|
ATANASI JORNET wrote: Hi everybody: In the program femm how could we force the program to use the non-linear B-H curve to simulate the motor at f=0.02 Hz. This kind of problem is time-harmonic analysis. Archive attached How could we calculate losses by eddy currents and hysteresis? I did two runs as you said, for rotor losses at 0,5Hz and for the stator losses at 50Hz multiplying the resistivity of all materials of rotor bay 100, but the losses are very small. Can affect the linearity to the solution?Currently, time harmonic problems only admit linear materials. If you specify a nonlinear material, the program ignores the BH curve and uses whatever has been entered in the edit boxes for linear permeability. It is possible to approximate the effects of nonlinear materials by just considering the effect on the fundamental and neglecting higher order harmonics. (See, for example, G. Paoli, O. Biro, and G. Buchgraber, "Complex representation in nonlinear time harmonic eddy current problems," IEEE Transactions on Magnetics, 34(5):2625-2628, September 1998) This seems like it might be a useful kludge, and I've been thinking about adding it in for a while. However, this is a non-trival change (and my computer at home has crashed), so I can't really say when this capability will be added. As far as the example that you've attached, I don't think you can adequately model your machine in femm as-is. All the flux leaks through the iron closing the rotor slots (with a predicted peak flux density of 5.3 T), giving unrealistic results. You might be able to head-scratch and figure out some sort of equivalent machine with open rotor slots that is "close enough" to your machine. In "real life," this iron would saturate out pretty early on, forcing flux to link the rotor bars. The eventual version with nonlinear time harmonic capabilities would address your problem, however. Dave.
|
begin:vcard n:Meeker;David tel;fax:781-890-3489 tel;work:781-684-4070 x-mozilla-html:TRUE url:http://members.aol.com/_ht_a/dcm3c org:Foster-Miller, Inc.;Electrical and Electronic Systems Group version:2.1 email;internet:dmeeker@xxxxxxxxxxxxxxxxx title:Senior Engineer adr;quoted-printable:;;350 Second Avenue=0D=0A;Waltham;MA;02451-1196;USA fn:David Meeker, Ph.D. end:vcard