One of the basic measures of any ATX power supply is the unit’s overall physical weight. This may seem rather simplistic but it generally holds that more industrial grade components and larger heatsinks equal a better PSU. In addition to being quite long the Galaxy is also heavier than any ATX power supply I have tested to date. The following graph illustrates how the Enermax Galaxy compares to some other popular power supplies.
(click to enlarge)
DC Output Voltage Load Regulation
To simulate real world and maximum loading conditions, the Galaxy 1kW PSU was connected to the load tester, supplied with 115 VAC, and allowed to burn-in for 24 hrs before voltage readings were taken. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. All rails were loaded during all of the tests except for the +12V5 output, which was only loaded during the last three tests. The DC output voltages were measured with a FLUKE digital multimeter.
The new ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances for the +12V1 and +12V2 outputs.
The following table lists the DC voltage results at different loads for the Galaxy 1kW PSU while operating on 115 VAC, 60 Hz. Note: the voltages for +12V1 and +12V2 were loaded equally and measured the same throughout all the tests.
The Galaxy 1kW PSU produced excellent voltage regulation on all of the outputs across a broad range of loads; even when exceeding the 1,000 watt output capacity. All of the major outputs stayed within Â±3%, which is very good!
AC Ripple (electrical noise) on DC Outputs
The amount of AC ripple present on the outputs was checked using an oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. I adjusted the O-scope time base to look for AC ripple at both low and high frequencies.
The new ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.
Ideally we would like to see no AC noise on the DC outputs — the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during two moderately heavy load tests for the eight main output voltages of interest.
The Galaxy 1kW power supply exhibited very good AC ripple suppression under light to moderately heavy loads, but under very heavy loads, the AC noise on the +3.3V and +5V rails increased substantially. During the final 1,033W load test, the AC ripple on the +5V output actually exceeded the design tolerance. In reality this is normal — as the DC load increases, typically so does the AC ripple. And since I’m actually exceeding the rated 1,000 watt capacity of the Galaxy PSU, I can’t really call this out of spec.
This illustrates one of the advantages of having a power supply with plenty of reserve capacity. In general, it’s a good idea to operate a PSU at no more than 50% to 60% of its maximum capacity. Doing so allows the PSU to run cooler/quieter, minimizes AC ripple, and places it close to the peak operating efficiency.