Product Description:

The PST625E.133-W thyristor unit is manufactured by Bosch Rexroth Indramat as part of the PST Thyristor Power Units series. It serves as a water-cooled power stage that controls large AC loads through phase-fired SCRs, allowing automated furnaces and resistance heaters to receive regulated energy. Heat is removed by a closed water circuit, and operation is permitted as long as the coolant inlet temperature does not exceed 30 °C. The module is intended for installations up to 2000 m above sea level and integrates metal-oxide varistor overvoltage suppression to protect its semiconductors from line transients.

The converter carries a nominal line current of 230 Arms, and its primary output can reach 400 A when limited to a duty cycle of 50%. A dedicated transformer rated at 155 kVA provides isolation and matches impedance between the mains and the thyristor bridge. Power leaves the unit through compression lugs sized for conductors with a cross-sectional area of 95 mm², which helps limit thermal rise at the terminals. Logic and sequencing are driven by the control supply, while the water jacket must keep outlet temperature within the permitted limit to protect semiconductor junctions. The unit is compatible with both 50 Hz and 60 Hz input frequency, so the firing circuit can maintain symmetrical conduction on either line standard.

Control interfacing is handled by a 24 VDC rail that powers PLC-addressable lines. The device accepts 16 discrete inputs and provides 12 discrete outputs for status and fault signaling. Its cabinet-mount chassis carries a protection rating of IP20, so it requires installation inside an enclosed panel with forced airflow that is separate from the water loop. The timer block uses the same control supply to coordinate gate pulses, and the MOV network clamps line surges during operation. Despite its current capacity, the assembly weighs 8 kg, which helps reduce mounting load in vertical rack installations.