Seasonic X-1050 PSU: Gold at Kilowatt+

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TESTING

For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals. Those who seek source materials can find Intel's various PSU design guides at Form Factors.

SPCR's PSU Test Platform V4.1. is the basic setup for the testing. It is a close simulation of a moderate airflow mid-tower PC optimized for low noise. There is one major change: The primary testing is done with the PSU NOT inside the hotbox but atop it, out of the heat path. This is in recognition of several realities that prevail today:

  • The vast majority of "serious" PC cases for the home builder place no longer position the PSU at the top back corner. They put the PSU at the bottom/back corner, mostly out of the path of heat from the other components in the case. This design concept took root with the Antec P180 going back over 5 years, and dominates the DIY case arena. This means the PSU generally has to dissipate only its own heat.
  • In earlier versions of SPCR's test platform, the internal temperature varied proportionately with output load. The tested PSU was subject to this heat, and operating ambient temperature rose with increased load, reaching >40°C and often much higher at full power. This was a realistic simulation of a mid-tower PC case where the PSU is mounted conventionally at the top back portion of the case.

With the current test, we're reversing our approach: The PSU will be tested briefly in the hotbox only to check on what happens to noise, fan speed and temperatures when it is used in an outmoded case design

Acoustic measurements are performed in our own anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces.

REAL SYSTEM POWER NEEDS: While we test the PSU to full output in order to verify the manufacturer's claims, most desktop PCs do not require anywhere near this level of power. The most pertinent range of DC output power is between about 40W and 400W, because it is the power range where most systems will be working most of the time. It is true that very elaborate gaming systems with two of today's most power hungry video cards might draw as much as another 300W.

TEST RESULTS

The ambient temperature was 21~23° (it rises over the duration of the test, due to the PSU testing itself), and the ambient noise level was ~10.5 dBA.

Seasonic X-1050 (SS-1050XM) Test Results
DC Output (W)
AC Input
(W)
Lost as Heat
(W)
Efficiency %
Power Factor
Exhaust
SPL* (dBA@1m)
20.9
29
8.1
72.0
0.90
22°C
0 / 16
38.9
54
17.1
72.0
0.94
23°C
0 / 16
65.3
82
16.7
79.6
0.99
25°C
0 / 16
89.8
104
14.2
86.3
0.99
29°C
0 / 16
146.8
168
21.2
87.4
0.99
34°C
0 / 16
199.6
223.0
23.4
89.5
0.99
39°C
12 / 16
251.0
276.0
25.0
90.9
0.99
46°C
12 / 16
301.3
333.0
31.7
90.5
1.00
46°C
13 / 16
399.6
438.0
38.4
91.2
1.00
42°C
14 / 16
499.4
548.0
48.6
91.1
1.00
44°C
16 / 16
699.8
787.0
87.2
88.9
1.00
45°C
26 / 26
1047.6
1200.4
156.4
87.0
1.00
46°C
40 / 40
Crossload Test
(1A on 5V and 3.3V lines; the rest on 12V line)
700
767
67
91.2
1.00
45°C
26 / 26
+12V Ripple (peak-to-peak): <12mV @ <250W ~ 36mV @ 1050W
+5V Ripple (peak-to-peak): <10mV @ <200W ~ 28mV @ 1050W
+3.3V Ripple (peak-to-peak): 10mV @ <200W ~ 28mV @ 1050W
AC Power in Standby: 0.3W
AC Power with No Load, PSU power On: 16.7W / 0.77 PF
* See text discussion about noise.


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. 80 Plus Gold calls for 90% efficiency at 50% of rated load, and 87% at 20% and 100% load.

At the super low 20W load, efficiency was decent but not great at 72%. Efficiency rose relatively slowly as the load was increased. 90% efficiency was reached around the 200W mark, and peaked a bit over 91% at 400~500W. It measured 87% at 1050W. The X-1050 passes 80 Plus Gold requirements easily at the 20% load, and meets them at 50% and 100% loads.

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%. Seasonic claims 3% tolerance on all lines.

At all load levels, the critical 12V line was within -0.26V (-2.2%) of 12V. It started a titch high at 12.1V and dropped with increased load to 11.74V (-2.2%) at full power. The 5V line also started a touch high at 5.1V (+2%), and went down to 4.86V at full load (-2.6%). The 3.3V line was rock steady at 3.35~3.30V throughout the testing. These are excellent results, staying well within Seasonic's stringent ±3%, and better than voltage regulation needs to be for any PC.

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 100 KHz or even higher). 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 very good at all power levels, generally staying under 15mV through the lower half of the power range. Even at maximum power, the 12V ripple stayed at just 34mV. It's close to the best we have measured.

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. Power factor was excellent for this model, running at or close to 1.0 through most of the loads and 0.9 even at just 20W load.

5. LOW LOAD TESTING revealed no problems starting at very low loads. The 0.3W power draw in standby (power switch on but load tester off with nothing loading the 5V standby line, like a USB device would do) is about the l owest we've measured. The draw of 16.7W with power on at no load is substantially higher than we've seen in most recent PSUs. This is not exactly anything to worry about, as the condition is not one you'll ever run into in real usage. We run the test as a matter of curiosity... and tradition: we've been reporting this for a long, long time.

6. LOW & 240 VAC PERFORMANCE

The power supply was set to 700W load at various AC input voltages. 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 higher mains voltage regions. We also used a hefty variac to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 120V norm.

Various VAC Inputs: Seasonic X-1050
VAC
AC Power
DC Output
Efficiency
244V
759W
700W
92.2%
120V
787W
700W
88.9%
100V
798W
700W
87.8%

Efficiency improved to over 92% at the higher voltage, which is the efficiency required for the 80 Plus Gold in 230VAC operation. The sample passed the 100VAC minimum input at 700W load without any issues. Neither voltage regulation nor ripple changed appreciably during these tests.



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