| 摘要 |
PURPOSE:To allow detection even of a slight imbalance of phase current by providing means for detecting a maximum value of each phase current within a preset time interval, and means for making a decision that the phase currents are imbalanced when the difference of maximum values exceeds a preset reference value. CONSTITUTION:Each phase current is detected through a current transformer 4 and fed to each bandpass filter 7 where only the basic wave component is extracted. Maximum value of the basic wave of each phase current during a predetermined time interval is then detected through a maximum current detecting means 8 and stored therein. The maximum values are compared each other through an imbalance decision means 9, which makes a decision that the phase currents are imbalanced if the difference between the maximum values exceeds a preset reference value. This detector can detect even a slight imbalance of phase current easily. |
