| 摘要 |
<p>PURPOSE:To eliminate an overvoltage suppressing resistor by shortcircuiting a starting main resistor during the regenerative braking and flowing a main motor armature current through the main resistor when the main motor generating voltage exceeds the specified value. CONSTITUTION:Contactors FS, L, R9 are closed and contactors R10 and R2- R8 are opened during the regenerative braking, and a starting main resistor is shortcircuited, and a current IN flows. When a regenerative load is eliminated in this state so that the induced voltage of a main motor rises, an overvoltage detector OVD operates to fire an overvoltage suppressing thyristor OVTh. In this manner, a current IE flows through the main resistor. Consequently, the overvoltage suppressing resistor can be eliminated.</p> |
