Hanlin Zhan

Novel Consequent-Pole Hybrid Excited Machine With Separated Excitation Stator

A partitioned stator hybrid excited machine is proposed, in which the permanent magnets and field windings are alternately placed on an inner stator separated from the outer stator having armature windings. This machine inherits the features of brushless machines and benefits from better space utilization. The operating principle and the effects of slot/pole combinations are investigated in detail. Further, based on 2-D finite-element analysis, the electromagnetic performances of the proposed machines, including back-electromotive force, cogging torque, flux regulation range, torque capability, power factor and torque-speed curve, are evaluated. The results reveal that the proposed machines can exhibit wide flux regulation range as well as good torque density. The prototype is manufactured and tested to validate the predictions.

Hybrid-Excited Switched-Flux Hybrid Magnet Memory Machines

The memory machine concept is recently extended to switched-flux (SF) machines, forming a series of SF hybrid magnet memory machines (SF-HMMMs). They exhibit the merits of good demagnetization withstand capability and effective flux adjustability. Nevertheless, the torque density is inevitably compromised due to the geometric conflict within the stationary part. Meanwhile, the inactivated dc coil, excluding online magnetization transients, results in system redundancy. Hence, in this paper, a new hybrid-excited (HE) concept is developed and implemented in a partitioned-stator SF-HPMM (PS-SF-HMMM). Thereby, the distinct synergies of a dual-magnet memory machine and an HE machine are achieved. With slight compensated field excitation, the torque can be improved at low-speed operation. Meanwhile, the high-speed constant-power region can be further extended without sacrificing high efficiency. The stator/rotor pole numbers are optimized first. The operating mechanism and optimal stepwise HE implementation over a whole operating envelop are then addressed. In addition, a comparison between PS-SF-HMMM with hybrid-excitation and its pure HE counterpart is established. Finally, both the finite-element simulation and experiments are carried out to verify the utility of the proposed HE concept.

Efficiency Enhancement of General AC Drive System by Remanufacturing Induction Motor With Interior Permanent-Magnet Rotor

Alternating-current motor drive systems consume the majority of global electricity, but most of them are still not efficient enough. This paper proposes a complete solution to the efficiency enhancement of general induction motor (IM) drive systems with the least cost and a high reliability. On the motor side, the squirrel-cage rotors of IMs are replaced with optimally designed interior permanent-magnet (PM) rotors without damping windings; meanwhile, other assemblies remained unchanged. Stators with both wye- and delta-connected windings are investigated, and super premium efficiency (IE4) is achieved on all the remanufactured motors in this paper. On the drive side, the maximum efficiency per ampere algorithm is realized based on the position-sensorless control to better exert the motor efficiency and reduce the system cost. For applications where an original IM is used under a grid drive, this paper safely switches the remanufactured interior PM synchronous motors from an inverter to the grid drive. A total of seven prototypes with different rated powers and velocities are remanufactured, and various experiments are provided as the verifications of the effectiveness and practicability of the proposed solution.

A Novel Zero-Sequence Model-Based Sensorless Method for Open-Winding PMSM With Common DC Bus

This paper proposes a zero-sequence model-based sensorless control strategy for open-winding permanent-magnet synchronous machine (OW-PMSM) with common dc bus. The third harmonic back electromotive force (EMF) in zero-sequence is utilized to estimate the rotor position information. The novelty is that the third harmonic back EMF is reconstructed based on the zero-sequence model together with zero-sequence current, instead of using voltage transducer and three phase resistance network which can be eliminated from the control system. Due to the essence of back EMF, the developed method is appropriate for the applications including wind power generation and motor drives operating above certain speed. Meanwhile, the phase shift-based space vector pulse width modulation method for OW-PMSM is also presented for easier implementation to form zero voltage disturbance in zero-sequence from the inverter side and hence the corresponding influence can be consequently minimized. The torque ripple, loss, and parameter sensitivity analysis are also carried out, as confirmed by predictions of two-dimensional finite element analysis. Due to the essence of decouple, the estimation can be more robust than the conventional fundamental model-based sensorless methods. Finally, the effectiveness of the proposed method is validated experimentally on a 3-kW OW-PMSM drive system with 2.5 kg·m2 total inertia.

Performance Comparison of Doubly Salient Reluctance Machine Topologies Supplied by Sinewave Currents

This paper comprehensively investigates the electromagnetic performance of 3-phase, 12-slot, and 8-pole switched reluctance machines (SRMs) with different winding configurations, i.e., double/single layer, short pitched (concentrated), and fully pitched (distributed). These SRMs are supplied by sinewave currents so that a conventional three-phase converter can be employed, leading to behavior which is akin to that of synchronous reluctance-type machines. Comparisons in terms of static and dynamic performances such as d- and q-axis inductances, on-load torque, torque-speed curve, and efficiency map have been carried out using two-dimensional finite-element method (2-D FEM). It is demonstrated for the given size of machine considered that for same copper loss and without heavy magnetic saturation, both single- and double-layer mutually coupled SRMs (MCSRMs) can produce higher on-load torque compared to conventional SRMs (CSRMs). Additionally, double-layer MCSRM achieved the highest efficiency compared to other counterparts. When it comes to single-layer SRMs, they are more suitable for middle-speed applications and capable of producing higher average torque while lower torque ripple than their double-layer counterparts at low phase current. Two prototype SRMs, both single layer and double layer, are built to validate the predictions.

Modular Permanent-Magnet Machines With Alternate Teeth Having Tooth Tips

This paper presents single-layer modular permanent-magnet machines with either wound or unwound teeth with tooth tips. The structures with wound teeth having tooth tips are suitable for modular machines with slot number higher than pole number to compensate for the drop in winding factor due to the flux gaps in alternate stator teeth, accordingly to maintain or even to increase their average torques. However, the structures with unwound teeth having tooth tips are suitable for modular machines with slot number lower than pole number to increase the winding factor and hence to further improve the machine performance. The phase back-EMF, on-load torque, iron and copper losses, as well as efficiency have been calculated using FE analysis for different slot/pole number combinations, and for different flux gap and tooth tip widths. It is found that by properly choosing the flux gap and tooth tip widths, both the on-load torque performance and the efficiency can be optimized for the investigated machines with different slot/pole number combinations. Experiments have been carried out to validate the FE results.

Analytical On-Load Subdomain Field Model of Permanent-Magnet Vernier Machines

Permanent-magnet vernier machine (PMVM) is a relatively new type of PM machines. An analytical subdomain model accounting for tooth-tips and flux modulation poles is developed to accurately predict on-load field distributions in PMVMs. Based on two-dimensional (2-D) polar coordinate and magnetic vector potential, this method solves the Maxwells equations in slot, air-gap, flux modulation pole slot (FMPS), and PM regions. Consequently, the electromagnetic performance such as cogging torque, back-electromotive force (EMF), electromagnetic torque, power factor, and magnet loss are calculated. In addition, the model can also be used for the evaluation of demagnetization withstand capability. The finite-element analysis (FEA) and experimental results validate the accuracy of the developed analytical model.

Comparison of Partitioned Stator Switched Flux Permanent Magnet Machines Having Single- or Double-Layer Windings

A novel type of partitioned stator switched flux permanent magnet (PS-SFPM) machine with either single-layer or double-layer windings is developed in this paper. The proposed PS-SFPM machines have two stators, which separately accommodate the armature windings and the PMs, and between which is the rotor made of iron pieces, while the number of stator poles with PMs may be equal or half of that with armature windings. All the machines are optimized under fixed copper loss for maximum average torque by genetic algorithm. Their electromagnetic performances are compared, such as open-circuit flux-linkages and back-electromotive forces (EMFs), cogging torque, static torque waveforms, average torque against current, PM utilization ratio, and flux-weakening performances. The results show that due to more PM usage and higher open-circuit back-EMF, the PS-SFPM machines having the number of stator poles with PMs the same as that with armature windings exhibit higher average torque, irrespective of the winding topologies, either single-layer or double-layer windings. However, the single-layer winding PS-SFPM machines having the number of stator poles with PMs half of that with armature windings have the best PM usage and the highest ratio of average torque to PM volume, as well as good flux-weakening capability. A prototype machine is manufactured and tested to validate the analyses.

Comparative Analysis of Partitioned Stator Flux Reversal PM Machines Having Fractional-Slot Nonoverlapping and Integer-Slot Overlapping Windings

This paper proposes a new partitioned stator flux reversal permanent magnet (PM) (PS-FRPM) machine having integer-slot overlapping windings, i.e., the slot number per pole per phase q is an integer, based on the magnetic gearing effect in stator-PM machines. Compared with the existing PS-FRPM machine with fractional-slot nonoverlapping windings, a more sinusoidal armature reaction magnetomotive force can be achieved in the proposed PS-FRPM machine with integer-slot overlapping windings, resulting in lower iron loss and PM loss. Electromagnetic performance of the PS-FRPM machine, which has q = 1 overlapping windings is analyzed and compared with PS-FRPM machine, which has q = 0.5 nonoverlapping windings by finite element (FE) analysis. FE results show that the proposed 24/10/12-outer-stator/rotor/inner-stator-pole PS-FRPM machine with q = 1 overlapping winding exhibits higher fundamental phase back-electromotive force, higher average electromagnetic torque and lower torque ripple, lower loss and higher efficiency, higher self-inductance but lower mutual inductance, higher d-axis inductance, and potential infinite flux-weakening capability compared with the 12/10/12-outer-stator/rotor/inner-stator-pole PS-FRPM machine with q = 0.5 nonoverlapping windings. Both prototype machines with q = 1 overlapping winding and q = 0.5 nonoverlapping windings are built and tested to verify the FE analyzes.

Nonparametric Sensorless Drive Method for Open-Winding PMSM Based on Zero-Sequence Back EMF With Circulating Current Suppression

This paper proposes a novel sensorless method for open-winding (OW)-permanent magnet synchronous machine (PMSM) (OW-PMSM) with circulating current suppression. First, a zero-sequence steerable space vector pulse width modulation together with zero-sequence controller (ZSC) is implemented to suppress the circulating current existing in the OW-PMSM drive system with common dc bus. Afterward, the zero-sequence back EMF reconstructed from the output signal of the ZSC is utilized to extract the position information via synchronous phase-locked loop-based position observer. Hence, the voltage transducer and resistance network used in the conventional zero-sequence back-electromotive force-based sensorless methods can be consequently eliminated. Moreover, the proposed method requires no machine parameters, such as winding resistance, d- and q-axis inductances which are indispensable for the conventional fundamental back-EMF-based methods. The voltage disturbance components due to the resistance, inductance, and rotating cross coupling voltage drops can be avoid. Therefore, stronger robustness against the variation of machine parameters due to load or temperature variation can also be obtained. Finally, the proposed method is validated via experiments on a 3-kW OW-PMSM drive system.