Acoustic noise cancellation techniques for switched reluctance drives

The levels of acoustic noise emitted by switched reluctance motor (SRM) drives are noted as being above those of competing variable speed drives. In other respects, the SRM drive offers distinct advantages. In a previous paper, the authors described a new technique for the cancellation of radial vibrations of the stator. This new technique was limited to power converters offering a zero voltage freewheel path. This paper describes further development of the technique which allows noise cancellation to be achieved with all types of power converter. The techniques disclosed in this paper include a smoothing method, a three-stage commutation method for converters with one switch per phase and a noise cancellation technique suitable for SRM drives incorporating an extended zero-voltage freewheel period for improved efficiency. The techniques are all compared, with experimental and simulated results.