Big rotor vs multiple small rotors in a Permanent Magnet Generator

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SUMMARY

The discussion centers on the efficiency comparison between two configurations of a Permanent Magnet Generator (PMG): Configuration A, featuring 2 large steel plates with 24 magnets each and an 18-coil stator, and Configuration B, consisting of 4 smaller plates sandwiching 3 stators. Both configurations utilize the same number of magnets and coils, theoretically producing equivalent voltage due to the same magnetic flux variation. However, Configuration A may yield higher voltage due to increased rotor speed, while Configuration B minimizes the impact of load-induced slowing due to its closer rotor axis. The efficiency of both configurations remains a critical consideration, particularly regarding I^2R losses.

PREREQUISITES
  • Understanding of Permanent Magnet Generator (PMG) design principles
  • Knowledge of electromagnetic theory, particularly magnetic flux and voltage generation
  • Familiarity with electrical load effects on generator performance
  • Basic concepts of I^2R losses in electrical circuits
NEXT STEPS
  • Research the impact of rotor speed on voltage output in PMGs
  • Explore the design considerations for optimizing coil placement in PMGs
  • Investigate methods to minimize I^2R losses in generator windings
  • Learn about the mechanical advantages of rotor configurations in generator efficiency
USEFUL FOR

Engineers and hobbyists involved in renewable energy projects, particularly those designing or optimizing Permanent Magnet Generators for improved efficiency and performance.

RobertSll
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Hello guys,
I am trying to build a permanent magnet generator, I have 48 magnets and 18 coils, and I am hesitating between 2 configurations.
Configuration A: 2 huge steel plates with 24 magnets on each and an 18 coil stator between them or
Configuration B: 4 smaller plates stacked to sandwich 3 stators, same total number of magnets and coils.
In theory, for both configurations, over 1 complete revolution the same number of magnets would pass over the same number of coils. Since voltage is proportional to the variation of flux in time, in config A the speed of the magnets being higher, a higher voltage is obtained, in an open circuit at least.
But when I add a load current will start flowing and that would slow the rotor. In config A the force will be applied far away from the axis making it easier to slow down the rotor while in config B it will have a smaller impact since it is closer to the axis. Having said all that do you think that I would have the same efficiency for both configurations?
 
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For the same power, higher voltage means lower current and lower I^2R losses in the windings.
 

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