Ayman Mohamed Fawzi El-Refaie

Performance testing and analysis of synchronous reluctance motor utilizing dual-phase magnetic material

While interior permanent magnet (IPM) machines have been considered state of the art for traction motors, synchronous reluctance (SynRel) motors with advanced materials can provide a competitive alternative. IPM machines typically utilize neodymium iron boron permanent magnets, which pose an issue in terms of price, sustainability, demagnetization at higher operating temperatures, and uncontrolled generation. On the other hand, SynRel machines do not contain any magnets and are free from these issues. However, the absence of magnets as well as the presence of bridges and centerposts limit the flux-weakening capability of a SynRel machine, and limit the achievable constant power speed ratio without having to significantly oversize the machine and/or the power converter. In this paper, a new material referred to as the dual-phase magnetic material, where nonmagnetic regions can be selectively introduced within each lamination, will be evaluated for SynRel designs. The dual-phase feature of this material enables nonmagnetic bridges and posts, eliminating one of the key limitations of the SynRel designs in terms of torque density and flux weakening. This paper will present the design, analysis, and test results of an advanced proof-of-concept SynRel design utilizing dual-phase material with traction applications as the ultimate target application.

Role of advanced materials in electrical machines

There has been a revived and growing role for electrical machines and drives across a wide range of applications. Such applications include, hybrid/electrical traction applications, aerospace applications, and renewable energy. All these applications present different set of requirements and challenges. The common trend is that there is a need for higher-performance electrical machines in terms of higher power/torque density, and higher efficiency while keeping cost under control. There has been a lot of work done around coming up with novel machine topologies, optimizing more conventional topologies as well as improved thermal management schemes. Like many other areas of engineering/research, advanced materials can play a key role in opening up the design space for electrical machines leading to a step improvement in their performance. This paper will present an overview of some of the key advanced materials that are either recently developed or are currently under development and their potential impact on electrical machines.

High specific power electrical machines: A system perspective

There has been a growing need for high specific power electrical machines for a wide range of applications. These include hybrid/electric traction applications, aerospace applications and Oil and Gas applications. A lot of work has been done to accomplish significantly higher specific power electrical machines especially for aerospace applications. Several machine topologies as well as thermal management schemes have been proposed. Even though there has been a few publications that provided an overview of high-speed and high specific power electrical machines [1-3], the goal of this paper is to provide a more comprehensive review of high specific power electrical machines with special focus on machines that have been built and tested and are considered the leading candidates defining the state-of-the art. Another key objective of this paper is to highlight the key “system-level” tradeoffs involved in pushing electrical machines to higher specific power. Focusing solely on the machine specific power can lead to a sub-optimal solution at the system-level.

Test Results for a High Temperature Non-Permanent-Magnet Traction Motor

Non-permanent-magnet machines are generally known to be less power dense than permanent magnet counterparts, but the absence of permanent magnets in these machines makes them well suited for high temperature applications. This offers a degree of freedom in improving their power density, because they can operate at higher electrical loading while maintaining acceptable efficiency. This paper presents a high temperature dc-biased reluctance machine that is structurally similar to a conventional switched reluctance machine. This non-permanent-magnet machine has a dc field winding and an ac three-phase armature winding. The machine is equipped with a high temperature 280 °C rated insulation system. Test results showing machine performance under continuous operation against the FreedomCar 2020 specifications as well as at high temperature up to 280 °C are presented. Compared with an initial design using conventional insulation designed for operation at 200 °C, the high temperature insulation system enabled the machine to operate at twice the temperature rise and achieve 43% increase in power.