This paper presents an accurate yet simple analytical model to predict the torque characteristics of an adjustable-speed permanent magnet eddy-current coupling in the low slip working area. Based on an improved magnetic equivalent circuit method, the flux density is quantitatively calculated, and then the general explicit expression of electromagnetic torque is developed. Moreover, the saturation effect of ferromagnetic materials
and the restricted slip have been reasonably taken into account. Compared with the 3-D finite element analysis and measurement results, the validity of this model is confirmed. In addition, several important parameters of
such devices are analyzed and discussed.