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Chlebosz W.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | Ombach G.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft
COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering | Year: 2013

Purpose - In order to reduce CO2 emissions of new cars many hydraulic and mechanical systems like e.g.: water pump, oil pump, power steering, clime compressor have been exchanged with pure electromechanical systems, which are driven only on request. This helps to reduce fuel consumption. This trend requires of utilization of modern brushless electric motors, which are controlled from power electronic control unit - ECU. In today's car can be found between 30 to 150 electric motors. Many of them are still simple brush type with ferrite magnets. Also in this area, drift in the direction of brushless motors can bee seen, because of higher efficiency, longer lifetime, lower noise, better EMC and more controllable torque vs speed characteristic. There are different technological solutions, which can been used in the area of brushless motors in order to reduce size and cost of single component. One major factor of BLDC/AC motor is rear earth permanent magnet material used during production. A magnet material cost could be in the range from 30 percent (basis price 2010) up to 90 percent (basis price 2011) of total material motor cost, depends on actual rear earth material price level. In order to reduce magnet cost, the aim of this paper is to find the most robust motor design, which can be resistant against maximum temperature and phase current amplitude for the same magnet material properties, coercive force - Hcj. This behaviour is called demagnetization property. Design/methodology/approach - Analysis was performed based on review of literature, own theoretical and practical research and experience in the area of electromechanical systems for automotive application. During motor analysis computer numerical simulation method, CAD and experiment were used. Findings - As a result, comparison of different motors' topologies with different properties of magnet materials is presented. The worked out methodology shows very good correlation between simulations and measurements. This work can be used in order to reduce test effort and reduce cost of design. Practical implications - The presented methodology reduces for new designs test effort and development cost and gives an implication of robust motor topology for demagnetization effects. Originality/value - It is the first paper where demagnetization effects have been studied theoretically and in laboratory in order to find the most robust design, reduce magnet cost by reduction of dysprosium content and develop simulation procedure for analysis of demagnetizations behaviours of interior and surface permanent magnet. © Emerald Group Publishing Limited. Source


Ombach G.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | Junak J.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft
2011 International Conference on Electrical Machines and Systems, ICEMS 2011 | Year: 2011

Since last decade many novel interior permanent magnets motors' (IPM) have been developed and introduced in a mass production. Such design has many advantages comparing to well known surface motors' designs; especially it is very robust in terms of permanent magnet requirements: a simple block shape and lower quality issue. These factors play very important role particularly if the costs of neodymium magnet (NdFeB) are under high price fluctuation. Utilization of the IPM motor for sensitive application requires a skewing to minimize cogging and torque ripple. Unfortunately, a skewed IPM motor operates in a field weakening area causing increase of a torque ripple and a motor vibration. This phenomenon is caused by the load dependent reluctance within axial motor's length. This paper describes the presented problem and possible solution for an IPM motor used in automotive area. © 2011 IEEE. Source


Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | Chlebosz W.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft
COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering | Year: 2014

Purpose - The purpose of this paper is to investigate torque ripple and magnetic force on the teeth in interior permanent magnet (IPM) machines over a wide range of speed operation for electrical power steering (EPS) applications.Design/methodology/approach - The flux-weakening capability of IPM machines has been analysed by finite element method considering the effect of cross-coupling between d- and q-axis current. The traditional method of analysing torque ripple is based on constant torque and flux-weakening region. However, the cross-coupling need to be considered when applying this technique to flux-weakening region. Meanwhile, the torque ripple with current amplitude and angle and with different speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth due to the separated teeth with stator yoke is also investigated during the constant torque and flux-weakening region.Findings - The torque ripple and magnetic force on teeth in IPM machine are dependent on current and current angle. Both the lowest torque ripple and magnetic force on teeth exist over the whole torque-speed region.Research limitations/implications - The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple and magnetic force on teeth are not considered in this application. The 12-slot/10-pole IPM machine has been employed in this analysis, but this work can be continued to investigate different slot/pole number combinations.Originality/value - This paper has analysed the torque ripple and magnetic force on the teeth in IPM machines for EPS application over a wide range of operation speed, which are the main cause of vibration and acoustic noise. The variation of torque ripple with current amplitude and angle as well as speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth is also investigated over the whole torque-speed region. © Emerald Group Publishing Limited. Source


Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | Chlebosz W.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft
IEEE Transactions on Industrial Electronics | Year: 2014

A rotor shaping technique with optimal third harmonic is presented to enhance the average torque of interior permanent-magnet (IPM) machines in this paper. The optimal value of third harmonic injected into the rotor outer surface shape has been derived and further confirmed by both finite-element analyses and experiments. The impact of the optimal third harmonic to the rotor shape on the electromagnetic performance, including harmonics in the back electromotive forces, cogging torque, average torque, and torque ripple, is investigated. It is demonstrated that without any modification of the costly rare earth permanent magnet employed for the inverse-cosine-shaped rotor, the average torque of the machine of an inverse cosine injected with an optimal third-harmonic-shaped rotor can be improved by > 6%. Simultaneously, the torque ripple remains almost unchanged, and the saliency ratio is also improved, further boosting the average torque. Finally, the machines with both conventional and optimal third harmonic rotors are prototyped and tested to validate the analysis. © 1982-2012 IEEE. Source


Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | Koch M.,Brose Fahrzeugteile GmbH and Co. Kommanditgesellschaft | And 2 more authors.
IEEE Transactions on Industry Applications | Year: 2014

This paper investigates the electromagnetic performance of an 18-slot/10-pole fractional-slot surface-mounted permanent-magnet (SPM) machine and compares its performance with conventional fractional-slot 9-slot/10-pole, 12-slot/10-pole, and integer-slot 30-slot/10-pole SPM machines by 2-D finite-element (FE) analysis (FEA). The winding factors of the 18-slot/10-pole machine are first analyzed, and then its back electromagnetic force, average torque, cogging torque, and torque ripple are investigated. In addition, the influence of stator current excitation on the average torque and torque ripple, the impact of end windings on the average torque, the flux-weakening capability, the fault-tolerant capability, the magnet loss, and the mutual coupling between phases are also studied by 2-D FEA. The results show that the torque ripple can be suppressed in the 18-slot/10-pole SPM machine, whereas the average torque can be improved compared with the 12-slot/10-pole SPM machine. The unbalanced magnetic force in the 9-slot/10-pole SPM machine can be eliminated. Although the flux-weakening and fault-tolerant capabilities are reduced compared with the conventional 9-slot/10-pole and 12-slot/10-pole machine, the mutual coupling between phases can be eliminated. The magnet loss is slightly higher than that of a 30-slot/10-pole machine but significantly lower than those in both 9-slot/10-pole and 12-slot/10-pole machines. Finally, the experimental results are given for validation of theoretical analyses and FE results. © 1972-2012 IEEE. Source

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