Pull-in criterion for reluctance motors

THIS SUBJECT is timely because of the recent improvement of reluctance motors to a point where they have considerable sales volume. The pull-in criterion is related to the maximum inertia that can be pulled into step for a given frame size in the rating set on that frame, expressed as a graph or by an equation. This paper derives this equation. A reluctance motor is a synchronous motor without rotor excitation. The pull-in criterion for synchronous motors with d-c excitation was studied by Edgerton and Fourmarier,1 and by Shoults, Crary, and Lauder.2 Although their results cannot be applied to the reluctance motor directly, they were found useful in checking certain steps.