Helen Pollock

Flux-Switching Motors for Automotive Applications

This paper presents a new class of brushless motor as an alternative to the permanent magnet brushed motor used in the automotive industry. The new flux switching motor is a very simple motor to manufacture and coupled with a power electronic controller requiring only two power semiconductor switches it has the potential to be extremely low cost in high volume applications. The design of the motor and its simulation using coupled circuit and time-stepping finite element analysis is presented. Tested performance has matched well with design targets and with simulation and is delivering performance comparable to a permanent magnet brushed motor. The new motor and drive are very robust, requiring only two power MOSFETs and a simple micro-controller to create an extremely low cost variable speed drive for automotive applications.

A permanent magnet flux switching motor for low energy axial fans

In this paper, a permanent magnet flux switching motor (PMFSM) is presented as an alternative to the more familiar brushless DC motor (BDC) used in low energy consumption axial fans. The PMFSM has permanent magnets as a part of the stator structure which also contains an armature winding. The rotor is a simple steel, salient pole structure. Simulated and experimental results are shown that demonstrate the proposed PMFSM can have improved efficiency compared with a comparable BDC motor and drive.

New method of power control for series-parallel load-resonant converters maintaining zero-current switching and unity power factor operation

A power supply incorporating a series-parallel load-resonant converter capable of efficient operation over a wide range of output power is presented. The series-parallel resonant converter is shown to have three resonant frequencies. Operation of the circuit at each of these resonant frequencies maintains zero-current switching and high-frequency operation. The resonant circuit is designed to have different circuit resistances at each resonant frequency. The power delivered to the circuit, and hence the load, will therefore vary depending on which resonant frequency the circuit is excited at. This is the basis of a new method of power control for load-resonant converters disclosed in this paper. A welding power supply is designed and constructed which delivers pulsed output currents of 150 A while operating at 100 kHz and 60 A at 65 kHz. The power supply contains an active rectifier and draws near unity power factor.

High Efficiency LED Power Supply

A new high efficiency light-emitting diode (LED) and an organic LED power supply are presented. An LED string is split into two sections. A first LED string is driven by a conventional dc-to-dc converter, while a second LED string is placed in series with the incoming dc supply current. Power is delivered to the second LED string without passing through the dc-dc converter, thus improving the system efficiency of the circuit. The equations presented show that the efficiency of the whole circuit will always be higher than the efficiency of the dc-dc converter alone. The performance of the new high efficiency circuit was tested and it was found that the new high efficiency circuit offered an improvement in efficiency of the LED driver of 3% at an automotive supply voltage of 14 V.