Abstract
Synchronous homopolar motors (SHMs) have 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 its 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 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.
Highlights
The synchronous homopolar motor (SHM) has been used in specific applications for over a century
The main advantage of the SHM is its simple and reliable construction with its brushless excitation located at the stator of the machine together with the armature winding
SHMs are utilized as generators in traction applications [1], aircrafts and trains [2], welding inverters [3], [4], etc
Summary
The synchronous homopolar motor (SHM) has been used in specific applications for over a century. The equivalent magnetic circuit was developed for a low power synchronous homopolar generator in [5] The advantage of this approach is the absence of the virtual excitation windings at the rotor teeth to simulate the field winding. The second parts of the equations introduce the linear density of the magnetic monopole, which simulates excitation flux This flux flows through the shaft sleeve and stator back iron between the SRSCs and is defined as follows:. Using the considered symmetry operation, the last boundary value problem is derived from the first when the rotor is rotated by 1/nph of the electrical revolution, and it appears excessive This additional boundary value problem is useful for the evaluation of the losses in the armature winding produced by eddy currents and for the stator or rotor core losses calculation.
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