The attempt of this paper is to examine the basic theory on the analysis of the effect of a shading coil fitted to an electromagnetic contactor, and to compare experimentally the attracting force of an AC electromagnetic contactor with that of a DC electromagnetic contactor, with varying the airgap length. Equations are also proposed for calculating the AC and DC attracting force per unit consumption wattage by using the circuit constants measured from the experiment, and these calculated attracting forces are compared with those actulally measured, and then, the experimental contactor is examined in the view of its design. The calculated attracting forces are appeared to coincide well with the measured ones and the experimental contactor fitted with shading coil is revealed not so well designed for reducing the fluctuation of the attracting force.

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