Zalman ZM500-RS 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 +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester. During this test the +12V1 input was connected to the power supply +12V2 rail while the +12V2 input was connected to the power supply +12V1 rail.
| 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 | 103.9 W | 196.9 W | 299.8 W | 399.5 W | 498.4 W |
| % Max Load | 20.8% | 39.4% | 60.0% | 79.9% | 99.7% |
| Room Temp. | 45.1° C | 44.8° C | 44.9° C | 45.3° C |
47.1° C |
| PSU Temp. | 56.4° C | 55.6° C | 55.5° C | 56.1° C | 57.8° C |
| Voltage Regulation | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 124.1 W | 230.1 W | 353.4 W | 480.1 W | 617.0 W |
| Efficiency | 83.7% | 85.6% | 84.8% | 83.2% | 80.8% |
| AC Voltage | 114.4 V | 113.3 V | 111.9 V | 110.6 V | 109.4 V |
| Power Factor | 0.992 | 0.996 | 0.997 | 0.997 | 0.998 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
Zalman ZM500-RS can really deliver its labeled wattage at high temperatures.
Efficiency was high when we pulled between 40% and 60% from its labeled wattage (i.e., between 200 W and 300 W), being between 84.8% and 85.6%. At light load (20% load, i.e., 100 W) and 80% load (i.e., 400 W) efficiency was still relatively high between 83% and 84%. At full load (500 W) efficiency dropped to 80.8%, still above the 80% mark.
This unit is 80 Plus Bronze certified, meaning that it should present 82% efficiency at full load. This didn’t happen because differently from Ecos Consulting we test power supplies at high temperatures, and efficiency drops with temperature (read our Can We Trust the 80 Plus Certification? article for more details).
Voltages were always inside the allowed range.
Although noise and ripple were inside the allowed range, noise level at +12 V outputs was too high during test five (around 105 mV); during test four it was around 80 mV. The limit is 120 mV and we always prefer power supplies generating half of this or less.
Figure 16: +12V1 input from load tester at 498.4 W (105.2 mV).
Figure 17: +12V2 input from load tester at 498.4 W (104.2 mV).
Figure 18: +5V rail with power supply delivering 498.4 W (29.2 mV).
Figure 19: +3.3 V rail with power supply delivering 498.4 W (22.6 mV).
When we tried to overload this power supply noise level at +12 V outputs was outside the maximum allowed value, and we only consider an overloading well succeeded if all parameters are within specs, which was not the case.