UPS input and output SC current

[kookypedia]

Hi Guys,
Running a short circuit on UPS system, I noticed short circuit current in UPS output is much less than SC current in input.
Am I missing something or it is always the case?

 

[ScottyUK]

The UPS often has an internal bypass transformer, the impedance of which limits the fault current available at the output. The inverter won't sustain short-circuit current for very long before it shuts down to protect itself, normally initiating a trip to the bypass supply.

The supply cables to the UPS will act to drop the available fault current quite quickly. The transformer supplying the board must be a decent size or abnormally low impedance - it's unusual to see a fault level greater than 40kA from an 800A service, that is more like the fault level you'd expect on the LV terminals of a transformer of around 2MVA.