| 摘要 |
PURPOSE:To eliminate factors which unnecessarily interfere the stable power supply by a method wherein, when it is judged that there is a possibility of abnormalities in current detecting parts, the judged results are outputted. CONSTITUTION:The currents of current transformers contained in current detecting parts 1 and 8 are sampled with a certain period to detect the currents of respective phases. It is judged whether there are abnormalities in the current transformer circuits, i.e., in the current detecting parts 1 and 8, or not by combined calculations of the facts such that, in a normal three-phase system, the sum of the current vectors of three phases is zero, that the current of a phase in which an open circuit exists is zero, etc. If the vector sum of the three-phase currents is not zero, the current detecting parts 1 and 8 judge that there is a possibility of abnormalities and, when an output part 5 judges that there is a possibility of abnormalities in the current detecting parts 1 and 8, the judged results are outputted. With this constitution, factors which unnecessarily interfere the stable power supply can be eliminated. |
