Advantages of permanent magnet synchronous motors

Advantages of permanent magnet synchronous motors

How it works

The permanent magnet synchronous motor uses permanent magnets to replace the excitation winding for excitation. When the three-phase stator winding of the permanent magnet motor (each phase differs by 120° electrical angle) is connected to a three-phase alternating current with a frequency of f, a rotating magnetic field moving at the synchronous speed will be generated. In the steady state, the main pole magnetic field rotates synchronously with the rotating magnetic field, so the rotor speed is also the synchronous speed. The stator rotating magnetic field always remains relatively stationary with the main pole magnetic field established by the permanent magnet. They interact with each other and generate electromagnetic torque, driving the motor to rotate and convert energy.

Advantages of permanent magnet synchronous motors

Compared with DC motors, permanent magnet synchronous motors do not have the disadvantages of DC motors such as commutators and brushes. Compared with asynchronous motors, they do not require reactive excitation current, so they have high efficiency, high power factor, large torque-to-inertia ratio, reduced stator current and stator resistance losses, and measurable rotor parameters and good control performance; compared with ordinary synchronous motors, they omit the excitation device, simplify the structure, and improve efficiency. The permanent magnet synchronous motor vector control system can achieve high-precision, high-dynamic performance, and a wide range of speed regulation or positioning control, so the permanent magnet synchronous motor vector control system has attracted widespread attention from scholars at home and abroad.

Compared with other motors, permanent magnet synchronous motors have the following advantages

Permanent magnets are used to replace the excitation winding in the rotor of a wound synchronous motor, thereby eliminating the excitation coil, collector ring and brush, and achieving brushless operation through electronic commutation, with a simple structure and reliable operation.

The speed of the permanent magnet synchronous motor always maintains an accurate synchronization relationship with the power supply frequency. Controlling the power supply frequency can control the speed of the motor. The permanent magnet synchronous motor has a relatively hard mechanical characteristic and has a strong ability to withstand disturbances in the motor torque caused by changes in load. The maximum torque can reach more than 3 times the rated torque. It is suitable for operation under conditions where the load torque changes greatly and is suitable for starting and accelerating electric vehicles.

The permanent magnet synchronous motor rotor is a permanent magnet and does not require excitation, so the motor can maintain synchronous operation at a very low speed and has a wide speed regulation range.

Compared with asynchronous motors, permanent magnet synchronous motors do not require reactive excitation current, so they have high power factor, small stator current and stator copper loss, and high efficiency.

Small size and light weight. In recent years, with the continuous application of high-performance permanent magnet materials, the power density of permanent magnet synchronous motors has been greatly improved. Compared with asynchronous motors of the same capacity, the size and weight have been greatly reduced, which is suitable for the limited space of electric vehicles.