Filament Power Supply for Electron Beam Welding Machine

This paper describes the design of a 255-W (17 V_rms, 15 A_rms) filament power supply for a 15-kW electron beam welding (EBW) machine. Simulations and results are also included. The filament of the EBW machine consists of a wire, which is heated by the current flowing through it. Although the filament power supply voltage is low (around 17 V) , it is not grounded. In fact, it is displaced -60 kV dc with respect to ground. Hence, the filament power supply has to be properly isolated. On the other hand, a well-regulated filament power supply is essential for maintaining the stability of the cathode temperature and, consequentially, the lifetime of the filament. In this way, a control method based on the primary voltage is presented, avoiding any feedback loop from the secondary side. The design process and the simulation and experimental results are included in order to verify the control strategy proposed.