The Allen-Bradley 140G-J3X3 circuit breaker is a molded case circuit breaker frame. It has a voltage rating of 600 Volts AC and a frame current rating of 250 Amps. The 140G-J3X3 circuit breaker has 3 poles and it can be employed to provide protection in circuits that use a 3-phase power source. The 140G-J3X3 circuit breaker supports a thermal-magnetic trip unit. Note that the thermal trip aspect provides overcurrent protection and short-circuit protection. This is enabled through mechanical means and heater elements. The breaker frame’s interrupt capacity is rated at 35 kiloAmps at 480 Volts AC. The 140G-J3X3 circuit breaker, as with other molded case circuit breakers, can be used in a single circuit breaker or feeder breaker to provide functionalities such as thermal and short-circuit protection. However, before installing the 140G-J3X3 circuit breaker, the application voltage, available short-circuit current, and amperage levels of the load or wiring that are going to be protected must be considered. Also, local guidelines and codes need to be taken into consideration.

The 140G-J3X3 circuit breaker, like other molded case circuit breakers that incorporate a magnetic trip, supports a magnetic trip current set at 1000% of the circuit breaker thermal rating. The breaker may be used for motor control-circuit transformers, although motor protection circuit breakers are preferred. The 140G-J3X3 circuit breaker, like other 140G molded case circuit breakers, is rated for 80% efficiency at a continuous load. The circuit breaker frame supports cables that can withstand a maximum temperature of 75 degrees Celsius. Note that cables rated for higher temperature may be used too, but it must not be loaded to carry more current than the 75 degrees Celsius ampacity of that size conductor for equipment marked or rated at 75 degrees Celsius.