capacitor motors

[joseph84]

How do you tell if the capacitor in a capacitor motor has ##### itself? My dust extractor (1hp hare and forbes) is playing up. It switches on the 1st time, but after turning it off and on several times it doesnt always fire up. I've checked the capacitor and it doesnt seem to have any burn marks or odour.

Is there a way of checking the capacitor? From memory i think its a 100uf, 250 volt.

cheers

Joseph

[Greg Q]

How do you tell if the capacitor in a capacitor motor has ##### itself? My dust extractor (1hp hare and forbes) is playing up. It switches on the 1st time, but after turning it off and on several times it doesnt always fire up. I've checked the capacitor and it doesnt seem to have any burn marks or odour.

Is there a way of checking the capacitor? From memory i think its a 100uf, 250 volt.

cheers

Joseph

The first thing I'd check is to make sure that the centrifugal switch isn't stuck. Are you hearing that distinctive CLICK every time the motor winds down?

The other way, and I'm not sure how you would accomplish this, but will the motor run if spun over manually?

Greg

[joseph84]

Thanks for the reply gregooryq. Ive checked the switch, and i do hear that clicking noise, when the motor winds down. I've even opened up the switch case to make sure all the wires are in tact. I have also tried spinning the motor manually and flicking the switch on but still wouldnt fire up.

[Greg Q]

Thanks for the reply gregooryq. Ive checked the switch, and i do hear that clicking noise, when the motor winds down. I've even opened up the switch case to make sure all the wires are in tact. I have also tried spinning the motor manually and flicking the switch on but still wouldnt fire up.

Hmmm. I had a capacitor fail visibly on a motor on Friday, but it still ran with a spin-up. Without help, it just hummed with a 50Hz noise. Does your motor make any noise when it fails to start? It could still be the switch. Do you have any way to check with a multi meter? I have had two of those cheapo Chinese switches fail this year, one on a dusty.

Greg

[joseph84]

doesnt make any noise when it doesnt fire up. just sits there dead. when it is working i do notices the motor does make a very slight pecular noise but nothing really to take notice about. I do have a multimeter but not too sure where to start checking

[Greg Q]

doesnt make any noise when it doesnt fire up. just sits there dead. when it is working i do notices the motor does make a very slight pecular noise but nothing really to take notice about. I do have a multimeter but not too sure where to start checking

I wonder if you can get it going then just tutn it off at the powerpoint. If the problem disappears then I'd say the switch is the culprit. I'm not sure about your unit-is the switch mounted on the motor?

Greg

[ubeaut]

Many capacitor start motors have a capacitor rated for about 3 starts an hour. The motor will still run if capacitor is shot but you will need to dive it a hand to get started by manually spinning the motor over. Bit hard on a dust extractor.

I have a very reliable drill and bandsaw both made in Taiwan but both had crummy capacitors. Replaced each with a big capacitor, cost around $30 some 20 years ago and haven't had a problem since. They are used almost daily with lots of stopping and starting.

Cheers - Neil :)

[Phil Spencer]

How do you tell if the capacitor in a capacitor motor has ##### itself? My dust extractor (1hp hare and forbes) is playing up. It switches on the 1st time, but after turning it off and on several times it doesnt always fire up. I've checked the capacitor and it doesnt seem to have any burn marks or odour.

Is there a way of checking the capacitor? From memory i think its a 100uf, 250 volt.

cheers

Joseph

Get your motor checked out by some one qualified to do it, one thing with capacitors they are filled with PCB's apart from causing cancer nasty skin persistent rashes can develop.

For that reason alone it is worth getting a qualified person to look at your motor, we get Taiwanese motors into our winding shop all the time with various problems, dodgy switches and general poor quality.

Regards

Phil

[Hickory]

No one mentioned the switch... Such motors use a magnetic switch (starter switch) Dust DO get in there. My switch failed and the same experience as you discribe occured. check out the switch.. Unplug Open blow out the dust clean the contacts and spray with a electric lubercant, etc. Might be the source of your problem.. If not the switch, Then carry the motor to a Motor shop and have them check it out. Headache is not worth the few $$$ you will save by electracuting yourself or grinding up you mitts trying to spin the impeller to get it started.

I bet it is either the capacitor has failed (and they do W/O exploding sometimes) or the switch is gommed up (technical term too complicated to go into right now) and full of residue.

Oops, I'm sorry, Gregory did mention the switch..... Smart boy Gregory

[Greg Q]

Hi Hickory. See? I was paying attention in troubleshooting 101;)

I don't think that most of the dust extractors sold here have magnetic coil switches, but rather simple push-button contactors. They still find ways to fail, though.

After googling motor capacitors the other day I have lost all faith in them. It seems that every manufacturer's caps are the subject of some product recall somewhere.

Greg

[joseph84]

thanks for the help guys. this morning i turned the damn thing on and it worked without any problems! I stopped and started it about 5-6 times and didnt show any signs that its faulty. Sure beats me??? Must have been a dusty switch or something, although the motor does make a slight howling noise from time to time but im thinking thats the air passing through??

[Greg Q]

thanks for the help guys. this morning i turned the damn thing on and it worked without any problems! I stopped and started it about 5-6 times and didnt show any signs that its faulty. Sure beats me??? Must have been a dusty switch or something, although the motor does make a slight howling noise from time to time but im thinking thats the air passing through??

From what I have read, I don't think that capacitors have intermitent failures, but those pesky switches do. Next time the motor starts howling, give it a love tap with a rubber mallet on the shaft end-I'd wager it might be bearings rearing their ugly heads.

Greg

[soundman]

On any of the :D low cost machines first point of likely failure is the cheap switch.
I've had 3 or 4 of them fail on various machines in my workshop. I'm getting to the point where I'll replace them as a matter of routine about he same time as I replace the incomming mains cord which is always too short.

You can usualy find a better quality switch that fits the hole just fine.

The contacts on the centrifical switch can often need cleaning but it doesn't sound like that problem to me.

cheers

[joseph84]

From what I have read, I don't think that capacitors have intermitent failures, but those pesky switches do. Next time the motor starts howling, give it a love tap with a rubber mallet on the shaft end-I'd wager it might be bearings rearing their ugly heads.

Greg


Greg, your a bloody legend! got out the hammer this morning and gave the thing the love tap to end all love taps! That howling noise is gone and i swear its sucking a lot better! I reccomend you all give it a try next time one of your power tools fail http://www.woodworkforums.ubeaut.com.au/images/icons/icon10.gif

[woodcutta]

Greg, your a bloody legend! got out the hammer this morning and gave the thing the love tap to end all love taps


Ah The old 'Percussive Maintenance' technique - do they still teach that at Trade School?:rolleyes:

[thatirwinfella]

Unplug Open blow out the dust clean the contacts and spray with a electric lubercant, etc. Might be the source of your problem..


compressed air is the best for this, go nuts in every part you can reach, but make sure you don't touch any of the windings of the motor if you blow that out too.

CRC contact cleaner is what you'd want to try on the switch mechanism. If there is a plastic casing on anything nearby be careful though as it can damage some plastics.

[Greg Q]

Ah The old 'Percussive Maintenance' technique - do they still teach that at Trade School?:rolleyes:

I dont know. It might be more of an aeroplane thing.:eek: