Power supplies manufactured by Delta Electronics are notorious for offering poor compatibility with UPSes. The problem is in their active PFC device. It is designed in such a way that at the moment of switching to the batteries it creates high short-term load on the UPS, triggering the latter’s protection. You can only solve this problem by replacing the UPS with a more advanced one (over 1000VA).
These three models are an example: neither of them could normally switch to the batteries when working together with my APC SmartUPS SC 620 even at a load of 250 watts. For comparison, power supplies with another design of active PFC or with no A-PFC altogether are compatible with this UPS at loads up to 330-360W when powered by the batteries.
So, if UPS compatibility is important to you, you will probably have to replace the native PSU of your newly bought Chieftec system case with another model.
Since each of these PSUs has joint voltage regulation, every output voltage depends not only on the load on its own power rail but also on the load on the other power rails. Let’s check out this dependence now.
The junior model delivers good, stable voltages. The voltages only violate the allowable 5% deflection when the load is greatly misbalanced towards the 5V rail, which is an impossible situation for a modern computer. The +12V voltage is good, the PSU easily delivering the specified 348W across it.
The GPS-450AA-101A draws a similar diagram except that the vertical axis has a different scale. That’s normal since these PSUs only differ in their wattage ratings but have the same circuit design.
The GPS-500AB-A isn’t good in this test. Its +12V voltage goes through the entire range from ‑5% to +5%. The performance of the 5V rail is worse, too.
So I can say it once again: there is no point in looking for the highest-wattage bundled power supply in a Chieftec system case. The specifications of the different models are very similar while the instability of the 500W model in my test makes it equal to the 450W unit in terms of effective performance.