What This Varistor Does on a 3RT7 S0 Contactor
The 3RT7926-1BB00 is a varistor-type surge suppressor designed to plug directly onto Siemens 3RT7 S0-size contactors. It clamps voltage transients from the coil circuit, protecting downstream PLC outputs and extending contactor life in inductive switching applications. It accepts both AC and DC control supply voltages: 24 to 70 V DC, and 24 to 48 V AC at both 50 Hz and 60 Hz. The varistor element absorbs the inductive kick when the contactor coil de-energizes, preventing the voltage spike from exceeding the coil's insulation rating.
Physical Fit and Panel Integration
This suppressor clips onto the contactor — no additional DIN rail space required. Its dimensions are 12 mm deep, 30 mm wide, and 19 mm high, so it adds negligible depth to the S0 contactor footprint. Mounting position is unrestricted, which helps in tight enclosures or when contactors are banked side-by-side. The operating temperature range is -10 to +55 °C, with storage from -25 to +70 °C. This covers most industrial control panel environments without derating.
Lifecycle and Sourcing Reality
RoHS compliance substance prohibition date is June 15, 2022, confirming it meets current EU substance restrictions.