Developments in D.C. disc machines : design, construction and performance of permanent magnet axial field motors for traction applications

Axial-field permanent magnet motors have been shown to offer improved efficiency and power density compared with conventional machines. The different aspects of the advantages of permanent magnet disc armature motors have been demonstrated. A technique is described by which the magnetic circuit is then designed for optimum motor efficiency. The development of criteria for the selection of machine parameters leads to a commuter program that produces a realistic design given only the desired rower, speed, and voltage as input data. An analytical model has been established to quantitively predict the degree to which the permanent magnet field is demagnetised by the armature current. A new method for armature construction (skeleton armature) is described which is more satisfactory than encapsulation for the necessary mechanical strength and rigidity. The high power to weight and high power to volume allows novel locations to be considered for the drive motor within the vehicle, and a new design of axle-mounted twin-rotor machine will also be described. Such relocation, together with belt reduction gear, reduces the weight and rower losses associated with other transmission components. The construction of a vehicle test facility to evaluate the performance of electric and hybrid vehicles is described. The Nova series hybrid vehicle was tested on the rig. The trials showed that the losses in belt drive transmissions were less than those in a conventional transmission.