Capacitor switching contactor — what the AC-6 rating means
The Siemens 3RT1617-1AB03 is a SIRIUS capacitor contactor, purpose-built for switching power factor correction capacitor banks under AC-6 duty. Its headline rating is 12.5 kVAr at 400 V — that is the maximum capacitive load it can make and break without welding contacts or causing transient overvoltages on the line. A standard power contactor of the same frame size would have a lower capacitive switching life; this part is designed for the high inrush current and repetitive daily switching that capacitor banks demand. Three NO main contacts carry the capacitor current; the built-in auxiliary block gives one NO and one NC contact for status feedback to the controller or for interlocking with the main breaker. The S00 frame takes a 45 mm wide footprint on the rail. Side-by-side mounting is permitted, so multiple capacitor steps can pack tightly in a PFC panel.
Lifecycle and replacement path
Termination and wiring note
Screw-type terminals on both the main current circuit and the auxiliary/control circuit. The S00 frame accepts the standard conductor sizes for a 20 A rated contactor — 2.5 mm² solid or stranded for the power path, 1.5 mm² for the control wiring. Strip length of 8–10 mm, torque to the manufacturer's specification on the nameplate.