Abstract: In order to be acceptable for safety critical applications, it is necessary for an electrical machine to allow continued operation despite an electrical short circuit in one of the operational phases of that electrical machine. It will be appreciated that an electrical short circuit creates excessive electrical current through the short circuit with significant heating and other detrimental effects. However, the electrical machine can operate with one operational phase disabled. In such circumstances, the present invention incorporates means for determining an electrical short circuit has occurred and then injects an electrical current approximately equal to or greater than the rated electrical current. In such circumstances, the operational phase or coil 4, 24, 34 is effectively protected despite the electrical short circuit and hence the electrical machine can continue to operate.

Abstract: In order to be acceptable for safety critical applications, it is necessary for an electrical machine to allow continued operation despite an electrical short circuit in one of the operational phases of that electrical machine. It will be appreciated that an electrical short circuit creates excessive electrical current through the short circuit with significant heating and other detrimental effects. However, the electrical machine can operate with one operational phase disabled. In such circumstances, the present invention incorporates means for determining an electrical short circuit has occurred and then injects an electrical current approximately equal to or greater than the rated electrical current. In such circumstances, the operational phase or coil 4, 24, 34 is effectively protected despite the electrical short circuit and hence the electrical machine can continue to operate.

Abstract: A switched reluctance electrical machine comprising a rotor 2 and coils 4 is arranged to provide constant power or torque output over a wider range of operational speeds. The coils 4 each include a tap T or a number of taps in order to allow the effective number of turns in each coil 4 to be altered dependent upon rotor 2 speed.