Motor switching and coil selection
The Siemens 3RT2038-3AL20-Z W96 is a size S2 power contactor rated for AC-3e/AC-3 duty at 80 A, switching 37 kW at 400 V. That AC-3 rating governs motor starting — it handles the inrush and breaking of squirrel-cage induction motors up to that load. Auxiliary contacts come as 1 NO + 1 NC, enough for a basic seal-in and status feedback loop. The main circuit uses screw terminals; the control and auxiliary circuit uses spring-loaded terminals — a mixed termination scheme that speeds panel wiring on the control side while keeping power connections serviceable.
Size S2 snaps onto DIN rail. The 114 x 55 x 130 mm envelope leaves room for adjacent overload relays and busbars in a standard 600 mm enclosure. Spring-loaded terminals on the control side accept 0.2–2.5 mm²; strip to 8 mm for reliable cage closure.