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 an Instek GPM-8212 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 of 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 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. As you will see, the hold-up time of the EMR1500EGT is much smaller than the minimum recommendation of the ATX spec. Larger hold-up caps are apparently needed, but they would increase the final cost significantly while also taking up more space on the PCB.

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 or relays; as a result, the lower the inrush current of a PSU right as they are turned on, the better. We measured a high inrush current with the EMR1500EGT because of the total capacity of the hold-up caps.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the EMR1500EGT. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80% and 100% 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.


Efficiency throughout 20-100% load is very high and peaks at 40% load with an impressive 92.66% reading. Apparently, Enermax did a fine job restricting energy losses with this platform, which allowed for extra-high efficiency even at the high ambient temperatures we conducted our tests in.
Regarding voltage (or load) regulation, the +12V rail went a little above 3% which is a little on the loose side. We should not forget that we are talking about a 1500 W monster here, so this rail has to cover a large watt range compared to a smaller capacity PSU. The minor rails, especially the 5V one, registered fairly good voltage regulation. The 5VSB rail stayed below 4%.