CPC G01K 7/01 (2013.01) [G01K 3/005 (2013.01); G01K 7/183 (2013.01)] | 18 Claims |
1. An electric device, comprising an inverter system to be coupled to phase windings of an electric machine to drive the electric machine, the inverter system comprising:
switching branches coupled between a DC supply voltage node and an intermediate node, each of the switching branches having a terminal to be coupled to a respective phase winding of the electric machine;
a shunt resistor coupled between the intermediate node and ground; and
control circuitry configured to apply control signals in accordance with a control scheme to the switching branches to cause the inverter system to drive the phase windings of the electric machine with a multi-phase AC power signal;
wherein the control scheme is divided into sectors, with each sector being divided into periods;
wherein the control circuitry is configured to, during at least some sectors of the control scheme:
during a first given period: measure a shunt voltage across the shunt resistor; and measure a drain to source voltage of a first calibration transistor, the first calibration transistor being a transistor of a given switching branch; and
determine a drain to source resistance of the first calibration transistor as a function of a resistance of the shunt resistor, the drain to source voltage of the first calibration transistor measured during the first given period, and the shunt voltage measured during the first given period; and
wherein the control circuitry is further configured to:
control driving of the given switching branch;
determine a temperature of the first calibration transistor during driving of the electric machine by the inverter system based upon the drain to source resistance of the first calibration transistor;
modify driving of the given switching branch so as to maintain conductivity of the first calibration transistor at a highest level at which the temperature of the first calibration transistor remains below a threshold temperature; and
cease driving of the given switching branch when the temperature of the first calibration transistor exceeds the threshold temperature.
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