The Allen-Bradley 140U-LTD3-D50 Trip Unit comes with the thermal/magnetic protection type and 500 Amps of rated current. It is compatible with 600 Amps, Frame L rated MCCBs. The adjustable current range of the magnetic trip is 2500 to 5000 Amps. The trip unit has a thermally sensitive device and a current sensitive device that are combined together to provide all the required functionalities. The 140U-LTD3-D50 Trip Unit has the ability to automatically open a contact in a short circuit or thermal overload situation. Its manual trip mechanism serves as a safety device. Its bimetallic strip causes a bend when it heats up. If a new trip rating is required, the trip unit can be replaced easily.

The 140U-LTD3-D50 Trip Unit is the part of a circuit breaker that provides required protections such as short circuit protection, thermal overload protection, and ground fault protection. This trip unit is situated in a thermal-magnetic circuit breaker to sense and provide overload and short circuit protection for commercial electrical distribution circuits. Its magnetic field ensures that when it has reached a high fault current level, it takes a short time to interrupt the current. The thermal trip provides protection through a heated bimetallic strip. The thermal-magnetic unit is ambient-temperature sensitive. The 140U-LTD3-D50 Trip Unit provides standard protection as well as protection for motor starters, transformers, and generators. The installation must be done before the circuit breaker is mounted and connected. Compare the nameplate data with the existing ratings to make sure that the trip unit is suitable for its intended applications. If the ambient temperature of the breaker is higher than 40 degrees Celsius, it will carry less current than its continuous current rating while creating unacceptable temperature conditions in the terminals.