The Siemens 3RT2037-1AH00 is a SIRIUS power contactor, Size S2, rated to switch motor loads at 65 A in AC-3 duty at 480 V — that's the figure that decides whether it fits a 30 to 50 hp motor circuit on a 480 V line. It pulls in with a 48 V 50 Hz coil, so the control transformer needs to match that voltage. Screw-type terminals on the magnet coil and main contacts accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire. An integral auxiliary switch is built in, rated 10 A at 24 V and derating down to 0.3 A at 220 V, so it can drive a PLC input or a pilot light without a separate relay block. The contactor also carries a 10 hp rating at 230 V for single-phase or lower-voltage three-phase loads.
Dimensions are 55 mm wide, 114 mm tall, and 130 mm deep, so it takes up a standard S2 footprint on the rail.
Duty cycle and operating conditions
Rated for 10 million mechanical operations typical, so it'll outlast most panel refreshes. Switching frequency maxes out at 800 cycles per hour for AC-1 resistive loads, 700 for AC-3 motor loads, and 200 for AC-4 plugging/reversing duty. Arcing time runs 10 to 20 ms; operating time (closing) is 10 to 18 ms.