A netizen suggested that a comparative explanation and analysis of the three-phase motor of the single-phase motor should be carried out . In response to this netizen’s question, we compare and analyze the two from the following aspects.
As the name suggests, there is only one phase wire for single-phase electricity, and its wire is composed of a live wire and a neutral wire; three-phase electricity has three phase wires, and its wires are three-phase four-wire, that is, three live wires and one neutral wire. You can convert a live wire and a neutral wire from the three-phase line to single-phase electricity. In the power supply line, all three-phase electricity enters the power site, and then it is converted to single-phase or three-phase power supply according to the actual load balance relationship and specific use.
The stator winding of the three-phase AC induction motor is composed of three-phase windings whose three phases differ by 120 electrical degrees in physical space. The physical phenomenon in which the formation of cutting magnetic lines between strips does work. When the three-phase stator winding of the motor is connected to the three-phase symmetrical alternating current, a rotating magnetic field will be generated, and the rotating magnetic field will cut the rotor winding. Therefore, an induced current is generated in the rotor winding of the closed path, and the current-carrying rotor conductor will generate an electromagnetic force under the action of the rotating magnetic field of the stator, thereby forming an electromagnetic torque on the motor shaft, driving the motor to rotate, and the direction of the motor rotation and the direction of the rotating magnetic field. same.
For single-phase motors, the stator winding is generally composed of a main winding and a secondary winding. According to different series classifications, the functions of the secondary windings are not the same. We take the capacitor-started single-phase motor as an example for AC. To make the single-phase motor rotate automatically, we can add a starting winding to the stator. The starting winding is 90 degrees different from the main winding in space. The phase difference is approximately 90 degrees, which is the so-called phase-splitting or phase-shifting principle. In this way, two currents with a difference of 90 degrees in time pass into two windings with a difference of 90 degrees in space, which will generate a (two-phase) rotating magnetic field in space. Under the action of this rotating magnetic field, the rotor can automatically start. After starting, when the speed reaches a certain level, the starting winding is disconnected by means of a centrifugal switch or other automatic control device installed on the rotor, and only the main winding works during normal operation. Therefore, the starting winding can be made into a short-time working mode.
In view of the limitations of power supply in different places, single-phase motors are more used in living places, while three-phase motors are mostly used in industrial fields.
Post time: Jul-28-2022