JPS555187A - Ac arc welder - Google Patents

Abstract

PURPOSE: To make arc generation stable and enable the DC component contents of welding current to be adjusted by connecting the secondary windings of the reactors respectively series-connected to SCRs of opposite current supplying directions with the magnetic flux directions of their respective cores being the same and inserting impedance elements between the secondary windings.

CONSTITUTION: Accumulation and release of energy by the first reactor L₁ is accomplished from the t₁ time up to the t₄ time and approximately constant welding current flows in the same direction. At the t₄ time, the second SCRTH₂ conducts and the first SCRTH₁ becomes non-conducting, thus the welding current IR abruptly changes. At the t₄ and afterward, the current flows through the impedance element I at the illustrated voltage generated in the second reactor L₂ but the TH₁ is non-conducting and therefore the welding current flowing in the L₂ decreases. At the t₅ time and afterward, the voltage of polarity opposite from the illustrated one is generated in the L₂ and the current flows through the second diode D₂, causing the voltage of polarity opposite from the illustrated one not attenuated by the element I to be generated in the primary winding of the L₁. At the t₆ time, the TH₁ conducts, thereby inducing large voltage and current in the L₁. Hence, the DC contents may be made variable by the element I.

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