Why should a single-phase AC motor start with a capacitor?
The running winding of a single-phase motor can only produce pulsating magnetic field - the electromagnetic field corresponding to any point of the motor stator, which can only be changed at this point, including polarity, direction and amplitude. That is, a rotating magnetic field cannot be formed.
Because only the formation of a rotating magnetic field, the squirrel cage rotor will rotate, only increase the starting winding, but start winding must be shifted to start capacitor winding current advance main coil current of 90 degrees, the rotating magnetic field motor to rotate (motor power will start after the resection of the starting capacitor).
The single-phase AC motor and capacitor are used to build the rotating magnetic field in order to make the motor run with the advantage of the current advance characteristic of the capacitor.
A starting winding is added to the stator, and the starting winding and the main winding are separated by 90 degrees in space. Connect a suitable capacitor starting after winding, the winding equivalent circuit becomes a resistor inductor and capacitor in series, as long as the capacitance value of the phase angle of voltage current meet ahead of a certain angle, such as 30 degrees; at the same time, if the current running winding perceptual hysteresis voltage of 60 degrees, then the current phase two the winding difference reached 90 degrees, the so-called phase separation principle. In this way, the two currents, which differ by 90 degrees in time, pass through two windings that are 90 degrees apart in space, which will produce (two phase) rotating magnetic fields in space, and the motor will rotate naturally.
