| 摘要 |
A three-phase thyristor (42, 43) controlled welding output supply requiring only a single firing pulse of short duration per phase per half cycle is shown. Once a firing pulse has been provided (122), a holding impedance (40) connected between the output electrodes (32, 34) is provided to the neutral terminal (18) of a wye wound secondary (17) to provide a path for holding current independently of the load presented by the arc. An improved firing control circuit includes in addition to the normal firing capacitor (82), a negative phase angle impedance (86, 87, 88) attached to one end of a conventional breakdown device (117) used to fire a master thyristor gate (119). Stepped up voltage (60) is provided to the control circuit for greater noise immunity. Also shown is a remote control (151) for controlling a reversible motor (150) to drive through a slip clutch (140), the main voltage controlling variable impedance (80).
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