Patent ID: 8587913

Claim:
An active current surge limiting apparatus for reduction of inrush current to an electrical load in response to detection of a disturbance in an input AC power supply coupled to the electrical load, comprising: a current-limiting circuit coupled between the input power supply and the electrical load, the current-limiting circuit comprising a parallel arrangement of (a) a negative temperature coefficient (NTC) component and (b) a relay having contacts that are in a normally-open position at start-up and close in response to a control signal to couple the input power supply to the electrical load and bypass the NTC component; a relay activator circuit responsive to the control signal for activating the relay to place the relay into a closed position; a voltage detector circuit coupled to the input power supply for detecting a disturbance occurring on the AC power supply; and a control circuit responsive to detection of disturbance by the voltage detector circuit for (a) providing the control signal to maintain the relay in the closed position during normal operation of the power supply and (b) open the relay in response to detection of the disturbance in the input power supply to couple the input power supply to the electrical load through the NTC component, said control circuit further operative to detect resumption of normal conditions on the input power supply close the relay between the input power supply and the electrical load, whereby inrush current that would result from removal of the disturbance is resisted by the NTC component when the relay is the open position.