The Siemens 6EP1961-3BA01 is a buffer module from the SITOP family, designed to bridge brief mains dips or hold up the 24 V DC bus during a controlled shutdown. It accepts a 24...28.8 V DC input and delivers an output equal to Vin minus approximately 1 V, rated for a continuous 40 A. Galvanic isolation between input and output keeps fault paths separate — important when the buffer feeds a safety PLC or motion controller that must not share a ground loop with the main rectifier.
The enclosure measures 70 mm wide, 125 mm high, 121 mm deep — fits a standard 70 mm slot in a gland-plate layout. Storage and transport tolerate -40 to +85 °C.
This is an active, factory-current part. The 40 A rating and 24 V DC input are the key BOM-fit parameters. Screw terminals accept 0.5...10 mm² at input and output — no special crimp tool needed. The green LED lights when supply voltage exceeds 20.5 V, giving a quick visual check during commissioning. MTBF at 40 °C is over 2.5 million hours, which aligns with a 10+ year service life in a controlled environment.