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UPS Frequently Reports a Bypass Alarm Because the Alarm Threshold is Too Low

Publication Date:  2013-02-17 Views:  84 Downloads:  0
Issue Description

On a UPS in a core equipment room of country S, the Fault indicator is on, bypass fault is displayed on the LCD, and an alarm tone is generated. The bypass parameters menu contains many records about abnormal voltages. Some voltage reaches 253 V, and some is only 107 V.

Handling Process

The site measurement result is as follows: The records about the 140 V voltage and 0 Hz frequency are normal because the voltage transiently drops to 0 V when an AC power failure occurs. The records about the 250 V voltage that frequently occur recent days are abnormal.
The site voltage measurement shows that the mains voltage is actually 250 V. The voltage may exceed the bypass voltage alarm threshold.

Root Cause

The bypass voltage alarm threshold is too low, so that a bypass failure alarm is generated when the mains quality is unsatisfactory.


Select Parameters and change the bypass voltage range from +15%/-25% to +20%/-25%.