What is a permanent magnet synchronous motor?

What is a permanent magnet synchronous motor?

Many products today are still driven by AC induction motors. However, engineers and equipment owners are starting to adopt permanent magnet motor solutions for many different applications—largely for their smaller size and higher efficiencies. Permanent magnet drive solutions are great for applications such as fans, blowers, and pumps.

A permanent magnet synchronous motor (PMSM) could be considered similar to a brushless direct current (BLDC) motor. Like BLDC motors, PMSMs are rotating electric motors that have permanent magnet rotors and wound stators. They have a three-phase stator layout which is designed to create sinusoidal flux distribution in the air gap, making the back electromotive force (BEMF) sinusoidal.

Magnets used for PMSM motors
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The three-phase stator poles are connected to an alternating current (AC) supply to produce a rotating electromagnetic field. At synchronous speed, the rotor poles are attracted and repulsed to and from the stator poles which creates the movement of the rotor. Our PMSMs use two possible configurations: they can have an internal (inner) rotor or an external (outer) rotor, depending on their application.

We use PMSMs for their low noise, high performance, and efficiency. They are also characterised by smooth rotation over the entire range of a variable speed motor, full torque control at zero speed, and fast acceleration and deceleration. To achieve such control, we use field-oriented control (FOC) techniques (also known as vector control) for our PMSMs. Learn more about FOC.

PMSMs’ power density is higher than that of induction motors with the same specifications, since there is no stator power dedicated to magnetic field production. Today, these motors are designed to be more powerful while also having a lower mass and lower moment of inertia, improving the dynamic performance of the electric drive.

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The key features of permanent magnet synchronous motors include:

  • A simple mechanical construction which is easy to maintain.
  • Rugged composition.
  • A high level of reliability (due to no brushes) even at high operating speeds.
  • Efficiency (almost zero losses on the rotor).
  • High torque-to-weight-ratio (torque density).
  • A variable speed drive (VSD).
  • Sensorless operation.
  • Precise torque and speed control.
  • Fast dynamic response.
  • Smooth torque production.
  • Quiet operation over the whole speed range.


Rob Keating

Rob is a content creator and copywriter for Fisher & Paykel Technologies. His work includes the Knowledge Hub, email, website and social media copy, along with customer communications.
More from this author
Permanent Magnet Synchronous Motor, (PMSM), electric motor, permanent magnets, variable speed control, torque density
October 20, 2022
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