Abstract: A co-axial cylindrical brushless DC motor has an internal cylindrical stator and an external rotor containing permanent magnets. The cylindrical stator has a substrate of reinforced plastics covered by several layers of helically wound annealed steel wire of about 1 mm diameter to provide a cylindrical magnetic layer of soft magnetic material just below the wound poles on or adjacent the outer surface of the stator.

Abstract: A permanent magnet rotary dynamo electric machine such as a high speed three phase brushless motor has at least one stator and at least one rotor spaced apart from one another by a cylindrical gap therebetween. A plurality of permanent magnetic poles are provided by a plurality of rare earth magnets positioned side by side on the inside of a cup shaped rotor and oriented parallel to the rotor axis. The stator has a plurality of wound poles of shallow depth which are wound on or close to the surface of a substrate of low magnetic permeability (less than 20 times that of air). The wound poles are positioned adjacent the cylindrical gap so as to intersect the magnetic flux paths between adjacent permanent magnetic poles.

Abstract: A regulator is disclosed for regulating a DC power supply such as an automotive alternator or generator which has a wide speed range and is hence capable of producing an output voltage and power which varies between wide limits. The regulator comprises electronic circuitry which allows the voltage at the alternator to rise while limiting the current therethrough, typically by means of pulse-width modulation; a DC-DC converter connected to the load; and circuitry to control the output voltage of the DC-DC converter within close limits. A permanent magnet alternator provided with a regulator of the type described is also disclosed.