Effectiveness of Noise Reducing Measures in Switched Reluctance Drives

Acoustic noise reduction in electrical drives can be achieved by either machine design or control measures. The corresponding strategies affect different parts of the acoustic noise transfer path and they can therefore be divided into different categories such as: reduction of the excitation, increase of transfer path impedance, decrease of radiation efficiency or reduction of the annoyance of the sound. In contrast to the first three strategies, the last does not necessarily result in a reduction of the resulting sound pressure level. Annoyance is a subjective impression but may be characterized well by psycho-acoustic quantities such as loudness, sharpness and tonality [1]. This paper begins with a detailed study of the acoustic noise transfer path. The derived theory is validated by numerical simulation and experiments. Finally, the effectiveness of the different noise reducing strategies as well as trade-offs are discussed.