Patent ID: 7421353

Claim:
A power controller capable of determining when a system reaches a maximum allowable energy, comprising means for: digitally monitoring a current, I, at fixed, average intervals, Δt; obtaining the square of the current, I 2 ; subtracting the square of the rated, current-carrying capacity of the system, I O 2 ; summing the values of (I 2 −I O 2 ) in a first register, the values in the first register always being greater than or equal to zero; comparing the sum in the first register to a first control value, K t , where K t is equal to the rectilinear hyperbola constant, K, of a constant energy plot of percent rated current as a function of time, ( FIG. 1 ), divided by the fixed average interval, K t =K/Δt, and a means for sending a control signal when the value in the first register equals or exceeds the first control value, K t .