# Designing a three phase permenent magnet generator

I am designing a three phase permenent magnet generator , and have a question.
as a magnet pair passes over a coil , inducing a voltage, that voltage is most dependent on ?
1) the angular velocity ( thats a given)
2) the pole strength
3) flux density
4) energy product.
5) thickness of the magnet ( not the width / length or diameter)

Assuming the diameter of the magnet is in the correct proportion to the coil for a three phase generator how is the the thickness of the magnet related to the induced voltage?
I have experimented with this , using 7/8" dia x 1/2" and 7/8" dia x 1" NdFeB magnets , with the same air gap , same coil , doubling the thickness only produced a 15 percent increase in voltage . why?
I was expecting to double the induced voltage .

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Gokul43201
Staff Emeritus
Gold Member
willib said:
Assuming the diameter of the magnet is in the correct proportion to the coil for a three phase generator how is the the thickness of the magnet related to the induced voltage?
I have experimented with this , using 7/8" dia x 1/2" and 7/8" dia x 1" NdFeB magnets , with the same air gap , same coil , doubling the thickness only produced a 15 percent increase in voltage . why?
I was expecting to double the induced voltage .
Can you provide a simple diagram of the geometry. It may just be that you are adding the extra thickness at a greater distance from the coil, and hence, not providing twice the field at the coil.

Gokul43201 said:
Can you provide a simple diagram of the geometry. It may just be that you are adding the extra thickness at a greater distance from the coil, and hence, not providing twice the field at the coil.
yes i have diagrams , but would like to ask first , are my thoughts on doubling the thickness , and hence getting double the voltage , essentially correct?

Gokul43201,
have you checked your private messages , i sent you one on feb 7th.
i dont know who else to turn to for an answer, the gap is adjustable and is essentially the same @ 0.460" , for both tests.
my test coils are 0.390" thick. i have several.
0.035" space top and bottom..
this is a dual rotor machine 24 poles , 48 magnets
magnets are 7/8" dia , coils are 1.75" dia,with a 7/8" hole
rotors are 10.8" dia

Thanks for the reply , i really appreciate it