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Unbalanced load correction through Symmetra PX UPS.

Archives: Power Distribution


Unbalanced load correction through Symmetra PX UPS.


What is the expected correction through a Symmetra PX UPS for an extreme unbalanced load seen downstream of the UPS.


As an example using a 250kW Symmetra PX equipped with 225kW of power modules it was noted that imbalance of 0%, 0%, 25% (A,B,C phases) saw correction occur only on the A and C phase upstream of the UPS.
Similar results were recorded for 50%,50%,100% (A,B,C phases).


When one phase is loaded considerably heavier, is it expected that the correction through the UPS (double conversion) would be shared mostly between 2 phases and not corrected equally across 3 phases? 



Adam Harding

Arup - Hong Kong

3 Replies 3
Administrator Administrator

Re: Unbalanced load correction through Symmetra PX UPS.

@AldebaranLopez  can you help with this question?

Alexandre Boulet
Schneider Electric - Exchange Launch Leader
Tags (1)
Commander Commander

Re: Unbalanced load correction through Symmetra PX UPS.

@Adam_Harding ,


Sorry for any delay in responding to your post but if this is specifically a UPS question, this forum is not the best place to look for help. If you need immediate help with a 3 phase UPS, I always suggest contacting your local support directly. If you still want forum help, I suggest using the 

3 phase section in the APC forums here:


more specifically:



If the UPS itself is not seeing an issue or if the question is more about how DCE, DCO, ITE, or ITA are seeing this asset, then please be more specific about how we can assist with those softwares as this forum is more specific to those products. Also, if it is specific to the monitoring software, please make sure you indicate how the UPS would appear to be working OK but how the software would appear to be working improperly.


Thank you,


Tags (1)
Ensign Ensign

Re: Unbalanced load correction through Symmetra PX UPS.

Hello Adam,


see a FAAT test made on SymPX300kVA with 2 phases at 50% and one at 100%. Upstream, at the input  the current is almost balanced.



hope it answers, your questionUnbalanced load FAT.png 

Alejandro Aldebaran Lopez
Channel Director, Commercial & Industrial; Secure Power Division
Tags (1)