Winding configurations which are applicable to a novel bearingless flux-switching permanent magnet motor with stacked structure are investigated, and one method to evaluate these winding configurations is also proposed in this paper. Firstly, the motor structure and the influence of coil connections on torque and radial force are illustrated, and the fundamental radial force expressions of two diametrically opposite coils are derived. Afterwards, two kinds of torque windings and four kinds of radial force windings for the motor are studied and the radial force models are derived accordingly. Following this, the radial force models are verified and the transient radial force and torque characteristics are investigated by finite element analysis. More importantly, an evaluation factor related to the winding copper losses is defined to evaluate the winding configurations. Finally, an optimal winding configuration is determined theoretically and a prototype motor is built to validate the effectiveness of the motor structure and the optimal winding configuration.

The three-degrees-of-freedom hybrid magnetic bearing (3-DOF HMB) is widely used in high-speed motors because of its compact size and small volume. This article focuses on a 3-DOF HMB under one topological type for researching the characteristics of 3-DOF HMBs. On the basis of this type, three structures (Structure 1: radial stator and rotor are fully solid irons, Structure 2: only radial stator is laminated iron, and Structure 3: radial stator and partial rotor are laminated irons) are considered. A dynamic magnetic circuit model considering eddy currents and leakage fluxes is established according to the three structures. Additional, dynamic and static characteristics are examined, the results of which are compared with those from finite-element method (FEM) approach. The frequency response characteristics of the three kinds of magnetic bearings are obtained through theoretical calculations and simulations. The results show that the eddy currents will cause amplitude attenuation and a phase lag in current stiffness, and the leakage fluxes will also have a certain effect on current stiffness. In addition, the static bearing capacity and dynamic bearing capacity at rated rotational speeds of the three structures are analyzed. Among the three structures in this article, the results suggest that Structure 2 and Structure 3 are feasible and effective when the rotor operates at the rated speed. When considering the yield strength and cost, Structure 2 is optimal. Finally, the three structures are designed and manufactured. A validation of the analysis is performed by comparing the FEM results and experimental results.

The error of the radial displacement sensor causes a deviation between the rotor levitation position of the bearingless motor (BM) and the geometric center of the stator. As a theoretical basis, force analysis of the rotor is performed first to analyze the effects caused by the aforementioned deviation. A radial levitation force modeling scheme for BM is proposed in this article, whose derivation is directly on the rotor coordinate system. The proposed modeling scheme has a simpler form of expression and a more straightforward physical concept than the traditional scheme. To completely compensate for the aforementioned deviation, a levitation position eccentricity compensation scheme for BM based on the tracking of the minimum antieccentric levitation current is proposed in this article. The proposed scheme takes the amplitude of the antieccentric levitation current vector as the index, which characterizes the degree of eccentricity of the rotor and dynamically adjusts the rotor levitation position in two dimensions and, finally, makes the rotor stably levitated at the optimal point, where the amplitude of the antieccentric levitation current vector is minimum. The absence of parameter dependence, ease of implementation, and generality makes the proposed scheme attractive. Meanwhile, the design of the displacement regulator can also be simplified. Sufficient simulation and experiments verify the effectiveness of the proposed scheme.

Purpose – The purpose of this paper is to examine the development and characteristics of industrial clusters in the province of Zhejiang, China with particular emphasis on the hosiery industry in the town of Datang. Design/methodology/approach – The study used case study methodology and data triangulation techniques based on archival research and reports of statistical agencies both at central and local government level. Findings – Industry clusters assist in regional economic development by increasing local competitive advantages and creating an industrial regional identity through specialisation which attracts resources, labour and capital for investment. The industrial cluster in Datang has been stimulated by the local entrepreneurial climate, effective local networks and support from local government. Practical implications – The hosiery industrial cluster in Datang is in a less-developed rural region characterised by low-level labour intensive industrial activity. Their ability to compete internationally is hampered by low levels of innovation. The global networks are controlled by buyers of product. Design and/or innovation capability could be improved by developing strategic alliances with Italian producers in the same industry. Originality/value – This paper contributes to our understanding of the problems facing industrial clusters in provincial China which, as yet are unable to match the design and branding capabilities achieved by clusters in similar industries in Castel Goffredo (Italy) where outstanding design and branding have enabled them to build a dominant position in the European market in higher added-value products.

To make bearingless motors (BMs) more competitive, it is imperative to reduce the cost while ensuring high performance. In this article, the driving system of the BM is optimized from the perspectives of the inverter topology and the control strategy. A dual-hybrid vector control driving scheme of the BM based on the double staggered parallel topology is proposed for the control performance and cost. Meanwhile, the levitation/torque stagger phase shift is adopted to lower the root-mean-square value of the dc-link current. The proposed driving scheme is compared with the traditional vector scheme based on a full-bridge topology on a bearingless pump system. It turns out that the two driving schemes are similar in current, speed, and rotor radial displacement fluctuation. The proposed scheme shows the advantages of simpler system structure and lower cost, so it is deemed as an attractive driving scheme for the BM.

The complex and varied application conditions place high demands on the levitation current control performance of the bearingless motor (BM) because levitation current control quality directly influences the characteristics of the levitation force. This paper focuses on optimizing the design of the levitation current control scheme based on the deadbeat control algorithm to enhance the high dynamic performance. In order to overcome the inherent drawbacks including digital control delay, model parameter errors and high-frequency noise that exist in deadbeat control, several novel and simple solutions are proposed. First, the effect of inherent problems on the levitation current control is given a quantitative analysis to serve as a theoretical basis. Then, a dual-sampling current prediction scheme based on a two-stage algorithm execution mechanism is proposed to compensate for the digital control delay and ensures the complete execution of the algorithm. Moreover, a real-time model parameter correction scheme based on the dual-sampling currents is proposed to solve the model parameter error. As for the high-frequency noise suppression, a scheme based on the deviation weight assignment is proposed by reasonably allocating the weight of the current vector deviation. Finally, the feasibility and superiority of the proposed levitation current regulator design scheme are verified by simulations and experiments on a bearingless motor pump.