This principle is that the single-phase winding only produces a vibrating magnetic field, but not a rotating magnetic field, so it is necessary to apply a current with different phases to the winding, which can be changed by capacitance or inductance. The phase of capacitor and inductor is opposite, which makes the motor rotate in the opposite direction.
One or four taps (that is, the main winding and the secondary winding lead out terminals respectively). In this case, as long as any pair of primary winding or secondary winding is reversely connected (any pair, two pairs are switched together to realize forward rotation), the reverse rotation can be realized?
Two or three taps (the capacitance of which is external, and one end of the main winding and the secondary winding are combined inside the motor) are connected to the power supply assuming that the male terminal is 1, and the two or three taps are one end of the main winding and the secondary winding respectively;
If the series capacitor rotates forward at 2 and backward at 3 (the primary and secondary windings of this motor are symmetrical, and the number of turns and wire diameter are the same).
Three or two strokes can't achieve positive and negative exchange.
Extended data:
The current interacts with the magnetic field to produce positive and negative electromagnetic torques. The forward electromagnetic torque tries to make the rotor rotate forward; The reverse electromagnetic torque tries to reverse the rotor. The superposition of these two torques is the resultant torque that drives the motor to rotate.
Whether it is a forward rotating magnetic field or a reverse rotating magnetic field, the relationship between their magnitude and slip is the same as that of a three-phase asynchronous motor. If the motor speed is n, the slip ratio is: forward magnetic field s+=(n 1-n)/n 1=s, and reverse magnetic field S-= (-n1-n)/-n1= s.
It can be seen that the main characteristics of single-phase asynchronous motor are:
N=0, s= 1, T=T++ T- =0, indicating that the single-phase asynchronous motor has no starting torque, and the motor cannot be started unless other measures are taken. When s≠ 1, T≠0, T has no fixed direction, which depends on the sign of S. Due to the existence of reverse torque, the resultant torque also decreases, so the overload capacity of single-phase asynchronous motor is low.
References:
Baidu encyclopedia-single-phase asynchronous motor