The Allen-Bradley 140U-JD3D3-D12 circuit breaker is a JD-frame molded case circuit breaker. It is part of the Bulletin 140U product range from Allen-Bradley which offers 15 to 1200 Amps rated circuit breakers with either an electronic or a thermal-magnetic trip unit. The ratings for breakers with electronic trip units range from a minimum of 70 Amps to a maximum of 1200 Amps and the ratings for circuit breakers with thermal-magnetic trip units range from a minimum of 15 Amps to a maximum of 800 Amps. The trip unit on the 140U-JD3D3-D12 circuit breaker is a fixed thermal–adjustable magnetic unit. The adjustable magnetic trip settings can be configured at 625 Amps, 700 Amps, 780 Amps, 860 Amps, 940 Amps, 1020 Amps, 1050 Amps, 1170 Amps, and 1250 Amps. The NEMA starter size for the 140U-JD3D3-D12 circuit breaker is 4 and the breaker can support 60 Horsepower output at 460 Volts AC and 60 to 75 Horsepower output at 575 Volts AC.

The 140U-JD3D3-D12 circuit breaker is a 3-pole device with a 30 to 39 kiloamps interrupting/breaking capacity. It can be used in electrical systems as a branch circuit protection breaker or as a main circuit protection breaker. The 140U-JD3D3-D12 circuit breaker can provide protection against ground faults, short circuits, and against current overloads. The 140U-JD3D3-D12 circuit breaker complies with the CE, CCC, and UL 489 standards. The presence of extremely high voltages and currents inside the breaker poses a serious threat to human safety. Therefore, only highly trained technicians with the relevant experience should be involved in designing electrical systems where the 140U-JD3D3-D12 circuit breaker is used as one of the system components.