Patent ID: 7579714
Filing Date: 2009-08-25
Classification: H02J

Abstract:
1. An uninterruptible power supply apparatus, comprising: a first power converter for converting an AC electric power inputted from a commercial power source into a DC electric power; a second power converter for converting said DC electric power into a desired AC electric power, to be supplied to a load; a storage means connected between said first power converter and said second power converter; a means including a potential transformer, for detecting an abnormality on said AC electric power inputted from said commercial power source, wherein said means for detecting determines said abnormality to be a complete power interruption or a temporary voltage drop based on a comparison of an input frequency of said AC electric power to a threshold frequency; a controller portion including a PWM circuit for controlling said first power converter, and for controlling said second power converter, wherein said abnormality detecting means inputs a frequency of the AC electric power inputted from said commercial power source through said potential transformer, whereby detecting an interruption if the frequency of the AC electric power deviates from a predetermined value, said controller portion continues to control said PWM circuit to let said first power converter supply current to said load based on an available input current from the commercial power source if said abnormality is determined to be the temporary voltage drop, and said controller portion stops said PWM circuit from controlling said second power converter thereby supplying current from said storage means to said load if said abnormality is determined to be the complete power interruption.