We have developed a UPS (7.5～40kVA) which generates low noise (The switching surge voltage is OV.) with a low-cost converter. Considering the fundamentals, we reanalyzed the generation mechanism of IGBT (600V-300A) switching surge voltage, and found a mounting technology that does not generate a switching surge voltage (= 0V) without a snubber. We also found that the switching surge voltage remained at about 20 to 30V, and did not exceed SOA of IGBT even when the UPS load output was short-circuited, thus improving the reliability of the unit. By using the plug-in method for the converter, the converters of all models are standardized, which simplifies maintenance.
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