The test equipment used can have a significant impact on measurements. In most cases, the difference will be due to input power measurement. The accuracy of the input power measurement is dependent on the power factor of the unit under test, as well as the base accuracy of the measuring equipment. If all equipment and setups were identical, it is still possible to have a difference in readings of twice the stated accuracy. For example, if a power analyzer has an accuracy of ± 0.1%, the worst-case difference could be as much as 0.2%.

If a unit fails to meet any 80 PLUS^® criteria for certification, the test for that unit is terminated. The second unit is then tested at the specific condition of failure. If the second unit passes, the second unit is tested thoroughly, and data is used for the report. The test is terminated if the second unit fails, and a report is issued with recorded failure data.

The AC source and DC load banks are manually set and adjusted at the initial start of the 15-minute interval. Adjustments of the AC source or loads are no longer adjusted during the 15-minute interval while the unit is in operation.

Each Unit Under Test (UUT) begins the test sequence at 0% load. For desktop power supplies, the next test point is at 2% load. However, if the desktop PSU is rated below 500 watts, this step is replaced with a fixed 10-watt load. The sequence then continues at 5%, 10%, 20%, 50%, and 100% load.

For server power supplies, the full test sequence includes 0%, 5%, 10%, 20%, 50%, and 100% load levels. At each load point, the unit is operated for a duration of 15 minutes prior to data collection as shown in Error! Reference source not found..

The ratings shown on the label of the test unit are entered into an Excel worksheet that performs a calculation based on the algorithm explained in the Generalized Test Protocol for Calculating the Energy Efficiency of Internal AC-DC and DC-DC Power Supplies (Version 6.7.2), Paragraph 6.1.1 Proportional allocation method for loading multiple and single-output AC-DC and DC-DC power supplies.

A LISN (Line Impedance Stabilization Network) and 1uF capacitor was added to the Generalized Test Protocol for Calculating the Energy Efficiency of Internal AC-DC and DC-DC Power Supplies (Version 6.7.2). The addition of the 50µH LISN provides a known and stable input impedance when measuring the input power factor of very lightly loaded power supplies (below 20% loading) while the 1uF capacitor is used as a low pass filter. Testing at several labs, including OEM labs, showed that the power factor readings were much more repeatable when using the LISN and 1uF capacitor.

For the 115V and 230V EU Internal Non-Redundant test bench, the Yokogawa WT5000E is employed to monitor and measure various input parameters, including input voltage (V), input current (A), input frequency (Hz), input power (Watts), power factor (λ), and input current total harmonic distortion (THD %)

To accurately measure output voltage for desktop power supplies tested at both 115V and 230V EU input, we connect sense leads from the Chroma 63640-150-60 and 63610-80-20 electronic load banks directly to the rear of the output connectors using piercing probes. These probes interface with the back of the cable connector that connects to the load, ensuring voltage is measured as close to the load input as possible. Measurements are logged every second during the 15 minute steady-state period for each load condition.

We use three high-performance, programmable 3-phase AC power sources for testing:

230V EU Internal, Non-Redundant tests are conducted at 50 Hz. All other tests-115V Internal Non-Redundant, and 230V & 277/480V Internal Redundant (for North American servers) are conducted at 60 Hz, and 380V DC Internal Redundant- is conducted at 0 Hz