Rotating Machines by Amatrol covers the function, operation, and performance characteristics of wound rotor motors. While VFDs and standard induction motors have replaced wound rotor motors in many applications, these motors are still used for heavy-duty, high torque applications such as industrial cranes and hoists. The 85-MT2D requires the Basic Electric Machines Learning System (85-MT2) and the DC Generators Learning System (85-MT2B) for use.