The Schneider Electric MasterPact MTZ3 LV839037 is a 4-pole drawout air circuit breaker rated for 6000 A continuous at 104 °F (40 °C), with an H3 breaking capacity code that delivers 100 kA Icu at 508 V AC and 85 kA Icu at 635 V AC per ANSI C37.50. It ships without a Micrologic trip unit, so you spec and install the protection relay separately — common practice on large-frame drawout breakers where the trip unit is ordered to match the coordination study.
The 6000 A frame at 40 °C ambient is the line-rated current; above that temperature you derate per the manufacturer's curve. The H3 breaking capacity means this breaker can safely interrupt 100 kA symmetrical at 508 V AC and 85 kA at 635 V AC — that's a high-fault installation, typically a main or large feeder breaker in an industrial switchgear lineup. The short-time withstand (Icw) is 85 kA for 0.5 s, which tells you it holds in on a delayed trip long enough for downstream breakers to clear a fault. Mechanical endurance is 12,500 cycles and electrical endurance 2,800 cycles per ANSI C37.50 — the electrical figure governs for a main breaker that sees infrequent fault interruption, while the mechanical count matters if you're using it for regular load switching.
Drawout mounting means the breaker chassis stays bolted to the switchgear while the removable cradle slides in and out — essential for maintenance and arc-flash safety because you can rack it to the test or disconnected position without pulling cables. The base-plate rails and 230 mm connection pitch are sized for standard ANSI metal-clad switchgear compartments. Neutral sits on the left; overall footprint is 40.5 in wide by 18.8 in tall by 16.8 in deep.