| 摘要 |
PURPOSE:To provide a safety measure to internal circuits by using two external power sources of different voltage levels, deciding whether the voltage of the inputted external power source is higher or lower by the initially set voltage level and changing over and setting the voltage to the state that driving can be executed by the external power source of the discriminated voltage. CONSTITUTION:Both of 1st and 2nd voltage regulating means 1, 31 of an arc working device are set according to the external power source of the higher voltage level Vb in the initial period prior to the supply of the external power source. An automatic change-over circuit 4 for the input voltage outputs a change-over signal after the prescribed time lag when said circuit judges the input of the lower external power source voltage Va. The 1st and 2nd voltage regulating means 1, 31 are set by this change-over signal to the state that the means can be driven by the lower external power source voltage Va. The driving of the deice is thereby safely and surely executed as against the fluctuation in the input voltage.
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