Motor-CAD force extraction example script

This sets up the operating points and threading options for a force/NVH calculation, then displays some key force orders from a 2d FFT that may be important for NVH.

Import PyMotorCAD and launch Motor-CAD, turning off pop-up messages.

import ansys.motorcad.core as pymotorcad

mc = pymotorcad.MotorCAD()
mc.set_variable("MessageDisplayState", 2)

Load a baseline model - in this case a template. For users, this would normally be a baseline model.

mc.load_template("e9")

Set 90 torque points per cycle, which will give us information up to the 45th electrical order. If using an induction motor, use IMSingleLoadPointsPerCycle_Rotating instead.

mc.set_variable("TorquePointsPerCycle", 90)

Enable multithreading for the force/NVH calculation

mc.set_variable("MultiForceThreading", 0)  # 0 is multithreaded, 1 is single threaded.

Set operating points, in this case for speed and torque definition.

operating_points_speed = [250, 4000, 8000]  # RPM
operating_points_torque = [250, 250, 100]  # Nm
num_operating_points = len(operating_points_speed)

# Make sure the table is the correct length before setting value
mc.set_variable("NumLoadPoints", num_operating_points)

# Set the values:
for operating_point in range(num_operating_points):
    mc.set_array_variable(
        "LoadPoint_Speed_Array", operating_point, operating_points_speed[operating_point]
    )
    mc.set_array_variable(
        "LoadPoint_Torque_Array", operating_point, operating_points_torque[operating_point]
    )

Note

For other motor types or options, the following may be needed:

• All motor types and options: LoadPoint_Speed_Array

• BPM or similar for torque based definition: LoadPoint_Torque_Array

• BPM or similar for current/phase advance definition: LoadPoint_Current_Array,

and LoadPoint_PhaseAdvance_Array - SRM: LoadPoint_Current_Array, LoadPoint_OnAngle_Array, and LoadPoint_OffAngle_Array - IM: LoadPoint_Current_Array and LoadPoint_Slip_Array

Run the electromagnetic FEA calculation, which calculates the forces.

mc.do_multi_force_calculation()

Define the orders that we want to extract as space and time order pairs. In this case, these are some of the important orders for a 48 slot, 8 pole motor.

The orders are defined as pairs of [Space order (positive or negative), electrical time order (0 or positive)]:

required_orders = [[0, 12], [0, 24], [8, 2], [-8, 10], [8, 14]]

Get information about the results.

# Number of cycles. If using this for an induction motor, use
# `IMSingleLoadNumberCycles_Rotating` instead
electrical_cycles = mc.get_variable("TorqueNumberCycles")

# Maximum number of space orders in results
mech_force_space_order_max = mc.get_variable("ForceMaxOrder_Space_Stator_OL")

# Number of operating points. In this example we have set this earlier in the script
num_operating_points = mc.get_variable("NumLoadPoints")

# Find how many slices (for skew) are available.
if mc.get_variable("SkewType") == 2:
    # Stepped skew
    rotor_slices = mc.get_variable("RotorSkewSlices")
else:
    rotor_slices = 1

Find the force density for each slice, at the different operating points and slices:

for rotor_slice in range(rotor_slices):
    print("\nSlice " + str(rotor_slice + 1) + ":")
    for operating_point in range(num_operating_points):
        print("\nOperating point " + str(operating_point + 1) + ":")

        print(
            "Results as: Space order, "
            "Electrical order, "
            "Force density amplitude (N/m^2), "
            "Force density phase (deg):"
        )

        for required_order in required_orders:
            required_space_order = required_order[0]
            required_electrical_time_order = required_order[1]

            # Results stored with negative space orders at the end, so apply offset
            if required_space_order < 0:
                raw_space_order = required_space_order + 2 * mech_force_space_order_max
            else:
                raw_space_order = required_space_order

            # If more than one cycle used, scale between electrical orders and internal orders
            raw_time_order = required_electrical_time_order * electrical_cycles

            # Find the force density using GetMagnetic3DGraphPoint:
            # Note the use of _Th1 for the 1st operating point in the name.
            # Note also that rotor slice numbering starts at 1.
            _, force_density_amplitude = mc.get_magnetic_3d_graph_point(
                "Fr_Density_Stator_FFT_Amplitude_OL" + "_Th" + str(operating_point + 1),
                rotor_slice + 1,
                raw_space_order,
                raw_time_order,
            )

            _, force_density_angle = mc.get_magnetic_3d_graph_point(
                "Fr_Density_Stator_FFT_Angle_OL" + "_Th" + str(operating_point + 1),
                rotor_slice + 1,
                raw_space_order,
                raw_time_order,
            )

            # Apply 2x factor due to FFT symmetry, unless on the 0th time order (mean)
            # This is equivalent to showing results with 'Positive time only'
            if required_electrical_time_order > 0:
                force_density_amplitude = force_density_amplitude * 2

            # Print the result. In a user workflow, this would usually be stored,
            # for example for use as an optimisation metric:
            print(
                str(required_space_order)
                + ",\t"
                + str(required_electrical_time_order)
                + ",\t"
                + str(force_density_amplitude)
                + ",\t"
                + str(force_density_angle)
            )

Slice 1:

Operating point 1:
Results as: Space order, Electrical order, Force density amplitude (N/m^2), Force density phase (deg):
0,      12,     5289.67358651236,       -42.5802899400492
0,      24,     453.251180041326,       -98.7354048892451
8,      2,      202959.448457606,       132.219642348957
-8,     10,     12707.2885600897,       -135.94008301821
8,      14,     3708.06040732994,       85.0613279816351

Operating point 2:
Results as: Space order, Electrical order, Force density amplitude (N/m^2), Force density phase (deg):
0,      12,     5324.90789753966,       -42.4629569682188
0,      24,     453.05842104109,        -97.8592418188736
8,      2,      202672.97029561,        132.31406185983
-8,     10,     12733.26169038612,      -135.715686728229
8,      14,     3715.48883698294,       85.2507957344407

Operating point 3:
Results as: Space order, Electrical order, Force density amplitude (N/m^2), Force density phase (deg):
0,      12,     2228.66606070318,       1.63975322938251
0,      24,     503.21206771458,        -148.398160244431
8,      2,      124341.0454491954,      121.089007345116
-8,     10,     6596.1423539073,        -139.503339954817
8,      14,     803.345344247258,       86.7804963490171