A stack is a combination of long proven flat thyristors and diodes with a copper and aluminum cooling fan. They are either self-cooled or wind-cooled.

Different blocking voltages of the devices and various types of connection methods enable the combination of various stacks.

Water-cooled stacks (or stacks with insulated water channels) for welding machines prevent false firing caused by condensation.


  • Various types of connections available, including center tap, double arm, inverse-parallel connection, multiple conversion, three-phase half wave, six-phase half wave and three-phase bridge.
  • The devices can be maintained by opening and closing the center bolt.
  • Welding machine stacks comply with JIS standard (JISC9319) WTh-C WTh-H.

Main Applications

Thyristor Leonard/speed control of induction motors/DC arc welding machines/power supply for chemical use/control power supply of resistance welding machines/plating power supply/power supply for temperature control of high power electric furnaces