Patent ID: 8488285

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) current limiter and (b) a relay having contacts that are in a normally-open position at start-up and a closed position in response to a relay control signal that couples the input power supply to the electrical load and bypasses the current limiter; an AC voltage peak detector circuit for providing a control signal when the value of the input AC power exceeds a predetermined voltage level; and a retriggerable pulse circuit responsive to the control signal from the AC voltage peak detector circuit for providing the relay control signal having a predetermined nominal duration, such that the relay is maintained in the closed position so long as the input AC power exceeds the predetermined voltage level on each cycle of a predetermined number of AC cycles, whereby the current limiter provides an impedance for reduction of inrush current to the electrical load upon startup and upon opening of the relay in response to expiration of the relay control signal and is bypassed upon closing of the relay.