Product Description:

The PST6250.115-W is a thyristor power unit engineered by Bosch Rexroth Indramat within the PST Thyristor Power Units series. It functions as the controlled switching element between plant mains and a welding transformer or other high-current load, delivering precise bursts of energy in automated production lines. By altering the conduction angle of its internal thyristors, the device shapes mains power into accurately timed pulses that match process duty-cycle requirements. This supports resistance welding applications that need repeatable energy delivery from cycle to cycle.

At the electrical input, the unit permits a mains nominal current of 230 A and produces cabinet losses of 110 W, while overall cooling losses can reach 420 W. A water-cooled heat sink removes this heat, and operation is allowed only when a minimum flow of 4 l/min is maintained and the water supply temperature remains below 30 °C. The cooling circuit may be pressurized up to 10 bar, and the pressure drop is 0.1 bar at the stated flow. Because the housing has a protection rating of IP20, the power unit must be installed inside a control cabinet. Integrated temperature monitoring and a 24 V timer supervise cycles that may not exceed a maximum duty of 50 %, and the line terminals require conductors with a 95 mm² cross-section. Two transformer power limits apply: 257 kVA at 20% duty and 162 kVA at 50% duty, providing suitable energy for spot-welding applications.

Program control is internal, and up to 256 parameter sets can be stored and recalled without an external controller. The stored programs support different welding routines, which helps the unit handle changing production sequences without repeated manual adjustment. The assembly weighs 15.5 kg, allowing installation on a panel shelf or slide-out drawer. For reliable service, the installation altitude must stay below 2000 m, which helps maintain dielectric strength and stable cooling performance.