K. T. Chau

Design and Analysis of Linear Stator Permanent Magnet Vernier Machines

This paper presents a new class of linear permanent magnet (PM) vernier machines which is suitable for low speed and high thrust force applications. The machine is composed of a tubular stator and a tubular translator. The stator consists of an iron core with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of stator teeth. The translator is designed as a simple tubular iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed machine are analyzed and verified.

Stator-Flux-Oriented Fault-Tolerant Control of Flux-Switching Permanent-Magnet Motors

Flux-switching permanent-magnet (FSPM) motors are a newly developed brushless AC (BLAC) machine having magnets in the stator. This paper proposes and implements a stator-flux-oriented (SFO) control strategy for fault-tolerant operation of FSPM motors. The key is to set the q-axis component of armature current invariant before and after the fault. In the rotor reference frame, by building a SFO-dq equation of the FSPM motor, the fault-tolerant control strategy is deduced. The finite-element method and the field-circuit cosimulation method are employed to analyze the performance of the FSPM motor drive. Finally, a dSPACE-based FSPM motor drive platform is built for experimental verification. Both the steady-state and dynamic performances at normal and fault-tolerant operations are tested, confirming that the proposed fault-tolerant operation can keep the output torque invariant while offering good dynamic performance during fault.

A Linear Doubly-Salient HTS Machine for Wave Energy Conversion

This paper proposes a linear doubly-salient high-temperature superconductor (HTS) machine for wave energy conversion, which is composed of a tubular stator and a tubular translator. Since the translator is a simple iron core with salient poles, it is so robust that it can be directly coupled with the reciprocating buoy. The stator consists of an iron core with salient poles, DC HTS field windings and 3-phase HTS concentrated armature windings. By using the finite element analysis, the proposed machine is quantitatively compared with its permanent magnet and copper-winding counterparts. Hence, it validates that its performance, especially the power density, can be improved greatly.

An improved coaxial magnetic gear using flux focusing

This paper presents a new topology of the coaxial magnetic gear (CMG) in which the permanent magnets (PMs) in the outer rotor are magnetized in tangential direction, hence offering the flux-focusing effect. By using the 2D finite element method, the influence of the main design parameters on the maximum pull-out torque of the proposed magnetic gear is investigated. Also, a quantitative comparison between the proposed topology and the conventional surface-mounted CMG employing radially-magnetized PMs (CMGRM) has been performed and the analysis results indicate that the torque transmission capability of the proposed one can be significantly improved.

A double-stator permanent magnet brushless machine system for electric variable transmission in hybrid electric vehicles

In this paper, a totally brushless electric variable transmission (EVT) machine system is proposed for hybrid electric vehicles (HEVs). The key is to cascade a double-stator permanent-magnet brushless (DS-PMBL) machine with an induction motor to form a new EVT machine system. It not only provides the merits of power splitting as other EVT systems, but also offers the unique advantage that the whole machine system does not involve any carbon brushes or slip rings. Hence, throughout the whole driving profile of HEVs, the proposed machine system can enable the engine operating at its optimal operation area at which its efficiency is the maximum. The control strategy and operation modes of the proposed EVT machine system are elaborated. The validity of system operation is verified by computer simulation. Finally, a DS-PMBL machine prototype is tested to verify its functionality.

A new modular flux-switching permanent-magnet machine using fault-tolerant teeth

This paper proposes a new 3-phase flux-switching permanent-magnet (FSPM) motor for fault-tolerant (FT) applications. The key is the new motor topology which incorporates the concept of FT teeth to provide the desired decoupling among phases. The proposed modular FSPM (M-FSPM) motor is quantitatively compared with the conventional FSPM motor. The analysis results show that the proposed M-FSPM motor not only retains the merits of high power density, strong mechanical integrity, good immunity from thermal problem and high torque capability, but also offers lower torque ripple, higher average torque and lower cost than the existing one. Furthermore, the experimental results confirm the validity of the proposed motor.

Simulation of the Linear Primary Permanent Magnet Vernier machine system for wave energy conversion

The purpose of this paper is to describe a Linear Primary Permanent Magnet Vernier (LPPMV) machine system for direct drive wave energy conversion. Firstly, the structure of the LPPMV machine is proposed and the operation principle of the proposed machine is depicted. Secondly, the mathematical model of the machine is derived based on the three-phase stator coordinate system. Then the control strategy of the maximum energy absorption is discussed. Finally, the simulation model is established based on Matlab/Simulink to investigate the performance of the control system. The simulation results are given to verify the feasibility of the LPPMV machine system for direct drive wave energy conversion.

A hybrid energy source based double-stator permanent magnet brushless motor drive for hybrid electric vehicles

This paper proposes a hybrid energy source (HES) based double-stator permanent magnet brushless motor drive (DS-PMBL) for hybrid electric vehicles (HEVs). The key is to design and apply a battery-ultracapacitor HES to the DS-PMBL HEV drive properly, incorporating the merits of both battery and ultracapacitor. The peaky charging and discharging currents are supplied or absorbed by the ultracapacitors. Both the system efficiency and the battery life are thus improved. Meanwhile, the dynamic voltage equalization of battery packs can be achieved by controlling ultracapcitors properly. The simulation results are presented to verify the validity of the proposed HES design.

Theory and comparison of the linear stator permanent magnet vernier machine

The purpose of this paper is to describe a theory study of the linear stator permanent magnet vernier (LSPMV) machine. The fundamental operating principle, design criteria, characteristics and performances of the machine are discussed in this paper. In order to confirm the advantages, a quantitative comparison between the LSPMV machine and the linear vernier hybrid (LVH) machine is performed under the conditions of the same magnetic loading, electric loading and rated speed by using the finite element method. The results show that the proposed machine has higher power density and lower cogging force than the LVH machine.

Optimal design of a double-stator permanent magnet brushless machine with series magnetic circuit

This paper presents the optimal design of an 18-slot 8-pole double-stator permanent magnet brushless (DS-PMBL) machine. The key is to optimize the split ratio, namely the ratio of the inner-stator outside diameter to the outer-stator outside diameter, to achieve the maximum torque density under the same copper loss. Both the finite element analysis and experimental results are given to verify the proposed optimal design.