Inputs

Introduction

The total number of user inputs is ten in addition to field winding and damper temperatures, set in Settings. Among the inputs, maximum field current, speed, back emf target point option, and the corresponding field current value are the only default parameters. The other six are available as advanced input parameters.

Standard inputs

Field Current definition mode

There are two common ways to define 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 field current (DC value).

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

Maximum field current (A)

Maximum field current density (A/mm2)

Speed

Back EMF target point

The main principle of the No-load test is to perform successive Back EMF tests for different values of field current, to extract a Back-EMF versus Field current curve. However, the full results of those Back EMF tests are not displayed. This input allows the user to indicate if a full Back-EMF test, and its results, should be presented in the output section. The default option is “No”.

Field current (A)

If the “Back EMF target point” is set to “Yes”, the user must provide a field current point in which will be perform the Back EMF test. When the choice of the field current definition mode is “Current”, the target DC value of the field current supplied to the machine “Field current (A)” (Target field current (A)) must be provided. The default value is the same as the “Maximum field current (A)” input.

Field current density (A/mm2)

If the “Back EMF target point” is set to “Yes”, the user must provide a field current point in which will be perform the Back-EMF test. When the choice of field current definition mode is “Density”, the target DC value of the field current supplied to the machine “Field current density (A/mm2)” (Target field current density (A/mm2)) must be provided. The default value is the same as the “Maximum field current density (A/mm2)” input.

Advanced inputs

Number of computations for If - field current

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.

Number of computations per electrical period

To get the Back EMF versus time, the flux through each phase of the machine versus rotor angular position is computed.

This computation is performed using Finite Element Modeling.

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.

Maximum harmonic order

To get the Back-EMF versus time, the flux through each phase of the machine is computed versus rotor angular position.

Harmonics are extracted from the frequency analysis (F.F.T. Fast Fourier Transform) of the Back-EMF signal versus time.

The default value is equal to 20. The minimum allowed value is 1.

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].

For more details, please refer to the document: MotorFactory_SMWF_ISP_IR_3PH_Test_Introduction – section “Rotor and stator relative position”.

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 modeling the skewing in Flux® Skew environment).

Mesh order

To get results, Finite Element Modeling 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.

The default level is second order mesh.

Airgap mesh coefficient

The advanced user input “Airgap mesh coefficient” is a coefficient that 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), inside the 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].