How do you wire a capacitor to a electric motor?

Answer 1

A capacitor resists a change of voltage, proportional to current, and inversely proportional to capacitance.

dv/dt = i/c

Capacitors can do various things. They can filter out high frequency transients, or power supply ripples, they can block DC while passing AC, they can participate with other components such as resistors and inductors to form filters - the list is endless.

Answer 2

The start capacitor on a "capacitor start" motor (not all AC motors are capacitor start) exists to provide starting current with a certain amount of delay between one set of motor windings and another. This causes a stronger imbalance in the forces in the motor, and causes it to start up. Once the motor approaches operating speed, the capacitor is no longer needed.

Capacitor start motors are more expensive because they have switching circuitry and a capacitor; however, they have much higher startup torque than normal induction motors.

Answer 3

When a capacitor is so introduced, the voltage lags the current by some phase angle. In these motors, the necessary phase difference between the Is and Im is obtained by introducing a capacitor in series with the starter winding. The capacitor used in these motors are of electrolytic type and usually visible as it is mounted outside the motor as a separate unit.

During starting, as the capacitor is connected in series with the starter winding, the current through the starter winding Is leads the voltage V, which is applied across the circuit. But the current through the main winding Im, still lags the applied voltage V across the circuit. Thus more the difference between the Is and Im, better the resulting rotating magnetic field.

Answer 4

The purpose of a Capacitor Start Motor is for the Capacitor to ABSORB some of the initial Current Flow (which is HIGH) to protect the Motor's wire windings. As the motor comes up to speed, the Capacitor slowly RELEASES the captured current.