Tester for a plurality of circuit breakers having a range of rated currents and multiple trip functions

摘要

A tester (21) for in situ testing of a plurality of circuit breakers (71-7n) having a range of rated currents and multiple trip functions, includes a plurality of power resistors (311-3112) of known impedance, an electronic switch (591-5912) associated with each power resistor connecting the resistor in series with the load terminal (15) of the circuit breaker under test (7n), and a controller (33) that turns on a number of the switches (591-5912) selected to collectively draw through the associated power resistors (311-3112) a test current that is a function of the rated current and sufficient to trip the circuit breaker (7n) within a selected time window. Turn on of the electronic switches (591-5912) is also controlled to generate a current waveform appropriate for the trip function being tested. In a self test mode, the value of each of the power resistors (311-3112) is verified as being within limits.