A PMSM motor (Permanent Magnet Synchronous Motor) is a type of electric motor that uses permanent magnets on the rotor and operates in synchronization with the stator's rotating magnetic field. The Permanent Magnet Synchronous Motor (PMSM) is an advanced type of AC (alternating current) electric motor that combines the benefits of both AC synchronous motors and permanent magnets. IPM motors are generally superior in performance, especially for demanding applications, but PMSMs are cost-effective and easier to control for simpler needs.
The Permanent Magnet Synchronous Motor (PMSM) is composed of two primary parts: the stationary stator and the rotating rotor.
• Stator Core (Laminations): The stationary part of the motor. It's built from thin, insulated sheets of silicon steel (laminations) stacked together. These laminations reduce eddy current and hysteresis losses when the motor operates on AC. The inner circumference of the stator core has slots.
• Stator Windings: Copper coils (typically three-phase) are placed within the slots of the stator core. When alternating current flows through these windings, they create a rotating magnetic field. The windings are insulated to prevent short circuits.
• Stator Housing/Frame: The outer casing that holds the stator core and windings in place, provides structural rigidity, and usually includes mounting feet or flanges. It often has fins or is designed for liquid cooling to dissipate heat.
• Rotor Core (Laminations): The rotating part of the motor, also made of laminated steel.
• Permanent Magnets: This is the defining feature of a PMSM. Permanent magnets are embedded within or mounted on the surface of the rotor core. These magnets create a constant magnetic field that interacts with the stator's rotating field.
• Surface Permanent Magnet (SPMSM): Magnets are attached to the outer surface of the rotor core. This design is simpler and offers a more uniform air gap.
• Interior Permanent Magnet (IPMSM): Magnets are embedded inside the rotor core laminations, often in V-shaped or tangential arrangements. This design provides mechanical robustness for high speeds and contributes reluctance torque, which is beneficial for field weakening and a wider speed range.
• Rotor Shaft: The central shaft to which the rotor core and magnets are attached. This shaft extends out of the motor housing and connects to the mechanical load.
This is the small, crucial space between the inner surface of the stator core and the outer surface of the rotor. The magnetic field passes across this air gap, facilitating the interaction between the stator and rotor magnetic fields. The size of the air gap significantly influences the motor's performance characteristics.
Located at both ends of the rotor shaft, within the end shields. Bearings allow the rotor to spin smoothly with minimal friction and support the mechanical loads from the shaft.
These are covers at either end of the motor housing that enclose the internal components and provide mounting for the bearings.
While not always integrated into the motor's physical core, a position sensor is almost always mechanically coupled to the rotor shaft (often at the non-drive end). This sensor provides precise feedback on the rotor's exact angular position to the motor's electronic control system (Variable Frequency Drive or inverter), which is critical for accurate commutation and efficient operation using algorithms like Field-Oriented Control (FOC).
Stator Magnetic Field: The stator, which is the stationary part of the motor, has three-phase windings (similar to an induction motor). When a three-phase AC power supply is applied to these windings, it creates a rotating magnetic field.
Rotor Permanent Magnets: The rotor contains permanent magnets (often made of rare-earth materials like Neodymium) that create a constant, strong magnetic field.
Magnetic Interaction and Synchronization: The permanent magnetic poles on the rotor are strongly attracted to and repulsed by the rotating magnetic poles of the stator's field. This magnetic "pull" causes the rotor to "lock in" and rotate at precisely the same synchronous speed as the stator's magnetic field.
Control System: To achieve precise control over speed and torque, PMSMs typically require a sophisticated electronic control system, most commonly Field-Oriented Control (FOC) or Vector Control. This system precisely controls the phase and magnitude of the AC current supplied to the stator windings to ensure smooth rotation, high efficiency, and dynamic performance.
| Feature | PMSM (Surface-mounted) | IPM (Interior Permanent Magnet) |
|---|---|---|
| Magnet Placement | On the rotor surface | Embedded inside the rotor |
| Torque Performance | Moderate torque | Higher torque due to reluctance torque |
| Field-weakening Capability | Limited | Excellent (better at high speeds) |
| Cost | Typically lower | Higher due to complex design |
| Efficiency | High at constant speed | Higher across a wider speed range |
| Thermal Stability | Lower | Better cooling, so higher stability |
| Control Complexity | Easier to control | Requires more advanced control |
Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs)
The dominant motor technology in many modern EVs due to their efficiency and power density.
Robotics
For precise motion control and high torque-to-inertia ratios.
Industrial Automation
Conveyor systems, machine tools, servo drives, pumps, fans, and blowers where energy efficiency and precise control are critical.
HVAC Systems
High-efficiency compressors and fans.
Elevators and Escalators
For smooth and efficient operation, often in gearless configurations.
Renewable Energy
Wind turbines (as generators) and other distributed generation systems.
Washing Machines (Direct Drive)
Allowing for more efficient and quieter operation without belts.
Medical Equipment
High-performance and reliable motion.
We are a custom gear motor supplier. We can customize and design PMSM motors for you according to your needs. There is always a motor that meets your needs.
