Product Description:

The PSI65C0.781-W1 is a medium-frequency inverter manufactured by Bosch Rexroth Indramat within the PSI Frequency Inverters series. Designed for resistance welding automation, it converts three-phase 400–480 VAC input into precisely timed high-frequency output that regulates heat generation at the electrode tips. By providing closed-loop current control, the unit links welding transformers to robot controllers and supports consistent nugget size with reduced spatter on high-volume production lines. Closed-loop regulation also helps the inverter respond to process variation during repeated weld cycles.

A water circuit keeps the electronics within temperature limits, and the housing is water-cooled through twin M16×1.5 ports with a pressure drop of 0.65 bar across the exchanger. Power terminals accept conductors up to 120 mm² per cable and use M10 connection screws that match the busbar geometry. The frame has an IP20 protection rating, so the inverter must be installed inside a cabinet. Correct mechanical fixing uses M6 mounting bolts tightened to 6 Nm, and 100 mm of free space is required around the chassis for air circulation to nearby components. The inverter can be mounted at elevations up to 2000 m without derating, while a 24 VDC logic rail supplies the low-power electronics and program memory stores 256 parameter sets for different weld schedules.

On the output side, the drive can deliver a 2400 A primary pulse that becomes 120 kA at the welding electrodes through the connected transformer. Continuous cooling must supply 10 l/min of water to keep semiconductor junction temperatures within range. A digital regulator updates every 1 ms, allowing welding current to track commanded profiles during squeeze, weld, and hold phases. The internal 2 A auxiliary supply powers sensors and contactors, and an Ethernet timer synchronizes weld initiation with the cell PLC. This arrangement supports quick changes between weld schedules for different materials and sheet thicknesses.