Power Supply Efficiency Formula - Calculate Power Supply Efficiency

[Kiriakos GR]

The huge downsize of our WWW this is copy paste and reprint of inaccurate information from piss-poor Blogs.

I was after Power Supply Efficiency Formula, and I did find the correct answer after a fifth attempt. 

Formula: Efficiency = (Energy input / output) x100 %

To better explore this, let's start from the DC side of my New triple DC load-tester  https://www.ittsb.eu/forum/index.php?topic=1745.0


12V  Rail = 11.90V x 21.8A  = 259.4   Watt
5V    Rail = 5.04     x 6.9A    =   34.77 Watt
3.3V Rail = 3.20     x 5.8A    =   18.56

DC SUM = 312.73 VA = Watt

AC Power meter measurement 373.4 Watt  

Efficiency =  312.73 (Input) / 373.4 Output = 0,8375200856989823   x100 =  83,75 200856989823 %


In order for us to have good clues of measured accuracy, we need to be aware first of measuring uncertainty range.
In this example the worst performer is the AC Power meter with +/_ 2%

[Andrew-88]

What was the mistake that you did find at the wrong formula?

But wait, the only thing that can go wrong this is Energy input / output, this to be reversed.
The reversed formula will give 119% instead ..     

So the NEW triple DC load, this is now verified as be successful 

[Kiriakos GR]

What was the mistake that you did find at the wrong formula?

But wait, the only thing that can go wrong this is Energy input / output, this to be reversed.
The reversed formula will give 119% instead ..     

So the NEW triple DC load, this is now verified as be successful 

All true about the formula. 
When I did use the wrong one and got 119%, my first thought was WTF is going on ? 

The triple DC load due the simplicity of the electrical design, it will deliver named VA-Watt load, at every PSU that all voltage rails does not sag under load, below the named output.
For example, original design calculation for 12V rail = 12.100V x 22A  = 266,2 VA | Watt 
Another parameter this is warm-up time of the Load-tester prior taking seriously any measurements.
I am going to need few more days, for testing and so to understand of how I should use it as comparison point.

[Andrew-88]

Good to know !! 

Thanks mate.