Faulty load detection for multi-phase electric motor

A method for obtaining an indication of a faulty load condition of a multi-phase electric motor with electric commutation driven by an electric drive unit comprising for each motor phase of the multi-phase electric motor, a respective high-side switch and a respective low-side switch,

• wherein:
• during operation of the multi-phase electric motor, the respective high-side switch and the respective low-side switch of each of the motor phases are cyclically switched on and off according to a switching scheme comprising cyclically recurrent time points,
• at the cyclically recurrent time points, for at least one of the motor phases, both the respective high-side switch and the respective low-side switch of the motor phase are switched to a respective high-ohmic state for a switch-off interval, and
• in case of the faulty load condition, a current continues to flow for a recirculation time interval equal to an expectation value valid for a fault-free operation of the multi-phase electric motor,
• the method comprising:
• (a) starting, at a start of the switch-off interval, a time measurement unit,
• (b) measuring the recirculation time interval for as long as the current that continues to flow has a sign-independent magnitude that remains larger than a predetermined threshold value,
• (c) continuing, in case the recirculation time interval is not terminated during the switch-off interval, the time measurement at least in a next switch-off interval until the recirculation time interval is terminated,
• (d) repeating, for additional switch-off intervals after a preceding high-side switch activation and/or after a preceding low-side switch activation of each motor phase, steps (a), (b), and (c) for the respective motor phase,
• (e) comparing (1) the measured recirculation time intervals for respective motor phases with each other and/or (2) the measured recirculation time intervals respectively for one motor phase in sequential succession with each other and/or (3) the measured recirculation time intervals with the expectation value or the expectation value range for the respective motor phase, and
• (f) determining, based on a deviation from the respective expectation value, the indication of the faulty load condition.