China Neodymium And Ferrite Magnets Manufacturer & Supplier 
During the operation of permanent magnet motors, temperature rise in the rotor is a relatively common issue. Particularly during high-speed operation, the permanent magnets and the rotor core are prone to generating a certain amount of loss; as the temperature rises, this not only affects the motor’s efficiency but, in severe cases, may also impair the magnetic properties of the permanent magnets. So, what are some effective solutions to address temperature rise in permanent magnet rotors?
Firstly, the use of injection-moulded permanent magnets could be considered. Injection-moulded permanent magnets have a relatively high electrical resistivity; when the motor is operating at high speeds, this can effectively reduce eddy current losses within the permanent magnets, thereby lowering the heat generated by the rotor. This is an option worth considering for motors with stringent requirements regarding temperature rise. Of course, the specific material to be used will need to be determined based on the rotational speed, magnetic properties and operating temperature.
Injection-moulded ferrite magnetic rotors
Secondly, the motor air gap can be adjusted appropriately. Whilst increasing the air gap will have a certain impact on the magnetic circuit and motor performance, in the case of rare-earth permanent magnet synchronous motors, a well-designed air gap can attenuate some of the harmonic magnetic fields and the resulting harmonic losses, thereby reducing surface losses in both the stator and rotor. However, a larger air gap is not necessarily better; it is necessary to strike an appropriate balance between temperature rise, efficiency, power factor and output performance.
The matching of the rotor slot profile and the number of slots also warrants attention. The use of semi-closed or closed slots can reduce losses on the surface of the rotor core and mitigate the effects of cogging current, whilst also reducing certain harmonics in the air-gap magnetic field. The matching of the number of slots also affects motor losses; generally, this requires appropriate design based on parameters such as the number of poles and rotational speed, with the aim of minimising combinations that are prone to significant harmonic losses.
The stator windings can also be optimised. For instance, by employing double-layer short-span distributed windings, it is possible to attenuate certain higher-order harmonics through the appropriate selection of winding spans, thereby improving the waveform of the air-gap magnetic field and reducing harmonic losses and heat generation.
If you encounter a rise in temperature in a permanent magnet rotor, you may wish to try the methods described above. Our company specialises in arc-shaped magnets and multi-pole magnetic rings for motors. Should you require a quotation or wish to view samples from our stock, please do not hesitate to contact us.
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