Motor Whoes...

[Darren]

 My millers motor is not very well,

Last night the motor start cap blew. Today I've fitted a new/old cap and now the motor will only run backwards....that's a strange one as I've no idea what make a single phase motor run t'other way without revering the wiring 

It's always got very hot, very quickly. So I guess it's been suspect since I've had it.

Might also explain why it wasn't drilling very well last night. Surprised I didn't notice this at the time...

[Bourne Bill]

did any of the factory installed smoke come out of it?

[Darren]

Sure did, filled the room too, stank a bit.....just from the cap, not the motor.
But I suspect the motor caused the cap to blow.

[Bourne Bill]

did you replace it with the correct cap? there are start caps, and run caps.

[Darren]

Old cap was 110V 200uf

One I had to hand is 220V 130uf  polyprop, there are some more somewhere, at least 100 of em, but can I find them. Mostly square PIO's but the uf rating won't be high enough.

Edit: read that as rated in 100's & 1,000's voltage range and low uf.
Oh and large 

[John Hill]

Darren,  single phase capacitor start motors will run in either direction and in fact you can usually make a uni-directional one reversable if you know what you are doing.

The way they work is that there are two wirings, the 'run' winding which gets full mains voltage through it and the 'start' winding which is in series with a capacitor.

In other words, thinking of the start winding alone, you have one end of the winding connected to the mains and the other end connects to the capacitor and the other end of the capacitor connects to the other mains lead.  Either the coil end or the capacitor is connected via the 'start' centrifugal switch which opens when the motor is spun up a little.

To reverse such a motor the combination of start winding and capacitor is reversed in the circuit.

Preci: You just connected something wrong.

P.S. Are you sure it is not a one of Bogstandard's left handed or American capacitors?

[Darren]

Preci: You just connected something wrong.

John, I haven't wired anything apart from a cap, it started going backwards before I even removed that, and with a new one in it's place. The caps are bi-directional so it doesn't matter which way they are connected.

I suspect the little mechanical start unit has failed as there are sparks coming from that area. I.E it's not releasing and taking the cap out of circuit.
Hence the blown cap, not designed to be left powered up, esp at 110V rating on 240V mains.

I've had a look at the start release mech now and it seems all loose and rather suspect. TBH I think it's best to bin the motor and fit another one.

[bogstandard]

If you had your wits about you Darren, you would get that heap of an engine running and do it mechanically. I used to work with a small holding chap that ran his old big miller from the power takeoff on his tractor. Even the mechanical power feeds worked. Noisy, but it got the job done.

Bogs

[John Hill]

Well Darren  I agree it sure seems like the centrifugal switch is pukaru which is a mechanical problem.

If you cant fix the switch you could use a push button as a 'starter', arrange it so that the start winding and the capacitor is only in circuit while the button is pressed.  Then to start the motor press and hold the button then turn on the power, let the button go when it has spun up.

[As always, take care with electricity]

[Darren]

If you had your wits about you Darren, you would get that heap of an engine running and do it mechanically. I used to work with a small holding chap that ran his old big miller from the power takeoff on his tractor. Even the mechanical power feeds worked. Noisy, but it got the job done.

Bogs

My car's not that bad John, ok it's not new I'll grant you......

BTW, I picked up one of those free running/fixed pulleys recently....so ya never know what may happen in that little shed yet...

[Darren]

Well Darren  I agree it sure seems like the centrifugal switch is pukaru which is a mechanical problem.

If you cant fix the switch you could use a push button as a 'starter', arrange it so that the start winding and the capacitor is only in circuit while the button is pressed.  Then to start the motor press and hold the button then turn on the power, let the button go when it has spun up.

[As always, take care with electricity]

I could do that, but I'd rather junk the motor. Somehow I don't trust it, well not untill it's been stripped and electrically and mechanically checked over first.

[John Hill]

Incidently, and only slightly off topic, if you have a reversable motor on your lathe such as mine and you move the handle too quickly from forward to reverse it will continue to run in the forward direction.

[If you do that cutting threads you might just break the tool, which I did.  Usually such mistakes on my part could be expect to have driven the tool post into the whirling chuck. ]