The asymmetric design of hairpin windings is known as a method for reducing AC losses in electric motors, especially at high frequencies. However, the design of the asymmetric winding is very critical to obtaining the best benefit regarding the efficiency and the thermal performance of the motor. Compared to the state-of-the-art in this paper, deep investigations are carried out to obtain the optimum design of the asymmetric hairpin windings while still employing a conventional manufacturing method. An analytical model is developed to speed up the investigation process, and the results of the analytical model are validated with a finite element method (FEM) model. The conclusions from the analytical investigation are considered in the design of an electric vehicle (EV) motor. The performance of the motor is studied for two different driving profiles to validate the rules of the asymmetric windings design and check the degree of dependency of the design of asymmetric windings on the application. It is proved that using asymmetric design reduces motor losses and improves thermal performance.

Elimination of the position sensor reduces the cost and simplifies the drive system. This paper investigates the sensorless operation of a synchronous reluctance motor (SynRM) equipped with a cage. The concept of active flux is extended to involve this type of motor (cage-rotor SynRM). The performance of the drive system under the proposed control method is compared to the reported technique in the literature for cageless SynRM. The sensorless operation of cage rotor SynRM is investigated under different operating conditions. Matlab/Simulink software is used for modeling and analysis of the proposed method. The obtained results assured the successful application of the extended concept to the cage-rotor SynRM.

Some applications expose the electric motor to severe thermal cycling, which negatively impacts the motor winding mechanically. Such impact results in loss of adhesion, abrasion, cracking, and wear of different components within the slot and the motor, leadingtodegradation or complete failure. Before relating the mechanical stress resulting from thermal stress to the failure of the motor, a deep investigation is carried out to understand the physical phenomena inside the slots as a reaction to heating and cooling. The first heating and cooling cycle in the life of a motor is the curing process of the impregnation material, and thereafter, many heatingcooling cycles occur during normal operation. In this article, mechanical strain on hairpin winding resulting from the curing process of the impregnation material is investigated to get an understanding of residual mechanical stresses inside a motor after curing. An impregnated specimen is exposed to thermal cycling to study the resultant mechanical stress and its related parameters. The experimental results are compared with the simulation results, and they correspond well. Different impregnation materials are checked to allow choosing the suitable combination of materials that exposes the motor to the lowest stress.