Multiphysics: Maxwell 3D - Icepak electrothermal analysis

This example uses PyAEDT to set up a simple Maxwell design consisting of a coil and a ferrite core. Coil current is set to 100A, and coil resistance and ohmic loss are analyzed. Ohmic loss is mapped to Icepak, and a thermal analysis is performed. Icepak calculates a temperature distribution, and it is mapped back to Maxwell (2-way coupling). Coil resistance and ohmic loss are analyzed again in Maxwell. Results are printed in AEDT Message Manager.

Perform required imports

Perform required imports.

import pyaedt
from pyaedt.generic.constants import AXIS

Set AEDT version

Set AEDT version.

aedt_version = "2024.1"

Set non-graphical mode

Set non-graphical mode. You can set non_graphical either to True or False.

non_graphical = False

Launch AEDT and Maxwell 3D

Launch AEDT and Maxwell 3D. The following code sets up the project and design names, the solver, and the version. It also creates an instance of the Maxwell3d class named m3d.

project_name = "Maxwell-Icepak-2way-Coupling"
maxwell_design_name = "1 Maxwell"
icepak_design_name = "2 Icepak"

m3d = pyaedt.Maxwell3d(
    projectname=project_name,
    designname=maxwell_design_name,
    solution_type="EddyCurrent",
    specified_version=aedt_version,
    non_graphical=non_graphical,
)

C:\actions-runner\_work\_tool\Python\3.10.9\x64\lib\subprocess.py:1072: ResourceWarning: subprocess 11996 is still running
  _warn("subprocess %s is still running" % self.pid,
C:\actions-runner\_work\pyaedt\pyaedt\testenv\lib\site-packages\pyaedt\generic\settings.py:383: ResourceWarning: unclosed file <_io.TextIOWrapper name='D:\\Temp\\pyaedt_ansys.log' mode='a' encoding='cp1252'>
  self._logger = val

Create geometry in Maxwell

Create the coil, coil terminal, core, and region.

coil = m3d.modeler.create_rectangle(
    orientation="XZ", origin=[70, 0, -11], sizes=[11, 110], name="Coil"
)

coil.sweep_around_axis(axis=AXIS.Z)

coil_terminal = m3d.modeler.create_rectangle(
    orientation="XZ", origin=[70, 0, -11], sizes=[11, 110], name="Coil_terminal"
)

core = m3d.modeler.create_rectangle(
    orientation="XZ", origin=[45, 0, -18], sizes=[7, 160], name="Core"
)
core.sweep_around_axis(axis=AXIS.Z)

# Magnetic flux is not concentrated by the core in +z-direction. Therefore, more padding is needed in that direction.
region = m3d.modeler.create_region(pad_percent=[20, 20, 500, 20, 20, 100])

Assign materials

Create a material: Copper AWG40 Litz wire, strand diameter = 0.08mm, 24 parallel strands. Assign materials: Assign Coil to AWG40 copper, core to ferrite, and region to vacuum.

no_strands = 24
strand_diameter = 0.08

cu_litz = m3d.materials.duplicate_material("copper", "copper_litz")
cu_litz.stacking_type = "Litz Wire"
cu_litz.wire_diameter = str(strand_diameter) + "mm"
cu_litz.wire_type = "Round"
cu_litz.strand_number = no_strands

m3d.assign_material(region.name, "vacuum")
m3d.assign_material(coil.name, "copper_litz")
m3d.assign_material(core.name, "ferrite")

True

Assign excitation

Assign coil current, coil consists of 20 turns, total current 10A. Note that each coil turn consists of 24 parallel Litz strands, see above.

no_turns = 20
coil_current = 10
m3d.assign_coil(["Coil_terminal"], conductors_number=no_turns, name="Coil_terminal")
m3d.assign_winding(is_solid=False, current=coil_current, name="Winding1")

m3d.add_winding_coils(assignment="Winding1", coils=["Coil_terminal"])

True

Assign mesh operations

Mesh operations are not necessary in eddy current solver because of auto-adaptive meshing. However, with appropriate mesh operations, less adaptive passes are needed.

m3d.mesh.assign_length_mesh(["Core"], maximum_length=15, maximum_elements=None, name="Inside_Core")
m3d.mesh.assign_length_mesh(["Coil"], maximum_length=30, maximum_elements=None, name="Inside_Coil")

<pyaedt.modules.Mesh.MeshOperation object at 0x00000279A5AF9D80>

Set conductivity temperature coefficient

Set conductivity as a function of temperature. Resistivity increases by 0.393% per K.

cu_resistivity_temp_coefficient = 0.00393
cu_litz.conductivity.add_thermal_modifier_free_form("1.0/(1.0+{}*(Temp-20))".format(cu_resistivity_temp_coefficient))

True

Set object temperature and enable feedback

Set the temperature of the objects to default temperature (22deg C) and enable temperature feedback for two-way coupling.

m3d.modeler.set_objects_temperature(["Coil"])

True

Assign matrix

Resistance and inductance calculation.

m3d.assign_matrix(["Winding1"], matrix_name="Matrix1")

<pyaedt.modules.Boundary.MaxwellParameters object at 0x00000279A5AF9FC0>

Create and analyze simulation setup

Simulation frequency 150kHz.

setup = m3d.create_setup(name="Setup1")
setup.props["Frequency"] = "150kHz"
m3d.analyze_setup("Setup1")

True

Postprocessing

Calculate analytical DC resistance and compare it with the simulated coil resistance, print them in the message manager, as well as ohmic loss in coil before temperature feedback.

report = m3d.post.create_report(expressions="Matrix1.R(Winding1,Winding1)")
solution = report.get_solution_data()
resistance = solution.data_magnitude()[0]

report_loss = m3d.post.create_report(expressions="StrandedLossAC")
solution_loss = report_loss.get_solution_data()
em_loss = solution_loss.data_magnitude()[0]

# Analytical calculation of the DC resistance of the coil
cu_cond = float(cu_litz.conductivity.value)
# average radius of a coil turn = 0.125m
l_conductor = no_turns*2*0.125*3.1415
# R = resistivity * length / area / no_strand
r_analytical_DC = (1.0 / cu_cond) * l_conductor / (3.1415 * (strand_diameter / 1000 / 2) ** 2) / no_strands

# Print results in the Message Manager
m3d.logger.info("*******Coil analytical DC resistance =  {:.2f}Ohm".format(r_analytical_DC))
m3d.logger.info("*******Coil resistance at 150kHz BEFORE temperature feedback =  {:.2f}Ohm".format(resistance))
m3d.logger.info("*******Ohmic loss in coil BEFORE temperature feedback =  {:.2f}W".format(em_loss / 1000))

Icepak design

Insert Icepak design, copy solid objects from Maxwell, and modify region dimensions.

ipk = pyaedt.Icepak(designname=icepak_design_name)
ipk.copy_solid_bodies_from(m3d, no_pec=False)

# Set domain dimensions suitable for natural convection using the diameter of the coil
ipk.modeler["Region"].delete()
coil_dim = coil.bounding_dimension[0]
ipk.modeler.create_region(0, False)
ipk.modeler.edit_region_dimensions([coil_dim / 2, coil_dim / 2, coil_dim / 2, coil_dim / 2, coil_dim * 2, coil_dim])

True

Map coil losses

Map ohmic losses from Maxwell to the Icepak design.

ipk.assign_em_losses(design="1 Maxwell", setup=m3d.setups[0].name, sweep="LastAdaptive", assignment=["Coil"])

<pyaedt.modules.Boundary.BoundaryObject object at 0x00000279A5898C70>

Boundary conditions

Assign opening.

faces = ipk.modeler["Region"].faces
face_names = [face.id for face in faces]
ipk.assign_free_opening(face_names, boundary_name="Opening1")

<pyaedt.modules.Boundary.BoundaryObject object at 0x00000279A58985E0>

Assign monitor

Temperature monitor on the coil surface

temp_monitor = ipk.assign_point_monitor([70, 0, 0], monitor_name="PointMonitor1")

Icepak solution setup

solution_setup = ipk.create_setup()
solution_setup.props["Convergence Criteria - Max Iterations"] = 50
solution_setup.props["Flow Regime"] = "Turbulent"
solution_setup.props["Turbulent Model Eqn"] = "ZeroEquation"
solution_setup.props["Radiation Model"] = "Discrete Ordinates Model"
solution_setup.props["Include Flow"] = True
solution_setup.props["Include Gravity"] = True
solution_setup.props["Solution Initialization - Z Velocity"] = "0.0005m_per_sec"
solution_setup.props["Convergence Criteria - Flow"] = 0.0005
solution_setup.props["Flow Iteration Per Radiation Iteration"] = "5"

Add 2-way coupling and solve the project

Enable mapping temperature distribution back to Maxwell. Default number Maxwell <–> Icepak iterations is 2, but for increased accuracy it can be increased (number_of_iterations).

ipk.assign_2way_coupling()
ipk.analyze_setup(name=solution_setup.name)

True

Postprocessing

Plot temperature on the object surfaces.

surface_list = []
for name in ["Coil", "Core"]:
    surface_list.extend(ipk.modeler.get_object_faces(name))

surf_temperature = ipk.post.create_fieldplot_surface(surface_list, quantity="SurfTemperature",
                                                     plot_name="Surface Temperature")

velocity_cutplane = ipk.post.create_fieldplot_cutplane(assignment=["Global:XZ"], quantity="Velocity Vectors",
                                                       plot_name="Velocity Vectors")

surf_temperature.export_image()
velocity_cutplane.export_image(orientation="right")

report_temp = ipk.post.create_report(expressions="PointMonitor1.Temperature", primary_sweep_variable="X")
solution_temp = report_temp.get_solution_data()
temp = solution_temp.data_magnitude()[0]
m3d.logger.info("*******Coil temperature =  {:.2f}deg C".format(temp))

Get new resistance from Maxwell

Temperature of the coil increases, and consequently also coil resistance increases.

report_new = m3d.post.create_report(expressions="Matrix1.R(Winding1,Winding1)")
solution_new = report_new.get_solution_data()
resistance_new = solution_new.data_magnitude()[0]
resistance_increase = (resistance_new - resistance)/resistance * 100

report_loss_new = m3d.post.create_report(expressions="StrandedLossAC")
solution_loss_new = report_loss_new.get_solution_data()
em_loss_new = solution_loss_new.data_magnitude()[0]

m3d.logger.info("*******Coil resistance at 150kHz AFTER temperature feedback =  {:.2f}Ohm".format(resistance_new))
m3d.logger.info("*******Coil resistance increased by {:.2f}%".format(resistance_increase))
m3d.logger.info("*******Ohmic loss in coil AFTER temperature feedback =  {:.2f}W".format(em_loss_new/1000))

Release desktop

ipk.release_desktop(True, True)

True