Types of Motor Magnets and Magnetisation Methods

Types of Motor Magnets and Magnetisation Methods

I. What are motor magnets?

Motor magnets are made of permanent magnet materials and are primarily used in permanent magnet motors. They are shaped like tiles, hence the industry term ‘motor magnets’.

II. What types of motor magnets are there?

Depending on the material used, there are generally three common types: neodymium-iron-boron motor magnets, ferrite magnets and aluminium-nickel-cobalt magnets.

III. What are the methods for magnetising motor magnets?

1. The magnets are magnetised individually before being installed in the housing, and assembly takes place after magnetisation. This is known as open-circuit magnetisation. As there is no external magnetic circuit during magnetisation, a closed loop is not formed; magnetisation is unlikely to reach saturation, which may affect the magnetic flux density of the magnets themselves.

2. The magnets are magnetised after being installed (and secured) in the housing, followed by assembly of the complete unit. This is known as closed-circuit magnetisation. The magnetic flux density is high after magnetisation. To meet the performance requirements of different motors, the waveform of the air gap magnetic flux density can be adjusted via the shape of the magnetising head. The disadvantage is that assembly is complicated and requires the use of specialised jigs for mirror-image assembly.

3. The magnet is installed in the housing (and bonded) before the finished product is assembled, and the entire unit is magnetised as a whole. This is a closed-circuit magnetisation method, and the magnetic flux density after magnetisation lies between that of the two methods described above.