| 摘要 |
Before a deterioration of a secondary current sensor is detected, a controller effects a feedback control process based on a secondary current from the secondary winding of a welding transformer which is energized by an inverter, for thereby controlling a welding current with a high degree of accuracy, e.g., an accuracy level of ~ 1 %. At the same time, it is monitored whether a detected value of a primary current from the primary winding of the welding transformer, which is detected by a primary current sensor, exceeds a predetermined allowable range with respect to a reference value of the primary current. If the detected value of the primary current exceeds the predetermined allowable range, then it is decided that the secondary current sensor is deteriorated. When the secondary current sensor is deteriorated, the controller switches from the feedback control process based on the secondary current to a feedback control process based on the primary current to control the welding current with a certain degree of accuracy, e.g., an accuracy level of ~ 3 %, without interrupting the welding process.
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