1. Can permanent magnet motors save power?

When the three-phase stator windings of a permanent magnet motor (each with a 120° electrical angle difference) are fed with a three-phase alternating current of frequency, a rotating magnetic field with synchronous speed is generated.

Under steady state conditions, the main pole magnetic field rotates synchronously with the rotating magnetic field, so the rotor speed is also synchronous, and the stator rotating magnetic field remains relatively stationary with the main pole magnetic field established by the permanent magnets.

The magnetic properties of rare earth permanent magnet materials are excellent, and it no longer needs external energy to establish a strong permanent magnetic field after magnetization, which can be used to replace the electric excitation field of traditional motors.

It can achieve high performance (such as high efficiency, high speed, and high response speed) that cannot be compared with traditional electrically excited motors and can be made into special motors that can meet specific operating requirements.

The combination of rare earth high-efficiency permanent magnet motors with power electronics and microcomputer control technology has improved the performance of the motor and transmission system to a brand new level.

High-efficiency permanent magnet frequency conversion motor always maintains high efficiency under any load, saving more than 38% energy compared with ordinary motors, and more than 10% energy compared with induction-type frequency conversion motors.

The superior performance of the motor can be started immediately after stopping, unlimited start and stop without affecting the life of the motor, and the starting current does not exceed 100% of the full load current.

Because the permanent magnet inverter motor has the advantage of low speed and high output pitch, it has a wider frequency control mode than the ordinary induction inverter motor.

The volume of the permanent magnet inverter motor is 30% smaller and 35% lighter than the same power motor, which makes maintenance easier.

Thus, it improves the performance and level of the technical equipment supported by it and is an important development direction for the motor industry to adjust the industrial structure.

2. Where is the permanent magnet motor used?

Compared with the power frequency motor, the permanent magnet synchronous motor is easy to control, the speed is determined by the power frequency, the operation is stable and reliable, and it does not change with the fluctuation of the load and voltage.

In view of the strict synchronization of the speed of the permanent magnet synchronous motor, it determines the advantage of the motor’s good dynamic response performance, which is more suitable for variable frequency control.

The permanent magnet motor is a kind of energy-saving motor, and it has been well promoted in many application fields, but not all working conditions and occasions are required or suitable to use permanent magnet synchronous motor, which is very worthy of discussion.

Theoretically, the permanent magnet synchronous motor is more suitable for loads with frequent load changes, and the motor often runs in the no-load or light-load state, such as lathes, punches, chemical fiber, textile, wire drawing equipment, and its final energy-saving effect is more obvious, the average power saving rate can reach more than 10%.

In many occasions, especially when the cage motor is selected, in order to make the equipment start smoothly, in most cases, the motor will be selected according to the maximum load of the equipment, which will inevitably lead to a relatively low load rate and a poor motor capacity during normal operation of the motor.

In the case of serious excess, when the motor is running, the efficiency is related to the size of the load.

Generally, when the motor is running without load, the efficiency is close to zero, and when the load increases, the efficiency also increases.

Efficiency is highest when the load reaches 70% of the rated load; therefore, the motor is most efficient, energy efficient, and economical when it is operated close to the rated load.

If the matching asynchronous motor is replaced with a high starting torque permanent magnet synchronous motor, the result of configuring the energy input on demand will play a great role in saving energy.

The advantage of the permanent magnet synchronous motor lies in its two lows and two highs, namely low loss, temperature rise, high power factor, and efficiency, which is also the pursuit of motor performance by people, which determines the market application status of the permanent magnet motors.

Therefore, when choosing a matching motor, we should conduct a comprehensive analysis based on the actual equipment and working conditions, not just stay on the motor itself, but fully consider the energy-saving effect of the system.