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')
../../../_images/mcv.png

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

../../../_images/loss.png

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.