help, motor problem

[Wayne Kerr]

I recently had to replace the pump on my washing machine as the old
pump was randomly failing to start. On examining the old pump I can find
nothing wrong with the impeller mechanism, which leads me to believe its
probably the small capacitor (used for starting the pump? - it has no
brushes). Does anyone know if this could be the likely reason and if so
what rating of capacitor should I replace it with if I experience a similar
problem in future? The only data shown on the body appears to be a part
number, no microfarad / voltage rating is shown - an approximate rating
would be a good start, I could then experiment until I get it right. PS its
a 230/250 volt machine if that makes any difference.

 

[Tzortzakakis Dimitrios]

Of course it has no brushes, since it?s an asynchronous motor.The capacitor
is used for creating a rotating magnetic field inside the stator, by means
of the single phase current that?s supplied to the machine.Actually, AFAIK
these pumps are so cheap that you shouldn?t even thin of repairing it.

 

[daestrom]

I recently had to replace the pump on my washing machine as the old
pump was randomly failing to start. On examining the old pump I can find
nothing wrong with the impeller mechanism, which leads me to believe its
probably the small capacitor (used for starting the pump? - it has no
brushes). Does anyone know if this could be the likely reason and if so
what rating of capacitor should I replace it with if I experience a similar
problem in future? The only data shown on the body appears to be a part
number, no microfarad / voltage rating is shown - an approximate rating
would be a good start, I could then experiment until I get it right. PS its
a 230/250 volt machine if that makes any difference.

Sounds like a single-phase AC motor. Given your symptoms, I'd look at the
centrifugal switch used to cut the start winding/capacitor out when the
motor comes up to speed. If it doesn't reclose when the motor stops, the
motor won't re-start (unless you kick it or jar it in someway to get the
switch contacts to close again).

daestrom

 

[ZForce]

You could test the capacitor by getting a multimeter and selecting the ohms
tester, then putting it across the cap, it should appear as a dead short
then rapidly fall towards an open circuit as it charges.

I doubt you pump is a cap-start run motor with a centrifigal switch, its
more likely a permanent-split cap motor, These by design have a low starting
torque, so maybe the bearings are flogged out in the motor or a bit of crap
is jamming it somewere.

As for a replacement cap, see if you can scavenge one off a discarded
appliance or something, The value isn't overly critical, just make sure its
rated at the correct voltage.