single phase induction motors

Thread Starter

zia iqbal

Joined Mar 4, 2009
Hello members,

Can you please explain how value of start and run capacitor is evaluated to start single phase induction motor. please explain separetly for start capacitor and runing capacitor.

waiting for answer


Joined May 18, 2009
In the absence of any replies, may I ask the same question as "Zia iqbal" but from a different angle? I am helping a farmer friend to sort out a 4hp squirrel cage motor. It looks like the run capacitor has blown. However I am reasonably sure that this and the start capacitor have been replaced in the past and probably by someone who was not sure what they were doing. The upshot is I am now not sure if the values and ratings are what they should be. The motor was manufactured by ACEC (Ireland) Ltd Waterford. Its type is AV2459 V1, Its rotation speed is 950 RPM and is rated at 220V 16 Amps (Image Attached). The motor I am certain is configured as a Capacitor Start - Capacitor Run with centrifugal switch in the aux winding/start capacitor circuit.

The rub however is the ratings of the capacitors, which are as follows:

What I suspect is the Start Capacitor: (Image Attached)
400-500uF, 120/150V RMS, 50/60Hz, Intermittent 3/1.67, 20/60/21/ELYT

What I suspect is the Run Capacitor: (Image Attached)
300uF ±10%, AC120V, 50/60Hz, AB1.7% ED, SD=3MIN,

The motor is normally connected to a 240Vac RMS single phase supply, and unless I am badly mistaken, the astute among you will have already realised that the electrical supply out rates that of the capacitors; hence my suspicions.

The above company that made the motor is as far as I can tell no longer trading, so without further ado, my question, as before. Does anyone have a method of determining the original design specifications for the two capacitors, or more likely, has anyone else a motor made by this company with the same spec which they would be kind enough to have a look at and let me know what the capacitor specs are.

With great anticipation, but if the truth be told, not a lot of hope on this long shot, I wait with bated breath.

With Kind Regards

Dave B