Vol.:(0123456789) 1 3 Journal of Electrical Engineering & Technology https://doi.org/10.1007/s42835-021-00991-3 ORIGINAL ARTICLE Asymmetrical Magnets in Rotor Structure of a Permanent Magnet Brushless DC Motor for Cogging Torque Minimization T. A. Anuja 1  · M. Arun Noyal Doss 1 Received: 31 August 2021 / Revised: 10 December 2021 / Accepted: 26 December 2021 © The Author(s) under exclusive licence to The Korean Institute of Electrical Engineers 2022 Abstract Drive motors are the mainstay in our day-to-day life. In drive motors, the Permanent Magnet Brushless DC (PMBLDC) motors are more prominent. It has excellent torque-speed characteristics. Compared to others, it has less maintenance cost. The Cogging torque is one of the crucial obstructions in PMBLDC Motor. It has always been a severe impact on the high performance of the machine. The cogging torque leads to the generation of immense vibration and noise. This paper introduces the magnet shaping method for the decrement of cogging torque in a PMBLDC motor. This asymmetrical rotor structure reduces the magnet locking between the rotor and stator. To obtain the asymmetrical rotor structure here, introduced rotor magnets with thicknesses 2.5 mm and 2 mm. Each of the two has the same pole arc 63 0 . These magnets had placed alternatively. This paper also derived an analytical expression of cogging torque with asymmetrical rotor magnets using the Virtual Work Method (VWM). The PMBLDC motor with the asymmetrical rotor had analyzed by 3D Finite Element Analysis (FEA). The simulation result by FEA had compared with the analytical results. It figured out that the cogging torque reduction in the two compared findings is almost alike. The proposed asymmetrical rotor structure is advantageous in minimizing the cogging torque. Keywords Cogging torque · FEA · Flux densities · PMBLDC motor 1 Introduction Permanent Magnet Brushless DC (PMBLDC) motors are expedient in terms of economical. Usage of less electrical energy, endurance, reduced spatial arrangement, and very little weight are the unique attractions of PMBLDC Motor. Moreover, these are using for high-performance commercial applications. Therefore, the requirement for BLDC has wid- ened in the field of applications. Reference [1] detailed the home appliances, automobiles, aerospace applications, and further growth of BLDC motor. A typical driving technique for UAV propellers using sensor less BLDC control is [2] discussed. The authors in [3] expressed the application of BLDC drives in fans and pumps. Because of the increasing power demand and increasing global warming scenario, we all need to be switching to the energy-saving system. The brushless DC motor is the better solution for satisfying future needs. BLDC motor is possessing high performance, high efficiency, high torque volume ratio, and high speed. Over the last two decades, numerous types of works con- ducted on the cogging torque of PMBLDC Motor. Cogging torque is one of the main obstacles of BLDC Motor. A fair number of methods exist for the minimization of cogging torque. Reference [4] introduce a new technique in single- phase BLDC motor. Applying dip and a dip angle in the air gap profile leads to the minimization of cogging torque. The authors in [5] propose a larger stator slot opening and teeth pairing technique to minimize the cogging torque in the BLDC motor. They concluded that teeth pairing is more effective than larger slot opening. An auxiliary slots and stator claw skewing method is introducing in [6]; both approaches expediently embodied at the level of punching the steel sheets. The article [7] discussed a collaborative technique of LHS and a GA for stator shape optimization design to pare down the cogging torque of single-phase brushless dc (BLDC). In [ 8] introduces a spoke type * M. Arun Noyal Doss arunnoyal@gmail.com T. A. Anuja taanuja@gmail.com 1 Department of Electrical and Electronics Engineering, SRM Institute of Science and Technology, SRM Nagar, Kattankulathur 603203, India