Working with our APC SmartUPS SC 620, the PSU was stable at loads up to 367 watts when powered by the mains and could switch to the UPS's batteries at 285 watts.
Cross-Load Voltage Stability
We must note that our testbed couldn’t provide the maximum permissible load on the +12V rail, yet we reached the PSU’s full overall load by using the other rails.
The most important +12V rail is ideally stable. It is within 1% of the required level in the range of practical loads and is never even 2% off at any other loads.
The +5V voltage is perfect at low loads, remains within 2% of the required level at medium loads (medium for this high-wattage PSU, of course) and goes out of the 2% range at high loads. That’s good (and much better than the AX1200), but we’ve seen better results in this test.
The +3.3V voltage deflects by over 3%, yet turns out to be more stable than the +5V voltage in the typical load range where it is only 1 or 2% off the required level.
Overall, the AX1200i delivers stable voltages, but breaks no records among PSUs with dedicated voltage regulation. On the other hand, it shows some progress over the similarly designed AX1200 which is less stable in terms of +3.3V and, especially, +5V.
Output Voltage Ripple
The high-frequency voltage ripple is weak on every power rail. We can see occasional voltage spikes on the +3.3V rail, yet they always remain within the permissible range.
The same goes for the low-frequency ripple (at the double frequency of the mains). Again, this is an improvement over the AX1200 model which used to have voltage spikes on the +12V rail.
Temperature and Noise
This test was carried out at the default settings, i.e. without our tweaking the PSU’s cooling system through the Corsair Link interface.
The PSU is cooled by a Yate Loon D14BH-12 fan which has a rated speed of 2800 RPM. The AX1200 model had the same fan for cooling.
Despite the same fan, the speed regulation algorithm is completely different. The fan doesn’t work at all until 50% load. Then it starts out at a low speed and smoothly accelerates, reaching 1200 RPM at full load. The peak speed is lower than the start speed of the AX1200’s fan!
As a result, the Corsair AX1200i is perhaps the best PSU in its category in terms of noisiness. It is quiet even after working for a while at full output power!
Efficiency and Power Factor
The PSU is 92.8%, 93.4% and 90% efficient at the reference loads of 20%, 50% and 100%. It shows its peak efficiency of 93.8% in the load range of 450 to 500 watts. These numbers meet the 80 PLUS Platinum requirements by some margin (we want to remind you that we carry out our tests on 230V mains whereas the 80 PLUS Platinum certification refers to 115V mains).
The power factor is very close to the theoretical maximum of 1 at loads above 450 watts.
The standby source does its job without any problems.