Traction Synchronous Homopolar Motor: Simplified Computation Technique and Experimental Validation

Abstract

The synchronous homopolar motor (SHM) has been attracting the attention of researchers for many decades. Various mathematical models of SHM have been proposed to deal with its complicated magnetic circuit. Among them, there are time-consuming 3D finite element models (FEM), equivalent circuit models neglecting some significant features of the machine design, and 2D FEM models with virtual excitation winding distorting magnetic field picture. This paper proposes a novel 2D FEM of SHM and shows that since there are no sources of excitation in the cross-sections of the rotor and stator stacks, no virtual elements are required. This model uses the general solution of the Gauss's law for magnetism containing excitation flux. The model is based on a set of magnetostatic boundary value problems for various rotor positions. The set of boundary problems is completed with the excitation equivalent circuit. The losses in the armature and field windings and in the stator and rotor magnetic cores are computed in postprocessing. All these computations are carried out for a single combination of stator and rotor stack. A symmetrization algorithm is proposed to extend the obtained results to the whole SHM. A comparison of the theoretical and experimental data for a nine-phase three-section 320 kW SHM is carried out. These SHMs were used in a mining truck with a carrying capacity of 90 tons. INDEX TERMS AC machines, automotive applications, brushless motors, electric vehicles, electromagnetic modeling, mining industry, traction motor.

Design Optimization of a Traction Synchronous Homopolar Motor

“…Then, the symmetrization procedure is applied to spread the results to the real SHM. A detailed description of the mathematical model of SHM is given in [11].…”

“…A symmetrized torque ripple is produced by a SHM as a whole. Details of TR and TRsym are given in [11].…”

“…The article [11] described a new method of the mathematical modeling of SHMs, which is based on the 2D FEM. In contrast to the mathematical models of SHMs based on the 3D FEM [7,8], this method requires less computation time and is less demanding on the available computing resources.…”

“…However, the traction SHM was developed without using any optimal design methods such as the genetic algorithm or the Nelder-Mead method. Therefore, the characteristics of the traction SHM described in [11] can be improved.…”

“…Synchronous homopolar machines have been known for a long time and are used in various equipment such as generators in aircrafts and trains [12], welding inverters [13], and flywheel energy storage systems [14]. Moreover, in [4,5,11,15,16], SHMs were presented as traction motors. In [17], the design of an SHM for a flywheel energy storage was considered with the use of 'manual' optimization of the SHM parameters based on a lumped model to obtain a higher efficiency of the machine.…”