The invention discloses an automatic arcing device for a vacuum consumable electric-arc furnace. A consumable
electrode is arranged at the bottom of a furnace chamber; an
auxiliary electrode is arranged above the consumable
electrode; the upper end of the
auxiliary electrode is connected with an
electrode stem; the upper end of the electrode stem is connected with a transmission shaft; a differential mechanism / speed
reducer is arranged at the upper end of the transmission shaft; the differential mechanism / speed
reducer is connected with a feeding motor and a fast motor; a programmable controller comprises an output module, an input module, a CPU (
Central Processing Unit) and a communication port;
arc voltage measuring leads are respectively led out from the electrode stem and a housing of the furnace chamber; the other ends of the
arc voltage measuring leads are connected with a
signal transformer and then connected with the input module of the programmable controller; a
voltage meter is connected with the
signal transformer in parallel; a displacement sensor is also connected with the input module; and the output module and the input module are both connected with a
motor controller. The invention further relates to a method for controlling arcing by using the arcing device; and the electrode stem is driven by the motor to strike an arc. The automatic arcing device for the vacuum consumable electric-arc furnace, disclosed by the invention, has the advantages of high arcing success rate, high arc distance control precision and high finished product ratio.