| 摘要 |
PURPOSE:To prevent overcooling of a stationary electric induction apparatus and reduce consumption power, by a method wherein ambient temperature and load current of the stationary electric induction apparatus are detected, and revolution speed of a motor for a cooling fan is controlled. CONSTITUTION:A tank 2 of a transformer 1 contains primary winding, secondary winding and insulation oil, and a cooler group 3 is attached to outside of the tank 2. The cooler group 3 is provided with a plurality of connecting tubes 4 leading to inside of the tank 2, and an oil feed pump 5 is connected to outlet side of the connecting tube 4. A plurality of fans 6 are installed corresponding to the connecting tubes 4 and can be driven by a motor 7, and input/output wires are connected to terminals within a junction terminal box. A motor control unit 13 is installed in addition to these devices. A current transformer 14 is contained therein, and primary side of the current transformer 14 is connected to power supply bus 11 and secondary side is to a converter 15. Output of the converter 15 is applied to an adder 16. The output is then supplied to an inverter 17 of variable frequency type, which in turn generates higher or lower frequency corresponding to the amount of the control current. The generated signal of variable frequency is inputted through the junction terminal box 9 into the motor 7 thereby revolution speed of the motor 7 is controlled. |
