Double-sided DC-Vernier reluctance linear machine (DS-DC-VRLM) is very suitable for long stroke industrial processing applications, taking advantages of magnet-free design, eliminated magnetic pull and high dynamic response. However, its low trust force density due to poor excitation ability of DC windings, has been a longexisting bottleneck. Aiming to boost the output thrust force of the DS-DC-VRLM, a novel high-order harmonic nonoverlapped toroidal winding design is proposed. The key is that the proposed armature winding makes full use of working harmonics modulated from both fundamental order and third-order harmonics generated by DC excitations, contributing to enhanced winding factor. Based on the finite element analysis (FEA), with the proposed winding design approach, DS-DC-VRLM could achieve 2.26 times higher thrust force than those with conventional concentrated winding under the same copper loss. In this paper, new winding arrangement of DS-DC-VRLM and its operation principle are introduced, along with some design considerations of it, such as slot/pole combinations, DC/AC current distributions and extra end teeth dimensions are discussed for performance improvement. Finally, the performances of this proposed machine are evaluated by prototype experiments to verify the correctness of FEA simulation results.
DC excited doubly salient variable reluctance machine has received more attention due to its robust rotor structure, low cost and permanent magnet-free. In this paper, a short-pitch distributed winding connection with improved fifth order harmonic is newly applied in this kind of machine to enhance the torque production under the same current excitation. Its electromagnetic performance is analyzed by finite element analysis. The simulation results verify that compared with the traditional concentrated winding distribution, the proposed winding arrangement can effectively improve the back EMF as well as the motor output torque density.
Variable reluctance linear machine (VRLM), which takes advantages of magnet free, simple structure and low cost, is one of the emerging candidates for long stroke application. However, due to the abundant harmonics in the air gap, the conventional modular linear machine suffered from thrust ripple which leads to vibration and acoustic noise problem. The thrust force ripple in VRLM is mainly caused by higher-order harmonics in the induced voltage and detent force. To furtherly suppress the oddorder harmonics in the induced voltage and detent force, a fractional pole-pair unequal module arrangement (FP-UMA) design, in which the distances of adjacent modularized mover segments are not equal, is proposed to VRLM and collaborated with complementary structure in this paper. The key is that the modularized movers are artificially designed to be unequally distributed regarding to spatial distribution to eliminate the odd-order harmonics in the induced voltage along with the thrust ripples they caused based on the quantitative analysis on the thrust ripple components. It is revealed that, with the proposed FP-UMA design, the thrust ripple ratio of the machine has been effectively relieved from 4.6% to 2.2% under copper loss of 450W. Further, some design guidelines for the proposed machine, such as position offset of modularized mover m2, DC loss ratio kdc and slot pole combinations are discussed. In addition, the feasibility of the proposed design method is evaluated by finite element method as well as experiments.
To combine the advantages of permanent magnet motor and electric excitation, a hybrid excitation Vernier reluctance motor is proposed in this paper. To make improved usage of working harmonics and relieve saturation effect in the stator core, a short-pitch distributed winding connection utilizing working harmonics modulated from fifth-order harmonics of DC excitation is newly applied to this machine, and tangentially-magnetized PMs are also introduced in this paper. The finite element analysis (FEA) simulation results verify that the proposed winding arrangement can achieve 26% higher output torque density compared to the conventional concentrated winding distribution and the slot PM can effectively alleviates the magnetic circuit saturation in the stator core.
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