The Siemens 3RT6926-1BB00 is a varistor-type surge suppressor designed for S0-size SIRIUS contactors. It clips onto the contactor coil terminals to suppress voltage spikes when the coil de-energizes — a standard practice to protect the coil driver and extend contactor life in inductive switching circuits. The varistor design handles both AC and DC control supplies, with a coil voltage range of 24 to 70 V DC and 24 to 48 V AC at 50 or 60 Hz.
The 12 mm depth and 30 mm width are the critical fit dimensions — this suppressor sits directly on the contactor coil terminals, so the envelope is fixed by the S0 contactor frame. It does not add panel depth beyond the contactor itself. The clip-on fastening method means no additional wiring or terminal blocks; it snaps onto the coil connections of S0 contactors like the 3RT1023 series. The AC/DC voltage coverage is the key selection parameter: 24 to 70 V DC spans standard 24 V DC control systems with headroom for 48 V DC rails, while the 24 to 48 V AC range covers 24 V and 48 V AC control transformers at both 50 and 60 Hz. If your panel uses 110 V or 230 V AC coils, this suppressor will not work — you need the higher-voltage variant in the same SIRIUS accessory family.
Integration note
Clip-on mounting to the contactor coil terminals — no DIN rail space consumed, no additional wiring. The suppressor sits between the coil terminals and the control wiring, so verify the control circuit polarity for DC coils: the varistor is polarity-sensitive in DC operation.