[Getdp] Permanent magnet in GetDP

Wed Aug 9 16:45:38 CEST 2017

Hi Jasper, 

Thanks for your answer. This is a good news ! However, at lunch time I thought about it a bit more and figured out that one has to take into account the fact that a permanent magnet is anisotropic and therefore we should use a permeability tensor instead of a scalar constant ... this will make the formulation much more complicated ! 

Cheers, 

Gilles 

> De: "Jasper" <funkybob at gmail.com>
> À: "Gilles Quéméner" <quemener at lpccaen.in2p3.fr>
> Cc: "getdp" <getdp at onelab.info>
> Envoyé: Mercredi 9 Août 2017 16:37:12
> Objet: Re: [Getdp] Permanent magnet in GetDP

> Hi Gilles,
> Your suggestion is typically the way I've done it in the past, specify by HcB
> and mu_r. From my understanding, in a NdFeB magnet at low temperatures this
> linear relation should be valid and the results have appear plausible so far
> :-)
> Keep in mind that once the relatively small difference between e.g. N40 and N42
> starts to matter in your simulation you should really consult your magnet
> supplier as the magnets typically have tolerances and are also not completely
> homogenous etc...

> Best regards,

> Jasper

> On Wed, Aug 9, 2017 at 11:55 AM, gilles quemener < [
> mailto:quemener at lpccaen.in2p3.fr | quemener at lpccaen.in2p3.fr ] > wrote:

>> Hi,

>> Following my previous message, I digged more into the .pro files of GetDP demos
>> magnet.xxx
>> and it seems that one could perhaps use both Hc and µ_r to distinguish between
>> NdFeB magnets grades.
>> In GetDP demos, the permanent magnets material could be defined as in
>> MaterialDatabase.pro w/
>> the following lines :

>> // NdFeB magnet N45
>> Materials() += Str[ "NdFeB_Grade_N45" ];
>> NdFeB_mur = 1.172; // Br = 1370 mT, Hcb = 930000 A/m and µ_r = Br / Hcb / µ_o
>> NdFeB_sigma = 2e5;
>> NdFeB_hc = 930000;

>> where µ_r and Hcb values have been taken from the ttypical table below.
>> Could anyone confirm or infirm this approach ?

>> 	Remanence
>> 	coercivity
>> 	coercivity
>> 	product

>> 	Br
>> 	Hcb
>> 	Hcj
>> 	B H max
>> 	µ = Br / Hcb 	µ_r= µ / µo

>> 	mT
>> 	kA/m
>> 	kA/m
>> 	kJ/m3
>> 	T/A/m

>> 	min 	typ 	min 	typ 	min 	min 	typ 	°C

>> N-35 	1170 	1120 	870 	920 	955 	263 	279 	80 	1.217391E-06 	0.969
>> N-38 	1220 	1260 	870 	920 	955 	279 	303 	80 	1.369565E-06 	1.090
>> N-40 	1260 	1300 	870 	920 	955 	303 	318 	80 	1.413043E-06 	1.124
>> N-42 	1300 	1330 	870 	920 	955 	318 	334 	80 	1.445652E-06 	1.150
>> N-45 	1330 	1370 	900 	930 	955 	334 	358 	80 	1.473118E-06 	1.172
>> N-48 	1370 	1410 	900 	930 	875 	358 	382 	80 	1.516129E-06 	1.206
>> N-50 	1410 	1440 	830 	850 	875 	382 	398 	80 	1.694118E-06 	1.348
>> N-52 	1430 	1480 	820 	840 	875 	398 	422 	80 	1.761905E-06 	1.402
>> N-33M 	1140 	1170 	830 	859 	1114 	239 	263 	100 	1.362049E-06 	1.084
>> N-35M 	1170 	1220 	870 	891 	1114 	263 	279 	100 	1.369248E-06 	1.090
>> N-38M 	1220 	1260 	900 	915 	1114 	279 	303 	100 	1.377049E-06 	1.096
>> N-40M 	1260 	1300 	930 	915 	1114 	303 	318 	100 	1.420765E-06 	1.131
>> N-42M 	1300 	1330 	950 	915 	1114 	318 	334 	100 	1.453552E-06 	1.157
>> N-45M 	1330 	1370 	980 	915 	1114 	334 	358 	100 	1.497268E-06 	1.191
>> N-48M 	1370 	1410 	1010 	980 	1114 	358 	382 	90 	1.438776E-06 	1.145
>> N-50M 	1410 	1440 	1030 	980 	1114 	382 	398 	90 	1.469388E-06 	1.169
>> N-30H 	1080 	1140 	810 	810 	1353 	223 	239 	120 	1.407407E-06 	1.120
>> N-33H 	1140 	1170 	830 	830 	1353 	239 	263 	120 	1.409639E-06 	1.122
>> N-35H 	1170 	1220 	870 	870 	1353 	263 	279 	120 	1.402299E-06 	1.116
>> N-38H 	1220 	1260 	900 	900 	1353 	279 	303 	120 	1.400000E-06 	1.114
>> N-40H 	1260 	1300 	930 	930 	1353 	303 	318 	120 	1.397849E-06 	1.112
>> N-42H 	1300 	1330 	950 	950 	1353 	318 	334 	120 	1.400000E-06 	1.114
>> N-44H 	1330 	1360 	970 	970 	1353 	334 	350 	120 	1.402062E-06 	1.116
>> N-46H 	1360 	1380 	980 	980 	1353 	350 	366 	120 	1.408163E-06 	1.121
>> N-48H 	1380 	1410 	1010 	1060 	1353 	366 	382 	120 	1.330189E-06 	1.059
>> N-30SH 	1080 	1140 	810 	860 	1592 	223 	239 	150 	1.325581E-06 	1.055
>> N-33SH 	1140 	1170 	830 	880 	1592 	239 	263 	150 	1.329545E-06 	1.058
>> N-35SH 	1170 	1220 	870 	920 	1592 	263 	279 	150 	1.326087E-06 	1.055
>> N-38SH 	1220 	1260 	900 	950 	1592 	279 	303 	150 	1.326316E-06 	1.055
>> N-40SH 	1260 	1300 	930 	980 	1592 	303 	318 	150 	1.326531E-06 	1.056
>> N-42SH 	1300 	1330 	950 	1000 	1592 	318 	334 	150 	1.330000E-06 	1.058
>> N-44SH 	1330 	1360 	970 	1020 	1592 	334 	350 	150 	1.333333E-06 	1.061
>> N-28UH 	1040 	1080 	770 	810 	1989 	199 	223 	180 	1.333333E-06 	1.061
>> N-30UH 	1080 	1140 	810 	860 	1989 	223 	239 	180 	1.325581E-06 	1.055
>> N-33UH 	1140 	1170 	830 	880 	1989 	239 	263 	180 	1.329545E-06 	1.058
>> N-35UH 	1170 	1220 	870 	920 	1989 	263 	279 	180 	1.326087E-06 	1.055
>> N-38UH 	1220 	1260 	900 	950 	1989 	279 	303 	180 	1.326316E-06 	1.055
>> N-40UH 	1250 	1280 	900 	950 	1989 	302 	326 	180 	1.347368E-06 	1.072
>> N-28EH 	1040 	1080 	770 	810 	2387 	199 	223 	200 	1.333333E-06 	1.061
>> N-30EH 	1080 	1140 	810 	860 	2387 	223 	239 	200 	1.325581E-06 	1.055
>> N-33EH 	1140 	1170 	830 	880 	2387 	239 	263 	200 	1.329545E-06 	1.058
>> N-35EH 	1170 	1220 	870 	920 	2387 	263 	279 	200 	1.326087E-06 	1.055
>> N-38EH 	1220 	1260 	900 	950 	2387 	279 	303 	200 	1.326316E-06 	1.055
>> N-25AH 	970 	1020 	730 	770 	2787 	180 	200 	220 	1.324675E-06 	1.054
>> N-28AH 	1040 	1080 	770 	810 	2787 	203 	218 	220 	1.333333E-06 	1.061
>> N-30AH 	1080 	1140 	810 	860 	2787 	220 	250 	220 	1.325581E-06 	1.055
>> N-25BH 	950 	1000 	710 	750 	3000 	170 	190 	230 	1.333333E-06 	1.061
>> Data upto temperature column from :

>> [
>> http://www.goudsmitmagnets.com/magnets-assemblies/permanent-magnets/neodymium-magnets-ndfeb/neodymium-magnets-ndfeb
>> |
>> http://www.goudsmitmagnets.com/magnets-assemblies/permanent-magnets/neodymium-magnets-ndfeb/neodymium-magnets-ndfeb
>> ]

>> Cheers,

>> Gilles

>>> De: "Gilles Quéméner" < [ mailto:quemener at lpccaen.in2p3.fr |
>>> quemener at lpccaen.in2p3.fr ] >
>>> À: "getdp" < [ mailto:getdp at onelab.info | getdp at onelab.info ] >
>>> Envoyé: Mercredi 9 Août 2017 10:21:31
>>> Objet: Permanent magnet in GetDP

>>> Hi,

>>> When simulating permanent NdFeB magnets in a homemade BEM program, I use a
>>> permeability of 1.05 and a remanent magnetization/field
>>> depending on the magnet grade as given for instance in the following table :

>>> Minimum Values
>>> Grade Br Hc (Hcb) Hci (Hcj) BHmax
>>> (T) (kA/m) (kA/m) (kJ/m³)
>>> N27 1.030 796 955 199
>>> N30 1.080 796 955 223
>>> N33 1.130 836 955 247
>>> N35 1.170 867 955 263
>>> N38 1.210 899 955 287
>>> N40 1.240 923 955 302
>>> N42 1.280 923 955 318
>>> N45 1.320 875 955 342
>>> N48 1.380 836 875 366
>>> N50 1.400 796 875 382
>>> N52 1.430 796 875 398

>>> Looking closer to the magnet.xxx files in the GetDP demos folder, I cannot
>>> figure out how the
>>> remanent magnetization is taken into account as only Hc seems to be used in the
>>> material definition.
>>> I would think that both Hc and Br should be used.
>>> How would one distinguish between N40 and N42 grades which have the same Hc
>>> values ? How the fact
>>> that an N50 magnet has a larger remanent field than an N40 one is accounted for
>>> in GetDP when
>>> Hc(N50) is smaller than Hc(N40) and equal to Hc(N27) ?

>>> Thanks a lot for any hints,

>>> Gilles

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