Choosing the Right Magnet for Your Motor

In industrial applications, the type of magnet you choose has major implications on motor design, project costs and overall performance. It’s important to make an informed decision in this step of the process.

But where do you start? How do you know what type of magnet to use?

Key Magnet Qualities to Consider

Before you make any decisions, it’s important to first understand the qualities that differentiate magnets and their potential applications.

• Remanence: the magnetic strength of the material.
• Energy Product: the maximum amount of magnetic energy that can be delivered at peak performance.
• Intrinsic Coercivity: the material’s resistance to demagnetization – essentially, a measure of stability as temperature increases.
• Curie Temperature:  the temperature at which a material’s magnetic properties are rendered ineffective.

Properties of the 4 Major Magnet Families

There are 4 main types of magnets – each with distinct properties. Understanding the various tradeoffs enables you to make the most informed decision possible.

Ferrite
Ferrite magnets have low intrinsic coercivity levels. Basically, they are cheap and stable. However, ferrite magnets have the lowest remanence and energy product levels. In order to produce high levels of torque, these magnets have to be large. Your entire motor design will have to accommodate this size and weight.

Aluminum Nickel Cobalt (AlNiCo5)
AlNiCo5 magnets offer the lowest intrinsic coercivity levels and are best for high temperature applications. They are stronger than Ferrite magnets, but remanence and energy product values are still low, requiring size and weight alterations in the motor.

Neodymium Iron Boron
Neodymium is a rare-earth element, so these magnets are expensive. Neodymium magnets also become unstable at high temperatures. However, they have high remanence and energy product levels. Neodymium magnets produce strong magnetic fields in a small package.

Samarium Cobalt
Samarium is also a rare-earth element. These magnets will be the most expensive. But, they have the highest remanence and energy product levels, and they’re stable at high temperatures. Samarium magnets are used in small, powerful motors that operate in high temperatures.

Understanding the properties of these materials is crucial. Once you align the needs of your project with the qualities of these magnets, you’ll be able to choose the right magnet for your motor.

To learn more, consult MCMA’s technical feature on magnets and motors.