Patent ID: 6703805
Filing Date: 2004-03-09
Classification: H02P

Abstract:
In a DC electric motor with a drive current being rotated in sequence through electromagnets on a rotor or a stator thereby generating a rotating magnetic field, said drive current at any instant flowing through a plurality of electromagnets operating in series, an improved rotor position detector comprising:a fixed impedance reference network comprising two components connected in series, each component having an impedance not affected by motor rotation; said components being connected in parallel to a plurality of driven electromagnets; the fixed impedance reference network and the driven electromagnets forming a bridge impedance network; a computational circuit having a first input connected to a node between the driven electromagnets, and having a second input connected to a node between the components of said fixed impedance reference network; wherein an output signal of the computational circuit is consistently related to an impedance ratio between the driven electromagnets; said impedance ratio depending on a relative rotational position between the rotor and the stator, thereby defining a rotor position relative to the stator.