Advantages and disadvantages of permanent magnet synchronous motor

What is the permanent magnet synchronous motor?

Before discussing the advantages and disadvantages of permanent magnet synchronous motor need to understand its basics. Permanent magnet synchronous motor is a device designed by using permanent magnets embedded in the steel rotor to create a constant magnetic field. This type of motor one of the best choices for a full range of motion control applications.

Its stator carries windings connected to an AC supply to produce a rotating magnetic field. Then at synchronous speed, the rotor poles lock to the rotating magnetic field. Permanent magnet synchronous motors are similar to brushless DC motors. Neodymium magnets are the most commonly used magnets in these motors.

Now we can discuss the advantages and disadvantages of permanent magnet synchronous motor


  • Low torque ripple

This motor has low torque ripple so it can generate constant torque. Also its ability to maintain full torque at low speeds.

  • High efficiency –

Permanent magnet motor full-load efficiency is higher than an AC induction motor. It’s a rotor magnet made by using a permanent magnet so this motor has high efficiency. Because its rotor hasn’t any coil so heat generation is less.

  • High power density –

The smaller size and less coil make a high power density. So it makes high speed at a low noise level. The heat transfer is also better, and the cooling system is simple.

  • Low maintenance cost-

The Permanent magnet synchronous motor has not any brushes so it has a low maintenance cost. But it needs to high initial cost.

  • Low heat generation –

It has only stator winding and no brushes so its heat generation is low compared with brush motor.

  • Small size –

It may offer a smaller size for more compact mechanical packages. So permanent magnet motor highly useful for industrial tasks.

  • DC power source –

Don’t need an extra DC power source for it. The AC supply is provided on the stator and the permanent magnets are on the rotor.


  • Permanent magnet synchronous motors require a drive –

Its rotor has constant magnetic but it needs the variable magnetic field so these motors want to variable frequency power source to start. Permanent magnet synchronous motors require a drive to operate it cannot run without a driver.

  • Complex control system-

Basically two methods of controlling motors there are armature current controlling and field current controlling. But in this type of motors, we can change only stator current. There is only one source in this motor AC supply on stator so the only way to control the motor is by controlling the AC supply on the stator. This needs a complex control system including power electronics and microcontrollers.

  • Cost –

Permanent magnet motor solutions tend to need a higher initial cost than AC induction motors so more difficult to start up than AC induction motors. (High-cost magnet-Permanent magnets and their performance is also based on the quality of magnet)


The Permanent magnet synchronous motors are widely used in robotics, machine tools, actuators, and it is being considered in high-power applications such as industrial drives and vehicular propulsion.

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