This paper provides an overview of the design and analysis of high-speed PM motors by focusing on prominent issues such as motor losses, temperature rise, rotor strength and vibration. The design challenges of high-speed PM motors are briefly described, and the application of various stator and rotor structures and materials is presented in electromagnetic design. Combined with the temperature distribution of the motor, various heat dissipation measures to suppress the temperature rise are summarized. Strength and dynamics analysis of the rotor are outlined with respect to the safety of rotor operation. The current status of coupled multi-physics domain design used to improve the comprehensive design capability of high-speed PM motors is reviewed. Future directions of technologies related to the design of high-speed PM motors are pointed out.

The transient overvoltage and oscillation phenomena, which are caused by its high switching speed in a solid-state DC circuit breaker based on the silicon carbide (SiC) metal–oxide–semiconductor field-effect transistor (MOSFET), are a crucial problem. This paper presents a simple and reliable method to manage such problem. An equivalent circuit model for SiC MOSFET is primarily established. The influence of stray inductance in energy absorption loop on the turn-off characteristics of the DC circuit breaker is then analyzed. Subsequently, possible typical overvoltage suppression methods, such as using a resistor–capacitor snubber circuit and increasing gate resistance and parallel capacitance between the gate and source, are simulated and analyzed. Thereafter, a peak voltage suppression method that does not sacrifice the fast switching capability of SiC MOSFET is proposed based on the different amounts of energy absorbed by metal oxide varistors (MOVs) with varying voltage levels. A basic principle for selecting a snubber MOV is proposed based on the voltage ratio of a snubber and an energy-absorbing MOV. Finally, the feasibility of the proposed method is verified via a small-scale principle prototype.

A change regulation of variation in drain current (d I _D /d t ) of silicon carbide (SiC) metal–oxide–semiconductor field‐effect transistors (MOSFETs) and their temperature dependencies are examined. Experimental results show that the magnitude of turn‐off d I _D /d t decreases with temperature and turn‐on d I _D /d t increases with increasing temperature. Further analysis shows that turn‐on d I _D /d t is better than turn‐off d I _D /d t in terms of temperature dependency and exhibits good linearity. This behaviour results from the positive temperature coefficient of the intrinsic carrier concentration and the negative temperature coefficient of the effective mobility of the electrons in the SiC MOSFET. Other factors that affect the temperature dependency of d I _D /d t , such as supply voltage, load current, and gate resistance, are also discussed. A temperature‐based analytical model of d I _D /d t for the SiC MOSFET is derived using fundamental device physics equations. The calculations generally fit the measurements well. These results are beneficial since they provide a potential approach for junction temperature estimation in the SiC MOSFET. In SiC MOSFET‐based practical applications, if turn‐on d I _D /d t is sensed, then the junction temperature can be derived from the relationship curve of turn‐on d I _D /d t versus temperature drawn experimentally in advance.

Due to our limited knowledge about silicon carbide metal–oxide–semiconductor field-effect transistors (SiC MOSFETs), the theoretical analysis and change regularity in terms of the effects of temperature on their switching characteristics have not been fully characterized and understood. An analysis of variation in voltage (dV_DS/dt) for SiC MOSFET during turn-on and turn-off has been performed theoretically and experimentally in this paper. Turn-off variation in voltage is not a strong function of temperature, whereas the turn-on variation in voltage has a monotonic relationship with temperature. The temperature dependence is a result of the competing effects between the positive temperature coefficient of the intrinsic carrier concentration and the negative temperature coefficient of the effective mobility of the electrons in SiC MOSFETs. The relationship between variation in voltage and supply voltage, load current, and gate resistance are also discussed. A temperature-based analytical model of dV_DS/dt for SiC MOSFETs was derived in terms of internal parasitic capacitances during the charging and discharging processes at the voltage fall period during turn-on, and the rise period during turn-off. The calculation results were close to the experimental measurements. These results provide a potential junction temperature estimation approach for SiC MOSFETs. In SiC MOSFET-based practical applications, if the turn on dV_DS/dt is sensed, the device temperature can be estimated from the relationship curve of turn on dV_DS/dt versus temperature drawn in advance.

Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have the advantages of high-frequency switching capability and the capability to withstand high temperatures, which are suitable for switching devices in a direct current (DC) solid state circuit breaker (SSCB). To guarantee fast and reliable action of a 400 V DC SSCB with SiC MOSFET, circuit design and prototype development were carried out. Taking 400V DC microgrid as research background, firstly, the topology of DC SSCB with SiC MOSFET was introduced. Then, the drive circuit of SiC MOSFET, fault detection circuit, energy absorption circuit, and snubber circuit of the SSCB were designed and analyzed. Lastly, a prototype of the DC SSCB with SiC MOSFET was developed, tested, and compared with the SSCB with Silicon (Si) insulated gate bipolar transistor (IGBT). Experimental results show that the designed circuits of SSCB with SiC MOSFET are valid. Also, the developed miniature DC SSCB with the SiC MOSFET exhibits faster reaction to the fault and can reduce short circuit time and fault current in contrast with the SSCB with Si IGBT. Hence, the proposed SSCB can better meet the requirements of DC microgrid protection.