Power supply Computation help please

[enigma^6]

Hi guys,

can someone check if i did this right? I've been trying to search for this type of power supply computation but i still haven't find any. I only used formulas i found from the internet and boylestad book...

using C= 100 micro
RL=200 ohm

If someone has a link to a computation of the same power supply ckt i'd really really appreciate it

another question is on rectifier part.. if Vrms is DC equivalent of Vac by definition how come VRMS is not equal to VDC? what's the difference. I understand that VR(RMS) from filter is different from VDC filter since ripple did not begin at V=0. But i am confused with rectifier

I'm also not so sure with the RS i got.

Thanks everyone

kat

[/img]:?:

 

[kiprono]

Vrms is equal to an equivalent dc value that would cause the same heating effect (i.e transfer same amount of energy) on a resistor. This is when the load is connected directly to the source and not through a rectifier or filter. The rectification efficiency of the converter which is less than 100% leads to losses hence output Vdc is not equal to output Vrms.

 

[enigma^6]

i see, rectification efficiency must be really low then approx 50% since Vr(rms) is around half of Vdc. I will also browse rectification eff. Thanks kiprono

how about my computation... anyone? did i use the right Vm = 29.17 (from rectifier output to regulator input)

i'm studying by myself... no teachers/classmates to ask ... just edaboard, boylestad and whatever i can find on the net

Thanks again

+kat

 

[kiprono]

Vdc is right.
But Vrms is wrong. Vrms=Vm/sqrt(2)=29.7/(sqrt(2)=21.0V;

 

[enigma^6]

Hmmm..

I think Vrms=Vm/sqrt(2) is used for Sinusoidal AC (with positive and negative half cycle)

From Boylestad & Nashesky 7th ed. appendix B

Vr(rms) = (V^2(rms) - V^2 dc) ^1/2
Vr(rms) = 0.308Vm (for full wave rectifier)
Vr(rms) = 0.385Vm (for halfwave rectifier)

 

[kiprono]

What you've just given is the rms of the ac component in the output voltage i.e. rms of the ripple. It seems Vr (or Vac) in your expression means ripple voltage and not output rms voltage of the rectifier.
The rms of the full-wave rectified output (both pulses positive) is the same as for the sine wave (with negative n +ve pulses).
(Vrms)=√[(Vdc)²+(Vac)²]

Get an introductory book on power electronics at the e-books upload/download section.

 

[jrguy8]

Vrms AC is equal to Vrms DC which is the rectified output. you wont get the same value in actual because there's already a filter, and the Vrms depends on the capacitor used because it controls the ripple, lesser ripple more closeness to Vm the value of Vdc.

 

[enigma^6]

@kiprono

OOOOOOHHHHHHHHHHH
V(rms) = Vrms=Vm/sqrt(2) is different from
Vr(rms) = 0.308Vm (for full wave rectifier)


thanks kiprono... you're really a big help!
any comment on my filter and regluator computation??

I saw some Power Electronics: Converters, Applications, and Design on e-books/download section... i will need to earn more points first then i will download it. you have any other recommendation ?

Thank you thank you!!!

@jrguy
thanks

 

[Help]

Hi enigma^6,

How many points you need to download the book? If you interested to gain the knowledge from this book. I will try to donat some point's for you to download the book.

Bst Rgd,
Help

 

[kiprono]

I would recommend this book: Power Converter Circuits by WILLIAM SHEPHERD and LI ZHANG found below:



Use the free mirror. You dont need any points for this.

 

[enigma^6]

Hi enigma^6,

How many points you need to download the book? If you interested to gain the knowledge from this book. I will try to donat some point's for you to download the book.

Bst Rgd,
Help

@help

kiprono recommended an e-book which only needs 5 pts Thanks anyway... that's very kind of you

Added after 29 seconds:

I would recommend this book: Power Converter Circuits by WILLIAM SHEPHERD and LI ZHANG found below:



Use the free mirror. You dont need any points for this.

THANKS