The 100 A rating means it protects a feeder or a large load; the thermal-magnetic trip handles both overload (thermal) and short-circuit (magnetic) events without an external relay.
Above 40 °C you must derate per the thermal curve — the datasheet's derating table governs real-world panel ambient. Mechanical durability is 20,000 cycles; electrical durability is 20,000 cycles at rated current and 10,000 cycles at 2× rated current (440 V). That is typical for a distribution breaker — not meant for frequent switching like a contactor, but fine for occasional on/off and fault protection. The TM-D trip unit is fixed thermal-magnetic — no interchangeable trip blocks. The magnetic pickup is factory-set; you cannot adjust the short-circuit threshold in the field. For applications needing adjustable magnetic pickup, look at the Micrologic electronic trip versions in the same NSXm family.
Mounts on a backplate (not DIN rail) — the 9-module pitch (81 mm wide, 137 mm tall, 80 mm deep) fits standard panel cutouts. Connection pitch is 35 mm with spreaders, 27 mm without. Terminals accept 2.5 to 95 mm² rigid aluminium/copper or 2.5 to 70 mm² flexible copper via Everlink lugs — covers most feeder cable sizes up to 95 mm². The toggle handle and flag indicator (green for auxiliary contacts present) are visible through the IP40 cover.