A NEW HYBRID BRUSHLESS DC MOTOR/GENERATOR WITHOUT PERMANENT MAGNET

The brushless dc (bldc) motor is a simple robust machine which has foundapplication over a wide power and speed of ranges in different shapes and geometry. this paperbriefly reviews the fundamentals behind the motor and also the different types of bldc motors vithdifferent geometries and then presents a new configuration for bldc motor/generator, which doesnot use a permanent magnet in the rotor. the proposed novel nlotor/generator consists of t'onlagnetically dependent stator and rotor sets (layers), vhere each stator set includes nine salient poleswith windings vrapped around them vhile, the rotor comprises of six salient poles. the magneticfield passes through a guide to the rotor then the stator and finally completes its path via the motorhousing. this is a three phase nl0tor/generator and every stator and rotor pole arcs are about 30°, anev pover electronic converter is also presented. this topology provides bidirectional control of thecurrent for each motor phase independently. this control scheme permits the motor to operate withany nulnber of phases at any tinle. in this converter, four pover svitches in the form of a bridgeconnection for each motor phase has been utilized therefore, the motor can operate by svitchingdifferent sequences for the current direction in each motor phase vindings and also otlers the choice.of having any number of phases to be on at any time. a proto-type nlotor/generator and the drivecircuit have been built and tested in the laboratory and the nunlerical and experimental results arepresented. due to the ruggedness of the proposed motor/generator in comparison vith theconventional and brushless dc motors used for automobile applications, this unit looks very promisingfor use as an integrated motor generator for hybrid vehicle.