How to electric: Capacitor Start induction run motor
Single phase capacitor start motors are maybe the most popular type of single phase electric motor. They have two sets of motor windings, a run winding and a start winding. The start winding is a heavier winding and is switched out of the circuit once the motor gets up to around 75% of the rated speed.
(3) is a centrifugal force switch that opens as the motor gets up to speed disconnecting the capacitor and start winding.
(1) Run winding
(2) Start winding
The capacitor strengthens the magnetic field in the start winding giving the motor much more starting torque. They are usually rated in microfarads with a voltage rating of 300 to 700 volts.
Some common problems with these motors is the centrifugal switch and the capacitor. If your motor just hums and will not start these are the first two things to check. Remove the capacitor and check it with a capacitor meter, another way to check a capacitor if you dont have a meter is to use an analog multimeter. Set the multimeter on a high resistance setting and apply the leads to the cap terminals (be sure to discharge the capacitor first), the meter needle will deflect to the right slowly as the cap charges, reverse the leads and the needle should again deflect to the right while the cap charges in the opposite polarity. This is just a basic check but normally if this works the cap is good.
To check the switch either remove the back of the motor and physically look at the switch contacts or refer to the wiring diagram of the motor and use an ohm meter to check continuity.