Critical - UPS: An input voltage or frequency problem prevents switching to bypass mode.

[belostenac]

In the last few weeks, the UPS MGE Galaxy 3500 40 kVA very often logs the event: Critical - UPS: An input voltage or frequency problem prevents switching to bypass mode. After a few seconds/minutes the error disappears and the message appears: Informational - UPS: An input voltage or frequency problem no longer prevents switching to bypass mode.

I suspect the problem is with the input voltage, which I would say from the logs is too high (log file attached).

What should we pay attention to and is there anything we could do to prevent similar events?

[al_buffington · Accepted solution]

Hi,

You are correct. This is likely due to the input voltage or frequency moving outside the acceptable range where bypass operation is supported but not enough to cause the UPS to transfer to battery operation. On the voltage side this is somewhere between +/- 10% and +/- 20% of the nominal input. The range of operation related to the frequency can be configured via the display (note: changes can only be made if the UPS output power is off). I believe that the default setting is +/- 10Hz but it can also be set for .1 Hz  or 3Hz. If your setting is something other than 10 then perhaps changing the setting could reduce the number of instances of the event.

When this event is active, the UPS would not be able to transfer to bypass if maintenance is required or if a fault were to occur which prevented the UPS running in normal operation.  Since this event is triggered by the utility voltage you would have to address this with either your site facilities personnel or with your local utility provider. 

I hope this helps.