To provide a power source device for an arc furnace which can control an arc current almost at a same level irrespective of an impedance inside the arc furnace.

The power source for an arc furnace to supply a direct current to the arc furnace by a power conversion unit includes a current adjusting means to work so that a deflection between a current set up value current and a current detected value of an arc current can become zero and a controlling means to control the arc current by driving a semiconductor element of the power conversion unit with an output of the current adjusting means as a control signal. The power source also includes a controlling signal correcting means 114 to correct a controlling signal by adding the arc voltage detected value to an output of the current adjusting unit 107A, when the arc detected value is suddenly changed and exceeds a predetermined value according to an impedance change inside the arc furnace by using a self-excitation conversion unit as a power conversion unit and using a current adjusting unit 107A of a short response time as the current adjusting means.

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