Most of the mechanical fault diagnosis methods of induction motors (IMs) are based on vibration signals. However, vibration sensors are expensive and require direct contact with IMs. This article proposes a data-driven mechanical fault diagnosis method for IMs using stator current signals, which is more convenient and low cost, since no additional sensors are required. Aiming at the weak representation of mechanical faults in current signals, an intelligent noise elimination method based on noise reconstruction model is proposed to improve the signal-to-noise ratio. Through the automatic feature extraction and classification of the residual current envelope spectrum, high diagnosis accuracy can be obtained even if some differences have existed among samples. The effectiveness of the proposed method is verified by high accuracy diagnosis results on two experimental platforms. The results show that the average diagnostic accuracy of the proposed algorithm for one bearing fault and two eccentricity faults can reach 96%. Even if the fault type and the fault degree are distinguished at the same time, an accuracy of 90% can be achieved for six kinds of bearing faults.

Homopolar inductor machine (HIM) has been applied in the field of flywheel energy storage system (FESS) due to its merits of simple structure, brushless exciting and low idling losses. The rotor of HIM not only plays the role of energy conversion, but also serves as a flywheel to store kinetic energy, which is different from other electrical machines used in FESS. Meanwhile, the HIM usually operates at high-speed to improve the power density and storage energy. To obtain good performance and high reliability, the design and optimization of HIM should consider multiphysics including storage energy, electromagnetic performance, rotor stress and dynamics, etc. However, the existing researches mainly focus on the analyzing of electromagnetic performance and lack multidisciplinary design. To solve this problem, a multidisciplinary design method of the HIM is proposed and investigated. Firstly, the operation principle of HIM is illustrated and the multidisciplinary design method is proposed. Then, the storage energy, electromagnetic performance (including no-load air-gap flux density, saliency ratio, torque and electromagnetic power), rotor stress and modal of HIM are deeply analyzed according to the proposed design flow. Finally, a prototype of HIM is manufactured and tested. The results calculated by finite element analysis are validated by experiments. The design method proposed in this paper provides a straightforward procedure for the multidisciplinary design of HIM.

Homopolar inductor machine (HIM) has been applied in the field of flywheel energy storage system (FESS) due to its merits of simple structure, high reliability and low idling losses. However, the HIM features unipolar air-gap flux density, which makes its power density lower than that of the electrical machine with bipolar air-gap flux density. Addressing this issue, a novel outer rotor homopolar inductor machine (OR-HIM) is proposed in this paper. Firstly, the special structure and operation principle of the OR-HIM are illustrated. Then, the unit motors (UMs) of the OR-HIM are obtained and investigated based on the magnetic equivalent circuit (MEC) method to facilitate the design. Moreover, the performance indexes including power density, output characteristics, losses and rotor stress of the OR-HIM are fully analyzed. Finally, a 13kW prototype is designed, manufactured and tested. The back electromotive force (back-EMF), load voltage, output torque and efficiency are measured and compared with those obtained by finite element analysis (FEA). The results indicate that the proposed OR-HIM is a promising candidate for the application of FESS.

The surface-mounted permanent magnet linear syn-chronous motor (PMLSM) is a good candidate for the Electromag-netic Launch System due to its merits of high-power density, power factor and efficiency. However, this kind of machine needs a lot of permanent magnets (PMs) on the long stator, which is costly. To solve this problem, a novel PMLSM is proposed in this paper. The stator of novel PMLSM has the consequent poles structure and the mover of novel PMLSM has two iron cores, which sandwiches a mover PM. Firstly, the structure and operation principle of the pro-posed PMLSM have been investigated. Then, the analytical calcula-tion of thrust and detent force is analyzed and the structural param-eters of the motor are optimized for larger thrust and less detent force. Finally, for a fair comparison, the proposed motor is designed and built based on an existing PMLSM with similar electromagnetic and geometrical parameters. The thrust performance indexes of the novel PMLSM are estimated and compared with the conventional surface-mounted PMLSM, which indicates that the proposed PMLSM can keep similar performances with the exciting PMLSM. Moreover, it has a simple structure, less thrust ripple and can save many PMs, which can help reduce costs.

A typical flywheel energy storage system (FESS) includes an electrical machine, a flywheel, and magnetic bearings, which are independent of each other. Therefore, the structure of FESS is complicated, which leads to the problems of high cost and low integration. This article presents a novel stator PM excitation solid rotor machine (SPE-SRM) for FESS, which integrates an electrical machine, flywheels, and a magnetic bearing. The design method of the SPE-SRM is presented specifically. First, the structure and operation principle of the SPE-SRM are illustrated. Second, the design and optimization of the flywheel-rotor are presented with considering of power, energy storage, and mechanical strength. Third, the magnetic equivalent circuit of the SPE-SRM is established to simplify the design. Besides, the armature reaction and leakage flux factor are investigated. Fourth, the performance indexes, including torque, suspension force, no-load back electromotive force (back-EMF), losses, and temperature rise are fully analyzed by the finite element analysis. Finally, a 22 kW prototype is manufactured and tested. The rationality of the concept and design is validated by experiments. The SPE-SRM has the merits of high integration, robust structure, and low cost, so it has the potential for wide application in FESS.