The Siemens 3RT2936-1JK00 is a SIRIUS surge suppressor — a varistor with an integrated LED indicator — designed to clip onto S2 and S3 frame contactors in the 3RT2.3 and 3RT2.4 families. It suppresses voltage spikes across the coil, protecting the contactor's control circuit and extending contact life on inductive loads.
This suppressor handles both AC and DC control voltages: 48 to 127 V AC at 50/60 Hz, and 24 to 70 V DC. That range covers the most common control voltages in European and North American panels — 48 V, 110 V, 120 V AC, and 24 V, 48 V DC — so one part number stocks across mixed-voltage cabinets. The LED gives a quick visual check that the suppressor is live and the coil circuit is energized.
Clip-on fastening to the contactor, any mounting position. At 14.5 mm deep, 30 mm wide, and 30 mm tall, it adds negligible depth to the contactor assembly — no extra DIN rail space needed. Temperature range is -25 to +60 °C operating, -40 to +80 °C storage, so it's fine inside a standard IP20 control cabinet without derating concerns.