| 摘要 |
Improved power factor control systems for polyphase induction motors operate the same at improved efficiencies. In one embodiment, voltages applied across each of the three motor windings are uniformly and sequentially phase controlled, and in another are applied in phase controlled fashion across only two of the three windings. In other embodiments, where the motor is always lightly loaded full sine waves of voltage are initially applied across all of the windings during motor startup, whereafter phase control is exercised over only two of the windings and the third is disconnected, while for motors which are usually lightly loaded, but may occasionally be subjected to heavier loads, power is selectively connected to the third winding in accordance with motor load conditions. To prevent motor instability when significant phase angle control is exercised over the winding voltages, it is also contemplated that the winding voltages be sequentially, cyclically and unevenly phase controlled to operate the motor in an unbalanced condition. |
