Three Phase Pneumatic DC Aluminium welding machine , Spot Weld Machine for Copper and Aluminum DESCRIPTION 1. 1000Hz Medium Frequency DC welding machine is the most advanced welding power supply technology in welding industry. It is three-phase power supply, through rectified by a special inverter, is converted into 1000Hz AC voltage and then is transmitted to a medium frequency transformer. Thus, the current is rectified in order to supply DC welding current. 2. Advantage: