Motor Applications of NdFeB Magnets
12/01/2020 Mike Guthrie

Quadrant typically use one of four different permanent magnet materials modern motors; Alnico, ceramic, SmCo, and NdFeB. Some motors still use Alnico. There are few, and these are high precision, low torque motors, with most emphasis on unchanging long-term stability. But are low torque and larger. Ferrite magnet-containing motors are very common. Can openers, less expensive power tools, and large speakers are common examples of motors using ferrite magnets.  They are used where motor cost is more important than motor size.  Motors containing Samarium Cobalt are used in aerospace and military applications.  But Samarium and Cobalt are costly and SmCo magnets’ energy products are much less than those of sintered NdFeB materials.  NdFeB can replace 99% of other magnet types in motor designs and are typical in any motor that requires high performance and compact size.

NdFeB-containing motors can provide more torque and withstand more demagnetizing forces than any other motor at room temperature. Quadrant provides NdFeB materials that available in the largest variety of energy products and coercivities and so can be used in a very large variety of motor applications. NdFeB grades typically range from 30-55 MGO energy product and have coercivities ranging from 12 to 34 kOe.  Their energy products have significantly exceeded those of every other permanent magnet material.  If you design a motor, chances are that a NdFeB magnet can provide superior performance in that motor.

Their high coercivity and relative ease of magnetization enables very small pole sizes. Magnet poles can have stable interpolar distances of ≤ 0.5 mm and so a very large number of poles can be magnetized, or magnetically printed.  This enables high pole counts for stepper motors or for motor tachometers.

NdFeB motors are varied and plentiful. They power anything from an electric toothbrush to manned aircraft; from a toy slot car to a Tesla and the robots that make them. They are extensively used in drone motors due to their high magnetic properties and light weight. Today’s coatings allow them to operate in satellites, in the body and in salt water scooters. 

Due to their large usage and material cost, sintered NdFeB materials were the first to be recycled in large volumes. This process began with disk drive head actuator magnets and has spread to sintered NdFeB production scrap and salvaged motors.

Bonded NdFeB magnets are an important, but often unrecognized material that is used when a lower energy product is sufficient and a complex shape is desired. Binders of rubber, nylon, epoxy, or plastic are typical, but others are available. These bonded NdFeB magnets are molded to complex shapes and don’t require subsequent fabrication.  Most are isotropic and so can be magnetized in any direction. Anisotropic bonded materials are also available to provide increased energy products in those complex shapes. They can be molded to allow very slim, or very flat motors to fit into specific spaces.  Some do not require coating because the binder completely encapsulates the NdFeB particles. They are used anywhere Br can be sacrificed for complex shape, where energy product can be sacrificed for thin cross section, & where multipole, or odd pole placement, is needed. 

Today's high-performance motors often contain NdFeB magnets. To design the best motor, Quadrant always considers the different magnet materials and their attributes. Contact us to learn more about Quadrant's magnetic products.