Noise reduction in a switched reluctance motor by current profile

摘要

Apparatus (10) for controlling the current profile (P2) in a single or polyphase SRM (M) during the active portion of a phase. Switches (S1, S2) are closed during an active portion of a phase to direct current flow into a winding (W). A Hall effect sensor (14) and other sensors are used to sense various operating parameters of the SRM. A PWM signal generator (16), or microprocessor (20) is responsive to the sensor inputs to provide PWM operating signals (G2) to at least one of the switches to control current flow to the winding. The operating signals modulate the switch(es) for switch operation to be controlled as a function of the signal characteristics of the operating signals. This allows the current supply to the winding to be in accordance with the current profile. According to the profile, current flow is initially rapidly increased from zero to a peak value (Ip') when the phase becomes active. The current is then allowed to decrease from this peak to a second and lesser value (Ip) by the time the phase becomes inactive. Current decays from this second value to zero when the phase becomes inactive. The transition in the current profile which occurs when the phase switches from active to inactive is no longer an abrupt transition, but is rather a more moderate one. This smoother transition reduces the amount of ringing in the motor, which normally occurs when current flow into the winding ceases, thereby to reduce motor noise. IMAGE