As part of a continuing investigation into the possibilities of small scale CHP in the home, a high
speed permanent magnet cylindrical 1 kW alternator has been designed and produced. The machine was
tested by attaching it to the turbine of a commercial turbocharger and driving it with compressed air.
Speeds of up to 36,000 rpm were reached before vibrations within the turbogenerator became excessive.
For a stator winding current density of 3 A/mm2, the alternator produced a power output of 360 W at
32,000 rpm, approximately a quarter of its 125,000 rpm design speed. The potential use of the inverted
Brayton cycle as an operating mode for a turbocharger acting as the unit’s prime mover was also
discussed.