Electron Beam Welding: Model of High Voltage Bias Transmission Line and Termination Circuits.

摘要

Three electron beam (EB) welding systems have experienced an excessive failure rate of the isolation transformer that supplies low voltage power to the high-deck control circuitry. The cost of this failure is $8K per transformer, plus installation, downtime expenses, etc. Nine transformers (twenty-two transformers since 1982) have been replaced in the last two years and represent a significant economic loss if this problem is not resolved. The commercial EB controller unit was purchased from Leybold-Heraeus Vacuum Systems, which has several other vendor-supplied parts. For example, the transmission line is a special build item and does not have published parameters. Off-line testing and model closure were required to attain these needed parameters. To obtain parameters for the transmission cable and to evaluate possible solutions, a model was constructed that predicts voltages and current for termination circuits and includes the four-conductor transmission cable used to bias and control the EB gun. To compound the problem, the entire high voltage deck is submerged in oil and limits the available space needed for termination circuits, etc. A low voltage test was performed that was used to attain good model closure and to provide critical cable parameters not previously available. The model was useful in assuring consistency for measured parameters and for estimating ''hard to measure'' parameters that were derived from test signals. Model closure was attained, and several possible termination circuits were evaluated. A termination for the transmission cable is proposed in this report. 6 figs.