Apparatus, methods and computer program products for inverter short circuit detection

A method of operating an adjustable frequency drive comprising an inverter configured to be connected to first, second and third phases of a load, a driver having an output coupled to control terminals of transistors of the inverter and a control input configured to receive control vectors and configured to responsively apply control signals to control terminals of the inverter, a controller configured to apply control vectors to the driver responsive to a command input and an output feedback, and a desaturation detector configured to detect desaturation of transistors of the inverter, the method comprising:

• the controller applying at least one test vector to the control input of the driver that causes the driver to turn on selected ones of the transistors of the inverter to create a fault current path for a potential fault of at least one phase of the output of the inverter for a test interval having a duration that is independent of the command input and the output feedback, including applying spaced-apart first and second test vectors to the driver that turn on respective first and second groups of the transistors, wherein the first test vector enables detection of a fault between a first phase and a second phase or a fault between the first phase and a third phase, and wherein the second test vector enables detection of a fault between the third phase and the second phase or a fault between the third phase and the first phase;
• and
• enabling or disabling further operation of the inverter responsive to an output of the desaturation detector that occurs in response to the at least one test vector, wherein further operation of the inverter is inhibited in response to the desaturation detector detecting desaturation of at least one transistor of the first and second groups.