Product Description:

The PST6250.201-W is a thyristor power unit manufactured by Bosch Rexroth Indramat for the PST Thyristor Power Units series. Installed downstream of welding transformers or resistive heaters, it modulates line power with phase-controlled thyristors so an automation controller can match output to process demand. The module acts as the high-current bridge between low-level digital commands and the load, integrating with cabinets that already use Rexroth drive and I/O technology. Because logic, cooling, and safety interfaces are embedded, power scaling can be added without additional discrete relays or timers.

It carries a protection rating of IP20, so the terminal field is touch-safe but must be housed inside a sealed panel. Heat from the thyristor stack leaves through a water-cooled baseplate, which avoids bulky fans. External control I/O, the auxiliary fan, and the stop circuit all share a single 24 VDC supply, which simplifies power distribution. Power bars accept conductors up to 95 mm², and the isolation transformer uses the same conductor size. The PROFIBUS-DP interface exposes 16 input bits and an equal number of output bits under module ID 9. An analog pressure output and three KSR selection outputs provide additional process connections.

Safety functions are hardware-based. A floating contact in the stop circuit can interrupt up to 3 A of control current, isolating the SCR stack without opening the power bars. To preserve coolant flow and service access, the installation layout reserves 100 mm of free space above and below the unit. Because the internal electronics only meet that lower protection class, the power unit must be installed inside an enclosure rated at IP54. Cycle timing is governed through PROFIBUS, and an initial dressing function is included to burnish electrodes before normal production starts.