Many air conditioner fans, EC fans, and brushless fans now use a type of magnet called an “injection-molded magnetic ring.” These are becoming increasingly common, especially in indoor and outdoor fans. So, what exactly is an injection-molded magnetic ring for fans? What are the common specifications and pole counts?
Simply put, an injection-molded magnetic ring for fans is a ring-shaped magnet. It is produced by mixing magnetic powder with plastic material, directly injection-molding it through a mold, and then magnetizing it with multiple poles. The most common type is the injection-molded ferrite magnetic ring. Additionally, there are injection-molded neodymium-iron-boron magnetic rings, which offer superior magnetic performance.
As for why injection-molded materials are so widely chosen, it is mainly because they are relatively inexpensive, wear-resistant, shatter-resistant, and easy to magnetize with multiple poles.
Radial multipole injection-molded ferrite rotor magnets

Regarding the number of poles, 8-pole configurations are currently the most common in EC fans and brushless fans.
There are countless specifications for magnetic rings, and no standard size. The outer diameter generally ranges from 20 to 55 mm, with an inner diameter of around 8 mm being the most common, and a height typically between 10 and 25 mm.
Many fan manufacturers now opt for off-the-shelf specifications. Given the high volume of demand in the fan industry, if specifications are similar, they can often simply adjust the dimensions or share molds, which saves a significant amount on tooling costs and speeds up the development cycle.
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