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

2019

Energies

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Due to the price and supply insecurities for rare earth metal-based permanent magnet (PM) materials, a search for new PM materials is ongoing. The properties of a new PM material are not known yet, but a span of likely parameters can be studied. This paper presents an investigation on how the remanence and recoil permeability of a PM material affect its usefulness in a low speed, multi-pole, and PM synchronous generator. Demagnetisation is also considered. The investigation is carried out by constrained optimisation of three different rotor topologies for maximum torque production for different PM material parameters and a fixed PM maximum energy. The rotor topologies used are surface mounted PM rotor, spoke type PM rotor and an interior PM rotor with radially magnetised PMs. The three different rotor topologies have their best performance for different kinds of materials. The spoke type PM rotor is the best at utilising low remanence materials as long as they are sufficiently resistant to demagnetisation. The surface mounted PM rotor works best with very demagnetisation resistant PM materials with a high remanence, while the radial interior PM rotor is preferable for high remanence materials with low demagnetisation resistance.interact with the demagnetisation magnetic flux density curve. Different rotor topologies have been studied previously. In [13], three topologies, similar to those studied here, are compared for use in 4-pole traction motors for trains. Similar topologies are compared for use as an aircraft starter-generator in [14]. Five different topologies, not including the spoke-type rotor, are compared in [15]. Ref. [16] also compares five different topologies, including the spoke-type rotor. Ref.[17] compares machines with Nd-Fe-B, Sm-Co and alnico for surface mounted 4-pole machines. Ref.[18] compares three machine configurations for interior v-shaped magnets for two different materials: the novel material NdFe 12 N x and a conventional Nd-Fe-B magnet. A spoke-type rotor with ferrites is compared to a rotor with surface mounted Nd-Fe-B magnets for a wind power generator in [19,20]. A comparison of demagnetization risk for the same generator types is presented in [21].The aim of this paper is to study how the magnetic properties of PM materials affect the machine design in low-speed radial flux PM generators. To our knowledge, there has not been any previous study combining material properties with rotor design and rotor topology choice. The results from this study could give hints on which property to improve when developing new PM materials as well as on the suitability of a material with certain magnetic properties for different generator topologies.

Section: Geometries and Rotor Topologiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Influence of Permanent Magnet Material Properties on Generator Rotor Design

2019

Energies

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“…The new model has been verified against transient FE simulations of two different machines. One is a 32-pole experimental wind power generator with a spoke type, ferrite PM rotor that is described in [12]. The other is a rough two-pole machine design with a buried PM rotor using neodymium-iron-boron PMs, similar to the one described in [13].…”

Section: Validationmentioning

confidence: 99%

Winding Design Independent Calculation Method for Short Circuit Currents in Permanent Magnet Synchronous Machines

2018 XIII International Conference on Electrical Machines (ICEM)

2018

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When designing permanent magnet (PM) synchronous machines the demagnetizing effect of armature short circuit currents on the PMs needs to be considered. In some cases there can be a need to estimate the demagnetizing field from the winding without knowing the winding scheme. To do this, a lumped parameter model of the dynamics of the magnetic field and armature current distribution is proposed. Validation of the model using two different machines shows acceptable agreement. The proposed model is found to be useful for its particular purpose of determining the approximate short circuit current distribution in the armature without knowing the winding design.

“…In response to the 2011 cost increase of neodymium-iron-boron (NdFeB) PMs there has been work on permanent magnet synchronous generators (PMSGs) using other, less expensive, rare earth metal-free kinds of PMs [1]. The design of one such PMSG is described in [2]; where a ferrite PM rotor is designed to replace a NdFeB PM rotor, while preserving the electrical properties of the machine. A generator has been retrofitted with the ferrite PM rotor, and is currently being experimentally evaluated.…”

Section: Introductionmentioning

confidence: 99%

Air gap magnetic flux density variations due to manufacturing tolerances in a permanent magnet synchronous generator

2016 XXII International Conference on Electrical Machines (ICEM)

2016

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The impact of manufacturing tolerances on the performance of a permanent magnet synchronous generator is investigated. A generator with a flux concentrating spoketype rotor, with ferrite permanent magnets, is used in the investigation. Measurements of the air gap magnetic flux density, the air gap length, as well as the magnetization and size of the permanent magnets have been performed. Correlations are calculated and causalities are discussed. It is found that the permanent magnets used are below tolerance in remanent magnetic flux density, that the air gap length is smaller than specified, and that the resulting air gap magnetic flux density is lower than specified. From the results it can be concluded that the design should be made with tolerances in mind and that quality control of parts, especially of PM magnetization, is important for machine performance.