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TEST RESULTS
The ambient temperature was 23~24°, and the ambient noise
level was 14~15 dBA. The PSU was allowed to run at each power level for about
20 minutes before any measurements were taken.
OUTPUT, REGULATION & EFFICIENCY: Seasonic
X-400 Fanless
|
DC Output Voltage (V) + Current (A)
|
DC Output
|
AC Input
|
Calculated Efficiency
|
+12V
|
+5V
|
+3.3V
|
-12V
|
+5Vsb
|
12.20
|
0.97
|
5.03
|
0.97
|
3.38
|
0.96
|
0.1
|
0.1
|
21.6
|
31
|
69.8%
|
12.20
|
2.69
|
5.03
|
0.97
|
3.38
|
0.96
|
0.1
|
0.1
|
42.6
|
53
|
80.4%
|
12.17
|
3.60
|
5.02
|
1.91
|
3.37
|
2.71
|
0.2
|
0.2
|
65.9
|
78
|
84.5%
|
12.17
|
5.27
|
5.00
|
2.77
|
3.36
|
2.56
|
0.2
|
0.3
|
90.5
|
106
|
85.4%
|
12.14
|
8.67
|
5.00
|
5.40
|
3.35
|
3.52
|
0.3
|
0.5
|
150.1
|
169
|
88.8%
|
12.10
|
12.13
|
5.00
|
5.37
|
3.33
|
5.21
|
0.4
|
0.5
|
198.2
|
215
|
92.2%
|
12.05
|
15.50
|
4.98
|
6.10
|
3.33
|
4.98
|
0.6
|
1.5
|
248.4
|
273
|
91.0%
|
12.05
|
18.50
|
4.97
|
7.10
|
3.31
|
6.97
|
0.7
|
2.0
|
299.8
|
330
|
90.9%
|
12.04
|
25.86
|
4.97
|
8.68
|
3.30
|
6.97
|
0.8
|
2.5
|
399.3
|
444
|
89.9%
|
Crossload Test
|
12.08
|
32.77
|
5.00
|
2.77
|
3.37
|
2.71
|
0.5
|
1.5
|
301.4
|
327
|
92.2%
|
+12V Ripple (peak-to-peak): <13mV @ <150W
~ 18mV @ 400W
+5V Ripple (peak-to-peak): <5mV @ <150W ~ 7mV @ 400W
+3.3V Ripple (peak-to-peak): 5mV @ <150W ~ 12mV @ 400W
|
NOTE: The current and voltage for -12V and
+5VSB lines is not measured but based on switch settings. It is a tiny
portion of the total, and errors arising from inaccuracies on these
lines is <1W. Three separate 12V loads were used, but as the X-400
has just one 12V line, all the 12V current was summed for simplicity.
|
OTHER DATA SUMMARY: Seasonic X-400 Fanless
|
DC Load (W) |
22
|
43
|
66
|
90
|
150
|
198
|
248
|
300
|
399
|
Intake °C |
24
|
25
|
27
|
31
|
35
|
37
|
37
|
39
|
43
|
"Exhaust" °C |
28
|
30
|
31
|
36
|
39
|
39
|
40
|
43
|
54
|
Temp Rise °C |
4
|
5
|
4
|
5
|
4
|
2
|
3
|
4
|
11
|
SPL ([email protected]) |
n/a
|
n/a
|
n/a
|
n/a
|
n/a
|
n/a
|
n/a
|
n/a
|
n/a
|
Power Factor |
0.89
|
0.97
|
0.98
|
0.99
|
0.99
|
1.00
|
1.00
|
1.00
|
1.00
|
AC Power in Standby: 0.3W / 0.1 PF
AC Power with No Load, PSU power On: 7.2W / 0.70 PF
|
NOTE: The ambient room temperature during
testing can vary a few degrees from review to review. Please take this
into account when comparing our PSU test data.
|
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
Gold standard requires 90% efficiency at 50% of rated load, and 87% efficiency
at both 20% load and full rated load.
Keep in mind that the testing for 80 Plus approval is done at
normal ambient room temperature. The 80
Plus Testing Guidelines (PDF) specify only that "ambient temperature
shall be maintained at 23°C ± 5°C throughout the test."
In contrast, the ambient temperature of the SPCR test system is directly proportionate
to the load. At low load, the air intake is at or just above room temperature,
but as load is increased, the temperature rises steadily. This is an extremely
tough test condition, as PSU efficiency naturally drops off at high and low
loads; combine high load with high temperature and it's essentially a PSU torture
chamber.
At the super low 20W load, efficiency was excellent at 69.8%,
compared to 65% in the X-650. Efficiency rose quickly as the load was increased.
80% efficiency was reached around the 40W mark, but our sample did not quite
reach 87% at 80W (as called for in the 80 Plus Gold requirement). It probably
consumed 1-2W more than required, as 86% efficiency was seen at 90W load. (A
Chroma PSU test report Seasonic ran on this very sample and sent along as part
of the reviewer package showed 87.84% efficiency at 80W load. We're inclined
to trust their Chroma report more than our own test result; there are undoubtedly
a few points of departure from "true" values on our homebrew rig.)
By 150W, efficiency reached nearly 90%. At 200W, >92% efficiency was reached.
With higher load, and higher operational temperature in the SPCR test box, efficiency
dropped a bit, but still remained just about at 90% even at full power, at over
40°C temperature in the hotbox.
These are great results, as expected. We've never seen such high
efficiency at such low loads, and the efficiency curve is extremely flat, despite
the absence of active cooling for the PSU. The 90% efficiency at full load was
a real surprise, as we expected it to sag much lower in the hot conditions.
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%.
At all load levels, the critical 12V line was within 0.2V (~1.7%)
of 12V, and even at the highest loads, it never dropped below 12V. This is excellent
performance. The 3.3V regulation was within 0.08V, while the 5V line was off
by 0.06V (2%) at worst. The sample exceeded Seasonic's own stringent 3% spec
for voltage regulation.
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 absurdly
low at all power levels. Even at maximum power, the 12V ripple stayed under
20mV. Along with the Seasonic X-650, it is the best ripple we've 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 near perfect throughout the test range.
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 much lower than normal.
6. LOW & 240 VAC PERFORMANCE
The power supply was set to 300W load with 120VAC through a hefty
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 110~120V 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.
Various VAC Inputs: X-400 @ 300W Output
|
VAC
|
AC Power
|
Efficiency
|
245V
|
321W
|
93.5%
|
120V
|
330W
|
90.9%
|
100V
|
340W
|
88.3%
|
Efficiency improved around 2.4% with 244VAC input at this load.
The sample passed the 100VAC minimum input without any issues. Neither voltage
regulation nor ripple changed appreciably during the test.
7. TEMPERATURE & COOLING
As mentioned earlier, the flipped over recommended position of
the X-400 Fanless gave it a distinct advantage in our PSU test hotbox. Nevertheless,
it's impressive how cool the unit really ran. Note that the "exhaust"
temperature isn't really that; the thermal sensor was simply stuck on the middle
of the back panel. Periodic spot checks with an infrared non-contact thermometer
showed temperatures of 65~70°C around the heatsinks and the main capacitor during
the 20~30 minutes of operation at full 400W load, which caused no distress whatsoever.
8. ACOUSTICS
Normally. this is the end of our electrical and thermal performance
analysis, and we move on to acoustics. However, there's simply no acoustics
to be discussed. There are also no recordings of the PSU's noise. The X-400
Fanless remained silent from no load all the way to full 400 load throughout
the testing period. This is not to say the silence was absolutely complete;
from 6" away, at some load combinations a faint buzz could be heard. But
for all practical purposes, the X-400 is indeed silent. We said this about the
Silverstone ST45NF; this Seasonic is at least as quiet.
9. LONG TERM, FULL POWER, THERMAL TORTURE TEST
This is a test we have never run on any PSU before: Long-term,
full load test without an exhaust fan in our PSU hotbox. It was mentioned earlier
that even running this box without the exhaust fan is not normal. Commercially
manufactured PSU load testers have non-defeatable, multiple high speed fans
to keep themselves cool. This is a major reason why we use our custom-cobbled
load tester: It lets us turn the fans off entirely when measuring or recording
PSU noise. So why run this test on the X-400 Fanless? Well, almost on a dare.
In direct discussions about the X-400 Fanless, Seasonic reps were
brimming with confidence that their new baby could not only perform just like
a fan-cooled 400-watter, but even deliver full power under extremely low airflow
conditions, such as one might find in a fanless (or single fan) silent PC. The
parts in the X-400 FL are apparently robust enough that if it was fan cooled,
it could easily be rated for 700W. This led to our running the normal tests
without an exhaust fan. When our Seasonic rep found out the 30 minute duration
of the 400W test load, he wanted us to try running it at full power for 24 hours,
as is often done for testing of mission-critical server PSUs which are
never fanless.
The challenge was on. So, the X-400 Fanless was set to full load
without any exhaust fan in the test hotbox, and left to run as long as possible.
It was decided early on that 24 hours continuous was not going to be practical.
For safety reasons, the test would be monitored regularly (about once every
half hour) by a physically present person. That's your author. The test was
begun at about 8 AM with 22~23°C ambient room temperature, and left to run until
11 PM that night, a total of 15 hours. The ambient temperature in the room climbed
to 26~27°C by 1 PM, stayed around there for several hours, and only declined
down to 24°C at 11 PM.
The temperature in the hotbox directly beneath the PSU ranged
56~60°C. Spot checks with the aforementioned infrared thermometer showed temperatures
inside the X-400 as high as 82~84°C; mostly it hovered close to but under 80°C.
The efficiency dropped as the PSU heated up. The 444W AC input seen after half
an hour rose gradually about 10~12W higher during the hottest part of the day.
The end result after 15 hours: The X-400 Fanless survived the
test. Furthermore, it worked perfectly the next day and ran another 12
hours at the same load and conditions. At the end of the second day, a 1500W
hair dryer was brought into play while the PSU was at full load, blowing the
hot air down into the open grill cover of the X-400 to see what would happen
with thermal overload. In a minute, the PSU shut down with a little click, the
Over Temperature Protection finally kicking in. The IR thermometer showed temperatures
of over 90°C around the main heatsinks. The AC cord was unplugged, the power
switched off for a few minutes, then it was turned back on with no change
to the load settings: The X-400 powered back up without a hitch and kept running.
The hair dryer was used several times to force OTP, just to check on the protection
function. It worked without a flaw about half a dozen times. The X-400 sample
is now powering a new system being set up for use in the lab.
It's hard to imagine any other fanless PSU surviving our long
term full power torture test... but it was a valid question that came up, a
question that we decided to answer in Fanless
PSU Torture Test Roundup.
10. IN A REAL SYSTEM?
How would the X-400 handle the heat in a real computer case where the
top would not be so wide open to the outside air? The answer is that it will
probably do fine in most systems (and modern cases) that are reasonably thought
out for cooling, even with minimal airflow. Consider the following points:
- The way most people and programs use real computer systems results in dynamic
constantly changing, that is power demand. Most computers run
pretty close to idle much of the time, with short peaks into high power. Even
modern 3D gaming doesn't redline the PC constantly, there is always some up/down
in power. In other words, our torture test of the X-400 Fanless is an unrealistically
extreme, worst case scenario.
- One of the advantages in a real computer is cooling by conduction from the
casing of the PSU to the metal case to which it is tightly bolted. This conduction
cooling is missing in our test hotbox.
- Since HTPC system are probably the first target market, consider that many
of the best HTPC cases we've reviewed have excellent airflow and open venting
in, around or near the PSU. Think of Antec Fusion, Fusion Max, Silverstone
GD05/06, for example all place the PSU with space over it and vent
holes or grills to the outside.
- Then there are the many mid-tower and larger cases that put the PSU at the
bottom, either with venting above or below, where you can experiment with
flipping the X-400 one way or the other. The X-400 would fare well in such
cases. Think Antec P180 series, Antec 3480 (with open vent above PSU), Antec
gaming cases, Fractal R2, Silverstone Raven and Fortress models, Coolermaster's
CM690, CM Storm, HAF series, and a dozen Lian Li models with bottom PSU placements.
In fact, the bottom mounted PSU is almost the rule among quality performance
cases these days.
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