When a safety-related fault in the motor controller is detected, the torque output of the motor cannot be effectively shut off in time\nand an overcurrent occurs at the moment of switching. The advantages and disadvantages of the open circuit and active shortcircuit\nmethods are analyzed. Combining the advantages of these two operations, this paper proposes a new mixed voltage\nmodulation method. It introduces a voltage modulation ratio that represents the duty cycle of the open circuit operation during a\nPWM period. This ratio is first set to a fixed value and gradually reduced to zero. The inverter is switched at a mixed operation and\nfinally remains in the active short-circuit mode. The current can be quickly converged by a freewheeling diode of open circuit.\nAfter switching to active circuit, the brake torque is safety. The effectiveness of this shutoff method was verified by simulations and\nexperiments. It shows that current fluctuations are suppressed and the torque output is also within a safety range. In addition, this\nshutoff method does not require any additional sensor information and is simple to implement.
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