Motor Magnets - Arcs, Squares, Radial Rings & Rectangles
July 19, 2016
Motor design is a true balance of all materials: magnets, stators, wire material, number of turns, etc. Picking the best magnet begins with knowing your overall objectives with torque, RPM, and start-up load.
This article will only focus on the permanent magnet options for motors. The three (3) most commonly used permanent magnets used in motors are Neodymium Magnets, Samarium Cobalt (SmCo) Magnets, and Ferrite / Ceramic Magnets. Below is a summary of each magnet material, and an overview of their advantages and disadvantages.
These magnets are the strongest magnets on the market and give the most magnetic field in a motor circuit. They come in many material variations, which can be found in the tables & curve section of our website. Below is a list of advantages and disadvantages:
- High Induction (Br). Grades 30-55
- Good resistance to demagnetization (Hci)
- High Flux density / sq. cm (MGOe)
- Correctly selected material will last indefinitely
- Can reduce size / weight / size of rotor & stator
- Large selection of material grades
- Can oxidize if not coated
- Lower working temp than some other materials
Neodymium Magnets will work well in an application that requires high stability, high induction over a lower operating temperature.
Samarium Cobalt Magnets
These magnets are the strongest magnets on the market after Neodymium Magnets. They come in several material variations, better known as SmCo 1-5, or SmCo 2-17. Below is a list of advantages and disadvantages:
- High Induction (Br). Grades 16-32
- Great resistance to demagnetization (Hci), up to 350C
- Excellent resistance to oxidation without coating
- High cost
- More brittle, easier to chip & break
Samarium Cobalt magnets will work well in a high temperature applications that requires a large resistance to demagnetization
Ferrite / Ceramic Magnets
These magnets are the most widely used in motors due to lower cost. But with the low cost comes other trade offs. Below is a list of advantages and disadvantages:
- Low cost
- Great resistance to oxidation
- Large abundance of raw materials
- Low Induction (Br), Grades 1-10
- Usually requires a mold
- May deteriorate in magnetic field over time.
- Lower resistance to demagnetization
Ceramic magnets will work well in an application where greater concern is given over the size & weight requirements.
Picking the Correct Magnet
Each motor design is very different. Check out the inventory of Arc Magnets, Square Magnets, Radial Rings, and Rectangle Magnets we have in stock. Don’t see the size, shape or material that you need, Request a Custom Magnet Quote.
About SM Magnetics: SM Magnetics is a privately owned company providing assistance from concept to production with magnetic circuit design, engineering support, material selection, and supply of magnetic materials and assemblies. Inquiries or requests for assistance can be made to firstname.lastname@example.org, or 205.989.4353.