Static numerical circuit interrupter with an inverse time-tripping function.

摘要

Microprocessor-based digital solid-state trip unit (48) generating an inverse time long delay and/or short delay trip by digital simulation of the heating and cooling of a bimetallic strip. A digital value (TETALR), stored in a RAM memory simulates the temperature of the bimetallic strip, this value being incremented when the current exceeds a preset pick-up (ILR) or on the contrary decremented if the current is lower than this pick-up (ILR). Tripping is caused when the stored value (TETALR) exceeds a maximum pick-up (TETAMAX). The microprocessor (48) computes the incrementation factor (DTETAE) in terms of the square of the current.