Load Regulation, Line Regulation and Cross-Loading
DC Output Load RegulationOf course one of the first things we want to see is how well this PSU can regulate the DC outputs and maintain stable voltages. To simulate real world and maximum loading conditions, the ABS/Tagan BZ800 800W PSU was connected to the load testers and supplied with a constant 115 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.
The new ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs. I have also included a second table of expanded tolerances (±1% to ±6%) for reference.
The following tables list the DC voltage results at the different loads for the ABS/Tagan BZ800 800W PSU while operating on 115 VAC, 60 Hz.
The PSU produced excellent load regulation on all of the outputs across a broad range of loads; even when delivering the maximum rated capacity of 800 watts DC power. The +3.3V and +5V rails stayed within 2% of the nominal voltage instead of the recommended +/-5% and the +12V outputs were even better, staying within 1%. Very good!
DC Output Line Regulation
In this test we are interested in seeing how well a PSU can maintain the various output voltages while the AC input line voltage changes. In the previous Load Regulation test, the AC line voltage was held constant at 115 VAC. Now we will look at how much the DC outputs change as the load is held constant and the AC line voltage is changed from 120 VAC down to 90 VAC.
The Line Regulation test was performed with the combined DC loads set to 600W. The AC input voltage to the power supply (via the Extech power analyzer) was adjusted using a Powerstat variable autotransformer.
There was virtually no measurable change in the DC outputs. Note: 90 VAC is well below the published AC input range of this PSU but it still delivered.
Cross-Loading Test
PC switching mode power supplies provide multiple DC output voltages. Ideally, the total load should be distributed across all the main outputs (+3.3V, +5V, +12V). This means that the combined +3.3V and +5V load should be proportional to the combined +12V load – as one increases, so should the other. Unfortunately, this is not always the case, especially in newer PCs that predominately use +12V and may put only minimal loads on the +3.3V and/or +5V rails.
Cross-loading refers to imbalanced loads. If a PC pulls 400W on the +12V outputs and only 40W (or less) on the combined 3.3V and +5V outputs, the resulting voltage regulation may suffer.
In the first test we put a heavy load (64A) on the +12V output and a light load on the remaining outputs. The ABS/Tagan BZ800 PSU had no problem delivering 768W on the combined +12V rails. With this large imbalance, the power supply managed to keep all the voltages regulated within spec.
In the second test we reversed the cross-load and placed a heavy load (169W) on the +3.3V and +5V outputs with a light load (4A/48W) on the +12V rail. Once again, the PSU passed this test as well.
Mine died after 10 years of use, i’ll try to fix it. It have been a very reliable power supply. And it was rough to choose a replacement psu, since every psu novaday is very dull compared to the tagan BZ800 For the drama, this psu got high voltage sparks betwen a 1ohm resistor on the high voltage side. The spark have dig a hole on the varnish and copper, and went through 5mm air gap to the next voltage regulator. The main circuit breaker have done his job, and everyone have saved the computer. The computer is still working great and i was ok tier to find the corsair shift, who seeem to be the last one to give a little bit of originality Novaday. The Tagan bz800 was a great psu and i hope i’ll fix it