Short Circuit Protection of Energy-Efficient Motors

More than 30 years ago the molded case circuit breaker industry developed a line of motor short circuit protective devices or “instantaneous trip breakers” that improved on the thermal magnetic or “inverse time breaker” in two distinct ways. First, the instantaneous only breaker (sometimes called a motor circuit protector) had no long time or “thermal trip.” It was deemed redundant since the overload relay or “heater” was providing this long-time thermal function.