Control of the torque and rotor power in a five-phase wound-rotor induction motor drive for rotary assembly platforms

This paper illustrates the control system of a five-phase wound-rotor induction machine that can be used in applications where, besides the torque generation, a certain amount of active power must be transferred to loads collocated on the rotor frame. This requirement is common in rotary assembly platforms, bottle filling and capping systems, that embed electric actuators, sensors and process controllers on a rotating disk. The use of a five-phase machine avoids the slipring contacts to feed the rotor load. However, the choice of the set-point values for the motor currents involves magnetic, electric and thermal constraints. The paper illustrates a methodology of analysis, and develops a technique to deliver power to the rotor loads through the third-order spatial component of the magnetic field, while keeping the motor torque under control and reducing the rotor current as much as possible to minimize the rotor Joule losses. The experimental tests on a scaled prototype demonstrate the practical potential of the machine