To assist in the evaluation of transient events on 50 Hz track circuits, a model of a double element vane relay has been developed. The model uses as its input the voltage waveform applied to the track coil but it can be extended to include the equivalent track impedance. The output of the model is the displacement of the vane and hence, whether the relay has picked up and if so, for what period of time.rnThe model has been developed and validated in stages by deriving the parameters used in each part of the model from test results.rnFor a number of transient events it can be shown that the time the relay contacts are closed (the dwell time) has a maximum value and tests have confirmed this This maximum dwell time is a function of the mechanical parameters of the vane and therefore does not depend upon any assumption made concerning the electrical aspects of the model.
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