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This paper aims at developing a compensation circuit for offsetting the decreased coil voltage value due to power disturbances such as voltage sags. Through a feedforward approach to reserve a compensation voltage in the voltage reservoir in advance, once when the voltage sag occurs in the coil voltage, a triggering signal is generated based on a feedforward-based calculating algorithm so as to trigger the compensation circuit for offsetting the decreased coil voltage. For verifying the effectiveness of our proposed compensation strategy, suppose that a simulation case where voltage sags occur, and the contacts disengagement phenomenon appears as a result of the magnetic force below the springs' tension. Through properly triggering compensation circuit, the reserved constant dc voltage is then to be superimposed with the line voltage. Although the movable part originally has started to disengage, but finally is still successfully reengaged before the contacts disengagement.
Date of Conference: 21-24 April 2008