SIRIUS S3 power contactor — 3RT5045-1AH00
The Siemens 3RT5045-1AH00 is a SIRIUS-branded power contactor in size S3, designed for motor switching and general load management in industrial control panels. Its rated insulation voltage of 1000 V and surge voltage resistance of 6 kV define the isolation coordination for a 400/690 VAC system — pollution degree 3 means it's rated for the conductive environment typical of a factory floor, not a clean room. Mounting is flexible: screw-fixed or snap-on onto 35 mm and 75 mm standard mounting rail. Main-circuit and auxiliary/control terminals are both screw-type, accepting 2x (2.5…16 mm²) solid/stranded or 2x (10…1/0) AWG. At 40 °C the minimum permissible cross-section is 50 mm²; at 60 °C it derates to 35 mm² — a detail that matters when sizing the incoming feeder under elevated ambient conditions inside a sealed enclosure.
Ratings and so-what for the buyer
Motor power ratings are given at 60 °C: 38 kW at 230 V, 66 kW at 400 V, 114 kW at 690 V. These are the figures that govern real-world motor starting in a warm panel — the AC-3 duty cycle (making and breaking locked-rotor current) is what the contactor is sized for, not the resistive AC-1 numbers. At 690 V the contactor handles 21.1 kW, matching the 114 kW at 60 °C derating curve. Electrical switching rates vary by duty: AC-1 allows 900 cycles/hour, AC-3 allows 1000 cycles/hour, AC-4 drops to 300 cycles/hour — the AC-4 limit reflects the harsher arc stress of plugging or inching duty. For high-cycling applications like conveyor indexing, stay within the AC-3 maximum of 1000 1/h. Auxiliary contact ratings cover the control-voltage range: 6 A at 24 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, 3 A at 400 V. These are the make/break capacities for the PLC output or relay driving the coil — a 24 VDC PLC output must be rated to switch the 6 A inrush of the contactor's own coil. That fuse size is the maximum allowed to keep the contactor within its conditional short-circuit rating — don't oversize it or the contactor may weld on a fault.
The storage limit governs handling during transit and warehouse idle — it's not a running condition.