Capacitors, Capacitance

Thread Starter

PaulEngineer

Joined Dec 21, 2016
217
Let's think! Hmm its a difficult question because I haven't learned this yet, but I will give it a try:

We need to know the basic, the full wave rectification:

Vdc=2Vm/π=0,637V=0,9Vrms

The full wave bridge rectifying power supply can be calculated by the following formula:

Say, we have frequency equal to 50Hz
V(ripple)=I(load)/f*C

Let's think here:

I(load)=U/R(load)*=>
I(load)=12VDC/12Ω=1A(load)

So:

U(ripple)=I(load)/f*C=>
U(ripple)=1/50*6800=136V(ripple)



*I don't know if I did it correct but let's hope I will learn at least ;-)
 

MrChips

Joined Oct 2, 2009
34,812
Let's think! Hmm its a difficult question because I haven't learned this yet, but I will give it a try:

We need to know the basic, the full wave rectification:

Vdc=2Vm/π=0,637V=0,9Vrms

The full wave bridge rectifying power supply can be calculated by the following formula:

Say, we have frequency equal to 50Hz
V(ripple)=I(load)/f*C

Let's think here:

I(load)=U/R(load)*=>
I(load)=12VDC/12Ω=1A(load)

So:

U(ripple)=I(load)/f*C=>
U(ripple)=1/50*6800=136V(ripple)



*I don't know if I did it correct but let's hope I will learn at least ;-)
Not bad but not quite right. You made two mistakes.

1) You can't get 136V ripple if the DC voltage is 12V.
2) This is full-wave rectification.
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
217
Then I don't know how to calculate this! Because in my school we just started to learn about capacitors! I don't know! I think I will try to learn harder! I will try to calculate it again!
 

MrChips

Joined Oct 2, 2009
34,812
For full-wave rectified AC, the ripple voltage is approximately

ΔV = I/(2fC)

Do you know how to arrive at this formula? That will make a good exercise.

You got it almost right the first time. Check your calculation again.
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
217
Ok I will try my best! So the calculation with this formula that I just learned is:

ΔV=I/(2fC)

As I calculated at the first time, I took this results:

Vdc=2Vm/π=0,637V=0,9rms

(Here I made a mistake) so the right calculation is

Say we have frequency about 50Hz, so:

ΔV=I/(2fC)

We don't know the I so we calculate:

I=U/R=>
I=12/12=
I=1A

So:
ΔV=1/(2*50*6800)=1.47V
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
217
Oooh! I've did the false formula! Hahahahahaha XDDDD! I didn't put the "2" in formula! That was fault calculation! Thanks MrChips
 

MrChips

Joined Oct 2, 2009
34,812
Oooh! I've did the false formula! Hahahahahaha XDDDD! I didn't put the "2" in formula! That was fault calculation! Thanks MrChips
No. Worse than that. You made a terrible mistake in your calculation.

Something else you should take away from your mistake.
Does the result make sense?
Does 136V ripple seem right to you?
Always question your result.
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
217
Here I should to say I was not quiet sure for my answer but as you said at the first time when I calculated it, I saw that, the result way bigger than I thought! I couldn't believe at the 1st time the result, and thought that it was right calculation! When you tried to say that the result is actually not bigger than 12, I thought maybe you are right! So I get hard learning about this! I saw your formula in the books but thought, this formula shouldn't be that formula as he saying! But when you post the formula that I missed, I didn't knew how to react XDDDDD! All this reading and I missed the basic formula XDDDD! But from this reading I learned much things! I can't believe in my eyes that I just found what actually makes the antenna work! It was the LC provision XDDDDDD (I know that the LC provision can be used for many applications but this is one of them XDDDDD) I just can't believe that all this time the answer was "right under my nose"! I have found why actually the RC provision is needed and what role its playing on the circuits! Sometimes its very important to learn from my mistakes because this mistakes will give me better knowledge! The electronics is very interesting occupation! I love it! And I will try my best to get a better knowledge, so as to from my series I will learn someone who needs help! That is my spirit! And I wish the better future for the AAC!

And all that thanks to you MrChips! Not just thanks to you but for all the representatives of AAC! You try very hard to guide someone who needs help, but for me the AAC, is something that solves my problems! Maybe I am rude sometimes, something that i try to change to myself, but I never forget the good things that other makes to me, so that in future I will multiply this good things and will reciprocate it one day :')!

Thank you very much, and I hope this website will be the 1st in the World!!

PaulEngineer
As known as
MEGADRAGSTER 288 the fired wolf
XDDDD
 
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