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TEST RESULTS
For a fuller understanding of ATX power supplies, please read the reference
article Power Supply Fundamentals & Recommended
Units. Those who seek source materials can find Intel's various PSU
design guides at Form
Factors.
For a complete rundown of testing equipment and procedures, please refer to
SPCR's
PSU Test Platform V.3. The
testing system is a close simulation of a moderate airflow mid-tower PC optimized
for low noise.
In the test rig, the ambient temperature of the PSU varies proportionately
with its output load, which is exactly the way it is in a real PC environment.
But there is the added benefit of a high power load tester which allows incremental
load testing all the way to full power for any non-industrial PC power supply.
Both fan noise and voltage are measured at various standard loads. It is, in
general, a very demanding test, as the operating ambient temperature of the
PSU often reaches >40°C at full power. This is impossible to achieve
with an open test bench setup.
Great effort has been made to devise as realistic an operating
environment for the PSU as possible, but the thermal and noise results obtained
here still cannot be considered absolute. There are too many variables in PCs
and too many possible combinations of components for any single test environment
to provide infallible results. And there is always the bugaboo of sample variance.
These results are akin to a resume, a few detailed photographs, and some short
sound bites of someone you've never met. You'll probably get a pretty good overall
representation, but it is not quite the same as an extended meeting in person.
REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output
(even >600W!) in order to verify the manufacturer's claims, real desktop
PCs simply do not require anywhere near this level of power. The most pertinent
range of DC output power is between about 65W and 250W, because it is the power
range where most systems will be working most of the time. To illustrate this
point, we conducted system tests
to measure the maximum power draw that an actual system can draw
under worst-case conditions. Our most powerful Intel 670 (P4-3.8) processor
rig with nVidia 6800GT video card drew ~214W DC from the power supply under
full load ? well within the capabilities of any modern power supply. Please
follow the link provided above to see the details. It is true that very elaborate
systems with SLI could draw as much as another 100W, perhaps more, but the total
still remains well under 400W in extrapolations of our real world measurements.
SPCR's high fidelity sound
recording system was used to create MP3 sound files of this PSU. As
with the setup for recording fans, the position of the mic was 3" from the exhaust
vent at a 45° angle, outside the airflow turbulence area. The photo below shows
the setup (a different PSU is being recorded). All other noise sources in the
room were turned off while making the sound recordings.
INTERPRETING TEMPERATURE DATA
It important to keep in mind that fan speed varies with temperature,
not output load. A power supply generates more heat as output increases, but
is not the only the only factor that affects fan speed. Ambient temperature
and case airflow have almost as much effect. Our test rig represents a challenging
thermal situation for a power supply: A large portion of the heat generated
inside the case must be exhausted through the power supply, which causes a corresponding
increase in fan speed.
When examining thermal data, the most important indicator of cooling efficiency
is the difference
between intake and exhaust. Because the heat generated in the PSU
loader by the output of the PSU is always the same for a given power
level, the intake temperature should be roughly the same between
different tests. The only external variable is the ambient room
temperature. The temperature of the exhaust air from the PSU is
affected by several factors:
- Intake temperature (determined by ambient temperature and power output level)
- Efficiency of the PSU (how much heat it generates while producing the required output)
- The effectiveness of the PSU's cooling system, which is comprised of:
- Overall mechanical and airflow design
- Size, shape and overall surface area of heatsinks
- Fan(s) and fan speed control circuit
The thermal rise in the power supply is really the only indicator
we have about all of the above. This is why the intake temperature is important:
It represents the ambient temperature around the power supply itself. Subtracting
the intake temperature from the exhaust temperature gives a reasonable gauge
of the effectiveness of the power supply's cooling system. This is the only
temperature number that is comparable between different reviews, as it is unaffected
by the ambient temperature.
On to the test results...
Ambient conditions during testing were 20°C and 19 dBA. AC input was 121V
and 60 Hz, measured at the outlet.
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OUTPUT & EFFICIENCY: FSP Green PS FSP400-60GLN
|
|
DC Output Voltage (V) + Current (A)
|
Total DC Output
(W)
|
AC Input (W)
|
Calculated Efficiency
|
|
+12V1
|
+12V2
|
+5V
|
+3.3V
|
-12V
|
+5VSB
|
|
12.25
|
0.97
|
12.24
|
1.74
|
5.08
|
0.99
|
3.31
|
0.00
|
0.1
|
0.2
|
40.4
|
58
|
69.7%
|
|
12.26
|
1.92
|
12.25
|
1.75
|
5.07
|
1.95
|
3.31
|
1.85
|
0.1
|
0.3
|
63.7
|
84
|
75.8%
|
|
12.26
|
2.88
|
12.26
|
1.75
|
5.06
|
3.77
|
3.30
|
2.73
|
0.2
|
0.5
|
89.7
|
114
|
78.7%
|
|
12.24
|
4.82
|
12.24
|
3.32
|
5.04
|
5.65
|
3.28
|
4.53
|
0.3
|
0.8
|
150.6
|
185
|
81.4%
|
|
12.23
|
5.76
|
12.23
|
5.02
|
5.05
|
7.32
|
3.29
|
6.29
|
0.4
|
1.0
|
199.3
|
245
|
81.3%
|
|
12.24
|
6.70
|
12.23
|
6.75
|
5.03
|
9.11
|
3.30
|
8.30
|
0.5
|
1.3
|
250.3
|
311
|
80.5%
|
|
12.24
|
7.87
|
12.23
|
8.22
|
5.09
|
10.88
|
3.31
|
9.90
|
0.6
|
1.5
|
299.7
|
376
|
79.7%
|
|
12.30
|
9.8
|
12.28
|
11.47
|
5.08
|
14.14
|
3.30
|
13.96
|
0.8
|
2.0
|
398.9
|
515
|
77.5%
|
NOTE: The current and voltage for -12V and +5VSB lines
is not measured but based on switch settings of the DBS-2100 PS Loader.
It is a tiny portion of the total, and potential errors arising from inaccuracies
on these lines is <1W.
The loading formula is the same one used by Efficient
Power Supplies, which can be downloaded as a PDF file from
the linked page. This is the testing arm of the 80
Plus program, which encourages the use of high efficiency power
supplies in computers in the US and Canada.
|
|
OTHER DATA SUMMARY: FSP Green PS FSP400-60GLN
|
|
DC Output (W)
|
40.4
|
63.7
|
89.7
|
150.6
|
199.3
|
250.3
|
299.7
|
398.9
|
|
Intake Temp (°C)
|
22
|
24
|
25
|
30
|
33
|
36
|
33
|
36
|
|
Exhaust Temp (°C)
|
28
|
30
|
31
|
37
|
41
|
45
|
47
|
52
|
|
Temp Rise (°C)
|
6
|
6
|
6
|
7
|
8
|
9
|
14
|
16
|
| Fan Voltage |
4.3
|
4.5
|
4.8
|
5.7
|
6.6
|
7.9
|
9.4
|
10.9
|
| SPL (dBA@1m) |
24
|
25
|
26
|
29
|
31
|
34
|
37
|
39
|
|
Power Factor
|
0.90
|
0.93
|
0.95
|
0.97
|
0.97
|
0.98
|
0.99
|
0.98
|
|
NOTE: The ambient room temperature during testing can
vary a few degrees from review to review. Please take this into account
when comparing PSU test data.
|
ANALYSIS
1. VOLTAGE REGULATION was excellent. None of the voltage rails ever
changed by more than 1%, minimum to maximum, and all were well within the required
5% of nominal at all voltages. The +3.3V rail in particular was almost always
within 0.01V of its nominal voltage. In addition, the Green PS did an excellent job of compensating for voltage
drops at higher output levels. In fact, the highest voltages on the +12V rails
were measured at full load.
2. EFFICIENCY as measured by our test setup did not reach the 85% claimed
by FSP. To be fair, the Green PS is targeted at the European market, most of
which uses 230V AC power that can be converted to DC more efficiently than the
120V power. With its peak at 81%, the Green power is still a very efficient
power supply, and it remained efficient even at full load.
The 77.5% efficiency and strong line voltages at full load suggest that the
Green PS is quite conservatively rated, and may be able to handle more than
its rated output in a well cooled system.
3. POWER FACTOR was quite variable for a unit with active power factor
correction, although it was always above 0.90. Although the numbers are slightly
lower than usual, they were not low enough to make much practical difference.
4. TEMPERATURE AND COOLING
For all loads below 250W output, the cooling efficiency proved to be perfectly
acceptable. Above 300W, the temperature rise across the unit jumped sharply,
but the absolute temperature did not increase significantly. This is very odd
behavior... but not quite as odd as the measured internal
temperature, which actually dropped at this output. I can think of no satisfactory
explanation for this unusual performance. It seems to be a
measurement anomaly that is meaningless.
As mentioned, the unusual layout and small heatsinks did not seem to have an
adverse affect on the internal cooling. According to our usual testing, the
Green PS is an average performer, no better and certainly no worse than the
majority of its competitors.
Subjectively, there seemed to be much more air than usual flowing through the
power supply. The air felt a little cooler than usual, but the measurements
did not bear this out.
5. FAN, FAN CONTROLLER and NOISE
In spite of the noise measurements, the Green PS actually sounded
quite good. The Yate Loon fan was not quite as smooth as the sleeve bearing
models, but it's not bad. For most of the lower output
levels, the noise was dominated by the whoosh of wind turbulence, which seems indicative of high
airflow.
Somewhere around 150-200W output (~33°C intake), a low pitched drone from
the motor became the dominant noise. Coincidentally, this
was also the point when the noise began to become intrusive. Even at full
speed there was still more wind noise than usual.
The fan controller was quite unusual, because it varied the fan voltage throughout
the output range, not just above a certain threshold. The fan started cold at
~3.7V (close to inaudible at 21 dBA@1m), but even at the extremely low load
of 40W it climbed to 4.3V. At this level, a small amount of turbulence noise
was clearly audible, but the motor drone was very difficult to make out.
The fan voltage continued to climb more or less constantly as the output increased
until about 200W output, when the rate of change began to increase.
Changes in fan speed were quite gradual, almost imperceptible. But, because
the speed is almost always changing, it is more likely to be noticed than a
model that stays steady until a certain internal temperature is reached. The
most noticeable point during our testing was around 150W output when the turbulence noise changed
to motor hum.
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