The working winding occupies 2/3 of the slots

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A single-phase asynchronous motor is powered by a single-phase network (from two wires). Such a motor can be made with one (working) winding on the stator, but in this case it has no starting torque and must be started manually. Such motors are used very rarely. To create a starting torque, the motor, in addition to the working winding, receives an auxiliary winding (which turns it, strictly speaking, into a two-phase one). The simplest auxiliary winding is a short-circuited coil covering the edge of the pole.

Such two-pole motors have a small starting torque (10% of the torque of a three-phase asynchronous motor of the same size) and are used in small motors (fans, record players, etc.), where a significant starting torque is not required. More powerful single-phase motors are made with an auxiliary winding, which, unlike the working winding, is not fed directly qatar telegram data from the network, but through a capacitor, inductor or resistance. Due to this, the current in the auxiliary winding is shifted in phase relative to the current in the working winding, and a rotating magnetic field is created in the motor carrying the rotor. The closer the phase shift between the currents to 90, , , the more symmetrical (closer to circular) the rotating magnetic field and the greater the starting torque.

The best results are obtained by connecting the auxiliary winding through a capacitor (Fig. 3-29, a- d).

The auxiliary winding can be switched on only during starting, for which special relays or centrifugal breakers located on the motor shaft are used, automatically switching off this winding after the motor starts, Fig. 3-20.6, g.

In this case, the starting winding is made with a number of turns of 60-100% of the working one (switching on via a starting capacitor) or 35-60% of the working one (switching on via a starting choke or resistance). This allows increasing the magnetic flux of this winding and thus the starting torque.