The Allen-Bradley 140U-K3L3-D40 UL Listed Molded Case Circuit Breaker is an electrical device that is intended to provide thermal overload and short-circuit protection to a wide variety of industrial control panel applications and devices. This 3-pole circuit breaker belongs to the K-Frame circuit breaker series,  and it is designed to supports back-feeding at 240/480 Volts AC (3-phase), and it is built with a space-saving design that also saves costs. The 140U-K3L3-D40 Circuit Breaker is designed for applications like control circuits, feeder circuits (distribution panels, small cabinets, and transformers), HACR, and high-intensity-discharge circuit applications. The 140U-K3L3-D40 Circuit Breaker is a 3-pole device that is designed for a circuit operating with 480 Volts AC voltage, and it has a maximum trip current rating of 400 Amps.

The 140U-K3L3-D40 Circuit Breaker also has an interrupting rating of 35 Kilo-Amps and a maximum insulation voltage rating of 750 Volts. The 140U-K3L3-D40 Circuit Breaker has an electronic trip unit, which uses a microprocessor-controlled trip action for enhanced protection, and it offers the users customized protection for specific application needs. This trip unit offers both long time delay and short time delay trip actions. This trip unit mimics the effect of a bimetal element and electromagnet in a thermal/magnetic circuit breaker and it automatically determines the amount of carrying current that is needed. For the long-time delay trip action, the trip unit delays the pick-up time by 1.05 to approximately 1.3 times the thermal rating, thus delaying tripping until the current reaches the set value. The 140U-K3L3-D40 Circuit Breaker has an open type of design and it comes with bolt-on standard screw terminals. It has an operating temperature range of -8 to 60 degrees Celsius and a maximum operating altitude of 2000 meters.