Can three-phase asynchronous motor connect to single-phase electricity? Give you two options

Answer: There are quite a number of types of AC asynchronous motors (single-phase motors for short), but the main difference of most series is their starting mode. There are mainly two kinds of starting: split-phase starting and cover-pole starting (also known as shaded-pole starting). The split-phase starting is also called split-phase starting, and it can be divided into two categories: resistance phase-splitting and capacitance phase-splitting. The latter has a wide range of applications and varieties, including single-value capacitor starting, single-value capacitor starting and running, and double-value capacitor. In addition to the above two types, there is also a single-phase AC motor called series excitation motor, which should be strictly called AC and DC dual-purpose motor.

 

(1) Single-phase AC asynchronous motor with split-phase starting

This kind of motor has two sets of windings, one of which is called starting winding, also known as secondary winding or auxiliary winding; the other is the main winding, also known as working winding. Generally speaking, two sets of windings are different in turn number and wire diameter, but for special purpose motors, such as those with both positive and negative steering, such as washing machine motors, the two sets of windings will be identical. The position of the main and auxiliary windings on the circumference of the stator core is 90 degree difference in electric angle (for two-pole motors, the space position difference is 90 degree; for four-pole motors, the space position difference will be 45 degree).

 

(1) Resistance phase separation type. In the auxiliary winding circuit of the motor, a resistance is connected in series or the auxiliary winding is designed to have a DC resistance greater than the main winding. Because the position of the two windings on the circumference of the stator core is 90 degrees different in electric angle and impedance, the current in the two windings has phase difference, which generates starting torque and makes the motor start. When the speed reaches about 80% of the synchronous speed, the power supply of the auxiliary winding is automatically disconnected by centrifugal switch, and the rotating magnetic field produced by the main winding makes the motor run. The circuit schematic diagram is shown in Fig. 18-1

(a).

 

(2) Single value capacitor starting type. The resistance in the resistor phase-splitting type is replaced by the capacitor (of course, the winding parameters will also change), that is to say, the single-value capacitor starting type single-phase motor. The circuit principle is shown in Fig. 18-1 (b).

 

(3) Single value capacitor starting and running type. Compared with the single-value capacitor starting type, it can be seen from Fig. 18-1 (c) that the single-phase motor of this type can be obtained by removing the centrifugal switch. The capacitor will be connected to the auxiliary winding circuit for a long time, so that the auxiliary winding will be energized during start-up and operation. This type of motor has simple structure and wide application.

 

(4) Dual capacitance type. Dual-value capacitive type is the combination of the first two capacitive phase-splitting motor circuits. The circuit principle is shown in Fig. 18-1 (d). Normally, the capacities of the two capacitors are different. The structure of this type of motor is complex, but its efficiency and power factor are high. It is often used in equipment with large capacity.