Inputs

1. Introduction

The total number of user inputs is equal to 13.

Among these inputs, 8 are default inputs and 5 are advanced inputs.

2. Standard inputs

Current definition mode

There are two common ways to define the electrical current.

Electrical current can be defined by the current density in electric conductors.

In this case, the current definition mode should be « Density »

Electric current can be defined directly by indicating the value of the maximum line current (the RMS value is required).

In this case, the current definition mode should be « Current »

Maximum line current, rms

When the choice of the current definition mode is “ Current ”, the maximum rms value of the line current supplied to the machine: “Max. line current, rms” ( Maximum line current, rms value ) must be provided.

Note: The number of parallel paths and the winding connections are automatically considered in the results.

Maximum current density, rms

When the choice of current definition mode is “ Density ”, the rms value of the maximum current density in electric conductors “Max. current dens., rms” ( Maximum current density in conductors, rms value ) must be provided.

Note: The number of parallel paths and the winding connection are automatically considered in the results.

Maximum Line-Line voltage, rms

The rms value of the maximum Line-Line voltage supplying to the machine: “Max. Line-Line voltage, rms” ( Maximum Line-Line voltage, rms value ) must be provided.

Note: The number of parallel paths and the winding connection are automatically considered in the results.

Command mode

One command mode is available:

  • The maximum Torque Per Amps (MTPA)

The first step of the process consists of computing the torque-speed curve and the second step is to compute the efficiency map bounded by the torque-speed curve.

More information is available on this topic in section 2.4 (Main principles of computation)

Maximum speed

The computation and analysis of the torque-speed curves are performed over a given speed range.

The maximum allowed value for the « Maximum speed » corresponds to 53000 rad/s - about 506000 rpm.

Note: As a function of the maximum speed value, following different cases must be considered:

  1. Case 1 : The maximum speed is lower than the base speed N base (corner point speed of the torque-speed curve) N max < N base .

    In that case, whatever is the command mode (MTPA or MTPV), the behavior of the machine will be studied over the speed range [0, N max ].

    This allows the user to precisely choose the range of speed to be considered for computing and displaying the torque-speed curve and especially maps like efficiency map.

  2. Case 2 : The maximum speed is greater than the base speed (corner point speed) N max > N base .

    The relevance of the maximum speed given by the user is analyzed to evaluate if it is reachable by the machine.

    If the user maximum speed is unreachable by the machine, the correction of this value is automatically performed.

    The resulting new maximum speed is linked to a limit torque. This limit torque is obtained by applying a reduction coefficient to the base point torque.

Rotor position dependency

It defines the rotor position dependency of electromagnetic data used for the optimization of the efficiency map such as D-axis magnetic flux, Q-axis magnetic flux, electromagnetic torque, iron losses. By default, the rotor position dependency is set to “No” but it can be set to “Yes”. In this case the computation will be done along the two dimensions Jd - Jq , with an additional fourth axis corresponding to the rotor position θr.
Note: This option allows to have a better accuracy in the evaluation of magnetic flux, electromagnetic torque as well as iron losses. It is worth noting that only with rotor position dependency that the rotor iron losses can be evaluated.

Additional losses

Note: “Additional losses” input is not available in the current version (The input label is written in grey).

User working point(s) analysis

It is possible to perform additional analysis on working point(s) located under the torque speed curve. The user input “ User working point(s) analysis ” (additional analysis on working point(s)) gives three possibilities to the user:

  1. User working point(s) analysis = None (=default mode)

    This corresponds to the basic configuration of the test, with no additional working point analysis.

  2. User working point(s) analysis = Single point

    This allows computing the machine performance on a working point which must be specified by the user with the targeted speed and torque.

    In that case the next two fields must be filled in with the targeted speed and mechanical torque.
    User working point analysis = Single point
    1 Select the “Single point” option to perform a computation on one working point.
    2 Define the targeted working point mechanical torque and speed.
    3 Button to validate and consider the user inputs
    4 Button to run the computation

  3. User working point(s) analysis = Duty cycle

    This allows computing the machine performance all over the considered duty cycle.

    This duty cycle must be defined by using the next field: "Duty cycle description" and by clicking on the button "Set values".

    Two ways are possible to fill in the table: either filling the table line by line or by importing an excel file in which all the working point of the duty cycle are defined.

Note: A working point is defined by a time, the speed, and the mechanical torque.
User working point analysis = Duty cycle
1 Select the “Duty cycle” option
2 Click in the button “Set values” of the field “Duty cycle” to open a dialog box to define the duty cycle.Refer to the next illustration which shows how to fill the Duty cycle table.
3 Button to validate and consider the user input data
4 Button to run the computations
Note: Once the efficiency map is computed and displayed all the additional computations dealing with the user working points are given instantaneously.
User working point analysis = Duty cycle – Dialog box to define the duty cycle
1 Dialog box opened after having clicking on the button “Set values” in the field “Cycle description”
2 Browse the folder to select an Excel file in which the duty cycle is described.
3 Button to refresh the table data when the considered Excel file has been modified
4 Fields to be filled in with data to describe the duty cycle to be taken into account
Note: A template corresponding to the Excel file format to be considered is stored in the folder Resource/ Template. An example of this template is displayed below.
Excel file template to define the duty cycle

3. Advanced inputs

Number of computed electrical periods

The user input “No. computed elec. periods” (Number of computed electrical periods only required with rotor position dependency set to “Yes”) influences the computation time of the results.

The default value is equal to 0.5. The maximum allowed value is 1 according to the fact that computation is done to characterize steady state behavior based on magnetostatic finite element computation. The default value provides a good compromise between the accuracy of results and computation time.
Note: The outcomes obtained at 0.5 or 1 electrical period are identical across all presented outputs, except for slight variations in rotor iron losses arising from the symmetrical assumption regarding the magnetic flux waveform on the rotor.

Number of computations for J d , J q

First, it is needed to compute the D-axis and Q-axis flux linkage in the J d - J q plane.

To get maps in the J d - J q plane, a grid is defined. The number of computation points along the d-axis and q-axis can be defined with the user input « No. Comp. for J d , J q » (Number of computations for D-axis and Q-axis currents) .

The default value is equal to 5. This default value provides a good compromise between accuracy and computation time. The minimum allowed value is 5.

Number of computations for speed

The “No. comp. for speed” ( Number of computations for speed ) corresponds to the number of points to be considered in the speed range from 0 to the maximum speed.

Half of these points are distributed from 0 to the base speed. The remaining points are distributed from the base speed to the maximum speed.

In both cases, base speed is considered as an additional point.

Note: If the user input parameter “ No. comp. for speed ” is an odd number, one discretization point is automatically removed.
Definition of the number of computations for speed

The default value is equal to 15. The minimum allowed value is 5. The maximum recommended value is 40.

Note: Increasing the number of computations can improve the convergence of the optimization used to define the torque-speed curve and the efficiency map. However, that also means longer computation time.

Number of computations for torque

With the “Low Speed” command mode, the number of computations for torque is imposed by the input parameter “ No. comp. for torque ” (Number of computations for torque) - Black points in the graph shown below.

The default value is equal to 7. The minimum allowed value is 3. The maximum recommended value is 20.

The number of computations for torque is imposed by the number of computations for speed in the speed range [N base ; N max ] (Red points in the image shown below).

The advanced user input parameter “ No. comp. for torque ” allows to finalize the grid within the torque range [0, T(N max )] at the maximum speed (Black points in the image shown below).
Definition of the number of computations for torque – MTPV command mode

Skew model – Number of layers

When the rotor or the stator slots are skewed, the number of layers used in Flux Skew environment to model the machine can be modified: “Skew model - No. of layers” ( Number of layers for modelling the skewing in Flux Skew environment ).

Mesh order

To get the results, the original computation is performed using a Finite Element Modeling.

Two levels of meshing can be considered for this finite element calculation: first order and second order.

This parameter influences the accuracy of results and the computation time.

By default, second order mesh is used.

Airgap mesh coefficient

The advanced user input “ Airgap mesh coefficient ” is a coefficient which adjusts the size of mesh elements inside the airgap. When the value of “Airgap mesh coefficient” decreases, the mesh elements get smaller, leading to a higher mesh density inside the airgap and increasing the computation accuracy.

The imposed Mesh Point (size of mesh elements touching points of the geometry) is described with the following parameters:

  • MeshPoint = (airgap) x (airgap mesh coefficient)

  • Airgap mesh coefficient is set to 1.5 by default.

    The variation range of values for this parameter is [0.05; 2].

    0.05 gives a very high mesh density and 2 gives a very coarse mesh density.

CAUTION: Be aware, a very high mesh density does not always mean a better result quality.

However, this always leads to a huge number of nodes in the corresponding finite element model. So, it means a need of huge numerical memory and increases the computation time considerably.

Rotor d-axis location

The computations are performed by considering a relative angular position between rotor and stator.

For the reluctance synchronous machines, the rotor d-axis location is defined and automatically used to perform computations.

This value is characterized by the saliency topology. This is important to keep in mind this information it.

For more details, please refer to the document: MotorFactory_2024.1_SMRSM_IR_3PH_Test_Introduction – section “Rotor and stator relative position”.