Nexus NX-5000 Silent PSU

TEST RESULTS

The ambient temperature was 22~23°, and the ambient noise level was 11 dBA. Please bear in mind that our testing platform utilizes separate loading apparatuses for 12V1 and 12V2, and data is collected accordingly, but in the NX-5000 12V1 and 12V2 are the same line, and they are treated accordingly in all data analyses.

1. EFFICIENCY — This is a measure of AC-to-DC conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or better at all output power loads. 80% efficiency means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher efficiency is preferred for reduced energy consumption and cooler operation. It allows reduced cooling airflow, which translates to lower noise. The 80 Plus Bronze standard requires 85% efficiency at 50% of rated load, and 82% efficiency at both 20% load and full rated load.

As with many modern power supplies, the NX-5000 has an efficiency curve that peaks around roughly half its rated load, and dropped off slightly towards zero and maximum load. Efficiency at about 65W, a reasonable idle load for modern systems, was a typical 77%. At about 90W, efficiency reached 81.8%, and we can expect that it would reach 82% by its 20% load of 106W, passing its first 80 Plus Bronze requirement. At 250W efficiency was greater than 85% with a measured peak of 85.9% at a 200W load. At at a 50% rated load of 265W, the efficiency would remain above 85% as specified.

Efficiency dropped down to 80.2% at the maximum load of 530W, which is below the 82% required for 80 Plus Bronze certification. This is caused by the demanding thermal environment of our test fixture, compared to the open-air tests performed for 80 Plus certifications. In our open-air tests, the NX-5000 still fell just short of the 82% efficiency target, at 81.5% at full load, but it's close enough that the anomaly can be written off to sample or test measurement variance.

2. VOLTAGE REGULATION refers to how stable the output voltages are under various load conditions. The ATX12V Power Supply Design Guide calls for the +12, +5V and +3.3V lines to be maintained within ±5%.

The NX-5000 performed very well, keeping all voltage lines within at least 3.4% of their rated value at all times throughout the tests. All lines experienced a maximum voltage overshoot at low loads, with a 0.92% peak on the 12V line, 3.4% peak on the 5V line, and 3.2% peak on the 3.3V line. The crossload test did not reduce the performance of the NX-5000's voltage regulation on any lines.

3. AC RIPPLE refers to unwanted "noise" artifacts in the DC output of a switching power supply. It's usually very high in frequency (in the order of 100s of kHz). The peak-to-peak value is measured. The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V line and 50mV on the +5V and +3.3V lines. Ripple on all the lines was quite modest, with a peak ripple of 35mV on the 12V line measured at full load, and peak ripples of 23mV and 21mV measured with a 400W load for the 5V and 3.3V lines, respectively.

4. POWER FACTOR is ideal when it measures 1.0. In the most practical sense, PF is a measure of how "difficult" it is for the electric utility to deliver the AC power into your power supply. High PF reduces the AC current draw, which reduces stress on the electric wiring in your home (and elsewhere up the line). It also means you can do with a smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating. The NX-5000 maintained a good Power Factor throughout the test, above 0.9 beyond 40W, and staying above .94 beyond 40W to full load. Though not the best power factor performance we've seen in a power supply with Active PFC, it's definitely good enough for 80 Plus Bronze certification.

5. LOW LOAD TESTING revealed no problems starting at very low loads. Our sample had no issue starting up with no load, either, and the power draw was very reasonable. Unexpected shutdowns were seen when the 12V line was suddenly unloaded to 0A, even when other lines were still drawing power, but this situation is extremely unlikely to occur with modern computer components, and their predominant use of the 12V line for motors, fans, and additional power for CPUs, GPUs, and many other components.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to a 400W load with 120VAC through the 20A variac in the lab. The variac was then dialed 10V lower every 5 minutes. This is to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 120V norm.

Most full-range input power supplies achieve higher efficiency with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, which was used to check power supply efficiency for the benefit of those who live in 240VAC mains regions.

Efficiency improved around 4.2% with 240VAC input at this load. The NX-5000 performed without any problems all the way down to 100VAC, with an efficiency drop of 2.9% at 100VAC from 120VAC. Neither voltage regulation nor ripple changed appreciably during the test.

7. TEMPERATURE & COOLING

The NX-5000 remained fairly cool throughout testing. The airflow across the back grille was not very uniform, which may have had an effect on exhaust temperature readings. Relatively large intake temperatures were also seen, possibly due in part to the fan pushing air back into the test setup via its front grille.

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