| 摘要 |
PROBLEM TO BE SOLVED: To continue operation by decreasing the output current of a power transformer in correspondence with the number of faulty semiconductor elements out of parallelly connected semiconductor elements and decreasing the output current of a rectifier in correspondence with the number of faulty semiconductor elements by lowering an overcurrent protection level. SOLUTION: A current reference value IRef, which is set with a current-reference setting device 7 in correspondence with the number of faulty elements of semiconductor elements detected with an element-fault judging circuit 6, is multiplied by [(number of elements-number of faulty elements)/number of elements]= (number of sound elements/number of elements), and Iset is obtained. A current-reference changing circuit 13, which reduces the current reference value to the current value that can be made to flow through the sound semiconductor elements, is provided. Furthermore, an overcurrent protecting circuit 11 comprising a overcurrent-level changing circuit 11-3, which reduces the overcurrent protecting level in correspondence with the number of faulty elements from the element-fault judging circuit 6, and a comparison operator 11-2, which compares and operates the changed overcurrent protecting level and an output current IF.B. of a rectifier 4 detected with a current detecting circuit 8 and outputs the overcurrent signal, is provided. |
