A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator

Petter Eklund,Sandra Eriksson,Mats Leijon,Stefan Sjökvist

doi:10.3390/machines2020120

Petter Eklund, Sandra Eriksson + Show 2 more

Open Access

https://doi.org/10.3390/machines2020120

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Journal: Machines	Publication Date: May 16, 2014
Citations: 20	License type: CC BY 3.0

Affiliation: Uppsala University, University of Southampton

Abstract

The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage.

Highlights

In the light of increasing prices of Neodymium-Iron-Boron, NdFeB, permanent magnets, PMs, it has become interesting to replace them with weaker but cheaper ferrite PMs [1]
The generator to be redesigned in this paper is part of an experimental setup, and is identical to the generator used in a 12 kW research wind turbine
A complete design for conversion of a generator with premagnetized NdFeB magnets into a novel design with ferrite magnets is presented

Summary

Introduction

In the light of increasing prices of Neodymium-Iron-Boron, NdFeB, permanent magnets, PMs, it has become interesting to replace them with weaker but cheaper ferrite PMs [1]. To investigate if such substitution is possible, an experimental generator for wind power, built using NdFeB PMs, was chosen to be redesigned to use ferrite PMs. In the redesign of the generator the stator was not to be changed, but the rotor and support structure could be replaced as needed. For the maximum energy product the difference is even larger. For ferrite PM the maximum energy product is typically 32 kJ·m−3 while it for NdFeB

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Conclusion