The low core losses and high yield strength of amorphous materials are attractive properties for ultra-high-speed rotor applications. This paper proposes an innovative interior permanent-magnet synchronous rotor for ultra-high-speed motors, which takes full advantage of those properties and eliminates the need for sleeves. In order to study the feasibility of the proposed rotor, the electromagnetic properties of the amorphous core are first measured and the challenges for producing such rotors are subsequently discussed. Then, by using numerical methods, the electromagnetic, mechanical, and thermal performances of an example motor with an amorphous rotor core are evaluated and compared to those of a motor with a silicon steel rotor core. Through experimental characterization of the material and multiphysics numerical modeling of an example motor, it is shown that the amorphous material has great potential for producing high power density ultra-high-speed motors.

Many superconducting power applications contain REBa $_{2}$ 3O $_{7-x}$ (or REBCO) coils, where RE stands for “rare earth”. Superconducting motors are very interesting for mobile applications like aviation, thanks to their high power per unit weight. In order to reduce the inductance, multi-tape conductors are often used in windings but parallel tapes present coupling AC loss. In this article, we analyze the AC loss of single coils and a full stator of a motor made of windings of parallel tapes, taking several coupling situations into account. Our computer modeling method combines self-programmed and commercial finite-element methods to calculate the current density and AC loss. We found that isolating the tapes along the length provides almost the same AC loss reduction as that obtained by full transposition. This reveals that there are still many unexploited strategies to reduce the AC loss in multi-tape conductors.

Currently, surface-mounted permanent-magnet (PM) rotors are more frequently employed than interior PM rotors in high-speed PM motors. It is mainly because the mechanical strengths of sleeve materials can be much higher than those of silicon steels. However, at high speeds, the current harmonics caused by pulse-width-modulation (PWM) converter induce high eddy current losses in PMs and sleeves when they are conductive. Moreover, because of the existence of non-magnetic sleeves, the surface-mounted PM motors have very poor flux weakening abilities. Interior PM motors can not only avoid sleeves, but also reduce the influence of the PWM converters. Moreover, they can provide additional reluctance torque and have better flux-weakening abilities. A major drawback of interior PM rotors is their low mechanical strengths, which limit their surface velocities. In this paper, high mechanical strength amorphous metal 2605SA1 is used to increase the surface velocity of an interior PM rotor. A surface-mounted PM rotor protected by carbon-fiber sleeve is designed to perform a comparison study. Both motors are built and tested. The advantages and disadvantages of the two motors in terms of mechanical, electromagnetic and thermal behaviors are evaluated.

It is well-known that spatial field harmonics will cause high eddy current losses in surface-mounted permanent-magnets (PMs) especially for the fractional-slot PM motors. However, the influence of temporal current harmonics, especially of the high-order temporal harmonics caused by pulse width modulation voltages from an inverter, lacks attentions. This paper studies the eddy current losses of the PMs caused by high-order current harmonics. In order to simplify the calculation and save computation time, analytical methods are used to predict the current harmonics caused by the PWM inverter, and the armature reaction field, the eddy current density and losses in the PMs generated by the current harmonics. Finite element analysis, coupling simulation and experimental studies are used to verify the analytical results. The study results show that the high-order current harmonics cause much higher eddy current losses than those caused by slotting and fundamental current even though the amplitudes of the high-order current harmonics are much lower.

Superconductors have been being applied to a variety of large-scale power applications, including magnets, electric machines, and fault current limiters, because they can enable a compact, lightweight and high efficiency design. In applications such as those mentioned above, superconducting coils are always a key component. For example, in a superconducting electric machine, the superconducting coils are used to generate the main flux density in the air gap, which is significantly important for the energy conversion. It is the performance of the superconducting coils that plays an essential role in determining the performance of the device. However, the performance of a superconducting coil is limited by its critical current, which is determined by temperature and the magnitude and orientation of the magnetic field inside the superconductors. Hence, in-depth investigations to estimate the critical current of the superconducting coils are necessary before manufacturing. Available transient simulation models to estimate the critical current are through the H - and T - A formulations of Maxwell’s equations. Both methods consider the same current ramp-up process occurring in experiments. Besides these transient models, static simulations can also be used: a modified load-line method and the so-called P -model, which is based on the asymptotic limit of Faraday’s equation when time approaches infinity. To find the best way to calculate the critical current, the four methods are used to estimate the critical current of a double pancake superconducting coils and results are compared with experiments. As a conclusion, T - A formulation, P -model, and the modified load-line methods are recommended for estimating the critical current of the superconducting coils.