The magnetic circuit is similar to the circuit, and the magnetic steel and the power supply can be compared. Only the thickness is increased, and the magnetic flux corresponding to the residual magnetism remains unchanged, but the internal reluctance becomes larger. When the reluctance of the external magnetic circuit remains unchanged, the magnetic flux of the external magnetic circuit will become larger.

About demagnetization: The corresponding magnetomotive force of the magnet increases, and the internal reluctance increases. Under the same demagnetization magnetic potential, the magnetic flux is small and the anti-demagnetization ability is strong.

Weak magnetic properties are as difficult as demagnetization analysis. On the other hand, the d-axis magnetic resistance is large and Ld is small, making it difficult to weaken the magnetic field.

The back electromotive force increases, the torque coefficient increases, the copper loss decreases, the iron loss is not constant, and the cost increases seriously.

Cogging torque: When the breath magnetic density waveform remains unchanged, the derivative of the magnetic energy to the angle increases, and the cogging torque increases.

Back-EMF waveform: Generally speaking, the magnetic density saturation of the teeth contains the third harmonic, the back-EMF waveform becomes flat, and the torque fluctuation increases.

Taking a motor model as an example, the IPM structure, parameterized motor magnet thickness, the performance is as follows:

01. The relationship between the air gap magnetic density and the thickness of the magnetic steel

The air gap magnetic density increases with the thickness of the magnetic steel, but not linearly.

02. Cogging torque

The cogging torque increases due to the increased air gap flux density. The tooth torque increases due to the enhanced air gap flux density.

03. Efficiency

In this example, the output torque is fixed, and the iron loss increases faster than the copper loss decreases after the magnetic steel increases.

04. Maximum output power

The thicker the magnet, the stronger the maximum output power capability.

05. Magnetic density of stator teeth

It is reasonable that the magnetic density of the teeth increases

The d-axis inductance decreases with increasing magnet thickness.

Test Data

From the actual test data: the thickness of the magnetic steel increases, and the performance of low-speed and high-speed increases.
The scheme is as follows:
Scheme 1: Thickness of stator core = thickness of rotor core = thickness of magnetic steel (thickness of stator core and rotor core are the same)

Scheme 2: Thickness of stator core = thickness of rotor core – 5mm = thickness of magnetic steel – 5mm (the thickness of rotor core is increased by 5mm compared with that of the stator core, other test conditions are unchanged, and both the low-speed and high-speed torques of the measured motors have increased (the temperature rise and heat generation were not measured).

As a key component of the motor, the magnet steel affects the performance of the motor. The thickness of the magnetic steel will affect factors such as the magnetic flux density, magnetic flux, and the reluctance of the motor, thereby affecting the performance parameters of the motor such as torque, efficiency, and output power:

The influence of the thickness of the magnetic steel on the magnetic flux density: The thickness of the magnetic steel has a direct impact on the magnetic flux density. The greater the magnetic flux density, the greater the torque of the motor. Therefore, under the same power and current conditions, the thicker magnet will produce higher torque.

The influence of the thickness of the magnetic steel on the magnetic flux: the magnetic flux is the magnitude of the magnetic flux generated by the motor, which is affected by the area and thickness of the magnetic steel. As the thickness of the magnetic steel becomes smaller, the magnetic flux will also decrease, so the efficiency of the motor will also decrease.

The influence of the thickness of the magnetic steel on the reluctance: the thickness of the magnetic steel will affect the reluctance, the smaller the reluctance, the more magnetic flux of the motor can be easily transmitted through the magnetic field, and the greater the torque and the higher the efficiency. In mechanical design, minimum reluctance is one of the key points for design optimization.

Therefore, the influence of different thicknesses of magnets of the same brand is practical, and different thicknesses of magnets will cause significant changes in the performance of the motor, and the influence is extremely severe.