| 摘要 |
PROBLEM TO BE SOLVED: To prevent damage of the load of a branch circuit caused by a failure of a neutral phase, when a large number of two-pole system branch breakers for 100 V circuits are arranged on both sides of a single-phase three-line system bus-bar. SOLUTION: Along with causing two right and left branch breakers 9 confronting each other to mutually share branch connecting bars 12 which connect a neutral phase bus-bar 3 and branch breakers 9, the two right and left branch breakers 9 confronting each other are also caused to mutually share a branch connecting bar 12 which connects a voltage-phase bus-bar 2 or 4 to the branch breakers 9. Consequently, a voltage to be supplied to the load of each branch circuit becomes only 0V, and the load is not damaged, even if screws 13 for screwing up the branch connecting bus-bars 12 of the neutral phase loosen and the neutral phase fails. |
