Method and apparatus for increasing a current sensing range in a polyphase motor system

A system comprising:

• a polyphase motor having first, second, and third phase leads;
• a power inverter module which supplies a first, a second, and a third phase current to the respective first, second, and third phase leads;
• a plurality of phase current sensors each connected to a respective one of the first, second, and third phase leads, and operable to measure a corresponding one of the first, second, and third phase currents;
• and
• a controller in communication with the plurality of phase current sensors, wherein the controller includes a processor and tangible, non-transitory memory on which is recorded instructions for increasing a current sensing range of the phase current sensors, wherein execution of the instructions by the processor causes the controller to:
• measure, via the phase current sensors, each of the plurality of phase currents;
• calculate an absolute value of each of the measured phase currents;
• separately compare each of the calculated absolute values to a saturation limit to determine whether only one of the sensors is saturated with respect to the saturation limit, with the remaining sensors being unsaturated sensors;
• extrapolate the phase current for the one saturated sensor from the measured phase currents of the unsaturated sensors by:
• calculating a temporary phase current value as a function of the phase currents of the unsaturated sensors;
• determining whether the absolute value of the calculated temporary phase current exceeds the measured value of the saturated sensor;
• determining whether a sign of the calculated temporary phase current value matches a sign of the measured current value of the saturated sensor;
• and
• using the calculated temporary phase current as an extrapolated phase current for the saturated sensor;
• and
• execute a control action of the polyphase motor using the extrapolated value only when the signs match and the calculated temporary phase current value exceeds the measured value of the saturated sensor, including at least one of controlling a function of the polyphase motor and recording a diagnostic code indicating a state of health of the polyphase motor.

A vehicle comprising:

• a transmission having a gear set and an output member;
• and
• a polyphase motor system which delivers motor torque to the gear set for powering the output member, the polyphase motor system including:
• a polyphase electric traction motor having a stator with a first, a second, and a third phase lead;
• a power inverter module which supplies a first, a second, and a third phase current to the first, the second, and the third phase lead, respectively;
• a plurality of sensors each connected to a respective one of the phase leads and operable to measure a corresponding one of the first, second, and third phase currents;
• and
• a controller in communication with the sensors, wherein the controller includes a processor and tangible, non-transitory memory on which is recorded instructions for increasing a current sensing range in the polyphase motor system, wherein execution of the instructions by the processor causes the controller to:
• measure, via the plurality of phase current sensors, each of the phase currents;
• calculate an absolute value of each of the measured phase currents;
• separately compare each of the calculated absolute values to a calibrated threshold to thereby determine whether only one of the phase current sensors is saturated with respect to a saturation limit;
• extrapolate the phase current for the saturated phase current sensor from the measured phase currents of all of the remaining phase current sensors when only one of the phase currents is saturated, by:
• calculating a temporary phase current value as a function of the unsaturated phase currents;
• determining whether the absolute value of the calculated temporary phase current exceeds the measured value;
• determining whether a sign of the calculated temporary phase current value matches a sign of the measured current value;
• and
• using the calculated temporary phase current as an extrapolated phase current for the saturated phase current;
• and
• execute a control action of the motor using the extrapolated value only if the calculated temporary phase current value exceeds the measured value and the signs match, including at least one of controlling a function of the polyphase electric traction motor and recording a diagnostic code indicating a state of health of the polyphase electric traction motor.