The 3RT2037-1NF30: The coil accepts 83-155 V AC or DC, with a 1.5 A inrush peak and just 2 VA holding power at 50/60 Hz — the control transformer can be sized for the inrush, not the steady-state draw.
Switching frequency and service life — the duty-cycle reality
Maximum switching rates vary by duty class: 800 cycles/hour in AC-1 (resistive), 700 in AC-3 (squirrel-cage motor start/run), 400 in AC-2 (slip-ring motor), and 200 in AC-4 (plugging/inching). The arcing time is 10-20 ms, and the operate time is 30-55 ms for both AC and DC coils — the total break time is under 75 ms, which matters for coordination with upstream short-circuit protection.
Auxiliary contact capacity and operating range
The main contacts are configured as 18-1 (normally open / normally closed) — verify your load circuit topology against this arrangement before wiring.