Energy flow in a 2-pole hysteresis coupling by poynting theorem

The production of torque in a hysteresis coupling is described by reference to the flow of energy in its air-gap and arbor regions and applying Poynting´s theorem to deduce the power crossing into the rotor annulus. The formulation of appropriate Poynting surface and vectors is given and the theory is applied to a 2-pole experimental coupling. The computed torque is shown to compare well with the measured values. The analysis brings out the significance of pole tips of the field system in controlling the development of torque. It is shown that the harmonics of the space MMF contribute appreciably to the total developed torque.