Product Description:

The PST6250.177-W is a thyristor power unit from Bosch Rexroth Indramat that belongs to the PST Thyristor Power Units series. The device uses phase-controlled silicon-controlled rectifiers to modulate line power, allowing accurate energy delivery to welding transformers, industrial heaters, and other resistive loads in automated processes. By gating the two incoming phases in coordination with external control logic, it supplies repeatable current pulses that can be synchronized with PLC timers and process sensors.

The unit delivers a continuous nominal current of 200 A, enabling medium-power resistance welders or furnace zones to receive stable RMS current under rated conditions. Its transformer interface supports loads up to 250 kVA, so the internal thyristors and busbars accommodate significant apparent power without saturation. While operating, the cabinet dissipates only 70 W of heat, simplifying enclosure ventilation. Control electronics draw from a galvanically isolated 24 V DC supply, separating logic from the main line voltage for safety. A maximum duty cycle of 50% limits conduction time per cycle and protects the semiconductors from overtemperature during intermittent but demanding sequences. The two-phase topology synchronizes firing pulses across both lines, and an integrated temperature sensor monitors the heatsink while terminal blocks accept conductors up to 95 mm².

Thermal management relies on a water-cooled heat exchanger, allowing the device to maintain full rating when ambient air remains at or below 45 °C. The housing carries a protection rating of IP20, so it must be mounted inside a guarded cabinet while still providing finger-safe live parts. Surge stress on the mains is limited by a metal-oxide varistor MOV that clamps high-energy transients. Altitude capability extends to 2000 m without derating, and ambient site temperatures can reach 55 °C before current reduction is required.