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Capacitive Start Motor

  1. Sep 30, 2004 #1
    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...?

  2. jcsd
  3. Sep 30, 2004 #2
    Hi paul11273:
    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.
  4. Oct 2, 2004 #3
    Great. Thanks for the explanation. I couldn't find that info on the web.
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