The Allen-Bradley 140U-K3D3-D40 UL Molded Case Circuit Breaker is an automatically operated electrical device that is designed to provide protection from short-circuit or thermal overload situations. This K-Frame circuit breaker is used in most industrial control panel applications, and its compact design makes it uniquely fit for applications with limited space. The 140U-K3D3-D40 Circuit Breaker supports back-feeding at 240 and 480 Volts AC input voltage, and it is suitable for HACR, high-intensity discharge, feeder circuit, and control circuit applications. The 140U-K3D3-D40 Circuit Breaker is a 3-pole circuit breaker with an operating voltage rating of 480 Volts AC and a maximum trip rating of 400 Amps. It has a maximum breaking capacity rating of 35 Kilo-Amps (KA) at 480 Volts AC, and it has an insulation rating of 750 Volts.

The 140U-K3D3-D40 Circuit Breaker has a rated mechanical lifespan of about 100,000 operations and an electrical lifespan of 10,000 operations. The 140U-K3D3-D40 Circuit Breaker has both a magnetic and a thermal trip unit that comprises a quick make/break contact, a lever mechanism, a bimetallic element, and an electromagnetic coil with an adjustable trip setting. The thermal overload protection is provided through the bimetallic element and the instantaneous over current protection is provided via the electromagnetic coil. The 140U-K3D3-D40 Circuit Breaker has an adjustable magnetic trip rating of 2000 Amps to 4000 Amps and a fixed thermal trip rating of 400 Amps. The 140U-K3D3-D40 Circuit Breaker has standard bolt-on screw terminals, and it has an open style enclosure design. It has a factory rated operating temperature range of -8 degrees Celsius to 60 degrees Celsius, and it has a rated maximum operating altitude of 2000 meters without de-rating.