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High torque density at low speed is one of the main characteristics of applications such as wind turbines and traction systems. Permanent magnet transverse flux machines exhibit this features owing to their high-energy magnetic flux, which is normal to current and motion vector. The machine's specific geometry magnifies cogging torque that further increases torque ripple, noise, and mechanical vibrations...
A dual-rotor axial field flux-switching permanent magnet (DRAFFSPM) machine is proposed and investigated in this paper. The static characteristics, such as the field distribution, the PM flux-linkage, the back-EMF, and the cogging torque, etc., are investigated based on the 3D finite element (FE) method. In order to gain sinusoidal back-EMF and reduce the cogging torque, the structure of the DRAFFSPM...
Cogging torque is a common design issue in Permanent Magnet Synchronous Machines (PMSMs). Altering the magnet shape is one of the solutions in reducing the cogging torque. This paper addresses the variation in the rotor magnet pole arc which would affect the cogging torque of the external rotor permanent magnet synchronous motor (ERPMSM). Analytical calculations to design a three-phase, 12slot/8pole...
This paper presents a method of reducing the cogging torque of transverse flux machines by shaping the poles of the rotor. A number of different techniques are presented and simulated. These simulations are verified by the construction of a number of rotors from which measured results have been obtained. Further to this, the rotors are applied to machines with different cogging torque reduction techniques...
This paper proposes a rotor tooth shaping method to reduce the cogging torque of an axial flux-switching permanent magnet machine. The rotor tooth is shaped in different configurations, including constant, trapezoidal, asymmetrical, extended, and square shapes. 3-D finite element analysis is performed to compare the proposed shapes of rotor tooth. Peak-to-peak cogging torque, fundamental flux linkage,...
Recently, outer-rotor electric machine become a research attention to be applied for in-wheel motor either in electric or hybrid electric vehicles (EVs). Among the competitor for in-wheel machines, the permanent magnet synchronous machine (PMSMs) with an outer-rotor have been used widely due to their high performances in terms of torque ad power. However, there is drawback cause by demagnetization...
The paper presents the concept and results of simulation and experimental research of a claw pole generator with hybrid excitation. Hybrid excitation is performed with a conventional coil located between two parts of the claw-shape rotor and additional permanent magnets which are placed on claw poles. Within the research first a simulation and next constructed experimental model has been developed...
Flux switching machines (FSMs) have been created to describe machine in which the stator tooth flux switches its polarity by following the motion of a salient pole rotor. In general, FSMs can be classified into three group clusters that are field excitation (FE) flux switching motor, permanent magnet (PM) flux switching motor and hybrid excitation (HE) flux switching motor. The main flux sources for...
This paper analyzes the cogging torque mechanism of the hybrid excitation flux switching motor. The finite element analysis (FEA) is used to study different cogging torque suppression methods of the motor. These methods include rotor skewing, variable tooth width, auxiliary slot, variable rotor arcs. By comparing these methods, we can say that rotor skewing can not only greatly reduce the cogging...
This paper discusses a method for reducing cogging torque and harmonic content of back EMF waveforms in modulated pole machines (MPMs). Tooth pitching is applied to a separate phase MPM in order to reduce the most prominent harmonics present in a three-phase MPM's cogging torque. Experimental results show that the application of tooth pitching to these machines can reduce the cogging torque and back...
With the aid of genetic algorithm (GA), global optimization with multiple geometry parameters are feasible in the design of switched flux permanent magnet (SFPM) machine. To investigate the advantages of global optimization over individual one, which has been used extensively for the design of SFPM machines, the comparisons between two approaches are carried out at the fixed copper loss and volume...
This paper presents a general method for predicting the cogging torque in surface-mounted permanent magnet machines having different slot sizes and uneven positions by synthesizing the cogging torque associated with each slot, which is obtained by the subdomain model. The developed model is applied to analyse the influence of imperfect slot openings on the cogging torque. It shows that machines having...
Flux concentrated permanent magnet transverse flux machine (FCPM-TFM) that is designed to achieve a compact design for in-wheel applications, has been set under test experiments to verify the published investigations that are demonstrated in [1-6] and achieved through many computer simulations via using FLUX3D, a 3D finite element (FE-) package from Cedrat. The study in this paper includes generator...
The paper presents a new method for simulation of the cogging torque in a PM machine. The method benefits the numerical functions for modeling the magnetic system of the electrical machine. To compute the cogging torque by the numerical functions, it is necessary to model the permanent magnets and permeance of the machine. In this paper, we introduce two improved numerical functions to model them...
An optimal design procedure, based on Hooke-Jeeves method, applied to a permanent magnet transverse flux motor (PMTFM) is presented in the paper. Different objective functions, as minimum cost, minimum cogging torques and maximum efficiency were considered. The results obtained for a low power sample PMTFM are given and commented.
Low cost and low cogging torque are the most important aspects in the design of direct drive PM wind generators. In this paper a low cost PM wind generator with an irregular, parallel slotted stator is analysed with respect to cogging torque. The sensitivity of average torque and cogging torque to machine dimension variations are investigated. From this a method is proposed whereby regions of low...
Cogging torque in permanent magnet machines causes torque and speed ripples, as well as acoustic noise and vibration. It is important to be able to accurately measure the cogging torque. This paper describes a simple test method for measuring the cogging torque waveform, together with finite element analyses. It is based on measuring the reaction torque on the stator and is suitable for both single-phase...
The flux-switching permanent magnet (FSPM) machine exhibits competitive torque capability and power density due to the high flux density. As a penalty, the cogging torque is relative large, resulting in unfavorable torque pulsation. Due to the simple and robust rotor construction, additional dummy slots are adopted to reduce the cogging torque without skewing magnets or teeth. The optimal dimensions...
The doubly-salient permanent magnet (DSPM) motor employing straight rotor and concentrated windings is conventionally operated by means of current chopping control in constant-torque region and angle-position control in constant-power region due to the trapezoidal back-EMF waveform. However, the rotor-skewing method can be used to improve back-EMF and inductances waveforms to be sinusoidal significantly...
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