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harmonic perturbation
Posted 2013年2月26日 GMT-5 10:03 Low-Frequency Electromagnetics Version 4.3a 5 Replies
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I assigned a 1 A current to a cylinder in mf physics using multi-turn coil and solved it with a 60Hz frequency using frequency domain. If I assign 0.1 A to the harmonic perturbation under this coil, what is this current actually? if this "harmonic perturbation" is a harmonic order, why we can not set the order of harmonic?
if this is not an harmonic order, how can we assign harmonic order {A(60Hz)+B(120Hz)} to a coil in frequency domain study.?
Regards,
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i believe there is a confusion on the term "harmonic" here for me, what COMSOL defines as the "harmonic perturbation" is a frequency domain amplitude (the "harmonic value) that adds to the static (1[A] in your case) load value
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Good luck
Ivar
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frequency domain means for a given frequency defined in the solver tab frequency entry, where you can define a range and it will sweep over that frequency range.
if you want to add 2 "harmonics" or two frequencies, hence also of 2 amplitudes you need to go to time domain I believe, and find a way to get rid of the initial conditions ringing before getting to a steady state case.
On the other hand you might be able to say your model is frequency independent and then do a frequency sweep/scan and then manually add the two results from the two frequencies
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Good luck
Ivar
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by the way, it's still nonsense for me to apply amplitude coil current in mf and then add harmonic perturbation in frequency domain. simply, the former should be dc and the latter should be ac. so when I apply zero to the former one and an amount to the latter one, it should work but the fields would be zero in this case. I'am really confused.
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I aould call it a "bug" perhaps a weakness that your load case is not pre-cooked. I agree it makes sens to have several modes. but these you can also add up one at the time.
For me the most important is to go back to the equations, be sure they remain consistent (among all physics too), as now this is the cas , then decompose your load case such to see what to do on the equations.
Otherwise it becomes a black-box ala A... where somebody has impleemented a give model set-up with limiting hypothesis that are wery difficult to chekc if we are in or out
The rule: a Freuqcy domain solving sets ALL right hand load values to amplitudes. The "harmic" add-on node adds up a small variation ontop of the basic one, and if you check the solver, it applies first a stationary (DC) case, then the frequency domain and here the harmonic nodes adds in. Check the doc ;)
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Good luck
Ivar