Thyristor power unit
The power section in AC welding systems consists of a pair of thyristors connected in anti-parallel. In simple terms, these are controllable diodes. They consist of an anode and a cathode, as known from diodes, and furthermore of a gate. This gate is a control terminal that can be used to set the phase angle.
A thyristor must be dimensioned in terms of switching current and reverse voltage. These values depend on the welding task and primary voltage of the planned welding system. These thyristor properties are documented in the corresponding leaflets.
Harms & Wende offers thyristor sets from 45 A to 5000 amperes switching current and in various blocking voltages. A blocking voltage of 440 V is standard. Higher voltages are required on special mains or for flash-butt welding.
See also: Dimensioning of power components