| 摘要 |
PROBLEM TO BE SOLVED: To prevent rush current or cross current from appearing in switching with no instantaneous stoppage of power supply and prevent sharp change in voltage after the switching, in a change-over controlling circuit of an uninterruptible power supply unit wherein a deviation between the output voltage (Voutdet ) of a CVCF (constant-voltage and constant-frequency) device and a set voltage (Voutset) is calculated by a comparing circuit and the calculated deviation is amplified by an AVR amplifier to generate a voltage command signal and the voltage of the CVCF device and that of a bypass power supply are added in switching with no instantaneous stoppage of power supply. SOLUTION: When a CVCF device is changed over to a bypass power supply, a deviation signal (output of a comparing circuit 3) between the voltage of the bypass power supply and a set voltage is added to the comparing circuit through an amplifier 15a which has a delay characteristic by which voltage is gradually increased. On the other hand, when the bypass power supply is changed over to the CVCF device, the output of a comparing circuit 3 is added to the comparing circuit 1 through an amplifier 15b which has a delay characteristic by which voltage is gradually decreased. |
