Zalman ZM600-ST 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.
The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test the +12VA input was connected to the power supply +12V1 and +12V2 rails, while the +12VB input was connected to the power supply +12V1 rail (EPS12V connector).
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12VA | 4 A (48 W) | 9 A (108 W) | 13 A (156 W) | 17.5 A (210 W) | 21.5 A (258 W) |
| +12VB | 4 A (48 W) | 9 A (108 W) | 13 A (156 W) | 17.5 A (210 W) | 21.5 A (258 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 6 A (30 W) | 8 A (40 W) |
| +3.3 V | 1 A (5 W) | 2 A (6.6 W) | 4 A (13.2 W) | 6 A (19.8 W) | 8 A (26.4 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 3 A (15 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 | 112.3 W | 237.9 W | 348.2 W | 469.4 W | 598.8 W |
| % Max Load | 18.7% | 39.7% | 58.0% | 78.2% | 99.8% |
| Room Temp. | 45.3° C | 44.6° C | 46.6° C | 47.6° C | 46.9° C |
| PSU Temp. | 46.4° C | 46.2° C | 48.5° C | 50.4° C | 47.8° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 133.1 W | 275.9 W | 411.4 W | 570.1 W | 757.0 W |
| Efficiency | 84.4% | 86.2% | 84.6% | 82.3% | 79.1% |
| AC Voltage | 109.6 V | 108.5 V | 107.4 V | 105.2 V | 104.4 V |
| Power Factor | 0.958 | 0.956 | 0.964 | 0.973 | 0.980 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
Zalman ZM600-ST can really deliver its labeled power at high temperatures.
Efficiency was really high between 84% and 86% when we pulled between 20% and 60% from the labeled wattage (between 120 W and 360 W). At 80% load (480 W) efficiency dropped to 82%, still a pretty decent number. At full load, however, efficiency dropped below the 80% mark. This unit has only the standard 80 Plus certification and it is always good to keep in mind that the 80 Plus numbers are collected with the power supply running at 23° C and since we test power supplies at temperatures of at least 45° C, our efficiency numbers are usually lower than those presented by 80 Plus (efficiency drops with temperature).
Voltages were always within the allowed range.
Power factor was between 0.95 and 0.98, which is below the numbers we usually see (0.97 to 0.99), because the active PFC circuit from this unit has only one transistor instead of two.
Noise and ripple levels were within the allowed range, but a little bit higher than we’d like to see, especially during test five, as you can see below. The maximum allowed is 120 mV on +12 V and 50 mV on +5 V and +3.3 V. All these numbers are peak-to-peak figures.
Figure 16: +12VA input from load tester at 598.8 W (96.4 mV).
Figure 17: +12VB input from load tester at 598.8 W (92.4 mV).
Figure 18: +5 V rail with power supply delivering 598.8 W (31.6 mV).
Figure 19: +3.3 V rail with power supply delivering 598.8 W (29.6 mV).
Now let’s see if this unit can deliver more than 600 W.
