A New Hybrid Brushless DC Motor/Generator without Permanent Magnet

The Brushless DC (BLDC) motor is a simple robust machine which has found application over a wide power and speed of ranges in different shapes and geometry. This paper briefly reviews the fundamentals behind the motor and also the different types of BLDC motors with different geometries and then presents a new configuration for BLDC motor/generator, which does not use a permanent magnet in the rotor. The proposed novel motor/generator consists of two magnetically dependent stator and rotor sets (layers), where each stator set includes nine salient poles with windings wrapped around them while, the rotor comprises of six salient poles. The magnetic field passes through a guide to the rotor then the stator and finally completes its path via the motor housing. This is a three phase motor/generator and every stator and rotor pole arcs are about 30º. A new power electronic converter is also presented. This topology provides bidirectional control of the current for each motor phase independently. This control scheme permits the motor to operate with any number of phases at any time. In this converter, four power switches in the form of a bridge connection for each motor phase has been utilized therefore, the motor can operate by switching different sequences for the current direction in each motor phase windings and also offers the choice of having any number of phases to be on at any time. A proto-type motor/generator and the drive circuit have been built and tested in the laboratory and the numerical and experimental results are presented. Due to the ruggedness of the proposed motor/generator in comparison with the conventional and brushless dc motors used for automobile applications, this unit looks very promising for use as an integrated motor generator for hybrid vehicle