An AC motor drive having an input connectable to an AC source having its neutral point connected to the ground and a three phase output connectable to an input terminal of an AC motor, the AC motor drive comprising: a pulse width modulation inverter that is connected to a DC link and having a plurality of switches (20; 44, 46, 48, 50, 52, 54) therein to control current flow and terminal voltages in the AC motor; and a fault detection and protection system connected to the PWM inverter, the fault detection and protection system comprising: a pair of current sensors (56, 58) to measure a current on a first phase and a second phase of the AC motor drive output; a voltage sensor to measure a DC link voltage on the DC link of the AC motor drive; a desaturation control circuit configured to determine a voltage and associated current across switches of the PWM inverter corresponding to a third phase of the three phase output; and a controller configured to: compare the current measured on the first phase and the second phase of the three phase output to a first threshold; compare the measured DC link voltage to a second threshold; compare the voltage across the switches (44, 46) of the PWM inverter on the third phase to a third threshold; and while the AC motor is at a standstill, detect a ground fault on one of the first, second, and third phases (40, 38, 36) of the three phase output to the AC motor based on the comparisons of the first and the second phase currents, DC link voltage, and voltage across the switches (44, 46) on the third phase, to the first, second, and third thresholds, wherein, in detecting a ground fault, the controller is further configured to: declare a ground fault when one of the first and the second phase currents is above the first threshold and the DC link voltage is above the second threshold; and declare a ground fault when the first and the second phase currents are below the first threshold, the DC link voltage is above the second threshold, and the voltage across switches (44, 46) of the PWM inverter corresponding to the third phase of the three phase output is above the third threshold. a pulse width modulation inverter that is connected to a DC link and having a plurality of switches (20; 44, 46, 48, 50, 52, 54) therein to control current flow and terminal voltages in the AC motor; and a fault detection and protection system connected to the PWM inverter, the fault detection and protection system comprising: a pair of current sensors (56, 58) to measure a current on a first phase and a second phase of the AC motor drive output; a voltage sensor to measure a DC link voltage on the DC link of the AC motor drive; a desaturation control circuit configured to determine a voltage and associated current across switches of the PWM inverter corresponding to a third phase of the three phase output; and a controller configured to: compare the current measured on the first phase and the second phase of the three phase output to a first threshold; compare the measured DC link voltage to a second threshold; a pair of current sensors (56, 58) to measure a current on a first phase and a second phase of the AC motor drive output; a voltage sensor to measure a DC link voltage on the DC link of the AC motor drive; a desaturation control circuit configured to determine a voltage and associated current across switches of the PWM inverter corresponding to a third phase of the three phase output; and a controller configured to: compare the current measured on the first phase and the second phase of the three phase output to a first threshold; compare the measured DC link voltage to a second threshold; compare the current measured on the first phase and the second phase of the three phase output to a first threshold; compare the measured DC link voltage to a second threshold; declare a ground fault when one of the first and the second phase currents is above the first threshold and the DC link voltage is above the second threshold; and declare a ground fault when the first and the second phase currents are below the first threshold, the DC link voltage is above the second threshold, and the voltage across switches (44, 46) of the PWM inverter corresponding to the third phase of the three phase output is above the third threshold.