Seventeam ST-550P-AM ASM Power Supply Review
Overload Tests
Contents
Before overloading power supplies we always test first if the over current protection (OCP) circuit is active and at what level it is configured.
In order to do that we first removed the auxiliary video card power cable from our load tester to make the +12V1 from the power supply to be connected on the +12V1 input from our load tester and the +12V2 from the power supply to be connected on the +12V2 input from our tester (with the video card cable connected the +12V1 input was connected to both +12V1 and +12V2 rails from the power supply).
Then we configured our load tester with a low (1 A) current on +12V1 and increased current at +12V2 until the power supply shut down. This happened when we tried to pull more than 28 A from +12V2.
The label states that each rail has a 20 A limit, so OCP was configured 8 amps above that. Usually manufacturers configure OCP circuit at a value higher than
what is printed on the label, but we personally like to see OCP configured at a value as close as possible to what is printed on the label.
Starting from test five we increased currents on +12 V, +5 V and +3.3 V to the maximum we could with the power supply still running inside ATX specs. The results are below. When we tried to increase one more amp at any output ripple would go to the roof, meaning that the unit stopped working correctly.
| Input | Maximum |
| +12V1 | 25 A (300 W) |
| +12V2 | 25 A (300 W) |
| +5V | 8 A (40 W) |
| +3.3 V | 8 A (26.4 W) |
| +5VSB | 2 A (10 W) |
| -12 V | 0.5 A (6 W) |
| Total | 671 W |
| % Max Load | 122% |
| Room Temp. | 47.7° C |
| PSU Temp. | 48.8° C |
| AC Power (1) | 864 W |
| Efficiency (1) | 77.6% |
| AC Power (2) | 871.0 W |
| Efficiency (2) | 77.0% |
| AC Voltage | 104.9 V |
| Power Factor | 0.997 |
Consider the results marked as "2", as they are the correct ones, measured with our precision power meter.