| 摘要 |
PURPOSE: To prevent an overvoltage at a chopper switching element, by controlling a chopper regenerative current in a chopper circuit on the basis of the chopper regenerative current and the maximum snubber current as a current reference is the chopper circuit. CONSTITUTION: A chopper regenerative current (ICHP-F) carried in a chopper reactor (LCH) is detected by a current detector (CT), and the current (ICHP-F) is subtracted from a current reference value (ICHP-R). The result is entered a current control unit (IC) and controlled to obtain an actual voltage reference. The current reference (ICHP-R) is set to the maximum snubber current to be estimated in the designing stage, so the chopper regenerative current becomes stationarily smaller than the current reference. In an unexpected overload state, when the snubber regenerative current is over a given level and the chopper voltage is over a maximum design voltage, a duty ratio of the chopper is lowered under current control. Then, the current is reduced to prevent damage by the overcurrent to a chopper switching element. |
