The attractions of switched reluctance motor (SRM) drives compared to conventional alternatives will be significantly enhanced if the optical rotor position sensor can be eliminated. Considerable attention has recently been applied to various methods for sensorless rotor position measurement, generally based on measurement of phase current and inductance or flux and a pre-knowledge of the magnetic characteristics. This paper comprehensively reviews the various methods previously suggested in both papers and patents for operation both at low and high speeds. Lower speed methods generally utilise the introduction of test signals into the phase winding whilst the winding is normally unenergised. Higher speed methods utilise the main excitation current waveform. In addition there are a number of miscellaneous methods which are considered.
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