Zi-Qiang Zhu

Bio: Zi-Qiang Zhu is an academic researcher from University of Sheffield. The author has contributed to research in topics: Stator & Magnet. The author has an hindex of 89, co-authored 1049 publications receiving 33963 citations. Previous affiliations of Zi-Qiang Zhu include Zhejiang University & Siemens Wind Power.

Electrical Machines and Drives for Electric, Hybrid, and Fuel Cell Vehicles

Abstract: This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cell vehicles, with particular emphasis on PM brushless machines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operating range, and a high maximum speed capability, as well as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improving the torque and power capability, are described

Electrical Machines and Drives for Electric, Hybrid, and Fuel Cell Vehicles Induction and switched-reluctance machines can provide the needed characteristics, but permanent magnet brushless machines offer a higher efficiency and torque density.

Abstract: This paper reviews the relative merits of induction, switched reluctance, and permanent-magnet (PM) brushless machines and drives for application in electric, hybrid, and fuel cellvehicles,withparticularemphasisonPMbrushlessmachines. The basic operational characteristics and design requirements, viz. a high torque/power density, high efficiency over a wide operatingrange,andahighmaximumspeedcapability,aswell as the latest developments, are described. Permanent-magnet brushless dc and ac machines and drives are compared in terms of their constant torque and constant power capabilities, and various PM machine topologies and their performance are reviewed. Finally, methods for enhancing the PM excitation torque and reluctance torque components and, thereby, improv- ing the torque and power capability, are described.

Influence of design parameters on cogging torque in permanent magnet machines

Abstract: The influence of various design parameters on the cogging torque developed by permanent magnet machines is investigated. It is shown that the slot and pole number combination has a significant effect on the cogging torque, and influences the optimal value of both skew angle and magnet arc, as well as determining the optimal number of auxiliary teeth/slots. A simple factor, which is proportional to the slot number and the pole number and inversely proportional to their smallest common multiple, has been introduced to indicate the "goodness"/spl beta/ of the slot and pole number combination. In general, the higher the "goodness" factor the larger the cogging torque.

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. III. Effect of stator slotting

Abstract: For pt.II see ibid., vol.29, no.1, p.136-142 (1993). A method for modeling the effect of stator slotting on the magnetic field distribution in the airgap/magnet region of a radial-field brushless permanent-magnet DC motor equipped with a surface-mounted magnet rotor is presented to allow the analytical prediction of the open-circuit, armature-reaction, and consultant magnetic field distribution under any specified load condition. It is shown that the conventional 1D relative permeance model, which is used extensively in the analysis of induction and synchronous machines, is inappropriate for permanent magnet motors, for which the proposed analytical method accounts for stator slot openings by the application of the conformal transformation method and a 2-D relative permanence function. The results of predictions from the analysis are compared with corresponding finite element analyses. >

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. I. Open-circuit field

Abstract: An analytical technique for predicting the instantaneous magnetic field distribution in the airgap region of radial-field topologies of brushless permanent-magnet DC motors, under any specified load condition and accounting implicitly for the stator winding current waveform and the effect of stator-slot-openings, has been developed. It is based on the superposition of the component fields due to the permanent magnet and the stator excitation. A 2D analytical method for predicting the open-circuit airgap field distribution in both internal and external rotor radial-field motor topologies is presented. It involves the solution of the governing field equations in polar coordinates in the annular airgap/magnet region of a multipole slotless motor in which the magnets are assumed to have uniform radial magnetization and a constant relative recoil permeability. Results for various radial-field motors are compared with predictions from corresponding finite element analyses. >

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Overview of Permanent-Magnet Brushless Drives for Electric and Hybrid Electric Vehicles

Abstract: With ever-increasing concerns on our environment, there is a fast growing interest in electric vehicles (EVs) and hybrid EVs (HEVs) from automakers, governments, and customers. As electric drives are the core of both EVs and HEVs, it is a pressing need for researchers to develop advanced electric-drive systems. In this paper, an overview of permanent-magnet (PM) brushless (BL) drives for EVs and HEVs is presented, with emphasis on machine topologies, drive operations, and control strategies. Then, three major research directions of the PM BL drive systems are elaborated, namely, the magnetic-geared outer-rotor PM BL drive system, the PM BL integrated starter-generator system, and the PM BL electric variable-transmission system.

Multi-level conversion : high voltage choppers and voltage-source inverters

Abstract: The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<>

Fractional-Slot Concentrated-Windings Synchronous Permanent Magnet Machines: Opportunities and Challenges

Abstract: Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.