Patent ID: 8405945
Filing Date: 2013-03-26
Classification: H02H

Abstract:
1. An apparatus to protect a power distribution unit (“PDU”) from an electrical fault, the apparatus comprising: an alternating current (“AC”) electrical input that receives a flow of AC electrical current for a PDU; a fuse that interrupts the flow of electrical current in response to the electrical current rising above a current rating of the fuse, the fuse interrupting the flow of electrical current according to an inverse time-current function that defines an opening time of the fuse based on an amplitude of the electrical current, the opening time decreasing as the amplitude of the electrical current increases; a current sensor that measures the amplitude of the electrical current and outputs a current amplitude signal that represents the amplitude of the electrical current; a relay that interrupts the flow of electrical current in response to an OFF signal and allows the flow of electrical current to continue from the AC electrical input in response to an ON signal, the relay comprising an electromechanical relay, the relay having a switching time; a fault module that receives the current amplitude signal, the fault module sending the OFF signal to the relay in response to the amplitude of the electrical current exceeding the threshold value, the relay, the fuse, and the threshold value selected such that the switching time of the relay is less than the opening time of the fuse for an amplitude of the electrical current between the threshold value and a maximum fault current value, the opening time of the fuse based on the inverse time-current function of the fuse, the fault module preventing the fuse from opening by sending the OFF signal to the relay to interrupt the flow of electrical current, the switching time of the relay comprising a time for the current sensor to measure the amplitude of the electrical current, send a current amplitude signal to the fault module, for the fault module to determine that the amplitude exceeds the threshold value, send the OFF signal to the relay, and for the relay to interrupt the flow of the electrical current; a remote command module that sends the OFF signal to the relay to interrupt the flow of AC electrical current to the electrical load in response to an OFF remote communications signal and that sends the ON signal to the relay to provide the flow of AC electrical current to the electrical load in response to an ON remote communications signal, the ON and OFF remote communications signals unrelated to detecting an overcurrent condition; and an AC electrical output that provides the flow of AC electrical current to an electrical load, the fuse and the relay disposed in a series configuration between the AC electrical input and the AC electrical output within the PDU.