HWASHI WL-MF-250K Vertical Type Metal Sheet Medium Frequency Inverter Spot Welding Machine DETAILED DESCRIPTION 1. MF Inverter Spot Welder is an advanced welding equipment. The 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 then the current is rectified in order to supply DC welding current. 2. The advantage is that it helps to greatly reduce the energy of iron