Issue: The UPS reports "Bypass not in range" or "Main Input Bad" alarms

Product Line: Smart-UPS On-Line SRT models

Cause:

Smart-UPS react to input conditions on a cycle basis (really fast), but their logging capabilities are not on par with professional measuring equipment (e.g. fluke multimeters or oscilloscopes). The smallest logging interval the UPS data log can do is 1 min. However, some input events may last only for a few milliseconds, and thus will not show up in the UPS data logs. However, the UPS will still react to them and log it in the event log in case there are temporary conditions that would prevent going to bypass, for example. 

Input THD levels can also contribute to this type of alarm. Typically a THD of 7.6% and above can result in the UPS reporting "Bypass not in range" or "Main Input Bad" alarms.

Resolution:

Adjusting the Bypass Upper/Lower settings may alleviate the frequency of the alarms being reported. To address the cause of the issue, the UPS input conditions need to be captured over a period of time and analyzed to understand what input factor is contributing to the issue: in some cases, it can be input THD, in others it may be distorted input, short transient events, or voltage and frequency temporarily out of range. Given that these input events can be very short (a few milliseconds), the resolution of measurement devices should be set to as high as possible to ensure everything is captured. 

The "Bypass not in range" type events are not fault events: they do not indicate a hardware fault with the UPS. They are informational events that indicate issues with input conditions.

Released for: Schneider Electric Singapore