| 摘要 |
PROBLEM TO BE SOLVED: To solve a conventional technical problem in which stopping time of a motor for feeding a welding wire is changed corresponding to the length of a cable, in the speed control device for the motor. SOLUTION: The number of revolution of the motor M is controlled in accordance with a motor control driving signal Sc; the value of a second relay driving signal Lb is arithmetically compared with a pre-determined disconnection detecting reference value Vr; if the second relay driving signal Lb is found larger than the reference value Vr, it is discriminated as abnormality of the cable, the comparison calculation signal Cp for detecting control cable disconnection is set at a low level; when the signal Cp is at a high level, the revolution of the motor M is maintained; when the signal Cp is at a low level, the revolution of the motor M is stopped, thereby setting the second relay driving signal Lb at a high level, closing the contact point of a second reduction relay RLY2, causing resistance loss in the current of an electromotive force generating at the time of reduction of the motor M, and thereby quickly reducing speed, in this speed control device for the motor for feeding a welding wire.
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