The Siemens 3RT2037-3AG20 is a SIRIUS S2 power contactor from the current-production line. It carries a 65 A AC-3 rating at 480 V, which is the number that decides motor-load fit for a 480 V three-phase supply — that's the full-load current it can switch under motor starting duty, not the resistive AC-1 figure. The main contact configuration is 18...1 (three poles normally open, one auxiliary normally closed).
The S2 frame is 55 mm wide, 114 mm tall, 130 mm deep. That covers most panel layouts without derating.
Terminals and switching frequency
Coil connection uses spring-type terminals — no screwdriver needed for the coil circuit, which speeds panel wiring. Main contact wire range: 2x (0.5...2.5 mm²) solid or stranded. Switching frequency varies by duty class: 800 operations/hour at AC-1 (resistive), 700 at AC-3 (motor start/run), 400 at AC-2 (slip-ring motor), and 200 at AC-4 (plugging/inching). The AC-3e maximum matches the AC-3 figure at 700 ops/hour.