Product Description:

The PST6250.333-L is a thyristor power unit manufactured by Bosch Rexroth Indramat within the PST Thyristor Power Units series. Designed for industrial automation, it modulates current from a welding or heating transformer so that process energy can be adjusted in real time. The recessed mounting style lets the housing sit flush in a switchgear panel, and integrated temperature monitoring protects the semiconductors during continuous service. When paired with an INTERBUS timer module, it accepts firing commands over the plant network for coordinated multi-zone control. This arrangement helps the unit support processes where heat input must be adjusted during each operating cycle.

The unit is fed by a control supply of 24 V DC that powers the gating electronics and diagnostic circuits. Its nominal output current is rated at 200 A, so a matching transformer must be selected to keep operation within the device’s thermal limits. Upstream transformer capacity can reach 250 kVA, giving headroom for large secondary currents in short-time welding or heating cycles. The semiconductors are kept within temperature limits by an air-cooled heat sink that draws ventilation through the cabinet. Front shields and finger-safe terminals meet the IP20 protection rating, which prevents accidental contact with live parts but still requires installation inside a switchgear cabinet.

For environmental limits, the thyristor module can be installed at altitudes up to 2000 m without derating, and it remains fully functional in ambient temperatures up to 55 °C. Cooling air entering the heat sink should not exceed 45 °C to keep junction temperatures within an acceptable range. During production cycles, the firing pattern may be held for a maximum duty cycle of 50%, while internal losses are capped at 70 W, allowing standard panel ventilation to remove excess heat. Field wiring can be accomplished with conductors up to 95 mm², which helps maintain low-impedance connections to high-current transformers.