Product Description:

The PST625-EL is a two-phase thyristor power unit manufactured by Bosch Rexroth Indramat for the PST Thyristor Power Units series. It sits between the plant controller and high-current AC lines, converting low-voltage logic signals into controlled phase-fired conduction for heaters, weld heads, and similar resistive loads in automated production cells. By integrating solid-state switching elements with dedicated logic circuitry and air cooling, the module supplies rapid current modulation while keeping cabinet space requirements modest. Phase-angle control also allows the load to be regulated smoothly instead of being switched only fully on or fully off. That behavior is useful where process heat or welding energy must track a command signal closely across repeated cycles.

Under forced-air cooling, the unit sustains a nominal output of 200 Arms, a level matched to a transformer capability of 141 kVA. For short bursts, it can source 365 A at a 30% duty factor, giving extra headroom for processes that need momentary energy surges. All control electronics run from a galvanically isolated 24 VDC logic supply and dissipate only 10 VA, so the thermal load inside the cabinet remains low. The switching bridge conducts current on alternate mains half-cycles, and the power terminals accept conductor cross-sections up to 95 mm² for the rated amperage. Continuous airflow through the ventilated heat sink keeps semiconductor temperatures within the permitted cooling-air range.

The power stage carries a front-panel degree of protection of IP20, so it must be installed inside an enclosure with a higher cabinet protection level. Control connectivity is handled by 16 opto-isolated discrete inputs and 12 transistor outputs, enabling the supervising PLC to select firing modes, read status bits, and interlock the unit with surrounding safety circuits. The isolated I/O also helps separate control signals from the power section, reducing the chance of interference on command lines. The assembly can operate at a repetitive duty cycle of up to 50 %, in ambient temperatures as high as 55 °C and at altitudes up to 2000 m without derating. This operating range suits applications that cycle power repeatedly during normal production.