Product Description:

The PST650-EW thyristor power unit is produced by Bosch Rexroth Indramat within the PST Thyristor Power Units series. It functions as a two-phase switching module that regulates welding currents by triggering silicon-controlled rectifiers in precise time windows. Installed between the mains transformer and the welding electrodes, the unit shapes each heat pulse so joint integrity can be achieved with repeatable energy input. Its compact frame is intended for cabinet mounting where automated cells need high current delivery and direct digital supervision. This arrangement supports repeatable weld sequencing in automated production lines where current timing must stay closely coordinated with clamping and motion commands.

Thermal management is handled by a water-cooled heat sink that requires a continuous flow of 10 L/min. The cooling circuit limits pressure loss to 0.9 bar, allowing connection to standard plant manifolds. The control board caps the conduction window at 50% of each half-cycle, yet the thyristor bridge can still supply up to 2500 A to the secondary without exceeding junction limits. Surge arresters based on MOV technology provide overvoltage protection, and the built-in discrete I/O allows a PLC to exchange enable, trigger, and status signals directly with the welding controller. Main power lugs accept large conductors so rated current can be carried with minimal temperature rise during repeated weld cycles.

The feeder side is specified for 800 A of line current, and the matched transformer can deliver 565 kVA when the unit operates at its highest thermal point. Component ingress protection is classified as IP20, restricting use to indoor cabinets that block accidental contact yet do not require sealed enclosures. A maintenance battery keeps the gate-drive reference at 3.6 V, preserving timing data during short outages. These operating characteristics make the unit suitable for resistance welding stations that cycle rapidly and require stable current control during repetitive production duty.