The constant growth of air traffic, the demand for performance optimization, and the need for decreasing both operating and maintenance costs have encouraged the aircraft industry to move toward more electric solutions. As a result of this trend, electric power required on-board of aircraft has significantly increased through the years, causing major changes in electric power system architectures. Considering this scenario, this paper gives a review about the evolution of electric power generation systems in aircraft. The major achievements are highlighted and the rationale behind some significant developments discussed. After a brief historical overview of the early dc generators (both wind- and engine-driven), the reasons which brought the definitive passage to the ac generation, for larger aircraft, are presented and explained. Several ac generation systems are investigated with particular attention being focused on the voltage levels and the generator technology. Furthermore, examples of commercial aircraft implementing ac generation systems are provided. Finally, the trends toward modern generation systems are also considered giving prominence to their challenges and feasibility.

This paper introduces an innovative thermal modeling technique which accurately predicts the winding temperature of electrical machines, both at transient and steady state conditions, for applications where the stator Joule losses are the dominant heat source. The model is an advanced variation of the classical lumped-parameter thermal network approach, with the expected degree of accuracy but at a much lower computational cost. A seven-node thermal network is first implemented and an empirical procedure to fine-tuning the critical parameters is proposed. The derivation of the low computational cost model from the thermal network is thoroughly explained. A simplification of the seven-node thermal network with an equivalent three-node thermal network is then implemented, and the same procedure is applied to the new network for deriving an even faster low computational cost model. The proposed model is then validated against experimental results carried on a permanent magnet synchronous machine which is part of an electro-mechanical actuator designed for an aerospace application. A comparison between the performance of the classical lumped-parameter thermal network and the proposed model is carried out, both in terms of accuracy of the stator temperature prediction and of the computational time required.

In electrical machine design, thermal management plays a key role in improving performance and reducing size. End-windings are commonly identified as the machine hot-spot. Hence, lowering and predicting end-windings temperature are crucial tasks in thermal management of electrical machines. This paper proposes and investigates a non invasive but effective cooling method that aims for a uniform cooling of a machine's winding by implementing direct cooling on its end-windings. Modelling and experimental results show that a 25% hot-spot temperature reduction on a particular application can be achieved. To analyse the proposed technique in detail, an accurate but computationally-economic lumped parameter thermal network is developed. Comparison between a ‘standard’ thermal network and its simplified equivalent (with less nodes) is presented where the models are developed and fine tuned based on experimental data. All the above is used to investigate the potential of the proposed end winding cooling method with different configurations of the methodology.

Electrical machines for transportation applications need to be highly reliable, particularly if they drive safety-critical systems. At the same time, another main requirement is represented by the significant torque density, especially for aerospace, where weight constraints are extremely stringent. For achieving high peak torque, an effective strategy consists in supplying the windings with a current greater than the rated value; thus, thermally overloading the machine for limited time periods. However, if the insulation is overheated, the machine lifetime is shortened and reliability issues can arise. This paper experimentally investigates the influence of short-time thermal overload on the insulation lifetime for low voltage, random wound electrical machines. The analysis is performed on round enamelled magnet wire coils, which are aged by accelerated thermal cycles. The obtained results are statistically processed through a two parameter Weibull distribution. According to the findings of the experimental data post processing, a lifetime prediction model is built. This model is employed for predicting the lifetime consumption of a motor embedded into an electromechanical actuator for aerospace application.

The ever-increasing demand for passenger air traffic results in larger airline fleets every year. The aircraft market forecast reveals an unprecedented growth for the coming decades, leading to serious environmental and economic concerns among airlines and regulatory bodies. Different approaches, for both airborne and ground operations, have been proposed to reduce and control emissions without compromising profit margin. For on-ground activities, the electric taxiing (ET) methodology is one of the suggested solutions for reducing the emissions and the acoustic noise in the airport, and for lowering the fuel consumption and operating costs. This paper thus aims to review and collate the more important literature related to electric taxiing systems (ETSs), in order to draw an inclusive picture regarding the current state of the art of a moving and growing sector that just started its first steps towards an ambitious target. After introducing the general concept of ET, elaborations on the benefits and challenges of available technologies are done with a detailed comparison of the different systems. Finally, recommendations for future research and outlook on ET are presented.

It is well known and widely accepted that the voltage source inverter (VSI) now dominates the world of electrical drives. Its success is probably due to its simplicity, high efficiency, and the widespread availability of VSs. This popularity has, in turn, influenced the evolution of the semiconductor industry, which has focused in recent years on devices tailored for VSIs. Thus, products such as depletion devices (normally off) and those without reverse voltage blocking have been widely marketed and used.