My son phoned me today saying my pillar drill had packed up. It's a big old thing, can't remember the make. He said it was working fine one minute then tripping the breaker as soon as he switched it on. On the side of the motor is a large capacitor which I recall had corrosion on the bottom of it. There is only one wire out of the capacitor, into the motor. It is fixed to the side of the motor with a clamp. I told him to unbolt it off the side and let it hang, not touching the motor. He phoned back saying it worked fine. What I'd like to know is, what does this capactor do and will it cause problems or damage if we remove it completly and if it will cause problems, where could we get a replacement?
- Thread starter Glyn
- Start date
Hello Glyn,
a capacitor is required to start the motor. It should have two wires and is connected in series with the start winding.
Just take the details off the can (if they are still legible?) and try a local motor rewind specialist .
If it is tripping the breaker it is not a good idea to isolate it from the motor as the body of the capacitor could become live (I have to assume the case is aluminium) and could be a serious hazard.
Alec
a capacitor is required to start the motor. It should have two wires and is connected in series with the start winding.
Just take the details off the can (if they are still legible?) and try a local motor rewind specialist .
If it is tripping the breaker it is not a good idea to isolate it from the motor as the body of the capacitor could become live (I have to assume the case is aluminium) and could be a serious hazard.
Alec
If you can read the info on the old capacitor: some sizes/specifications of "Motor Run" capacitors are cheaply/easily available from Maplin.
Motor Run Caps
Motor Run Caps
Thanks for the info folks, I've not had chance to look at it yet but, Piman, you say it's needed to start the motor, my son says it runs fine with it disconnected?
Debs, thanks for the link. Theres a maplin local to me. If I can match it up I'll get one seeing as they are so cheap.
When my son phoned to say it had packed up, I was kind of gutted. I reckon it would cost a fortune to replace with something of a similar standard. It's a big old thing, solid build and so heavy we really struggled to lift it onto the bench.
Debs, thanks for the link. Theres a maplin local to me. If I can match it up I'll get one seeing as they are so cheap.
When my son phoned to say it had packed up, I was kind of gutted. I reckon it would cost a fortune to replace with something of a similar standard. It's a big old thing, solid build and so heavy we really struggled to lift it onto the bench.
Hello Glyn,
single phase motors do not self start but need a capacitor\start winding to initiate the start. Once running the capacitor can be disconnected. Some older motors had a centrifugal switch to do just that. They will start without a capacitor if you spin the shaft but that could be dangerous so I wasn't going to suggest it.
Alec
single phase motors do not self start but need a capacitor\start winding to initiate the start. Once running the capacitor can be disconnected. Some older motors had a centrifugal switch to do just that. They will start without a capacitor if you spin the shaft but that could be dangerous so I wasn't going to suggest it.
Alec
might be a 2 wire cable, I've not had chance to go look at it yet. I'll try to get down there today. Piman, you say older motors had a centrifugal switch to disconnect? Is that possibly the click you hear when it gets up to speed?
If the capacitor is beond recognition, could you possibly tell what size replacement i'd need off the motor details? (HP, RPM e.t.c.)
If the capacitor is beond recognition, could you possibly tell what size replacement i'd need off the motor details? (HP, RPM e.t.c.)
Thats right Glyn your capacitor would be if its connected like a brooks Ive got, live - one side of centrifugal switch - other side of switch - capacitor - other terminal capacitor to the start winding, the motor details would help yes, but different manufacturers used different capacitors but would give you a ball park figure to go for. The click you hear is the switch yes.
Thanks for all the help folks, I won't know what I'm up against till I get down to look at it. I'll probably be back to ask some more questions later after I've looked at it. I'd love to keep the old thing running and wouldn't like to think for the sake of a capacitor it was scrap.
The closer the microfarad and voltage ratings are to the original capacitor the better; `though I have successfully used a lower-capacitance valued capacitor on a non starting air-compressor (just-until the correct value motor run capacitor became available) without any short term negative effects.
Please be careful and remember the usual caveats regarding electrical safety and isolation when testing repairing the drill motor/capacitor Glyn....especially-so if (as you suspect) the old cap. has faulted as a short-circuit/discharge to it`s casing
Right, went down, took motor off, took capacitor off. Rtbcomp was right, there are 2 wires but none are insulated! Just bare wire through a plastic tube, connected to the motor. One side was connected to the live incomming conector the other side had it's own connection. Does that sound right? The capacitor is a 55uf, 275V. The ones at maplin, the largest is 30uF but 440V. I take it that would not do?
I'll do some phoning around on Tuesday.
Debs, thank you for the safety warning, one thing I won't take chances with is electric. I'm very careful with stuff I can't see hear or smell. You mentioned testing? I honestly wouldn't know where to start.
Thanks again.
I'll do some phoning around on Tuesday.
Debs, thank you for the safety warning, one thing I won't take chances with is electric. I'm very careful with stuff I can't see hear or smell. You mentioned testing? I honestly wouldn't know where to start.
Thanks again.
rtbcomp
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The voltage is just a maximum safe working voltage. It's uF that's important, within tolerances.
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Search Ebay for Motor Capacitor
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Hey everyone, thanks for your help. It's sorted now. Took it to a friend of a friend who flicked the end off the tube with the capacitor in. (I thought the tube was the capacitor) he put a meter thing on the terminals and on the case and said there was nothing wrong with it. He said it would have been the bare wire shorting to earth. He then soldered a new cable onto the terminals, sealed the tube with some black stuff, fastened it back on, connected it all up and it ran! I made sure he put his hand on the motor to convince me it was safe and he lived so I'll put it back together now. I've learnt something I never knew about motors today! Thanks again everyone.
