Material

Conductors

The conductors is a list of dict items that describe the material properties of

Name	Unit	Description
name		identifier
desc
spmaweight	g/cm³	specific mass (density)
elconduct	S/m	electrical conductivity at 20°C
tempcoef	1/K	temperature coefficient
thcond	W/(m K)	thermal conductivity
thcap	J/K	thermal capacity

Example:

condMat = [
  {"name": "Al", "spmaweight": 2.7,
   "elconduct": 33e6, "tempcoef": 3.9e-3},
  {"name": "Cu", "spmaweight": 8.96,
   "elconduct": 56e6, "tempcoef": 3.9e-3} ]

Magnetizing Curve

The MagnetizingCurve is a container of magnetizing curves (eg. lamination or PM material) that can be referenced by the model mcvkey attributes. It can either point to a directory of MC/MCV-File or hold a list of magnet curves which are identified by name.

Each magnetizing curve is described by the following properties

Attribute	Description	Unit	Default
name	Identifier of this curve
ctype	Type of curve		1
desc	Description
curve	List of dictionaries with bi (list of induction values) hi (List of field strength values) and angle which can be missing in case of 1 curve	T, A/m, deg
ch	hysteresis loss factor		0
cw	eddy current loss factor		0
ch_freq	hysteresis exponent		0
cw_freq	eddy-current exponent		0
b_coeff	induction loss exponent		0
Bo	reference induction	T	1.5
fo	reference frequency	Hz	50
fillfac	iron fill factor		1
bsat	saturation induction	T	2.15
rho	specific weight	kg/dm3	7.65
losses	dict of loss values (optional)

The loss factors and exponents are used in the Jordan loss calculation formula:

(cw*(f/fo)**cw_freq + ch*(f/fo)**ch_freq)*(B/Bo)**b_coeff

The Reader object which is included in the mcv module can be used to read MCV/MC files.

Permeability and polarisation calculation example:

MUE0 = 4e-7*math.pi

mcv = femagtools.mcv.Reader()
mcv.readMcv('magnetcurves/M270-35A.MCV')
r = mcv.get_results()

bh = [(bi, hi)
      for bi, hi in zip(r['curve'][0]['bi'],
                        r['curve'][0]['hi']) if bi > 0 and hi > 0]

ji = [b-MUE0*h for b, h in bh]
muer = [bx/hx/MUE0 for bx, hx in bh]

Using a magnetizingcurve to write a mcv file:

mcvData = dict(curve=[ dict(
   bi=[0.0, 0.09, 0.179, 0.267, 0.358,
       0.45, 0.543, 0.6334, 0.727,
       0.819, 0.9142, 1.0142, 1.102,
       1.196, 1.314, 1.3845, 1.433,
       1.576, 1.677, 1.745, 1.787,
       1.81, 1.825, 1.836],

    hi=[0.0, 22.16, 31.07, 37.25, 43.174,
        49.54, 56.96, 66.11, 78.291,
        95, 120.64, 164.6, 259.36,
        565.86, 1650.26, 3631.12, 5000, 10000,
        15000, 20000, 25000, 30000, 35000, 40000]
    )],
    name='m270-35a',
    desc=u"Demo Steel",
    ch=4.0,
    cw_freq=2.0,
    cw=1.68)

 mcv = femagtools.mcv.MagnetizingCurve(mcvData)

 mcv.writefile('m270-35a')

Note

if the curve data is used in a stator or magnet slot model there is no need to create the file explicitly. Femagtools will take care of that during the model creation.

Loss Values:

Key		unit	dim.
B	list of flux density values	T	n
f	list of frequency values	Hz	m
pfe	list of loss values		nxm
cw	eddy current loss coeff
cw_freq	eddy current exp
b_coeff	flux density exp
fo	base frequency
Bo	base flux density

Example:

{"B": [0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.8],
 "f": [50.0, 400.0, 1000.0],
 "pfe": [[0.08,  0.29, 0.56, 0.92, 1.44, 2.25, 2.94],
         [0.137, 4.73, 9.87, 20.3, 31.7],
         [5.5,  18.5, 25.8,  71.5]],
 "cw": 1.248, "cw_freq": 1.6631, "b_coeff": 2.19661, "fo": 50.0, "Bo": 1.5}

Note

missing values are extrapolated using the steinmetz formula

Magnet Material

list of dict objects each having a unique name (or id) and a set of parameters that describe the magnet properties.

Parameter	Description	Default	Unit
name	Name of magnet material
mcvkey	name of nonlinear B(H) curve
orient	Magnetizing orientation	cartiso
rlen	Relative length	1.0
remanenc	Remanence Induction Br		T
relperm	Relative Permeability
spmaweight	Specific Mass	7500	kg/m³
temcoefbr	Temperature Coefficient of Br	-0.001	1/K
temcoefhc	Temperature Coefficient of Hc	-0.001	A/m/K
magntemp	Magnet Temperature	20	°C
magncond	Electr. Conductivity	625000	S/m
magnwidth	Magnet segment width (obsol.)	0.0	m
magnlength	Magn. segment length (obsol.)	0.0	m
magnsegwidth	Magnet segment width	0.0	m
magnseglength	Magnet segment length	0.0	m

Note

• name must be unique within list. It may be used as reference in the magnet model of the machine.

  Example:

  magnets = [dict(name='MX-333', remanenc=1.2, relperm=1.05)]
  

• mcvkey is used for material that have a non-linear BH curve.

• the key orient describes the field orientation (mcartiso, mpoliso, martaniso, mpolaniso)

• rlen defines the relative length

  Example:

  magnets=[dict(name='BH53M', mcvkey='BH53M',
                orient='mcartiso', rlen=1.0)]
  

• The mcvkey can either reference a file or an entry in the magnetizing curve dict.