Overload Tests

We were really curious to see how much power this unit could really deliver, because by the project used we suspected it could deliver far more than what was labeled – especially because we had already reviewed Antec EarthWatts 500 W, which uses the same design, and it is not only labeled at 500 W but could deliver up to 577 W.

We tried to see not only the maximum power we could extract from this power supply with it still working inside its specs, but also if all its protections are working correctly. As you know by now, power supplies usually burn when we try pulling more than it is capable of handling if it doesn’t feature overload protection (OLP or OPP; these two acronyms mean the same thing).

Since we were already pulling from the +12 V output almost the maximum our load tester can deliver to this output – 33 amps – we removed the power supply EPS12V connector from +12V1 input and installed it on the +12V2 input from our load tester. Then starting from pattern number five described in the previous page we started increasing current until the power supply turned off. We figured out that if we pulled more than 44 A (528 W) from +12 V (22 A from the motherboard, video card and peripheral cables and 22 A from EPS12V) the power supply wouldn’t turn on. Phew, we were really cold sweating expecting the worst – that this power supply would explode. But since it shut down, we could testify that overload protection was in action, which is terrific.

Then we increased current on +5 V and +3.3 V to see if we could pull even more. Under the current configuration if we pulled more than 7 A from these rails the power supply would shut automatically down.

With this maximum configuration (44 A from +12 V, 7 A from +5 V and 7 A from +3.3 V – i.e., a total of 596 W!) the power supply would turn on and work for around 30 seconds, after that the power supply would shut down due to overload. Isn’t that great to have a power supply with overload protection in action? You can do whatever you want and it doesn’t explode!

We decreased two amps from the +12 V output and we could make our 450 W power supply to work stable at 570 W at 48° C and with 81% efficiency! Holy cow! You can see the summary for this test in the table below.

Input Maximum
+12V1 20 A (240 W)
+12V2 20 A (240 W)
+5V 7 A (35 W)
+3.3 V 7 A (23.1 W)
+5VSB 2.5 A (12.5 W)
-12 V 0.8 A (9.6 W)
Total 571.9 W
% Max Load 127.1%
Room Temp. 47.8° C
PSU Temp. 48.9° C
AC Power 705 W
Efficiency 81.1%

Under this test all outputs were within specs and noise level was still very low, 47 mV at +12V1, 58.2 mV at +12V2, 19.2 mV at +5 V and 13.2 mV at +3.3 V. Astonishing.

Corsair VX450W Power SupplyFigure 18: Noise level at +12V1 input from our load tester at 570 W.

Corsair VX450W Power SupplyFigure 19: Noise level at +12V2 input from our load tester at 570 W.

Corsair VX450W Power SupplyFigure 20: Noise level at +5 V with power supply delivering 570 W.

Corsair VX450W Power SupplyFigure 21: Noise level at +3.3 V with power supply delivering 570 W.

Short circuit protection (SCP) worked fine for both +5 V and +12 V lines. It seems that over current protection (OCP) is configured with a value far above what is written on the label, as we could pull up to 44 A from the +12 V rail, while the label says the limit is 33 A.

Over load protection (OLP a.k.a. OPP) was in action, shutting down the unit if we pulled more than it could handle, preventing it from burning.

When the power supply fan is running slowly it is really quiet, but as soon as it starts spinning at its full speed noise level becomes somewhat high.

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.