David Allan Torrey

Robust non-permanent magnet motors for vehicle propulsion

There has been growing interest in electrical machines that reduce or eliminate rare-earth material content. Traction applications are among the key applications where reducing cost and hence reduction or elimination of rare-earth materials is a key requirement. This paper will assess the potential of three non-permanent magnet options in the context of vehicle propulsion applications: 1) a conventional Switched Reluctance Machine (SRM), 2) a DC-biased Reluctance Machine (DCRM) and, 3) a Wound Field Flux Switching Machine (WFFSM). The three machines were designed to achieve the hybrid vehicle traction requirements of 55kW peak and 30kW continuous over a speed range going from 2800rpm to 14000rpm. Their performance will be compared and the key opportunities and challenges will be highlighted. Preliminary experimental results for the DCRM will be presented.

Sinusoidal Reluctance Machine With DC Winding: An Attractive Non-Permanent-Magnet Option

Important global efforts are underway toward lowering the cost of electric machines for electric and hybrid vehicles by reducing or eliminating the use of rare earth materials which have been experiencing significant price increases and volatility. Non-permanent magnet electric machines are a potential solution and are increasingly investigated by researchers worldwide. This paper presents a DC biased reluctance machine which is structurally similar to a conventional switched reluctance machine. This type of machine has a DC field winding and an AC three phase armature winding. It uses a conventional three phase inverter for the armature and an additional auxiliary DC/DC converter for the field winding. This reluctance machine is designed to achieve hybrid vehicle traction requirements of 55kW peak at 2800 rpm and 30kW continuous over a speed range going from 2800 rpm to 14000 rpm.

Sinusoidal reluctance machine with DC winding: An attractive non-permanent magnet option

Important global efforts are underway toward lowering the cost of electric machines for electric and hybrid vehicles by reducing or eliminating the use of rare-earth materials which have been experiencing significant price increases and volatility. Non-permanent-magnet (non-PM) electric machines are a potential solution and are increasingly investigated by researchers worldwide. This paper presents a DC-biased reluctance machine, which is structurally similar to a conventional switched reluctance machine. This type of machine has a DC field winding and an AC three-phase armature winding. It uses a conventional three phase inverter for the armature and an additional auxiliary DC/DC converter for the field winding. This reluctance machine is designed to achieve hybrid vehicle traction requirements of 55 kW peak at 2800 r/min and 30 kW continuous over a speed range going from 2800 to 14 000 r/min.

Test results for a high temperature non-permanent magnet traction motor

Commercially available hybrid and electric vehicles are generally using rare earth PM motors because of their compactness and very good efficiency. But the supply security and price volatility of rare-earth materials are still major concerns for the hybrid and electric vehicle industry. Hence, global efforts are underway in several countries on using reduced or non-rare earth materials, developing non-permanent magnet solutions and taking cost out by trading off between material properties and cost. 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 provided appropriate stator winding insulation materials are used. 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 which 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 280oC rated insulation system. Test results showing machine performance under continuous operation against the FreedomCar 2020 specifications as well as at high temperature up to 280oC are presented. A 43% improvement in power density was achieved by going to high temperature.

Performance comparison of switched reluctance motor with sinusoidal and conventional excitation

Switched reluctance motors (SRMs) are popular due to their advantages of simple and robust construction, wide speed range, and fault tolerance. Commonly cited limitations of SRMs are acoustic noise and the need for a different inverter configuration. It has been reported that when the SRM phases are excited with sinusoidal bipolar currents, there is significant reduction in acoustic noise. Further, with this excitation scheme, the voltage source inverter (VSI) configuration commonly used for all AC drives can be used for this motor. Another advantage of sinusoidal excitation is that well established position sensor-less control schemes used for other AC machines can be used. This paper discusses a sinusoidally excited fractional HP switched reluctance motor (SRM) for use in appliances. It is found that the advantages mentioned above are achieved at the cost of other performance parameters. Simulation results comparing efficiency, inverter VA rating, width of constant power region and radial forces for sinusoidal and conventional excitation schemes are presented. Further, a prototype of the motor is fabricated, and experimental results are presented.

Recent Advances of Power Electronics Applications in More Electric Aircrafts

Recent advances in power electronics have significantly promoted the development of more electric aircraft (MEA). This paper presents a review of the power electronic applications in MEA that were presented in the literature in the past decade, ranging from the component level such as power semiconductor devices and solid-state circuit breakers, to various power converter topologies, high-voltage AC (HVAC) and high-voltage DC (HVDC) power system architectures for MEA. Opportunities and challenges of using emerging power semiconductor devices, power converter topologies and various system architectures are discussed.

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.