Why does the motor need capacitance when the machine starts?
Only single phase ac motor USES capacitance, dc motor and three-phase ac motor do not need. The two single-phase motor coil does not produce a rotating magnetic field, must be in one of the series capacitance on the coil, make this branch of the current in another coil current in advance, the ability in a rotating magnetic field between the two coils, rotor rotation.
In the picture, a positive reverse circuit is shown, and the switch hits the "positive" in the upper part of the circuit. The switch hits the bottom "inversion" to connect the capacitor to the upper one. There is no need to think about capacitance charges.
Only for single phase ac motor, because a single winding is unable to form a rotating magnetic field, the electric capacity of a rotating magnetic field is formed after phase-shifting three-phase don't need to, so it can synthesize a rotating magnetic field
