Inputs

Standard inputs

Sharing data between tests

An import button is available for allowing sharing the data simulated in Flux between “Characterization / Model / Map” and “Performance mapping / Efficiency map” tests.

Indeed, by implementing the rotor position dependency option for the model map test and efficiency map test of synchronous machines, this update facilitates the seamless transfer of settings, inputs, and crucially, simulated data in Flux between the two tests. As they use the same Flux data in most cases and significant computation time is required to obtain it, users can now accelerate the test resolution and optimize their workflow.

To streamline this process, an import button has been introduced in both the “Characterization / Model / Map” and “Performance mapping / Efficiency map” tests of the following machines:

Reluctance Synchronous Machines - Inner rotor
Synchronous Machines with wound field – Inner Salient Pole - Inner rotor

Note: The import button will be added to the tests of Synchronous machines – Permanent magnets - Inner & Outer rotor in the next version.

Upon completing a model map test, users can activate the import button in the efficiency map test GUI. This enables them to effortlessly import the settings and corresponding Flux data from the previous test, eliminating the need to rerun Flux for identical data, a step that typically consumes a substantial portion of computation time during efficiency mapping.

Conversely, upon concluding an efficiency map test, users can use the import button in the efficiency map test GUI to import settings and Flux data from the efficiency map test, further enhancing workflow efficiency.

Note: Only the most recent test results can be imported, saved test results are not yet able to be imported.

Note: While there are shared settings and inputs between the tests, each test may have its own unique settings and inputs. In such cases, the default settings, and inputs of the second test are automatically applied.

Note: When importing from the efficiency map test to the model map test, the quadrant setting defaults to the value specified in the model map test. For certain machine types (SMWF: 2nd quadrant, SM-RSM: 1st quadrant), specific quadrant selections are applied.

Note: In instances where quadrant inputs lead to incompatibility between the model map test and the efficiency map test, only settings and inputs are imported. A warning is issued, and Flux simulation is initiated to rectify the discrepancy.

Table 1. Import function in Model Map test and Efficiency Map test to accelerate test resolution. Example for Wound field synchronous machines

1	Open model map test environment when an efficiency map test is available for import
2	Click the import button and import the settings, inputs, and Flux data of the latest efficiency map test
3	Open efficiency map test environment when a model map test is available for import
4	Click the import button and import the settings, inputs, and Flux data of the latest model map test

Standard inputs ––––--

Operating quadrants

It defines the quadrants in the Jd - Jq plane where the test will be carried out. Options allow computing and displaying 1, 2 or 4 quadrants.

By default, the considered quadrants are the “1st and 2nd” (i.e., the grid is defined for both negative and positive values of the current in the d axis and positive ones in the q axis). This option is chosen as default because the Synchronous Machine with wound field heritages the characteristic of both Synchronous Machine with Permanent Magnets and Reluctance Synchronous Machines which work respectively in the second and the first quadrant in the motor operating mode.

The other possible values for this input are “2nd”, “2nd and 3rd“, and “all”.

Current definition mode

There are 2 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 ».

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

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

Max. field current

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

Note: The number of parallel paths is automatically considered in the results.

Max. field current density

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

Note: The number of parallel paths is automatically considered in the results.

Max. line current, h1 rms

When the choice of current definition mode is “Current”, the maximum rms value of the line current supplied to the machine “Max. line current, h1 rms” (Maximum line current, first harmonic rms value) must be provided.

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

Max. current dens. h1, rms

When the choice of current definition mode is “Density”, the maximum rms value of the current density in electric conductors “Max. current dens., h1 rms” (Maximum current density in conductors, first harmonic rms value) must be provided.

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

Maximum speed

The analysis of test results is performed over a given speed range to evaluate losses as a function of speed, like iron losses, mechanical losses, and total losses.

The speed range is fixed between 0 and the maximum speed to be considered « Maximum speed » (Maximum speed).

Rotor position dependency

It defines the "rotor position dependency", where the test will be carried out. 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 three dimensions If - Jd - Jq, with an additional fourth axis corresponding to the rotor position θr.

Note: In case the rotor dependency is set to “Yes”, whatever the operating quadrant choice, the finite element computation is done over all selected quadrants (in case the rotor dependency is set to “No”, symmetries are used).

Advanced inputs ––––--

No. computed elec. 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.

No. comp. / elec. period

The number of computations per electrical period “No. comp. / elec. period” (Number of computations per electrical period) influences the accuracy of results and the computation time.

The default value is equal to 40. The minimum allowed value is 13. This default value provides a good compromise between the accuracy of results and computation time.

Note: The real number of computations per electrical period can be equal to the requested one +/- 1. That is due to our internal computation process since the raw computation is performed over one electrical half period. The result of a whole electrical period is rebuilt from the raw data.

Figure 1. Number of computations per electrical period

No. comp. for Jd,Jq

To get maps in the Jd-Jq plan, 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 current Jd, Jq » (Number of computations per quadrant for D-axis and Q-axis phase currents).

The default value is equal to 6. This default value provides a good compromise between the accuracy of results and computation time. The minimum allowed value is 5.

No. comp. for if

Computation of the back-EMF:
To compute the Back-EMF for different magnetization states, the field current If is discretized from zero to its maximum value.
The number of computation points for the If discretization can be defined with the user input « No. comp. for If » (Number of computations for field current).
The default value is equal to 6. This default value provides a good compromise between the accuracy of results and computation time. The minimum allowed value is 5.
Computation of maps in Jd,Jq plan:
To get maps along the If dimension, the field current is discretized from zero to its maximum value. The number of computation points along the If - axis can be defined with the user input « No. comp. for If » (Number of computations for If - axis field currents).
The default value is equal to 6. This default value provides a good compromise between the accuracy of results and computation time. The minimum allowed value is 5.
Note: If one uses more than one quadrant, the total number of computations for Jd and Jq will be calculated based on the No. comp. for current Jd, Jq input and the number of quadrants. For example, if No. comp. for current Jd, Jq is set to 10 and the quadrant is set to “1st and 2nd “, then the total number of computations for Jd is 10, but 19 for Jq considering Jd = 0 is shared between both quadrants

No. comp. for speed

The number of computations for speed corresponds to the number of points to consider in the range of speed. It can be defined via the user input “No. comp. for speed” (Number of computations for speed).

The default value is equal to 10. The minimum allowed value is 5.

Rotor initial position

By default, the “Rotor initial position” is set to “Auto”.

When the “Rotor initial position mode” is set to “Auto”, the initial position of the rotor is automatically defined by an internal process.

The resulting relative angular position corresponds to the alignment between the axis of the stator phase 1 (reference phase) and the direct axis of the rotor.

When the “Rotor initial position” is set to “User input” (i.e. toggle button on the right), the initial position of the rotor considered for computation must be set by the user in the field « Rotor initial position ». The default value is equal to 0. The range of possible values is [-360, 360].

Notice: The computations are performed by considering the relative angular position between the rotor and stator.

This relative angular position corresponds to the angular distance between the direct axis of the rotor north pole and the axis of the stator phase 1 (reference phase).

The value of the rotor D-axis location, which is automatically defined for each saliency part.

Below is illustrated the Rotor and stator phase relative position

The relative angular position between the axis of the stator phase 1 (reference phase) and the rotor D-axis position must be controlled to perform the tests. See the picture below which will allow defining the working point of the machine.

Figure 2. Definition of rotor initial position – Rules for direction

The winding axis of the reference phase is defined from the phase shift of the first electrical harmonic of the magneto motive force (M.M.F.).

Skew model – No. of layers

When the rotor magnets or the stator slots are skewed, the number of layers used in Altair 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).

Note: When there is magnet step skew topology, the number of layers is defined at the design level.

Mesh order

To get the results, Finite Element Modelling computations are performed.

The geometry of the machine is meshed.

Two levels of meshing can be considered: 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, increasing the computation accuracy.

The imposed Mesh Point (size of mesh elements touching points of the geometry), inside the Altair Flux software, is described as:

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 giving a very high mesh density and 2 giving 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 for huge numerical memory and increases the computation time considerably.

The impact of the airgap mesh coefficient on resultant meshing is illustrated bellow: