| 摘要 |
<p>AC control apparatus includes a plurality of selectable switches (11) connected to a tapped load (10) and arranged to alter the magnitude of the volt-amp product consumed by the load. The switches (11) are activated by control means which includes a zero current detector (12), a decision circuit (14) and switching logic (13). The switching logic is responsive to a decision in the decision circuit and to the detector (14) to change switch at zero switch current. The decision circuit (14) may be made responsive to an input or load parameter, and where the tapped load (10) comprises a tapped transformer having an output for connection to an external load, the parameter may be a function of the output voltage. The switches (11) as preferably semiconductor devices such as triacs. As an alternative, the tapped load may comprise a motor.</p> |
