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NCEES #519 Power


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#1 threatta

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Posted 10 April 2010 - 08:06 PM

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

#2 CLTEE49

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Posted 10 April 2010 - 11:35 PM

QUOTE (threatta @ Apr 10 2010, 09:06 PM) <{POST_SNAPBACK}>
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..

#3 pelaw

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Posted 11 April 2010 - 12:28 AM

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.

#4 threatta

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Posted 11 April 2010 - 06:29 PM

Thanks. Those answers make better sense.

#5 threatta

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Posted 11 April 2010 - 06:30 PM

Thanks. Those answers make better sense.

#6 dianevp

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Posted 04 April 2011 - 10:17 PM

QUOTE (pelaw @ Apr 10 2010, 07:28 PM) <{POST_SNAPBACK}>
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?


#7 afacemire

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Posted 08 April 2012 - 08:25 PM

check out this applet. it helps:

http://services.eng....s1/ch05s1p1.htm

#8 JillSuzanne

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Posted 02 April 2013 - 10:57 PM

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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