Capacitor switching – what the ratings mean
The 3RT2637-1AF05 is a SIRIUS capacitor contactor, size S2, designed specifically for switching power-factor-correction capacitor banks. Unlike a standard contactor, it includes pre-charge resistors to limit inrush current when the capacitors are switched on – without those, the transient could weld the main contacts or trip upstream protection. The switching capacity is voltage-dependent: at 230 V AC it handles 6 A, at 400 V AC it handles 3 A, and at 690 V AC the rating drops to 0 A, meaning this size is not intended for 690 V capacitor banks. Maximum switching frequency also falls with voltage – at 400 V it can cycle 100 times per hour, at 600 V only 32 times per hour. That matters for fast-switching PFC banks; if your system cycles more often, you need a larger contactor or a different topology.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The mounting position is flexible – ±180° rotation on a vertical surface, and ±22.5° tilt forward or backward. That helps when fitting into a crowded panel where the capacitor bank sits at an odd angle. Wire termination uses screw-type terminals on the magnet coil; power wiring accepts solid conductors up to 4 mm² (2x per terminal) and stranded up to 50 mm² (1x). The S2 frame size – 65 mm wide, 114 mm tall, 130 mm deep – is compact enough for multi-contactor PFC assemblies.