| 摘要 |
PURPOSE:To prevent a smoothing condenser from being damaged by connecting a dummy resistor when a voltage between the terminals of smoothing condensers connected in series unbalances over a specified range. CONSTITUTION:A converter device 1 converts 3-phase AC powers into a DC power, and supplies it to smoothing condensers 2a, 2b connected in series therewith and a load 4. In this case, resistors 6a and 6b, 6c and 6d are connected in series as a detector for detecting a voltage unbalance between terminals P-Q, Q-N, and the capacitors 2a, 2b are provided in parallel. Further, a comparator 7 connected with an input terminal between the connecting midpoints (a) and (b) of resistors 6a-6d, a transistor 8 driven by the output, and a dummy resistor 9 provided in parallel with a smoothing condenser 2a through the transistor 8 are provided. Thus, when the terminal voltage of the condenser 2a rises and the other drops so that the voltage difference between the terminals becomes over the specified range, the transistor 8 is conducted to connected the resistor 9 in parallel with the condenser 2a. |
