| 摘要 |
PURPOSE:To balance voltages of filter capacitors by discharging excessive charges upon occurrence of voltage unbalance between filter capacitors split in series. CONSTITUTION:In case of a three-level inverter wherein filter capacitors 6A, 6B are split in series, one filter capacitor 6A(6B) has a voltage of 0V while the other filter capacitor 6B(6A) has a voltage of 1500V. In this case, a switching element 5B(5A) in an overvoltage control circuit connected in parallel with the filter capacitor 6B(6A) charged with higher voltage is conducted to discharge the filter capacitor 5B(5A). When conduction of the switching element 5B(5A) is interrupted at a point where voltages of the filter capacitors 6A, 6B are balanced, unbalance of voltage can be eliminated. According to the constitution, voltages of split filter capacitors 6A, 6B can be balanced. |
