| 摘要 |
PURPOSE:To reduce an accessory loss and to prevent frequent adjustable speed of changes of load electric current of a transformer by variable speed controlling an induction motor of a cooler for the transformer with a variable voltage and variable frequency inverter. CONSTITUTION:A rate-of-change limiter 10 is provided between a function generator 8 and a variable voltage and variable frequency inverter 9. A load current of a transformer 1 detected by a current transducer 7 is changed into a frequency signal corresponding to a load factor of the transformer by the generator 8, and is added to an adder 10a in the limiter 10. An output of the adder 10a is level-detected by a comparator 10b. Then, a variable speed control by the inverter 9 changes slowly the number of revolutions. Therefore, reduction of an accessory loss will be effected and a frequent adjustable speed by a change of a load electric current of the transformer will be prevented. |
