Patent ID: 8294401

Claim:
An electrical machine system for converting electrical energy into mechanical energy and/or mechanical energy into electrical energy, the machine comprising a stator and a rotor, the stator having one or more electrical windings wherein at least one electrical parameter of the windings have a cyclic variation related to rotor position; at least one control device for controlling supply of electrical current to or from the or each said electrical winding, and at least one rotor position sensor means for detecting at least one electrical signal related to the cyclic variation of at least one electrical parameter of the or each said electrical winding wherein at least one said rotor position sensor means comprises the steps of measuring the said electrical signal at least once during any part of an electrical cycle, conversion of the at least one measured electrical signal to a ratiometric quantity representative of an estimate of the rotor position, conversion of the ratiometric quantity directly into a time quantity by multiplication of the ratiometric quantity by a time representing a proportion of the period of the cyclic variation in the electrical parameter and using the said time quantity in a calculation to maintain the current passing through the or each said electrical winding in synchronism with rotor rotation.