Patent ID: 8643989
Filing Date: 2014-02-04
Classification: H01H,H02H

Abstract:
1. A method for reducing inrush current to an electrical load in response to anticipation of the inrush current due to detection of a disturbance occurring within a quarter to one half cycle in an input AC power supply coupled to the electrical load, comprising the steps of: at the initial application of power from the input AC power supply at start-up, limiting the current to the electrical load by connecting a current limiting impedance between the input AC power supply and the electrical load; coupling the input AC power supply to the electrical load after startup by removing the current limiting impedance; monitoring the voltage of the input AC power supply at a node between the current limiting impedance and the electrical load to detect a disturbance in the input AC power supply occurring within a quarter cycle to one half cycle of the AC power; detecting a disturbance in the input AC power supply that would cause an inrush current to the electrical load after the disturbance has ended; in response to detection of the beginning of a disturbance in the input AC power supply, connecting the current limiting impedance between the input AC power supply and the electrical load; repeatedly monitoring the voltage of the input AC power supply at a node prior to the current limiting impedance to detect the end of the disturbance in the input AC power supply, while maintaining the current limiting impedance; and in response to detection that the disturbance in the input AC power supply has ended by return of the voltage to a normal level, coupling the input AC power supply to the electrical load by removing the current limiting impedance, whereby inrush current to the load is impeded at start-up and in response to detection of a disturbance in the input AC power supply.