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| Synchronous motor rotor excitation effect on current draw |
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| duak:
I had a different reply here originally but wasn't happy with it. I googled "synchronous motor line current vs excitation" and got a bunch of interesting results. One of which is "synchronous motor V curves". I didn't specialize in power but it did ring a bell once I saw the shape of the curves. I looked that up: https://en.wikipedia.org/wiki/V_curve Bottom line, line current increases, power factor changes and in some cases the motor may become unstable and probably stalls. It looks like these curves are determined empirically and one would need much more detailed information to get anything more than a rough number. As an aside, my sons are in high school and sometimes have trouble with math and physics. I swear that sometimes the questions are written in authentic frontier gibberish because they're so hard to figure out. Once that's done, the problem itself is usually easy. Cheers, |
| Simon:
My problem with this question is that they have not furnished me with the knowledge to answer it properly. So i have to make some assumptions and provide an answer of little practical value. I really wonder with this course if the questions are clever or just lazily put. |
| Simon:
I am confused, If i use trig as per below on my V (239.6) and E (338.85) on my calculator I get 294V instead of 239.4, I did this to test the formula before using it on new values and getting a wrong answer. Yet if i use this online calculator the answer is correct: https://www.calculator.net/triangle-calculator.html?vc=45&vx=239.6&vy=338.85&va=&vz=&vb=&angleunits=d&x=78&y=26 c = √b^2 + a^2 - 2ba·cos(C) = 239.60313 |
| Simon:
And the answer is that I had my calculator on radians not degrees. |
| RudiB:
Hello all, apologies for digging up an old thread but I am stumped also with this question. I can't see a way forward with it and my tutor has basically just told me that it's a trick question (???). Anyway do I actually need to do any calcs for this or just provide a statement, eg. leading PF and lagging PF and that E would change also. Really appreciate any help as I'm keen to put this question to bed as been stuck on it for a good few hours now. Thanks |
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