2022 ITTSB Project: Triple Rail DC dummy load 330W for ATX PSU testing

[Kiriakos GR]

I did start writing a document named as: ITTSB.EU Triple DC Load tester electrical specification ..
But this alone it would not deliver the complete pack of details, speaking of the maximum of my new DC Load testing capabilities at my lab.

I am now consider the text bellow as summary and epilogue, which this fill me up with unimaginable pride and happiness.  
Everything when as planed.
My triple DC load it has worked so far for five hours at max load and medium load, and all three circuits they did prove their robustness and stability.

I will simply say that I did won and at this battle too.
This is (or was) a combination of electrical design, metal processing skills, proper selection of parts, and an extremely well planed strategy from start to finish.     

Some one might think this project as the poor man testing DC load, I have news for you, analog electronics helped science to build or develop first tools for space technology and to explore outer space.
Now feel free to build or become a maker of your own spaceship. 

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ITTSB.EU Triple Load tester electrical specification

3.3V Rail load options:
Low 1.8A = 5.94 VA (3.30V)
High 5.9A = 19.47 VA

5.0V Rail load options:
Low 1.45A = 7.25 VA (5.00V)
High 6.7A = 33.5 VA

12 Rail load options:
Load OFF = 370mA (dual DC fan for cooling) on all times.
Low 4.5A (12.00V)
Step 2 = 9A
Step 3 = 13.5A
Step 4 = 18A
Step 5 = 22.5A
Actual sum this is 22.87A (load + cooling) = 274.44 VA

All rails combined 327.41 VA   

By the use of my additional electronic DC load (110W), this is adjustable from 200mA ~ 9.4A at 12.00V and this is 112.8VA
https://www.ittsb.eu/forum/index.php?topic=1316.0

Both DC load unit combined as one, they can now stress the 12V rail up to 32.27A.
Combined use of loads can stress any computer power supply up to 440.21 VA and or 440.21 DC Watt.

Examples of computer PSU unit wattage VS obtained testing DC load in percentage:
450W = 97.83 % (testing load)
500W = 88.04 %
550W = 80.04 %
600W = 73.37 %
650W = 67.73 %
700W = 62.89 %
750W = 58.70 %
800W = 55.30 %
850W = 51.79 %
900W = 48.92 %
 
INTEL ATX12V Power Supply Design Guide, considers as Test pass, any DC rail deviation +/- 3% of the named output (at full load).
Eventually this +/- 3% of voltages deviation, this is expected to be included and or influence the sum of obtained testing DC load in percentage at fixed resistive loads.
 
The good news are that TOP-10 of the chart of PSU manufacturing brands, they compete so to improve 12V rail voltage regulation at tighter specification (lesser than 3%).
And therefore 5V rail along 3.3V rail and their wattage combined, this is a small portion of energy compared to the load caused at the 12V rail, which is a much higher quantity of electric energy.
Seasonic at their top models, advertises +/- 0.5% at 12V rail as voltage regulation.
 
80 Plus certification program, this requires 50% of load for PSU efficiency validation.
My new PSU testing platform this is sufficient to test up to 900W PSU unit, but a true high performance AC power meter, this is still missing from the lab.
 

In conclusion, the new build testing setup at my lab, which includes and or combine the use of triple resistive DC load along of my electronic DC load, now delivers to me a wide range of choices at load testing.
Both DC load unit’s they now offer to me a combination of settings (adjustments and control), along of the ability for me to adjust or fine-tune the testing load with a great precision if this is required.

[overvolt]

Some one might think this project as the poor man testing DC load, I have news for you, analog electronics helped science to build or develop first tools for space technology and to explore outer space.
Now feel free to build or become a maker of your own spaceship. 

Do not bother with what others might think.
Very few own such a well organized workshop (mini factory) as you do.
The end-product this is second to none, and it can won an award at any DIY contest.   

[Andrew-88]

Therefore combined two DC loads, can do 80Plus efficiency testing up to 900W PSU. 
How many more secrets you do have under your sleeve?

 

[Kiriakos GR]

Thank you both for the delivery of positive energy!

Now I feel satisfied and I can move on. 

[Kiriakos GR]

Both DC load unit combined as one, they can now stress the 12V rail up to 32.27A.
Combined use of loads can stress any computer power supply up to 440.21 VA and or 440.21 DC Watt.

Today I have all the answers about how total loading capacity due both loads 440.21 DC Watt., this translate as wattage at input AC Side.
Due the fact that entire DC load this is resistive,  even one low-cost power meter this can measure energy at minimum error.

Resistive load alone = All rails combined 327.41 VA   
Programmable load = 11.5V at 9.0A =  103.5 VA
Total = 430,91 VA
AC side this measured  476.6 Watt ( input 235V AC)
AC side this measured  745.1 W   ( input 90V AC)


In conclusion, the combined loads at DC side, this is of what exactly required for 750W PSU (at the label) testing.
Especially when testing input voltages at the range 90 ~ 240V AC.
When I did the original design, of Triple Rail DC dummy load , I could not calculate or foreseen, PSU loading behavior at 120V AC and or lower.