What is a permanent magnet motor

A permanent magnet motor is a type of motor that uses permanent magnets to generate a magnetic field, without the need for excitation coils or excitation currents. It has the characteristics of high power density, high control accuracy, and low noise. It uses permanent magnet materials (such as rare earth samarium cobalt, neodymium iron boron, etc.) as rotors to drive the motor through the “reluctance torque” generated by the permanent magnets.

What is an asynchronous motor

Conventional asynchronous motor, also known as induction motor, is an AC motor that uses the interaction between a rotating magnetic field and induced current in the rotor conductor to generate electromagnetic torque, thereby driving the motor to rotate. It consists of a stator and a rotor. When the stator is energized, it generates a rotating magnetic field, and the rotor induces current in the magnetic field and rotates under the action of electromagnetic force.

Their differences

Mechanism of magnetic field generation

Permanent magnet motor: using high-performance permanent magnet materials (such as neodymium iron boron, samarium cobalt, etc.) as the magnetic source, directly installing permanent magnets on the rotor to generate a constant magnetic field. This design simplifies the motor structure, eliminates the need for excitation current, and thus improves efficiency.
Conventional asynchronous motor: The rotating magnetic field generated by the stator current induces current in the rotor, thereby generating electromagnetic torque. This process requires additional reactive power consumption, and the rotor resistance will consume some useful work, resulting in relatively low efficiency.

Efficiency and power factor

Permanent magnet motor: Due to the elimination of excitation and iron losses, as well as the reduction of current harmonics, permanent magnet motors can maintain high efficiency over a wide range of speed and load conditions. Meanwhile, its power factor is close to 1, reducing the reactive power burden on the power grid.
Conventional asynchronous motors: At light or full loads, the efficiency of asynchronous motors may be lower than that of permanent magnet motors, especially at low speeds where the efficiency decrease is more pronounced. In addition, the power factor of asynchronous motors is usually low, requiring additional compensation equipment to improve the power factor of the power grid.

Speed regulation performance

Permanent magnet motor: Due to the presence of permanent magnets, the motor has high synchronous torque and small moment of inertia, making it easy to achieve fast response and precise control. Through advanced vector control technology, permanent magnet motors can maintain stable operating performance over a wide range of speed and load conditions.
Conventional asynchronous motors have relatively poor speed regulation performance, especially at low speeds, where efficiency and power factor significantly decrease due to the influence of rotor resistance. Although speed regulation can be achieved through devices such as frequency converters, the cost is high and the control is complex.

Advantages of permanent magnet motors

Choosing a permanent magnet motor brings many significant advantages: it relies on high-performance permanent magnets as the magnetic field source, achieving high-efficiency operation, especially under partial loads, effectively reducing energy consumption and operating costs; At the same time, permanent magnet motors have higher power density and can output greater power under the same volume or weight, improving equipment performance and reducing costs. In addition, its excellent dynamic performance, wide speed range, and significant energy-saving effect make permanent magnet motors perform well in the processes of starting, braking, and speed regulation, further promoting green energy and sustainable development.

Application video of permanent magnet motor