What are the common types of variable frequency motors

Variable frequency motor refers to the general term for motors driven by frequency converters. Variable frequency speed regulation is currently replacing traditional mechanical speed regulation and DC speed regulation schemes with fast speed due to its advantages such as high efficiency, wide speed regulation range, high accuracy, smooth speed regulation, and stepless speed regulation.
Common variable frequency motors include three-phase asynchronous motors, DC brushless motors, AC brushless motors, and switched reluctance motors.

1、 Three-phase asynchronous motor
A three-phase AC motor generates a rotating magnetic field on the circumference of the stator gap due to the three-phase AC current in the stator winding. The speed of this rotating magnetic field is called synchronous speed, denoted as n. The actual motor speed n is lower than synchronous speed, so it is generally referred to as a three-phase asynchronous motor. In principle, we can know that the speed of a three-phase asynchronous motor is directly proportional to the frequency of the stator power supply. Variable frequency speed regulation is a speed regulation method that changes the frequency of the stator power supply of an electric motor, thereby changing its synchronous speed.
With the rapid development of electronic technology, the application of variable frequency variable speed three-phase AC asynchronous motors is becoming increasingly widespread. It has gradually replaced various other variable speed motors. Variable frequency variable speed three-phase asynchronous motors are widely used in the industrial field due to their simple structure, convenient manufacturing, easy maintenance, good performance, and reliable operation.

2、 DC brushless motor
Brushless DC motors use semiconductor switching devices to achieve electronic commutation, replacing traditional contact commutators and brushes with electronic switching devices. It has the advantages of high reliability, no commutation sparks, and low mechanical noise, and is widely used in high-end recording consoles, video recorders, electronic instruments, and automated office equipment. A brushless DC motor consists of a permanent magnet rotor, a multi pole winding stator, a position sensor, etc. Position sensing converts the current of the stator winding in a certain order based on the change in rotor position. The working voltage of the stator winding is provided by an electronic switch circuit controlled by the position sensor output.

3、 Switched Reluctance Motor
Switched Reluctance Motor (SRM) is a new type of continuously variable speed motor that has emerged with the development of modern power electronics, control technology, and digital computer technology. It is a typical electromechanical integrated product. Due to the use of the principle of minimum reluctance, it is called a reluctance motor, and also because the coil current on/off and magnetic flux state are directly controlled by the switch, it is called a switched reluctance motor.

Switched reluctance variable speed motors have excellent speed regulation performance and high-speed operating characteristics, combining the advantages of DC transmission and ordinary AC transmission. They are gradually being applied in fields such as household appliances, general industry, servo and speed regulation systems, traction motors, high-speed motors, aerospace equipment, and automotive auxiliary equipment, becoming strong competitors in AC motor speed regulation systems, DC motor speed regulation systems, and brushless DC motor speed regulation systems.