| abstract |
A starting control apparatus for an AC load includes a bidirectional triode thyristor switching device connected in series between an AC power source and the load, a rectifying circuit connected in parallel to the bidirectional triode thyristor switching device, a first time constant circuit connected between output terminals of the rectifying circuit which discharges to turn on the bidirectional triode thyristor switching device when the charged potential reaches a predetermined potential, a second time constant circuit connected between the output terminals of the rectifying circuit and having a time constant larger than the time constant of the first time constant circuit and maintaining the charged potential in the ON state of the bidirectional triode thyristor switching device, and a speedy charging device which rapidly increases the charged potential to the sustaining potential of the second time constant circuit during the recharging period for the first time constant circuit while recovering the controlling ability of the bidirectional triode thyristor switching device and which gradually decreases the period for charging the first time constant circuit to the predetermined potential. When the load is an inductive load such as an induction motor, a third time constant circuit having a time constant larger than the time constant of the second time constant circuit is preferably connected between output terminals of the rectifying circuit. |