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. You will find more details about our equipment and the review methodology we follow In this article. 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 specification without input power. It is, in other words, 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 at 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.



Unfortunately, the SS-460FL failed to register over 16 ms of hold-up time like its bigger brother. Apparently, a higher capacity APFC capacitor is needed to do so.

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 smaller APFC capacitor leads to really low inrush current, something that is very good, of course. But the same small capacitor is also responsible for this unit's subpar hold-up time result below the 16 ms threshold, which makes it both a blessing and a curse to the SS-460FL's performance. As we see it, the same cap as with the SS-520FL should be used in the lower capacity model, since the former managed to squeeze by our hold-up time test successfully.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the SS-460FL. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100% and 110% of the maximum load that the PSU can handle. In addition, we conducted two more 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, and, in the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.


The SS-460FL had no problem delivering 110% of its maximum-rated power for quite a long time at an ambient that reached almost 45°C, which is impressive, since it is a fanless unit that has to cope with very high internal temperatures at such high ambient. As you can see from the table above, at 110% load, the temperature exceeded 65°C, a pretty high reading around the top of the unit where the hot air exits the unit's enclosure. Yet efficiency was, despite the tough conditions we conduct the above tests in, very high throughout, and voltage regulation was simply amazing. All main rails registered a deviation well below 1%, with the 5V rail as our king of the hill on those charts. Only its bigger brother, the SS-520FL, managed to outperform the SS-460FL in overall voltage regulation.

The only downside we were able to glean out of these measurements was the low PF reading during the 20% - 60% load tests. The PF reading should, since this is a Platinum unit, be above 0.95 with at least 50% load. We spotted exactly the same problem in the SS-520FL; however, it isn't as important to residential customers who only pay for Real and not Reactive Power. But a high PF is still somewhat desirable because it puts less stress on the mains power grid.