How to Size a Magnet for an Electric Generator

An electric generator provides backup electricity during power outages and when you're camping away from the electrical grid, but many people are building their own electric wind and water generators in order to produce their own power at home. If you are making an electricity generator, you need to know how to select the right size of magnet in order to get the most out of the machine. The easiest type of generator to make in the home workshop is the pancake style, as it uses simple parts attached to flat plates.

Measuring tape
Rotor plate
Stator plate
Calculator

Instructions

- 1
  Measure the diameter of the rotor plate, in inches. The rotor is a plate mounted onto an axle. The wind blades or water wheel cause it to rotate, hence the name. The magnets will mount on the rotor plate.
- 2
  Count the number of coils on the stator plate. The coils are mounted on a fixed plate facing the rotor. As the magnets move past the coils, the constantly changing magnetic field induces current to flow in the coils.
- 3
  Multiply the diameter of the rotor by 3.14. The will give you the circumference of the rotor. Divide the circumference by the number of coils on the stator. The result is the amount of space on the rim of the rotor that each magnet can take up. You want your magnets to be as close to this size as possible.
- 4
  Find the widest magnets that you can as close to this length as possible. Multiply the width of the magnets by two. Subtract the result from the diameter of the rotor. This result is the diameter of that part of the rotor where the bottoms of the magnets will lie. If this number is less than six times the length of one of the magnets, then the magnets are too wide. Find narrower magnets.

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