Protection circuit for AC user current connection units - has measurement input connected at line to be monitored and comparator

摘要

The protection circuit also includes an output circuit (11), controlled from a comparator (7), whereby the overstepping or understepping of a determined limiting value at the measurement input (6), activates a determined protection measure across the comparator (7) and the output circuit (11), so that pref. a sequence of current pulses or an AC current modulated with a higher frequency, is led across the current connection unit. A measuring signal reflecting the rise in current speed(dI/dt) produced at the line (5) to be monitored, pref. the rise in current speed in the respective pulse or the respective cycle, is led to the measurement input (8) of the comparator (7). The determination of the rise in current speed takes place by determining the current end value at the end of a specific time span or a max. current reached during a pulse or cycle or by determing a corresp. converted voltage end value. USE/ADVANTAGE - Protection circuit for current connection units esp. for AC current users esp. AC motors fed from inverters. Known protection circuit developed to give fault current protection, also at very low speeds at very low terminal voltage.