Investigation of a Reduced Cost Solution to Implement Integrated Safe Torque-OFF Function in Cascaded H-Bridge Induction Motor Drives

Safe Torque-OFF (STO) is a common and basic functional safety function for motor drive systems. Typically, integrating STO function to cascaded H-bridge induction motor drive systems requires turning off all cells to achieve zero torque at the motor. The paper aims to reduce system cost and complexity by investigating the effectiveness of interrupting a minimum number of cells per phase to achieve STO functionality. The effect of different types of factors such as the motor control system, operation condition, and load characteristics is studied. Analysis validation has been conducted using medium voltage drive simulation in MATLAB/SIMULINK.