General Electric THKM3F Circuit Breaker

The THKM3F is typically supplied as a frame-only breaker without lugs. For a 1200A application, you can install GE lug kits such as the TCAL121, which accepts four 250 to 350 kcmil copper or 250 to 500 kcmil aluminum conductors per phase. The TCAL81 lug kit is also compatible for applications up to 1000A.

The THKM3F is part of the General Electric K1200 Line and utilizes a TKM frame. It is designed for heavy industrial and commercial panelboards that accommodate K-frame molded case circuit breakers.

The thermal magnetic trip unit provides dual protection. The thermal component offers long time delay protection against gradual overloads, while the magnetic component provides instantaneous trip protection against severe short circuits.

ABB acquired GE Industrial Solutions in 2018. Because of this transition, newly manufactured THKM3F breakers may feature ABB branding on the label or packaging. These units are identical in form, fit, and function to the legacy GE models.

The THKM3F features a bolt-on connection. It must be securely bolted directly to the panelboard busbars using the appropriate hardware, ensuring a stable connection capable of handling its 1200-amp load.

Installation should only be performed by a licensed electrician. Ensure the panel is completely de-energized before bolting on the breaker, and verify that the 35kA interrupting rating meets or exceeds the available fault current at the installation point to prevent equipment failure during a short circuit.