Permanent magnet couplings transfer torque between two shafts without any mechanical contact. The calculation of transmissible torque is an important task. The relevant study for the last two decades is brief summarized. Various methods such as experiential

finite element and analytical methods are introduced and compared. The paper presents

for the first time

calculated torque equation by method of equivalent magnetic charge. This approach is proved to be a precise and easy method for the designing of magnetic couplings.