Decreasing the mass of a wheel hub motor by improving the design of a motor’s electromagnetic circuit is discussed in this paper. The authors propose to increase the number of magnetic pole pairs. They present possibilities of mass reduction obtained by these means. They also analyze the impact of design changes on losses and temperature distribution in motor elements. Lab tests of a constructed prototype, as well as elaborated conjugate thermal-electromagnetic models of the prototype motor and modified motor (i.e., motor with increased number of magnetic poles) were used in the investigation. Simulation models were verified by tests on the prototype. Results of calculations for two motors, differing by the number of pair poles, were compared over a wide operational range specific to the motor application in the electric traction. A detailed analysis of the operational range for these motors was also made.

The article presents the analysis of operational parameters and thermal analysis of the wheel hub motor during operation in the car drive. The authors proposed an analysis of the operation of the wheel hub motor mounted in a hybrid car, during Artemis driving cycles and while driving on the road with different slopes. The simulations were carried out in the Ansys Motor-CAD program. The calculations are based on coupled models of the electromagnetic circuit and thermal models of the motor. The conducted research is a proposal of an approach to the design of electric vehicle propulsion motors, which allows us to consider problems related to predicting at the motor design stage what are its possibilities and what risks during operation in a real drive. The analysis also includes the impact of the applied motor control strategy and the variation of the supply voltage. These are aspects that are extremely important in wheel hub motors, as they are weight-optimized motors with a limited volume and a relatively high power and torque density.

The drive system of an electric car must meet road requirements related to overcoming obstacles and driving dynamics depending on the class and purpose of the vehicle. The driving dynamics of modern cars as well as size and weight limitations mean that wheel hub motors operate with relatively high current density and high power supply frequency, which may generate significant power losses in the windings and permanent magnets and increase their operating temperature. Designers of this type of motor often face the need to minimize the motor’s weight, as it constitutes the unsprung mass of the vehicle. Another limitation for motor designers is the motor dimensions, which are limited by the dimensions of the rim, the arrangement of suspension elements and the braking system. The article presents two directions in the design of wheel hub motors. The first one involves minimizing the length of the stator magnetic core, which allows for shortening of the axial dimension and mass of the motor but involves increasing the thermal load and the need for deeper de-excitation. The second one involves increasing the number of pairs of magnetic poles, which reduces the mass, increases the internal diameter of the motor and shortens the construction of the fronts, but is associated with an increase in the motor operating frequency and increased power losses. Additionally, increasing the number of pairs of magnetic poles is often associated with reducing the number of slots per pole and the phase for technological reasons, which in turn leads to a greater share of spatial harmonics of the magnetomotive force in the air gap and may lead to the generation of higher power losses and higher operating temperatures of permanent magnets. The analysis is based on a simulation of the motor operation, modeled on the basis of laboratory tests of the prototype, while the car is driving in various driving cycles.

Electric mine motor thermal models aiding design and setting thermal protections: The paper presents original modified thermal networks for calculations of the temperature field in induction mine motors under steady and transient conditions aiding design and setting thermal protections. They can be used for location of the hottest places in motor elements in order to place in them sensors for temperature measurements. They can be also applied to determining the equivalent thermal constants of windings needed when setting microprocessor thermal protections.