Multiple single phase weld control systems from a polyphase power source

A weld control system, supplied by a polyphase voltage source, consists of multiple and separate single phase weld controllers. The single phase weld control systems have their separate power modules combined into a single power module assembly for more efficient cooling and electrical interfacing. The single power module consists of a semiconductor switch for each phase of the polyphase voltage source and a single chiller plate for mounting and cooling the switches. The chiller plate functions as a heat sink and is machined to create a series of channels that become coupled together to form a continuous tube having a single input and a single output for a coolant liquid. A SCR pair, housed in a single package in a back-to-back configuration having an isolated base construction. The base has good thermal conductivity between the heat generating semiconductors in the package and the base. This allows the SCR packages to be mounted onto the single chiller plate and still maintain the necessary voltage isolation between each phase voltage.