Permanent magnetic fault-tolerant motors have been developed rapidly due to their high reliability and have been widely used in many special fields. Compared with the conventional module faulttolerant motor, the module combined stator permanent magnetic fault-tolerant motor (MCS-PMFTSM) with unequal span winding has two sizes of span coils in each operation module, which realizes the electrical decoupling and mechanical decoupling between the module motors and solves the problem that the span of the double-layer winding of the conventional modular fault-tolerant motor can only be 1. Winding parameters of the unequal span are calculated, on the basis of which the operation performance of MCS-PMFTSM can be analyzed. The performance of MCS-PMFTSM in the normal operation and three failure operations (open circuit failure, Short circuit fault, concurrent failure) are analyzed by finite element method, which proves that it has good fault tolerance. The 12kW100r/min MCS-PMFTSM prototype is tested to verify the correctness of the analysis method and the rationality of the proposed MCS-PMFTSM.

To solve the problems of large-size machining and complex control of fault-tolerant permanent magnet machines, a module-combined stator permanent magnet synchronous machine is proposed in this paper. The winding of the module-combined stator has two forms: large and small spans. The independent power supply of each module is adopted to decouple the electricity between each module, which enhances the manufacturing flexibility and the fault-tolerant ability of the motor. A mathematical model of the module-combined stator permanent magnet synchronous machine is established, and the design method of the machine is summarized. Then the analytical formula of the radial force acting on the stator under asymmetric operation is deduced. In addition, the torque-angle characteristics of the machine and the factors affecting the radial force are studied. Finally, the machine is prototyped, and both simulation and experiment are used verify the rationality of the proposed design.INDEX TERMS Module-combined stator, asymmetric operation, torque-angle characteristic, fault-tolerant.

Given the problem that the drive system of the traditional mine transportation winch outputs a large traction force through the cooperation of an induction motor and reducer to meet the needs of a large traffic volume and heavy-load starting, this paper studies a low-speed and high-torque dual-stator permanent magnet direct drive motor with a separated magnetic circuit. The inner motor is a torque motor, and the outer motor is a direct drive motor, which is characterized by no magnetic circuit coupling and independent control. The proposed motor has an excellent heavy load starting ability and operation efficiency, and it improves the output torque without increasing the motor volume, which belongs to a special application. According to the working characteristics of the inner and outer motors and the constraints between the overall dimensions, the size equation is derived, and the design principles of the electromagnetic parameters, pole-slot combination and winding structure are described. The torque characteristics and temperature rise characteristics of the motor are simulated using the finite element method and compared with the torque performance and electromagnetic materials cost of the single stator low-speed and high-torque permanent magnet motor with different rotor structures. The results show that the proposed motor has a high torque density and starting torque, and it greatly reduces the motor volume on the basis of a small cost difference.

In the field of ship propulsion, highly reliable propulsion motor is one of the key factors for the stable operation of the drive system. This paper proposes a new modular stator low‐speed high‐torque fault‐tolerant permanent magnet motor (MCS‐PMFTSM) for the direct‐drive ship propulsion system. The unequal‐span winding is used for enhanced fault‐tolerant as well as modular operation of the motor. Each module is isolated electrically and mechanically, while the maintenance procedure is greatly simplified by the structure that uses external radiation installation. Introducing the new structure and operating principle of the MCS‐PMFTSM, the basic size equation of the motor is derived followed by the analysis for the selection of the number of poles and slots. The rotor structure of the motor is then optimized using the genetic algorithm. The finite element method is used to analyze the motor performance under normal and various fault‐tolerant conditions. In addition, the electromagnetic vibration of the proposed motor is also examined under different operating conditions. Finally, a 12 kW 100 r/min 3 × 3 modular prototype is developed to experimentally validate the excellent performance of the proposed motor under both normal and fault‐tolerant operating conditions. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Low-speed and high-torque direct-drive permanent-magnet motors have found wide applications primarily due to their outstanding performance characteristics. The special applications of these motors demand high reliability against the motor drive system, that is, the power system should have a certain level of fault tolerance. Therefore, the fault-tolerant motor drive system has been the focus of research all over the world. Many fault-tolerant motors can only deal with the open-circuit fault of the winding or drive, and their capability of fault tolerance is substantially limited. When in operation, the short-circuit fault caused by the ageing of winding insulation may result in more serious hazards than the open circuit in the winding. Such serious faults should be tolerated by the fault-tolerant system. Moreover, the simpler maintenance or shutdown repair upon completion of fault-tolerant operation of large-sized fault-tolerant motors should also be considered. Therefore, a permanent-magnet fault-tolerant motor with module combination stator (MCS-PMFTSM) and unequal span winding is proposed. By changing the winding structure of the conventional motor the modular operation of the whole motor is achieved, which not only provides the motor with a high fault tolerance capacity but also reduces the downtime during repair and maintenance. In this work, the structure and operating principles of the MCS-PMFTSM are described followed by the evaluation of the operation performances of the MCS-PMFTSM under different fault conditions and various control strategies. The faulttolerant capacity of this new machine is then analysed, and the prototype is tested with a power of 12 kW and a rated speed of 100 r/min. Both theoretical analysis and test results demonstrate the outstanding operation performance and high fault tolerance of the motor.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Module-combined stator permanent-magnet machines have several independent stator modules and each module can be controlled independently. To predict the magnetic field distribution of modulecombined stator permanent-magnet machines accurately under asymmetric conditions, this paper proposes a novel nonlinear subdomain and magnetic equivalent circuit hybrid analytical model. The main novelty of the proposed nonlinear hybrid analytical model is representing nonlinear effect by equivalent current sheets on the edges of slots. Equivalent current densities are calculated from magnetic equivalent circuit and used as boundary conditions in the improved subdomain model. The values of the equivalent current sheets are obtained in an iterative algorithm. The nonlinear hybrid analytical model considering saturation effect can accurately calculate magnetic field distribution and electromagnetic performance even under overload conditions. The finite element analysis is performed to validate the accuracy of the proposed model. A prototype with three stator modules is manufactured and the experimental results verified these predictions.INDEX TERMS Magnetic field prediction, saturation effect, hybrid model, module-combined stator.

Baoping Gan, Non-member Bingyi Zhang a , Non-member Yunfei Liu, Non-member Guihong Feng, Non-member Compared with multi-phase single-module permanent magnet motors, three-phase multi-modularized permanent magnet motors have stronger fault tolerance ability, widely used in aerospace, ship propulsion, and other special fields. Especially in ship directdrive propulsion, low speed and high torque modular combined stator fault-tolerant permanent magnet motor (MCS-FTPMSM) has high torque density, and fault-tolerant operation conditions may appear in actual operation, so it is essential to analyze the temperature of the fault-tolerant motor accurately. This paper analyzes the temperature of MCS-FTPMSM under different operating conditions and determines the longest operating time of the motor under different fault-tolerant operating conditions based on the 3D electromagnetic-temperature bi-directional coupling method. Among them, the loss of the motor is calculated by the 3D electromagnetic field, which is added to the 3D temperature field as an excitation, and then the material properties in the 3D electromagnetic field are updated according to the calculated temperature distribution. The cyclic iteration method is used to make the calculated temperature deviation less than the given error value. When analyzing the electromagnetic loss of the motor, the field-circuit coupling method is adopted to consider the influence of the current time-harmonics of the controller on the loss of the motor during actual operation. Finally, the 12kw100r/min 3 × 3 modular prototype was tested. By comparing the results of experiments, one-way coupling method (OWCM) and bi-directional coupling method (BDCM), it is found that the electromagnetic-thermal bi-directional coupling can more accurately predict the temperature of the fault-tolerant motor.

The low‐speed and high‐torque modular fault‐tolerant permanent magnet motor has the strong fault‐tolerant ability, and can make the motor output torque act on the load directly, and the system has the highest transmission efficiency, which is especially suitable for ship propulsion. In the electric ship direct‐drive propulsion system, the motor is the core of the power system. Because the motor is directly connected with the load, the intermediate buffer mechanism is canceled, so the smooth operation of the motor is put forward to higher requirements. Especially in some fault‐tolerant operations, the unbalanced radial force generated by the asymmetric operation may cause the motor to vibrate greatly, which will reduce the operational life of the motor and even bring new faults. In serious cases, the whole transmission system will be damaged. Therefore, it is necessary to study the vibration of the fault‐tolerant motor under different operating conditions. In this paper, the module combined stator fault‐tolerant permanent magnetic synchronous motor for ship direct‐drive propulsion is taken as the research object. Based on the Maxwell tensor method, the radial force wave expressions of the motor during regular operation and fault‐tolerant operation are derived, and the harmonic order and frequency, which have a significant influence on vibration are summarized. The radial force of the motor under different operating conditions with different control strategies is calculated by the finite element method, and the harmonic components are analyzed by the two‐dimensional Fourier transform. On this basis, the vibration of the motor and the mechanical strength of the rotor support frame are analyzed. The research results of this paper provide some reference for the subsequent vibration reduction strategies of fault‐tolerant motors. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.