The Siemens 3RK1903-1BD00 is a PM-D F3 fail-safe extension module designed for motor starter power distribution in safety circuits. It creates an additional potential group with a configurable delay of 0.5 to 30 seconds, and plugs onto the TM-PF30 base unit. The module is rated for a control supply voltage of 20.4 to 28.8 VDC and communicates over the local bus.
The module is 30 mm wide, 117.5 mm deep, and 196.5 mm high — it occupies one standard 30 mm slot on the DIN-rail-mounted TM-PF30 carrier. The safe state is load circuit open, meaning any fault or power loss drops the outputs to a de-energized condition.
Rated for safety applications up to SIL 2 per IEC 61508 and Category 3 per EN ISO 13849-1. The safe failure fraction (SFF) is 99 %, and the average diagnostic coverage (DCavg) is also 99 %. The probability of dangerous failure per hour (PFHD) under high demand is 1.3E-9 1/h, which places it well within SIL 2 limits. Hardware fault tolerance (HFT) is 1, and the device is classified as Type B per IEC 61508-2. Electrical endurance is rated at 200,000 operating cycles typical; mechanical service life is 10,000,000 cycles typical.