Seventeam ST-380PAS Power Supply Review
Load Tests
Contents
We conducted 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 load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
For the 100% load test we had to use two patterns. On the first one, test number five, we respected the 252 W limit for the +12 V rail that was printed on the label. In order to achieve that, we had to pull less current from +12 V than we’d like to, and more current from +5 V and +3.3 V. After this test we tried to pull 100% load from the power supply the way we like: pulling more current from +12 V and less current from +5 V and +3.3 V. This was test number six.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “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 both were connected to the single +12 V provided by this power supply.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 | Test 6 |
| +12V1 | 2.5 A (30 W) | 5.5 A (66 W) | 8 A (96 W) | 10.5 A (126 W) | 10.5 A (126 W) | 13 A (156 W) |
| +12V2 | 2.5 A (30 W) | 5 A (60 W) | 7 A (84 W) | 10 A (120 W) | 10 A (120 W) | 13 A (156 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 W) | 15 A (75 W) | 6 A (30 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 5 A (16.5 W) | 14 A (46.2 W) | 6 A (19.8 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2 A (10 W) | 2.5 A (12.5 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) | 0.5 A (6 W) |
| Total | 80.1 W | 161.1 W | 228.8 W | 305.3 W | 387.1 W | 381.0 W |
| % Max Load | 21.1% | 42.4% | 60.2% | 80.3% | 101.9% | 100.3% |
| Room Temp. | 45.9° C | 44.5° C | 47.8° C | 49.0° C | 47.0° C | 47.1° C |
| PSU Temp. | 49.0° C | 47.9° C | 51.2° C | 52.1° C | 51.9° C | 51.1° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass | Pass |
| AC Power (1) | 94 W | 182 W | 261 W | 351 W | 462 W | 449 W |
| Efficiency (1) | 85.5% | 88.5% | 87.7% | 87.0% | 83.8% | 84.9% |
| AC Power (2) | 99,1 W | 184,5 W | 271,8 W | 366,4 W | 478,8 W | 465,9 W |
| Efficiency (2) | 80.8% | 87.3% | 84.2% | 83.3% | 80.8% | 81.8% |
| AC Voltage | 113.3 V | 112.6 V | 111.3 V | 110.3 V | 109.1 V | 109.7 V |
| Power Factor | 0.982 | 0.991 | 0.993 | 0.994 | 0.995 | 0.995 |
| Final Result | Pass | 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. The active PFC circuit from this power supply is excellent, as you can see (only at 20% load we saw something different than 0.99, but 0.98 is still excellent).
This power supply achieved a very high efficiency when we pulled 40% from its labeled power (152 W): 87.3%. At 60% (228 W) and at 80% (304 W) loads efficiency was also very good, at 84.2% and 83.3%, respectively. At light load (20% load, i.e., 76 W) and at full load (380 W) efficiency dropped a lot, but still above the 80% mark.
Voltage stability was another highlight from ST-380PAS, with all voltages inside 3% of their nominal values(i.e., voltages were closer to their nominal value than needed, as ATX spec allows voltages to be up to 5% from their nominal values, 10% for -12 V).
And finally we have noise and ripple, which were below the 120 mV (+12 V) and 50 mV (+5 V and +3.3 V) limits set by ATX specs, especially +12 V, which was around only ¼ of the maximum allowed. Below you can see the results for test number six.
Figure 16: +12V1 input from load tester at 381 W (31.2 mV).
Figure 17: +12V2 input from load tester at 381 W (31.6 mV).
Figure 18: +5V rail with power supply delivering 381 W (30.4 mV).
Figure 19: +3.3 V rail with power supply delivering 381 W (30.4 mV).
Now let’s see if we could pull more than 380 W from this unit.