Complex Imaginary Test 1 Problem 70

[BamaBino]

CI's solution says that Vab is the same as the line-line voltage of the AC source. And the answer is 125V*sqrt(3)=217V choose (D).

I disagree. It is asking for the PEAK VOLTAGE, which is never greater the 125V*sqrt(2) = 177 V.

Thanks.

 

[rick.conner]

I emailed josh 10/12 on this and have not heard back. once I do I will post his response. Hopefully someone will verify what you and I think.

 

[BamaBino]

I emailed josh 10/12 on this and have not heard back. once I do I will post his response. Hopefully someone will verify what you and I think.

Do you agree that the peak-voltage would be 177V ?

 

[Wildsoldier PE]

I think that diagram have something weird...if you look closely he have phase a, b and C touching the same point without passing thru any load....isn't that supposed to create a 3phase fault? I could be wrong...i'm not a power electronics expert.

 

[rick.conner]

Bama-bino: yea I agree with your answer though this definitely my worse subject.

 

[rick.conner]

I just emailed Josh again asking about for the solution. If I don't hear a response by tomorrow morning I'll email the GA Tech person whom is very quick at responding.

 

[ElecPwrPEOct11]

I emailed josh 10/12 on this and have not heard back. once I do I will post his response. Hopefully someone will verify what you and I think.

Do you agree that the peak-voltage would be 177V ?

I had an issue with this question too. This problem shows a rectifier which has a DC output = input line voltage. So I agree with CI's answer that Vab will be the same as the line voltage, or sqrt(3) * 125 = 217V. However this is the rms value. The problem asks for the peak voltage which will be 217 * sqrt(2) = 307V.

 

[DK PE]

I had an issue with this question too. This problem shows a rectifier which has a DC output = input line voltage. So I agree with CI's answer that Vab will be the same as the line voltage, or sqrt(3) * 125 = 217V. However this is the rms value. The problem asks for the peak voltage which will be 217 * sqrt(2) = 307V.

I arrive at the same answer but maybe thinking differently ... For a six pulse 3Φ rectifier I believe the peak output voltage is √2 * Erms-line

I see a tiny Φ in the 125 = VΦ in problem statement which could lead me to believe that it is a line-neutral voltage.

My best answer is therefore peak voltage is √2 * 125 * √3 = 306V but I acknowledge this isn't my strongest area.