The Working Principle Behind the Outstanding Performance of Permanent Magnet Synchronous Motors

A power revolution is quietly underway in today's industrial and consumer sectors, driven by the pursuit of high efficiency, energy savings, and precise control. At the heart of this revolution is the permanent magnet synchronous motor (PMSM). With its superior performance, the PMSM is gradually replacing traditional induction and DC motors, becoming the power source of choice in high-end sectors such as new energy vehicles, industrial automation, home appliances, and aerospace.

This ingenious "magnetic pole interlocking" mechanism has brought about a revolutionary performance breakthrough. Unlike traditional asynchronous motors, which rely on a speed differential to induce electricity, permanent magnet synchronous motors achieve "absolute synchronization" between the rotor and the magnetic field. This zero-slip operating mode completely eliminates excitation losses in the rotor windings at a physical level, achieving a qualitative leap in energy conversion efficiency. More notably, the strong excitation magnetic field provided by the permanent magnets requires no external electrical energy to maintain.
This not only significantly reduces operating energy consumption but also enables the motor to output greater torque within the same size, facilitating the miniaturization and lightweighting of equipment. It is precisely this structural advantage, based on physical principles, that has enabled permanent magnet synchronous motors to achieve breakthroughs in three key dimensions: efficiency, power density, and control accuracy, laying a solid foundation for their widespread application across various industries.

As the name suggests, a permanent magnet synchronous motor (PMSM) uses high-performance permanent magnets (typically neodymium iron boron (NdFeB)) to create the excitation magnetic field. Its basic operating principle can be summarized as "magnetic pole interlocking":

The stator generates a rotating magnetic field: The stator (the stationary part) of the motor is wound with three symmetrical windings. When three-phase AC power is applied, it generates a magnetic field that rotates at the synchronous speed.

The rotor's permanent magnets follow the motor synchronously: The rotor (the rotating part) of the motor is embedded with permanent magnets, which generate a strong, fixed magnetic field. The stator's rotating magnetic field "attracts" the rotor's permanent magnet field, forcing the rotor to rotate at the exact same speed (the synchronous speed).

This "synchronous" characteristic is the key difference between PMSMs and asynchronous motors (induction motors). In asynchronous motors, the rotor needs to "slip" to cut through the magnetic flux lines to generate current, and thus torque. This inevitably leads to energy loss and speed fluctuations. PMSMs, on the other hand, achieve zero-slip operation through direct magnetic field interaction, fundamentally laying the foundation for their high efficiency, high power density, and high control precision.