Nowadays, magnetic gears (MGs) have become an alternative choice for mechanical gears because of their low maintenance, improved durability, indirect contact between inner and outer rotors, no lubrication, and high efficiency. Generally, although these advantages, MGs suffer from inherent issues, mainly the Cogging Torque. Therefore, Cogging Torque mitigation has become an active research area. This paper proposed a new Cogging Torque mitigation approach based on the radial slit of the ferromagnetic pole pieces of MGs. In this method, different numbers and positions of slits are applied. The best results are gained through an even number of slits which shows promising results of Cogging Torque mitigation on the inner rotor with a small mitigation in the mean Torque on both rotors. This work is done by using Simcenter and MATLAB software packages. The inner rotor’s Cogging Torque has mitigated to 81.9 %, while the outer rotor’s Cogging Torque is increased only by 2.75 %.

In brushless Interior Permanent-Magnet (IPM) motors there exists an oscillatory Torque that is induced by the mutual interaction of permanent magnets mounted on the rotor and a slotted structure formed on the stator, generally called the Cogging Torque. This undesirable Torque mainly causes vibration, position inaccuracy and acoustic noise from brushless IPM motors. This paper investigates the inuence of geometric parameters on the Cogging Torque of brushless IPM motors. An exterior-rotor brushless IPM motor, with embedded magnet poles in a V-shape, is introduced. With the aid of commercial finite-element analysis software, Cogging Torque waveforms of brushless IPM motors are accurately calculated. The effects of geometric parameters on the Cogging Torque, including magnet span angle of the rotor, shoe depth and shoe ramp of the stator, dummy slots notched on the stator, depth of the dummy slot and dummy slots notched on both the stator and rotor, are discussed. Ten design cases, with different values of design parameter, are presented to effectively mitigate the Cogging Torque. Design case X of the brushless IPM motor, with dummy slots on the stator, performs better than the original brushless IPM motor, with a 79.1% decrease in the peak value of the Cogging Torque.

One of the important issues in designing high-performance brushless direct current (BLDC) motors is reducing the Cogging Torque since it results in mechanical vibration, audible noises, and Torque ripples, which adversely impact the performance of the motor, which is awkward high-accuracy applications. This paper proposes an optimum design for BLDC motors aimed at reducing the Cogging Torque based on the capability of metaheuristics algorithms in finding the optimal solution. For this purpose, a simplified Cogging Torque equation is used as the objective function whose design variables include air gap length, magnet height, slot height, slot opening, and motor axial length. These are the five most influential parameters of Cogging Torque. On the other hand, we employ not only the old metaheuristics algorithms like the Genetic Algorithm (GA) and Simulated Annealing (SA) but also more recent algorithms such as Keshtel Algorithm (KA) along with the hybrid ones to benefit from their strength. The simulation is performed in the Matlab package. First, five selected optimization algorithms are applied and the results are investigated. The results of all the algorithms show a significant reduction in the Cogging Torque. Eventually, the proposed algorithms are compared to one another in terms of their value of Cogging Torque. The results show the superiority of the KASA algorithm in comparison with the others.

Performing fast and accurate methods for modeling the electrical machines has been the subject of several studies and many authors proposed different procedures to attain this aim. Beside the accuracy, the speed of the method is of great concern. On the other hand, the capability of the method to be changed according to the need is another important issue. Finite Element method provides relatively accurate results but it is time consuming and changing the parameters, once the model designed is difficult to be done. Magnetic Equivalent Circuit method is rather a new concept to model the electrical machines. The most important feature of the method is its flexible accuracy which can be determined due to the user's desire. Another important characteristic is the capability of the method in changing parameters. In this paper, a permanent magnet synchronous motor is modeled using Magnetic Equivalent Circuit; the values of the magnetic flux density and magnetic field intensity are calculated. Afterward, the generated output Torque is calculated using Maxwell Stress Tensor. The comparison between the results of the MEC model and the Finite Element Analysis reveals the sufficient accuracy of the proposed method. Finally, a new method is proposed for Cogging Torque minimization which is based on the Torque pulsation originated from an auxiliary winding. The result shows a significant reduction in the amplitude of the Cogging Torque.

Cogging Torque reduction of axial flux permanent magnet brushless dc (PMBLDC) motor is an important issue which demands attention of machine designers during design process. This paper presents magnet notching technique to reduce Cogging Torque of axial flux PMBLDC motor designed for electric vehicle application. Reference axial flux PMBLDC motor of 250 W, 150 rpm is designed with 48 stator slots and 16 rotor poles of NdFeb type permanent magnet without notching. Three dimensional finite element modeling and analysis is performed to obtain Cogging Torque profile of initially designed reference machine. Notches are created on permanent magnets and its influence on Cogging Torque is analyzed with 3-D finite element modeling and analysis. It is analyzed that magnet notching is an effective technique to reduce Cogging Torque of axial flux PMBLDC motor.