SIRIUS S6 power contactor — 3RT1056-6AT36
The Siemens 3RT1056-6AT36 is a SIRIUS S6-size power contactor with a 575-600 V AC coil, screw-type coil terminals, and an integrated auxiliary switch. It's built for motor switching in industrial control panels where the coil voltage matches a 575-600 VAC control bus — common in North American 600 V class installations. Size S6 frame means the main power terminals accept stranded cable from 25 to 120 mm², so it handles motor feeders up to roughly 200-250 A depending on duty. The coil pulls in at 24 V rated value 10 A on the auxiliary contacts, with the main poles rated for AC-3 switching at 750 operations per hour.
Duty cycle and switching frequency
The contactor's maximum switching rate varies sharply by duty class: 800 ops/h for AC-1 resistive loads, 750 ops/h for AC-3 motor starting, and only 130 ops/h for AC-4 plugging/reversing. That AC-4 limit is the one that catches panel builders — if your application involves inching or reversing under load, you need to respect that 130 ops/h ceiling or the contactor will overheat. Arcing time runs 10-15 ms, with total opening time 40-60 ms on both AC and DC control. The 0.8 power factor at 50/60 Hz matches typical motor loads.
Mounts via screw fixing with a 9 mm hole. That forward clearance is the tightest dimension — make sure the panel door or gland plate doesn't crowd the arc chute. Envelope is 172 mm high, 120 mm wide, 170 mm deep. The main cable entry uses the 25-120 mm² stranded range; auxiliary wiring accepts 2x 0.5-1.5 mm² solid or 2x 0.75-2.5 mm² stranded, max 2x 4 mm².