The Siemens 3RT7037-1AL20 is a Size S2 contactor with three normally-open main contacts and an AC coil rated for 230 V at both 50 Hz and 60 Hz. The screw-type terminals on both the main and auxiliary/control circuits make it a straightforward replacement in existing panels — no retooling for cage-clamp or ring-tongue.
Dimensions are 112 mm high, 55 mm wide, 115 mm deep — the S2 footprint. Accepts 2 × (0.5 … 1.5 mm²) solid or stranded, or 2 × (0.75 … 2.5 mm²) with ferruled ends. The auxiliary contact block is field-addable — the product extension for auxiliary switches is supported.
Coil and control considerations
The AC coil draws 0.36 A at 50 Hz, 0.38 A at 60 Hz. Closing power is 0.76 W DC holding power — a low steady-state draw that keeps the coil cool in continuous duty. Auxiliary contacts are rated for PLC-level signals: the contact reliability spec says they're acceptable for PLC control at 17 V, 5 mA.
For type of coordination 2 (limited short-circuit damage), the required upstream fuse is a gL/gG NH 3NA: 100 A. For type of coordination 1 (no damage to the contactor, but may need contact replacement), the fuse is gL/gG NH 3NA: 160 A. These are the fuse ratings the manufacturer specifies — use them to size the branch circuit protection. Mechanical endurance is not explicitly listed, but the switching frequency limits are: 800 operations per hour maximum at AC-3 (motor starting), 250 operations per hour at AC-4 (plugging/inching). Shock resistance is 15g for 5 ms and 8g for 10 ms sine pulse — enough for most industrial machinery but not for high-g mobile applications.