| 摘要 |
PURPOSE:To prevent the arc cut at the arc starting time in small current zone by adding the sum of stationary current setting bias and the initial current setting bias at arc starting time as the reference input to the error amplifier which is in a current control circuit and by releasing the initial current setting bias after the prescribed time. CONSTITUTION:The initial current setting bias v2 becomes the reference input (-) of an arithmetic amplifier IC2, being added to the stationary current setting bias v1 because of analog switch IC5 being closed at the arc starting time and the power source for weld awaits with the state of higher output than that at steady time. It becomes the initial current value (v1+v2) when the welding current is passed but the analog switch IC5 is opened by the output A of a reversing amplifier IC6 becoming to LOW after the lapse of the prescribed time. Accordingly the initial current setting bias v2 is released and the input (-) of the operational amplifier IC2 is converted in a slope shape to the stationary current which is determined only by the v1 thereafter with the discharging of a capacitor C1, so no arc cut is caused by the vibration in the current waveform.
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