# Half Wave Ractifier



## saw (Oct 13, 2014)

Is the Vrms to Vmax in HWR is (Vrms= Vmax/ sqr2 )or (Vrms= Vmax/2)

I see in PPI book page 27-6 the second formal and on NCEES problem 515 the first formula.

Thanks


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## Ken PE 3.1 (Oct 13, 2014)

it is Vmax/sqrt 2.

The easiest way I found to remeber is that 120V rms = 169 V max.


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## saw (Oct 13, 2014)

in this case the full rectifier and half rectifier Vmax both will be calculated the same way. (Vmax = Vrms X sqr2). Is that correct?


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## ali1361 (Oct 15, 2014)

In HWR Vrms= Vmax/2. Refer to this http://en.wikipedia.org/wiki/Rectifier.


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## saw (Oct 17, 2014)

If Vrms= Vmax/2 per the Wikipedia and PPI, then why NCEES problem 515 is using Vrms= Vmax/ sqr2? I am not sure which one to believe.


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## PEoct (Oct 17, 2014)

yeah true, its so damn confusing,,,,,,,, gurrrrrrrrrrr


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## knight1fox3 (Oct 17, 2014)

First of all (and please don't take this the wrong way), engineering principles should not be extracted from wikipedia. Just because they are there, does not make them right. And that goes for anything on the internet. Go with what's in your references. If you'd like to know more on rectifiers, consult the analog elec book I had, micro-electronic circuits by sedra and smith.


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## dayrongarcia (Oct 19, 2014)

Vrms = Vmax/sqrt(2) per all my reference books.


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## iwire (Oct 23, 2014)

Half-wave

Vrms= Vp/ 2


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## MTO (Oct 23, 2014)

Vrms= Vmax/ sqr2.....from other material out side of Wikipedia


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## Kovz (Oct 27, 2014)

Per the NCEES FE Reference Manual: Page 197

Effective Or RMS Value: For Half-wave rectified sine wave,

Xeff = Xrms = Xman/2


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## Kovz (Oct 27, 2014)

Of course I had a type in the post above this and can't figure out how to edit. Xeff = Xrms = Xmax/2


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## Kovz (Nov 17, 2014)

I ran into this same issue on CI Exam 3, Problem 37.

I am still confused how to treat a HWR. Should it be sqrt2 or 2?


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## KatyLied P.E. (Nov 17, 2014)

Per Graffeo's book, Vmax = Vrms x sqrt 2 (EE's Guide to Passing the Power PE Exam). Vrms = Veff. There maybe an error in your PPI version. I am also looking at section 27-6, example 27.3 in the PPI and it shows sqrt 2. I saw in your original post where you said your PPI shows 2 instead of sqrt2. Mine is the 8th edition.


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## MyBeardAndMe (Mar 21, 2015)

So I ran into the same issue today... doesn't look like anyone has clarification.

PPI says in Table 27.2 (1st edition, 3rd print) that Vrms/Vm is 1/2.

Complex Imaginary and NCEES say sqrt(2)

The PPI Errata does not cover the issue.


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## dayrongarcia (Mar 24, 2015)

Half Wave ----- Vrms = Vp/2

Full Wave ----- Vrms = Vp/sqrt(2)


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## MyBeardAndMe (Mar 27, 2015)

So in NCEES 515, does it not matter if the circuit is half wave or full wave? I agree with dayrongarcia, but in NCEES' explanation for the half wave rectifier, they state reverse voltage is twice the peak value or 2*sqrt(2)


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## Kovz (Mar 27, 2015)

MyBeardAndMe said:


> So in NCEES 515, does it not matter if the circuit is half wave or full wave? I agree with dayrongarcia, but in NCEES' explanation for the half wave rectifier, they state reverse voltage is twice the peak value or 2*sqrt(2)




See page 181 of Graffeo. I don't think it matters if it's full wave or half wave because 115 is asking for the reverse voltage of the diode.


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