Brushless motors

[racket]

HI all,
I have a brushless motor on my air compressor at home, the other day it was running and then just stopped. when i turned it on it just makes a loud humming noise but doesnt run. The motor has a 40uF capacitor fitted on it, how do I check the capacitor without a cap tester, I,ve buzzed the motor and the winding seems to be OK, do you think the capacitor has gone.

Many thanks

 

[breezer]

its an induction motor, i doubt its the capacitor, its probably the internal windings.

what did you "buzz" the motor with?

if you "buzz a capacitor " it should work, then slowly fade as it becomes charged

 

[racket]

When I say buzzed, I mean I,m getting continuity through the windings, forgotten the reading. Do you think the capacitor is a run capacitor, ie the windings require the capacitor in series or parralell to allow it to run. I'll pobably try a new cap as there only cheep and if that doesnt work then I know the motor is kapput.

Cheers for your help

 

[Stoday]

Most induction motors have a (smaller) starting winding that's connected in series with a capacitor and a switch. The switch opens when the motor has started otherwise the starting winding would burn out.

The most likely fault is the switch is stuck in the open position.

 

[racket]

This motor only has the one windind and no external or centrifugal switch, the motor you are suggesting is like a fridge motor, me being a fridge engineer i know this type, I just havnt come across a 3Kw motor like this before with only one capacitor and no brushes.

Cheers anyhow

 

[breezer]

me being a fridge engineer

chill out

 

[kendor]

If you are able to do so and with care, remove motor and give the shaft a twist when on and it should start spinning if so the cappy needs replacing.