Capacitors on induction motor tools

message from mike on 12 May 2004

I've had two tools die on me in the last fortnight. The first was a
cement mixer and the second a table saw. Both had induction motors
and in both cases it was the capacitor that supplies the starting
torque that failed... an acrid smell followed by a humming and a
failure to rotate, cured by a shove to the blade or barrel.

Both tools were under guarantee and the manufacturers were happy to
put spare capacitors in the post but since I generally take care of
tools and don't recall overloading either of them, I was wondering
what put the kibosh on the capacitors in the first place?

The mixer manufacturer said that the capacitor should cope with a full
load from a standing start even though they recommend starting the
drum empty.

Is capacitor failure a general problem with induction motors?

Mike

G&M replied to mike on 12 May 2004

No. Are you running them from mains or a generator. If the latter suspect
this isn't performing to spec.

mike replied to G&M on 13 May 2004

Thanks for the reply. They're both being run from the mains.

Ian Stirling replied to mike on 12 May 2004

Were you at the time starting them frequently?
The capacitor is not rated for the continuous starting current, just
intermittent.

They can also dry out over time.

mike replied to Ian Stirling on 13 May 2004

Thanks for the reply.

Yes, they'd been started fairly frequently at the time. The table saw
is a cheapie but I'd have expected the mixer to be made of sterner
stuff.

geoff replied to mike on 12 May 2004

Yes

Archived message: Capacitors on induction motor tools (UK D-I-Y Home Improvement)