Molded Case Circuit Breakers are evaluated to the Tri-
National Standard across North America Molded-Case Circuit
Breakers, Molded-Case Switches, and Circuit-Breaker
Enclosures. In the US, this standard is UL 489 [6], in Canada
CSA C22.2 No. 5 [7] and in Mexico NMX-J-266-ANCE [8].
This standard requires that all designs of MCCBs be
subjected to many thousands of endurance test operations at
100% rated current. Fig. 2 shows a sample of the required
endurance testing included in the standard.