| 摘要 |
PROBLEM TO BE SOLVED: To make a low voltage power source unnecessary, eliminate the need of enlarging an electric heater and an electric supplying cable, etc., and reduce production cast, in an operational method for preventing the discharge in a furnace during operation in a vacuum furnace. SOLUTION: The temp. in the furnace is raised by supplying the electric current to the electric heater in vacuum state, and before satisfying the development of vacuum discharge accompanied with the rising of the temp. in the furnace, the electric source of the heater is temporarily shut off or loaded into the low voltage. Further, atmospheric gas is introduced in the furnace, and after raising the gas pressure in the furnace so as not to satisfy the condition for developing the vacuum discharge, the electric current is again supplied to the electric heater.
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