SIRIUS S2 Coupling Contactor — 24 VDC Coil, Screw Terminals
The Siemens 3RT2037-1KB40-0HT0 is a SIRIUS-branded coupling contactor in the S2 frame size, designed for interlocking or sequencing two contactors in applications such as reversing motor starters or mains changeover circuits. The coil is rated 24 VDC with a holding current of 10 A at 24 V, and the main contact configuration is 18 normally open plus 1 normally closed (18 NO + 1 NC). Mounting is via screw fixing or snap-on onto 35 mm DIN rail per DIN EN 60715, with a width of 55 mm, height of 114 mm, and depth of 130 mm. The coil connection uses screw-type terminals, accepting 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire. An auxiliary switch is integrated, and the contactor includes a mechanical interlock feature inherent to the coupling design.
Duty Ratings and Switching Frequency
Maximum switching frequency varies by duty category: 800 operations per hour at AC-1 (resistive), 700/h at AC-3 (squirrel-cage motor starting), 400/h at AC-2 (slip-ring motor), and 200/h at AC-4 (plugging/inching). The AC-3e rating matches the AC-3 figure at 700/h. These limits govern thermal rise in the contactor; exceeding them risks accelerated contact wear. Arcing time is 10 to 20 ms, and the DC operating time (coil pull-in/drop-out) is 30 to 55 ms. Inrush current peak at coil energization is 2.6 A. The contactor's mechanical life is typically 10 million operations.
Environmental and Clearance Specifications
These spacings must be maintained for proper heat dissipation and arc containment.