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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. 


Neodymium Magnets
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:

Neodymium Magnets

Advantages

  • 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

Disadvantages

  • Can oxidize if not coated
  • Lower working temp than some other materials

Summary
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:

Samarium Cobalt Magnets

Advantages

  • High Induction (Br). Grades 16-32
  • Great resistance to demagnetization (Hci), up to 350C
  • Excellent resistance to oxidation without coating

Disadvantages

  • High cost
  • More brittle, easier to chip & break

Summary
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:

 

Ferrite / Ceramic Magnets

Advantages

  • Low cost
  • Great resistance to oxidation
  • Large abundance of raw materials

Disadvantages

  • Low Induction (Br), Grades 1-10
  • Usually requires a mold
  • May deteriorate in magnetic field over time.
  • Lower resistance to demagnetization

Summary
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 sales@supermagnetman.com, or 205.989.4353.


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2 comments


  • [Reply from SuperMagnetMan]

    Jay Frost,
    I understand completely – I used these cars when I was a kid and that got me fascinated about electric motors and laid the foundation for me becoming an electrical engineer. :) We store our ceramic magnets all stuck together in a line. That works just fine. You do not want to store them in any way where they can have an opposing field nearby. Ceramic magnets have very low resistance to demagnetization and pushing two repelling ceramic magnets face to face will demagnetize them. If you have stacks of them I would put some spacer material – usually cardboard – in between the rows. Otherwise stacking them should be just fine. :)

    Thanks for asking.
    George Mizzell
    SuperMagnetMan

    George Mizzell on

  • I race H.O. scale slotcars,,about the size of a Hotwheels car,,,,,have an armature Ceramic motor magnets,,,my question is I have so many,,how should I store the magnets that I’m not using? Is it ok to store them together or separately? Thanks for your help Jay

    Jay Frost on

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