UPS static bypass vs STS

[Pgee630]

Hi,

If I have 2 separate UPS systems supplying a load through a downstream STS (input from the 2 UPS systems, what would happen if e.g. there is an inverter fault at UPS A (primary source to STS) - 1. UPS A transfer to the internal static bypass while STS still stick to UPS A as primary source; OR, 2. STS will transfer from primary to secondary source (UPS B) before the UPS A switch to internal static bypass?

If it is "2", then the STS will quickly transfer back to primary source (UPS A) once UPS A switch to internal static bypass?

Thanks

 

[mparenteau]

Would need to know the "pick-up" time of the UPS system and the STS. If the STS is faster, then it should switch first, but if the UPS is faster, then I would expect transfer to static bypass.

Mike

 

[Pgee630]

I'm just wondering what would that be the case normally? OR really a case by case?

 

[ScottyUK]

Are the two UPS’s locked in phase? If they are then difficult to say which will be fastest, if they’re asynchronous then the internal SBS will probably be faster as the output phase-locks to the bypass supply.

 

[PKJENNY]

Hi Scotty,

The 2 UPS are synchronized.
So in that case with the said setup, there may be a chance of multiple switching where there is, say, an inverter fault, which is not desirable?

Thx