| 摘要 |
PURPOSE:To make the title device inexpensive by a method wherein the neutral point side of a 3-phase AC machine is connected through a delta connection and current transfomerless, detecting current between lines, are provided. CONSTITUTION:In a 3-phase AC motor 3, connected to buses 1 through breakers 2 and switches 4, neutral point side is connected through a delta connection. Current transformers 6 for detecting overcurrent are attached to connecting wires between the lines of the 3-phase AC motor 3. The outputs of the current transformers 6 control a contact 8 driving a switch control coil 5 through an overcurrent tripper 7. The rated current of the current transformer 6 can be 1/3<1/2> of the rated current or the line current of the 3-phase AC motor 3 since the connection of the current transformer is the delta connection. Accordingly, the current transformer, whose rated current is smaller compared with a current transformer for detecting line current, can be used. |
