Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, a second Picoscope 3424), and a CEM DT-8852 sound level meter. In this article, you will find more details about our equipment and the review methodology we follow. Finally, we conduct all of our tests at 40-45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40-45°C being derived from a standard ambient assumption of 23°C and 17-22°C being added for the typical temperature rise within a system.

Primary Rails Voltage Regulation

The following charts show the voltage values of the main rails, recorded over a range from 60W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation

The following chart shows how the 5VSB rail deals with the load we throw at it.

Hold-up Time

The hold-up time is a very important characteristic of a PSU and represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations as defined by the ATX spec without input power. In other words, it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms with the maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.



The PSU failed to meet the minimum allowed hold-up time that the ATX spec specifies. It, nevertheless, still managed to register over 13 ms of hold-up time.

Inrush Current

Inrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays and bridge rectifiers; as a result, the lower the inrush current of a PSU right as they are turned on, the better.



The registered inrush current is low and barely exceeds 30 A, so it won't stress switches and circuit breakers.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the TRIATHLOR FC 550 W. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100%, and 110% of the maximum load that the PSU can handle. We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 2 A. In the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.

Efficiency is high enough for a Bronze unit and peaks at 88% with a 50% of maximum-rated-capacity load. This is a very good reading yet you should, with 115 VAC, expect 1-1.5% lower efficiency. The PSU also proved to be resilient to high temperatures, since it managed to deliver its full power at over 46°C, although Enermax states that its maximum operating temperature is only 40°C.

Voltage regulation at +12V is excellent for a product of this category and price range, but is only average on the minor rails since they clocked in at over 3%. That said, real life scenarios will hardly stress the minor rails like we did given only a few components draw power from them, and even those require very little power in most cases.

As you can see from the table above, the unit's fan worked extra hard in an attempt to effectively move the heat out of the enclosure. We apparently pushed the small PSU too far and the fan profile showed its teeth. For those of you that want to know the output noise in terms of down-to-earth ambient temperatures, check the last graph on the next page.