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, and a second Picoscope 3424), and a CEM DT-8852 sound level meter. This article will give you more details about our equipment and the review methodology we follow. Finally, we conduct all of our tests at 40°C-45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, with 40°C-45°C being derived from a standard ambient assumption of 23°C and 17°C-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 60 W 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

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 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 hold-up time is much lower than the minimum allowed time the ATX spec ascribes. However, we are pretty sure the Hercules-1600 will easily surpass the 16 ms threshold with more realistic loads in the 1-1.2 kW range.

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 it is turned on, the better.



This unit's inrush current is pretty high, though not among the highest we have ever measured, which is obviously a good thing.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the Hercules-1600. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100%, and 110% of the maximum load 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 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail could handle while the load on the minor rails was minimal.

Voltage regulation on +12V rail was pretty good for a unit of such monstrous capacity. It could be much better on the other rails, but what matters the most in a modern unit is its load regulation at +12V. Also, this unit's maximum output power left us speechless, especially because it did so at 48°C. The Hercules-1600 doesn't have the slightest problem operating at incredibly high ambient while delivering crazily high power levels. Here we should note that either the fan profile is really strange or the fan controller in our sample was broken, which is more likely since the fan rotated at the same low speed regardless of load or ambient. Afraid of the unit exploding, we pushed the turbo switch into its "on" position during the full load tests. Though we pushed the PSU really hard, it didn't blow up, nor did its fan spin up past 900 RPM. We think Rosewill and High Power should look into the fan's rotational speeds; however, we must stress that the PSU doesn't need a ton of cooling with loads up to 1.2 kW. Efficiency was to our surprise pretty high, peaking at 92.4% and only dropping significantly during the full load test.

The low PF (Power Factor) reading the Hercules registered will probably not concern residential consumers who only pay for real power (watts), but the PF reading dropped especially low at full load instead of increasing, which is new even to us. The APFC circuit apparently needs to be redesigned to properly deal with this PSU's huge power demands, which would also allow it to form a more efficient current waveform.