A permanent magnet machine (PMM) has a kinetic portion electrically coupled to a power conversion portion. Motive power is provided to the kinetic portion by a torque applied to a motive shaft coupled to a prime mover, such as an aircraft engine or an automobile engine. A control circuit includes a switch disposed between the kinetic portion and output feeder cables of the power conversion portion. A first sensor is effective to detect a first fault condition in either the feeder cables or the power conversion portion and a second sensor is effective to detect a second fault condition in the kinetic energy portion. The first sensor is effective to open the switch when a first fault condition is detected and the second sensor is effective to apply a voltage to a winding within the kinetic portion generating an opposing counter torque on the motive shaft where a combination of torque and counter torque exceeds a fracture yield strength of said motive shaft causing it to fracture. The second fault condition is then rendered safe while the prime mover may continue normal operation.