Abstract
This article analyzes the behavior of induction disc overcurrent relays as a function of the frequency. A model for the simulation of the electromechanical device is shown, and this model is verified by experimental measurements. Experimental results were obtained for three overcurrent relays from different manufacturers, by varying the magnitude of injected current and the time dial setting (for wide ranges of frequencies, which were selected for the tests). Experimental results are in concordance with the developed model, and the average percentage errors are in the order of 2%. The braking effect due to the magnetic fluxes created by the operative current can easily be included (or not) in the model, and it is shown that the inclusion of this effect: (a) improves the accuracy of the model, for tests in the linear zone of the ferromagnetic core; (b) can be useful to obtain accurate results for the non-linear zone of the ferromagnetic core, although the model was developed by assuming linearity of the ferromagnetic core. On the other hand, some inaccuracy could be expected for the time dial setting because this adjustment is performed by a continuous movement in a calibrated knob; this fact can easily be included in the model, in order to improve the accuracy of results of simulations.
Published Version
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