Capacitive Start Motor

[paul11273]

Someone was talking about a capacitive start motor today, and this caught my interest.
From what I understand, it basically uses a capacitor in order to help get it started. This is used in situations where a large torque is required to get it going.
Here is my question. Once it's started, what happens to the capacitor? Does it stay connected? Is it disconnected via a relay after a certain time period, etc...?

Thanks.

[4newton]

Hi paul11273:
Someone was talking about a capacitive start motor today, and this caught my interest.
From what I understand, it basically uses a capacitor in order to help get it started. This is used in situations where a large torque is required to get it going.
Here is my question. Once it's started, what happens to the capacitor? Does it stay connected? Is it disconnected via a relay after a certain time period, etc...?The capacitor is used to phase shift the voltage and provide current to a lower impedance winding. This provides two phase voltage at a higher current to start the motor. The motor is a basic inductance run motor but can not provide the phase shift required at start up. The motor must be rotating to shift the phase.

After the start a centrifugal switch that opens when the motor reaches the desired speed switches the capacitor and the low impedance winding out of the circuit.

[paul11273]

Great. Thanks for the explanation. I couldn't find that info on the web.