Product Description:

The PST6250.336-L thyristor power unit is produced by Bosch Rexroth Indramat for the PST Thyristor Power Units series. It forms the controlled secondary of resistance welding installations, gating current through nine thyristor output pairs to deliver programmable energy pulses. The module receives firing commands over an Interbus-S network and translates them into phase-angle-controlled mains cycles, letting automation controllers adjust weld heat in real time. By combining power switching and thermal management, it provides a dedicated interface between low-level sequencing logic and heavy industrial transformers.

Control electronics draw 24 V DC for compatibility with typical cabinet power rails. At 200 A, the bridge dissipates only 70 W, which reduces the cooling load on the air-cooled chassis. It can drive transformers up to 250 kVA, and the unit operates with a 50% duty cycle to protect the power semiconductors during repeated welding pulses. Forced air moves across the heat sinks, so liquid cooling is not required. The housing measures 463 mm high, 239 mm wide, and 280 mm deep, which helps it fit stacked panel layouts. An Interbus-S link and an INTERBUS timer synchronize current bursts with PLC commands, and nine outputs are available for the electrode set. Operation is permitted at ambient temperatures up to 55 °C without derating.

Up to 256 weld programs can be stored locally, allowing parameter sets to be recalled without reloading data over the network. Terminals accept conductors up to 95 mm², which matches the current rating while helping keep losses low. A steel enclosure with an IP20 rating shields live parts while remaining open enough to maintain the required airflow path. Despite its capacity, the unit weighs only 12.5 kg, which helps reduce mounting load in cabinet installations.