Motor direction

[lyledunn]

We have a little 2.3Kw 1-p capacitor start induction motor. When supplied at 230 volts ac(UK), the motor operates fine. However, its direction of rotation is arbitrary. When switched on it could run either clock or anti-clock.
I am afraid I am not a motor man but I am interested in just what might be causing this. Regards,

Lyledunn

 

[dpc]

Without some starting circuit, the single-phase motor is happy turning either direction - it has no inherent starting torque.

Capacitor start should give it a definite starting torque in a preferred direction. Perhaps the capacitor circuit has opened up, or the centrifugal switch is bad.

 

[mdonner]

If you had to (re)wire the capacitor, make sure it is connecte between the common and the "start" connections.
The start-common measured resistance is noticeably higher then the run-common resistance.

 

[SteveKW]

Typically, an open start circuit would NOT let the motor run at all. It would just sit there and not turn. The most common reason that I see for a motor take off in any direction is because the start windings have "shorted" to the run windings!

I suggest you take it to your local electric motor repair shop!

 

[stardelta]

I will go with Steves suggestion of shorted turns as a strong possibility, but I wouldnt dismiss the start winding circuit if the motor is showing this fault when connected to the driven load. If its a pump or a fan or even a compressor the liquid or air flow could be turning the motor just enough to give some direction to the run winding field. This effect is known as "Windmilling".

 

[lyledunn]

stardelta,
I see your point. this motor has been taken off load so there is nothing to get the motor running. I know that the capacitor will cause a phase displacement and thus initiate a start but if it is open circuit would I be right in saying that starting would not be possible without a little help to get rotation going as you suggest?
The unit has been sent to specialists for repair but it is still nice to speculate.
Steve, how does such a condition cause rotation in an ad-hoc direction?
Thanks to all.
Regards,

Lyledunn

 

[GusD]

Hi Lyledunn

I would venture to say that you have shorted windings and a
consequent loss of full starting torque.if windings are sound ,motor would spin in only one direction.

Thanks GusD