Single-phase series-excitation motor is a single-phase AC asynchronous motor, which is AC/DC. Therefore, it is also called AC/DC series-excited motor. Because of its high speed, small size, large starting torque and adjustable speed, it can be used on DC power supply or single-phase AC power supply, so it is widely used in power tools.
The motor is mainly composed of a stator rotor and a bracket. The stator consists of a salient pole core and a field winding. The rotor consists of a hidden pole core, an armature winding, a commutator, and a rotating shaft. And so on. A series circuit is formed between the field winding and the armature winding through a brush and a commutator.
The working principle of the single-phase series-excited motor is based on the DC series-excited motor. The principle is as shown:
The field winding and the armature winding are connected in series, on the DC power supply, according to the main flux Φ and the armature current The direction of Ia, according to the left-hand rule, can determine the direction of rotation of the rotor, in a, it is rotated counterclockwise; if the polarity of the power supply is reversed, as shown in Figure b, because of the series excitation motor, the main flux Φ And the armature current Ia also changes direction at the same time, according to the left-hand rule, the rotor turns unchanged, and still rotates counterclockwise.
Therefore, after the series-excited motor is added with single-phase AC voltage, As shown in Figure c, although the polarity of the power supply changes periodically, the rotor always maintains a constant steering. Therefore, the series-excited motor can be applied to both AC and DC power supplies.