Design and Analysis of a High Torque Density Hybrid Permanent Magnet Excited Vernier Machine

Abstract

Permanent magnet (PM) excited vernier machines capable of high torque density have good potential for electric vehicles while requiring high rare earth PM consumption. To achieve a high torque density at a reasonable material cost, hybrid PM excited vernier machines incorporating both expensive rare earth and low-cost ferrite magnets are investigated in this paper. Various combinations of PM arrangements for the hybrid permanent magnet excited vernier machine are investigated to acquire low cost and superior torque density. The best solution obtained is that the PM on the stator adopts rare earth material while the rotor uses ferrite. Furthermore, the PMs on the stator are arranged in an iron-cored Halbach array, which can reduce leakage flux and enhance flux density effectively and the ferrite PMs are used in the rotor, therefore, high-temperature demagnetization is avoided. Then, the reluctance torque and the cogging torque can offset each other effectively, which is beneficial to reducing the torque ripple and smoothing the electromagnetic torque. Finally, a prototype is manufactured and tested to verify the correctness of the theoretical analysis.

Influence of Magnetic Remanence and Coercive Force on the Electromagnetic Output of Permanent Magnet Machine

“…It is worth noting that the compared machines have negative mutual inductance values, implying that its actual coil current directions should have been the reversed polarities. More so, the predicted ratio of mutual-inductance to self-inductance listed in Table 2 reveals that lower value of the inductance ratios, which are paramount for effective fault-tolerance capacity, is obtainable in the rare-earth PMs; these results are supported by the long-established fault-tolerance concept detailed in [22] and reemphasized in [23]. The computed self-inductance and mutual-inductance are obtained using Eqs.…”

Optimal gear ratio selection of linear primary permanent magnet vernier machines for wave energy applications

“…The operation principles of LPPMVMs are the same as magnetic gears. Hence, the combination of slots and poles of linear vernier structures is defined based on the relationship of the magnetic gearing effect [24, 25]: $$$$\begin{equation} Z=P_{\text{PM}}\pm P_a \end{equation}$$$$where Z is the number of translator teeth, $$P_{\text{PM}}$$ is the number of PM pole pairs, and $$P_a$$ is the number of armature winding pole pairs. Equation () indicates the selection of slot/pole combinations can be obtained by employing two different relationships based on the magnetic gearing effect: $$$$\begin{equation} Z=P_{\text{PM}}+P_a \end{equation}$$$$ $$$$\begin{equation} Z=P_{\text{PM}}-P_a \end{equation}$$$$The gear ratio (GR) is an important criterion to define the electromagnetic performance of vernier structures, which can be expressed as the ratio of the number of PM pole pairs to the number of armature winding pole pairs.…”

“…The operation principles of LPPMVMs are the same as magnetic gears. Hence, the combination of slots and poles of linear vernier structures is defined based on the relationship of the magnetic gearing effect [24,25]:…”

Comparative Analysis and Design Optimization of Ferrite-Based Surface PM Vernier Machines

“…This allows the power factor of the SPMVM to be improved without sacrificing magnet flux and torque [15,16]. To achieve high torque density at reasonable cost, a hybrid-excited SPMVM [17] utilizing both NdFeB and ferrite magnets has been proposed.…”