In the modern electrical field, synchronous motors and asynchronous motors are two common types of motors. They each have their own characteristics and play an important role in different scenarios. So, what are the differences between synchronous motors and asynchronous motors? Next, we will conduct an in-depth analysis from multiple dimensions.
Working principle:
(I) Synchronous motor:
The operation of a synchronous motor strictly follows the “synchronous” principle, and the speed of its rotor is always consistent with the speed of the rotating magnetic field generated by the stator. This characteristic stems from its working mechanism: the rotor of the synchronous motor is equipped with a DC excitation winding, which is excited by an external DC power supply to make the rotor generate a magnetic field with a fixed polarity. When three-phase alternating current is passed through the stator winding, a rotating magnetic field is generated. The rotor magnetic field and the stator rotating magnetic field attract each other, and the rotor will rotate synchronously with the rotating magnetic field at the same speed.
(II) Asynchronous motor:
The operation of an asynchronous motor has a different logic. Its rotor speed is always lower than the speed of the stator rotating magnetic field. There is a speed difference, which is called “slip”, which is the origin of the name of the asynchronous motor. When three-phase alternating current is passed through the stator winding of an asynchronous motor to generate a rotating magnetic field, the rotor conductor generates an induced electromotive force and an induced current due to cutting the magnetic flux lines. The induced current is subjected to force in the magnetic field, thereby driving the rotor to rotate. Since the rotor conductor can only cut the magnetic flux lines when there is relative motion with the rotating magnetic field, the rotor speed must be lower than the rotating magnetic field speed.
Structural characteristics:
(I) Synchronous motor:
The structure of the synchronous motor is relatively complex. In addition to the stator part being similar to the asynchronous motor, the rotor part is its significant difference. The rotor of a synchronous motor is generally divided into salient pole type and hidden pole type.
(II) Asynchronous motor:
The structure of the asynchronous motor is relatively simple. Its stator is also composed of an iron core and a three-phase winding made of laminated silicon steel sheets, which is used to generate a rotating magnetic field. For the rotor part, squirrel cage asynchronous motors are the most common; the rotor winding of the wound asynchronous motor is similar to the stator winding, and is connected to the external circuit through collector rings and brushes. This structure facilitates the insertion of resistors in series in the rotor circuit to improve the starting and speed regulation performance of the motor.
Application scenarios:
(I) Application fields of synchronous motors
In the power system, synchronous motors are the most important power generation equipment in power plants; in the industrial field, synchronous motors are often used in equipment with extremely high speed accuracy requirements, such as rolling mills and spindle drives of precision machine tools.
(II) Application fields of asynchronous motors
Asynchronous motors have been widely used in daily life and industrial production. In household appliances, such as electric fans, washing machines, refrigerators, etc., asynchronous motors are used as power sources; in industrial production, asynchronous motors are widely used in fans, water pumps, compressors, conveyor belts and other equipment to meet various production needs.
Although both synchronous motors and asynchronous motors bear the heavy responsibility of converting electrical energy into mechanical energy, they have obvious differences in working principles, structural characteristics, application scenarios, etc. These differences enable them to show their strengths in different fields and jointly promote the development of modern industry and life.