The 140U-MTD3-D60 trip unit is a thermal-magnetic trip unit for M-frame circuit breakers from the Allen-Bradley Bulletin 140U product line. The specification for the rated current of the 140U-MTD3-D60 trip unit is 600 Amps. The magnetic trip setting is configurable, and the magnetic trip settings range from a minimum of 3000 Amps to a maximum of 6000 Amps. The magnetic trip setting can be changed by setting the position of the buttons provided on the individual poles for this purpose. A screwdriver can be used for making the desired magnetic trip adjustments. The thermal trip setting is fixed at 600 Amps. The working temperature range for the 140U-MTD3-D60 trip unit is from -8.9 to 60 degrees Celsius. To prevent trip unit damage, Allen-Bradley recommends the tripping of the breaker before the trip unit is installed.

The Allen-Bradley 140U series comprises molded case circuit breakers and molded case switches (isolators). Both electronic and thermal-magnetic trip units can be ordered. The rated current supported by the electronic trip units ranges from 70 to 1200 Amps and the current range supported by thermal-magnetic trip units ranges from 15 to 800 Amps. The 140U series circuit breakers can be used for the protection of main and branch circuits against overloads, ground faults, and short circuits. The 140U series circuit breakers are compact devices that enable space conservation inside the panelboards and switchboards where they are installed. Other features of the 140U breakers and accessories like the 140U-MTD3-D60 trip unit include a wide interrupting capacity range and rotary variable-depth operating mechanisms. The 140U series is approved by the CE, CCC, UL, IEC, and KEMA - KEUR standards.