| 摘要 |
PURPOSE:To detect and remove the restriction and malfunction of a motor for a cooler even when a drive frequency is lower than the rated frequency by breaking a motor power when the current for energizing the motor exceeds the predetermined threshold value as the function of a power frequency. CONSTITUTION:Necessary cooling medium cools a transformer by a cooler 2 which forcibly feeds by a motor the medium. The current for energizing a variable frequency power source 14 for driving the motor at a variable speed in response to the load state of the transformer is detected by a detector 17, and the current of the motor detected by the detector 17 is compared by a comparison discriminator 19 with the predetermined threshold value as the function of the power frequency of the motor. When the current of the motor exceeds the predetermined threshold value as the function of the power frequency for the period longer than the predetermined period, the motor power is broken. |
