abstract “ac motor drive, method for detecting an earth fault in an ac motor drive and system for detecting an earth fault in an ac motor drive” a system and method for detecting earth faults in an ac motor drive are revealed. A fault detection and protection system for an ac motor drive includes current sensors for measuring first and second phase output currents, a voltage sensor for measuring a dc link voltage, and a desaturation control circuit for determine a voltage and associated current through the pwm inverter switches for a third phase of the output. a controller compares the first and second phase currents, the measured connection voltage and the voltage across the pwm inverter switches in the third phase, for a plurality of limits. The controller detects a ground fault in one of the first, second, and third phases of the three-phase AC motor output based on comparisons of the first and second phase currents, the dc link voltage, and the voltage across the limit switches. 1/1
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