SilverStone Element ST50EF-Plus 500 W 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.
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 the +12V1 input was connected to both +12V1 and +12V2 rails,
the same thing happening with the +12V2 input.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 4 A (48 W) | 7 A (84 W) | 11 A (132 W) | 14.5 A (174 W) | 18 A (216 W) |
| +12V2 | 3 A (36 W) | 7 A (84 W) | 10 A (120 W) | 14 A (168 W) | 18 A (216 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 5 A (25 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) | 6 A (19.8 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 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) |
| Total | 102.0 W | 193.1 W | 294.5 W | 392.8 W | 490.9 W |
| % Max Load | 20.4% | 38.6% | 58.9% | 78.6% | 98.2% |
| Room Temp. | 46.9° C | 45.9° C | 46.8° C | 47.9° C | 50.0° C |
| PSU Temp. | 50.1° C | 49.6° C | 49.2° C | 50.8° C | 55.4° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 125.1 W | 230.8 W | 355.6 W | 487.2 W | 633.0 W |
| Efficiency | 81.5% | 83.7% | 82.8% | 80.6% | 77.6% |
| AC Voltage | 112.4 V | 111.1 V | 109.5 V | 106.7 V | 105.6 V |
| Power Factor | 0.924 | 0.962 | 0.975 | 0.977 | 0.971 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
SilverStone Element ST50EF-Plus can really deliver 500 W at 50° C, which is really good. Efficiency when we pulled between 40% and 60% from its maximum labeled power (between 200 W and 300 W) was really good, between 82.8% and 83.7%. At 80% load (400 W) efficiency dropped to around 80% and at full load it dropped below the 80% mark, at 77.6%. It is very important to remind that our tests are tougher than the ones promoted by the 80 Plus organization, which test power supplies at a room temperature of only 23° C, a temperature impossible to be achieved inside a typical PC. Since efficiency drops with temperature and we pulled 500 W at more than double the temperature used by 80 Plus our result was lower than the one provided by this institution. In our opinion our results are more realistic.
There are two claims on Element ST-50EF-Plus that we must check whether they are true or not. The first one is the “±3% cross regulation.” The ATX specification says that all outputs must be within 5% of their nominal values, except for the -12 V output, which has a 10% tolerance. So SilverStone is claiming that this power supply has a tighter regulation than required by the ATX specification. This proved to be true, expect for the -12 V output, which was always outside this 3% range.
The second claim present on the power supply label is “PFC > 0.96.” As you can clearly see on the table above, power factor was below this value during test one, with the power supply delivering 20% of its labeled power (100 W).
Ripple and noise levels were always below the maximum allowed (120 mV for +12 V and -12 V outputs and 50 mV for +5 V and +3.3 V outputs). During test number five, with the power supply delivering 490.9 W, noise level at +12V1 input was of 68.6 mV, at +12V2 it was of 74.8 mV, at +5 V it was of 24.2 mV, at +3.3 V it was of 26.6 mV and at -12 V it was of 47.8 mV. All numbers are peak-to-peak figures.
Now let’s see if we could pull more than 500 W from this unit.