Zuosheng Yin

As aircraft increasingly transition toward more-electric/all-electric architectures, the demand for higher power density in aviation motor systems continues to grow. However, prolonged high-power-den-sity operation significantly intensifies the challenges of motor thermal management. To address this issue, this paper proposes a hybrid cooling topology based on a Permanent Magnet Synchronous Motor with Tooth-tip Span Angle Modulation Configuration (TSAM-PMSM), which inherently exhibits both high power density and high reliability. For the stator, cooling copper tubes using aviation kerosene as the coolant are integrated into the inter-phase air gaps and double-layer winding slots of the TSAM-PMSM. This enables long-term safe operation at high power density without requiring a separate heat exchanger, thereby further improving the system power density and simplifying the cooling system. By adding cooling slot structures around the copper tubes, low-reluctance magnetic paths are provided for the flux linked with the tubes, greatly suppressing eddy current losses in the copper tubes. For the rotor, a titanium-alloy hollow shaft with copper thermal bridges is proposed to address the heat dissipation challenge of the thin, high-heat-density copper shielding layer. This enhances the rotor’s thermal stability and further reduces the temperature rise of the permanent magnets. A Lumped Parameter Thermal Network (LPTN) is established for both the stator and rotor, enabling rapid analytical calculation of the steady-state temperature rise of key components in the TSAM-PMSM. FEA results demonstrate that the proposed hybrid cooling topology allows the TSAM-PMSM to operate continuously at a current density of 12 A/mm² while meeting the temperature rise requirement.

Current-source inverter (CSI) is considered as a promising candidate in the permanent magnet synchronous machine drive system, for its higher reliability and mitigated electromagnetic interference. In this article, the control scheme of CSI-fed five-phase machine drives with pentagon winding connection (PWC) is investigated. Filter capacitors are in parallel with each winding to bypass the pulsating current. The vector space distribution of PWC-CSI is presented which is different from that of star winding connection-CSI (SWC-CSI). A novel dual-plane space vector modulation is proposed to actively control the third harmonic component. To address the parallel resonance issue, the dual-loop current controller is adopted. Inner voltage loop is for resonance damping, whereas outer current loop is for current regulation. A precise s -domain model of current controller is built for the stability evaluation and parameter tuning. A comparative analysis between five-phase PWC-CSI and SWC-CSI is carried out. The PWC configuration can enhance the harmonic suppression, and exhibits lower dc-link voltage than SWC under the same condition. To explore the fault tolerant capability of PWC-CSI, the inverter single-phase open-circuit fault is analyzed and the post-fault current forms of four remaining healthy phases are recalculated. Experiments are performed to validate proposed schemes.

Current-source inverter is considered as a promising candidate in the permanent-magnet synchronous machine drive system for its superior current waveforms and inherent capability of withstanding the short-circuit failure. However, the resonance issue is yielded, resulting from the paralleling of machine inductances and filter capacitors. Very limited control bandwidth can be retained if only considering the passive damping of winding resistance. In this article, the decoupled active damping current controller in the synchronous frame is investigated. The impedance analysis is performed to make a more intuitive demonstration on the damping mechanism, which reveals that the virtual impedance is not always linearly correlated with the damping gain. The digital delay is crucial for the accurate assessment on the damping effectiveness, and the z -domain discrete model is established to emulate the real circumstance. The quantified analysis is performed on deriving the stable boundaries of controller parameters. The frequency responses and root trajectories are illustrated to validate the conclusions. The optimized parameters are obtained by the proposed tuning procedure, which realizes a balance between the damping effect and the bandwidth performance. Finally, the experiments are performed to verify the proposed control schemes.

A 60-slot/22-pole five-phase machine with hybrid single-/double-layer fractional slot winding is proposed to improve torque under third harmonic current injection condition. Design process of the proposed machine includes two steps of first combining two sets of 20-slot/22-pole machine windings and then shortening coil-pitch. Due to the special structure of the proposed machine, torque-contributing space harmonics in magnetomotive force (MMF) are improved, and redundant space harmonic in MMF which causes high eddy current loss in permanent magnets is suppressed. The proposed machine is evaluated under two modes of third harmonic current injection, namely constant rms and peak harmonic injection. Compared with 20-slot/22-pole machine, the proposed machine achieves higher torque and lower losses under both third harmonic current injection conditions. Besides, the performance of the proposed machine when injecting only the first or third harmonic current is also analyzed.

A novel 36-slot/14-pole dual three-phase permanent magnet synchronous machine (PMSM) is proposed to suppress non-working space harmonics in the synthesized magnetomotive force (MMF) and improve torque density simultaneously. The machine adopts unequal coil-turns winding and special stator core which includes two different types of slots, namely double-layer slots (DLSs) and single-layer slots (SLSs). The special structure of the machine improves the working space harmonic and eliminates lower non-working space harmonics in MMF, which leads to torque promotion and permanent magnet (PM) loss reduction. Harmonic content in MMF of the proposed machine is derived from theoretical analysis and verified by finite element (FE) calculation. Besides, the proposed machine is compared with existing machines, from aspects of MMF, back electromotive force (EMF), torque, losses, efficiency, unbalanced magnetic force (UMF), and torque-speed characteristic. The proposed machine has higher torque density, higher efficiency, and lower PM loss than existing machines.

In this article, we investigate the short-circuit (SC) fault-tolerant control (FTC) method for a five-phase permanent-magnet synchronous machine (PMSM) with surface-mounted permanent magnets. By relieving the constraint of zero d -axis armature magnetomotive force (MMF) and restraining the backward-rotating MMF components to be zero, round-rotating armature MMF with maximum q -axis armature MMF is achieved, which enables five-phase PMSM to output maximum smooth torque with lower losses and higher efficiency under SC fault condition. To ensure smooth postfault operation in full-speed range, the influence of winding resistance on SC current is further considered, which improves low-speed operation performance. The proposed FTC method features sinusoidal currents with equal amplitude, which ensures better control simplicity and postfault thermal uniformity between phases. The finite-element analysis and experiments are carried out to verify the proposed method.

The open-end winding multi-phase permanent-magnet (PM) machine driven by full-bridge inverter is a potential choice for safety-critical application fields. Based on the open-end winding multi-phase PM machine system, comparative investigations of the inverter short-circuit (ISC) fault and winding terminal short-circuit (WSC) fault are carried out to indicate the special characteristics of the ISC in aspects of short-circuit (SC) current characteristics and post-fault performances. The analytical prediction of the SC current under ISC fault is investigated based on the results of WSC conditions. The maximum SC current estimation, SC current rms value variation, and torque harmonic component distribution under the two fault conditions are further investigated. The results can be used for ISC fault diagnosis, PM demagnetization evaluation, and post-fault performance prediction of ISC fault. The post-fault hardware reconfiguration method is further provided to alleviate the effect of ISC fault and reduce the difficulty of compensation.

Based on rotating rhombus method (RRM), an equal-magnitude sinusoidal current compensation strategy is proposed to improve the post-fault performance of five-phase PMSM with short-circuit fault. RRM is a graphic method which is proposed to obtain optimal compensation currents, and the equal-magnitude phase currents are treated as rhombic current vectors. To maintain the same magnetomotive force (MMF) under fault condition, the geometric relations of rhombus are used to derive phase angles of the compensation currents. The effectiveness of the proposed strategy is verified by a 10-slot/8-pole five-phase PMSM, and the torque ripple caused by short-circuit fault is significantly reduced. Besides, the proposed strategy is compared with an existing strategy from aspects of toque, torque ripple, losses, and efficiency, and the proposed strategy has advantages of balanced copper loss of the healthy phases and lower inverter cost.