Patent ID: 7268558

Claim:
A tester for testing a circuit breaker under test, said circuit breaker under test including a line terminal, a load terminal having a voltage, and a designated rated current, said tester comprising: a plurality of load elements each having a nominal fixed impedance; an electronic switch associated with each of said load elements, said electronic switch, when turned on, electrically connecting a corresponding one of said load elements in series with the load terminal of said circuit breaker under test and in parallel with none or with a number of other of said load elements electrically connected in series with said load terminal; a controller structured to turn on a number of said electronic switches selected to draw through a corresponding number of said load elements a test current selected as a function of the designated rated current for said circuit breaker under test and sufficient to trip open said circuit breaker under test; and a pulse width modulation circuit cooperating with said controller and with said electronic switches associated with said load elements, said pulse width modulation circuit being structured to provide a constant magnitude of said test current to accommodate variations of said nominal fixed impedance or variations of the voltage of said load terminal.