The high-speed (HS) electric machines are gaining attention in several different applications, and the development of advanced materials, electronic components, and control algorithms is pushing ahead the technological speed limits. In the electromagnetic sizing of HS machines, the mechanical and thermal involvements are very tight to make it necessary to deal with all the different aspects at the same time. This paper aims to summarize and discuss the electrical and the mechanical aspects involved in the HS machine design, highlighting the main issues and the tradeoffs that the designer has to consider. Furthermore, the correlation between volume reduction and speed increase, based on commercial high-frequency rotor-stator units, is also presented.

In order to improve aircraft efficiency, reliability and maintainability, the aerospace world has found in the progressive electrification of on-board services the way to reduce or to remove the presence of the hydraulic, mechanical and the bleed air/pneumatic systems. This concept is called more electric aircraft (MEA), which involves the introduction of the electromechanical actuators (EMAs) and the electro-hydraulics actuators (EHAs) for the actuation of the flight surfaces of wide-body aircraft, moving from the ¿fly-by wire¿ to the ¿power-by wire¿ concept. The resulting step change in aircraft electrical loading will have far reaching implications for the electrical generation system. Considerable effort is being directed towards realizing the so-called more electric engine (MEE), which foresee an integration of the electrical generator directly inside the main gas turbine engine. Also the entire electrical distribution system is subject to radical revisiting, with a trend which is leaving the constant frequency AC energy distribution in favor of variable frequency or DC solutions. Hence, it is evident the MEA trend increments the technical challenges and research topics for the electrical engineering in the aeronautic applications. The aim of the paper is the presentation, from the electrical engineering point of view, of some of the most challenging application of electric machines and drives in the incoming new aircraft generation. There are too many on board electric components and systems to be analyzed: the authors centre the attention on the most safety critical drives: flight surface actuators, fuel pumps and generators.

In this paper, four thermal models for the stator-winding temperature prediction in short-time thermal transient are presented and experimentally validated. The lumped-parameter networks, based on physical representation of the stator components, are composed of multiple RC cells in cascade. In particular, starting from a fourth-order thermal network, the model complexity is progressively reduced to a third-, second-, and then down to a first-order system. The proposed models and their predicted temperature evolutions are discussed in detail and validated by means of a full experimental approach on an industrial 7.5-kW induction motor. Finally, the behaviors of the proposed thermal models are corroborated by some considerations drawn by the analytical solution of the models.

This paper presents an accurate and efficient method for predicting the iron losses in pulsewidth modulation (PWM) inverter-fed induction motors. The method was initially proposed for the prediction of iron losses in a nonoriented soft magnetic material with the same supply conditions. The proposed method requires the separation of the iron losses in the hysteresis and eddy-current components and the average rectified and rms of the PWM voltage values. Starting from the iron losses measured with a sinusoidal supply and the PWM waveform characteristics, a fast and reliable prediction of the iron losses in the motor with the new voltage supply can be obtained. The proposed method has been proved on an induction-motor prototype capable of providing good accuracy in the iron-loss measurement. The comparison between the measured and predicted iron losses with the PWM supply has shown excellent agreement, confirming the validity of the method.

This paper deals with a shaft-line-embedded multiphase electrical machine to be connected to the high-pressure shaft of an open-rotor jet engine. An asymmetrical six-phase induction machine (IM) is proposed for this application. The main focus of this paper is on the control of the six-phase IM, to verify its overload capabilities and postfault operations. The implemented control uses a direct-flux vector control scheme based on a double-stator approach, where each three-phase winding set is independently controlled. This way, the fault-tolerant behavior of the drive system is enhanced. Complete details of the adopted flux observer are included; torque and speed control loops are implemented in a dedicated multiple three-phase drive, and a scaled prototype (10 kW, 6000 r/min) has been tested. The overload capability has been verified both in generation and motoring mode, for different speeds and torque up to 150% of the rated one. Finally, the transitions between healthy and faulty modes are reported for open phases and encoder faults. The obtained results demonstrate the feasibility of the proposed drive solutions.

Multiphase drives are convenient for high power/high current applications as they allow the reduction of the phase current for given rated power and phase voltage. In addition, they possess inherent fault-tolerant capability due to their redundant structure. Therefore, the multiphase drives represent a promising solution for safety-critical applications, such electrical ship propulsion, railway traction, Hybrid/Electrical Vehicles (HEV/EV), wind power generation, More Electric Engine (MEE) and More Electric Aircraft (MEA) applications. Moreover, the additional “degrees of freedom” can be exploited for integrated battery chargers. Although the literature reports many machine design solutions and control techniques for multiphase drives, the penetration of the multiphase solutions in transportation electrification and energy production is still too limited. For this reason, the paper contains a brief overview of the multiphase solutions for transportation electrification and energy production. In addition, the paper includes a generic modeling approach of multi-three-phase machines that can be used when the multiphase drive is treated as modular independent three-phase units. Experimental results are provided for a reduced scale prototype of a twelve-phase multiphase induction motor drive using a control scheme based on the multi-three phase approach.