# NCEES #519 Power



## threatta (Apr 10, 2010)

Can someone please provide a better explination of this solution? What has been posted thus far isn't getting me there. Thanks.


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## CLTEE49 (Apr 10, 2010)

threatta said:


> Can someone please provide a better explination of this solution? What has been posted thus far isn't getting me there. Thanks.


Kaplan gave a good explanation of rectifiers in Chapter 14. The diodes turn on when voltages are positive. I normal three phase rectifier looks like answer (A). You will see a peak when the current in phase a is positive and either the current in phase B or C is also positive. You will see a negative peak when phase a is negative and either b or c is also negative.

With fuse C blown, you will only see a peak when phase A is positive/negative and phase B is also positive/negative.

Hope that makes since..


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## pelaw (Apr 10, 2010)

I think the key to this problem is understanding what is asked. The problem asks ONLY for PHASE A. Not for the circuit.

Second part is understanding that PHASE A will (1) have one peak over a cycle, 1/60s, and (2) one negative peak as it will carry the return current from phase B.


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## threatta (Apr 11, 2010)

Thanks. Those answers make better sense.


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## threatta (Apr 11, 2010)

Thanks. Those answers make better sense.


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## dianevp (Apr 4, 2011)

pelaw said:


> I think the key to this problem is understanding what is asked. The problem asks ONLY for PHASE A. Not for the circuit.
> Second part is understanding that PHASE A will (1) have one peak over a cycle, 1/60s, and (2) one negative peak as it will carry the return current from phase B.


What part does the capacitor play in the current waveform?


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## afacemire (Apr 8, 2012)

check out this applet. it helps:

/&gt;http://services.eng.uts.edu.au/~venkat/pe_html/ch05s1/ch05s1p1.htm


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## JillSuzanne (Apr 2, 2013)

Just as a reality check and going back to being aware of what the question is asking, the_ ia_ that they refer to in the question is not the _ia _that they refer to in the diagram, right?

And Phase A means the Phase A at the motor?


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