I am going to pull it and take it to a local motor shop I have worked with before they are very good and can fix most any motor.

Thanks for all the help, you guys are a real asset!

 

[bigmark1972]

I did not notice any broken rotor bars.