Patent ID: 8810177

Claim:
A system comprising: a polyphase permanent magnet synchronous electric machine having a negative d-axis current; a DC bus; an AC bus; a DC power supply; a power inverter module (PIM) that is electrically connected to the DC power supply via the DC bus, and to the electric machine via the AC bus, wherein the PIM includes a set of semiconductor switches that are controlled to convert an AC voltage to a DC voltage, and vice versa; and a controller in communication with the PIM that is configured to: detect a fault condition in the system; determine an initial deadtime; set pulse width modulation (PWM) duty cycles of all phases of the electric machine to 50% such that all phases switch simultaneously; apply a polyphase OPEN state to the AC bus in response to the detected fault condition; and transition to a polyphase SHORT state as a remedial action by automatically inserting an adjustable deadtime at each PWM switching transition of the PIM over a calculated ramp duration, thereby transitioning from the initial deadtime to a minimum deadtime over the calculated ramp duration; wherein the transition reduces peak overshoot of the negative d-axis current of the electric machine during the detected fault condition.