Compared performances of homopolar and bipolar hybrid excitation synchronous machines

This paper presents a description, operating principle and experimental study of two hybrid excitation synchronous machines in motor and generator modes. These machines combine two flux sources: permanent magnets, located in the rotor, and field coils, located in the stator avoiding sliding contacts. Thanks to this particular configuration the air gap flux can be easily controlled, without any risk of magnets demagnetisation. Two machines are thoroughly studied in this paper. They have the same stator but different rotors. Tests are performed on the prototype machines to assess their flux weakening capability, torque (motor mode), output power (generator mode) and efficiency characteristics. The first prototype has a homopolar configuration whereas the second one has a bipolar configuration. These two configurations are compared using experimental measurements. The advantages and drawbacks of each configuration are also reported.