| 摘要 |
PROBLEM TO BE SOLVED: To reduce the stored energy loss of an internal snubber circuit by making the capacity of an internal snubber capacitor smaller than that of an external snubber capacitor. SOLUTION: When S2 is turned off with S1, S3, and S4 of four self-arc- extinguishing elements off and S2 on, a snubber capacitor C2 is over charged in a route A. The over-charged voltage is discharged by the recover current of a clamp diode D5 and is discharged, passed through a snubber capacitor C1 further, so that the total voltage of C1 and C2 decrease until it reaches that of C5, C7, C8. If Q is taken as a charge amount discharged through C1 from the capacitor C2, the voltage drop components ΔV1, ΔV2 of C1, C2 are expressed by ΔV1=Q/CF1, ΔV2=Q/CF2. Therefore, to make ΔV2 larger than ΔV1, it is sufficient that the capacity CF2 of C2 be made smaller than the capacity CF1 of C1. It is thus possible to reduce the stored energy of an internal snubber circuit consumed. |
