We made several tests with this power supply as described in the article
Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different loads patterns, trying to pull around 20%, 40%, 60%, 80% and 100% of its labeled maximum capacity (under “% Max Load” we list the actual percentage that was used), watching how the reviewed unit behaved under each load. On the table below we list the load patterns we used and the results for each load.
If you add all the powers listed for each test you may find a value different from what posted under “Total” below. Since each output can have a slight variation (e.g. +5 V output working at 5.10 V) the actual total amount of power being delivered is slightly different from the calculated value. On “Total” row we are using the real amount of power being delivered, as measured by our load tester.
+12V1 and +12V2 are the two independent +12V inputs from our load tester and during our tests the +12V1 input was connected to the power supply +12V1 (main motherboard connector and peripheral power connectors) and +12V2 (video card power connector) rails at the same time, while the +12V2 input was connected to the power supply +12V2 rail (EPS12V connector).
All tests were conducted with the fan from the power supply manually set to its maximum speed. This was done so the results wouldn't be biased by a fan speeding on different speeds during each test.
Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
+12V1 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
+12V2 | 4 A (48 W) | 8 A (96 W) | 12 A (144 W) | 16 A (192 W) | 20 A (240 W) |
+5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 6.5 A (32.5 W) |
+3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 W) | 6.5 A (21.45 W) |
+5VSB | 1 A (5 W) | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) |
-12 V | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) | 0.5 A (6 W) |
Total | 115.2 W | 219.0 W | 331.8 W | 436.9 W | 545.8 W |
% Max Load | 20.9% | 39.8% | 60.3% | 79.4% | 99.2% |
Room Temp. | 45.4º C | 46.5º C | 47.3º C | 48.2º C | 49.6º C |
PSU Temp. | 46.6º C | 47.5º C | 48.1º C | 49.5º C | 50.3º C |
Voltage Stability | Pass | Pass | Pass | Pass | Pass |
Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
AC Power (1) | 137 W | 255 W | 391 W | 526 W | 675 W |
Efficiency (1) | 84.1% | 85.9% | 84.9% | 83.1% | 80.9% |
| AC Power (2) | 143.4 W | 263.7 W | 401.2 W | 536.7 W | 684.0 W |
| Efficiency (2) | 80.3% | 83.0% | 82.7% | 81.4% | 79.8% |
| AC Voltage | 113.2 V | 111.3 V | 109.4 V | 108.6 V | 106.9 V |
| Power Factor | 0.969 | 0.988 | 0.993 | 0.996 | 0.997 |
Final Result | Pass | Pass | Pass | Pass | Pass |
Updated 06/24/2009: We re-tested this power supply using our new GWInstek GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Under light load (20% load, i.e. 110 W), the active PFC circuit from this unit isn't as good as when operating under higher loads, but 0.969 is still a good number.
Seventeam ST-550P-AM presents a good efficiency around 83% when you pull between 40% and 60% from its labeled load (betwen 220 W and 330 W). At light load (20% load, i.e. 110 W) it delivers 80.3% efficiency - low, but still above 80% - and when you pull 80% from its labeled capacity (440 W) it shows 81.4% efficiency. The only problem is when fully loaded efficiency drops below the 80% line (but by very little).
Ripple and noise were at excellent levels. Noise level at +12 V outputs was always below a quarter of the maximum limit. Noise level at the +5 V was always below 15 mV (the maximum allowed is 50 mV) and at +3.3 V was always below 13 mV (the maximum allowed is also 50 mV). These numbers are peak-to-peak figures and are far better than the ones presented by ST-550P-AG.
Below you can see noise level when we were pulling 545.8 W (test number five) from this power supply.
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Figure 17: Noise level at +12V1 input from our load tester with the reviewed unit delivering 545.8 W (25.6 mV).
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Figure 18: Noise level at +12V2 input from our load tester with the reviewed unit delivering 545.8 W (28.8 mV).
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Figure 19: Noise level at +5 V input from our load tester with the reviewed unit delivering 545.8 W (14.4 mV).
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Figure 20: Noise level at +3.3 V input from our load tester with the reviewed unit delivering 545.8 W (12.2 mV).
Let’s now see if we could pull even more power from Seventeam ST-550P-AM.
