Inputs

Introduction

The total number of user inputs is equal to 14 for a machine without skew and 15 for a skewed machine.

Among these inputs, 8 are standard inputs and 7 or 6 are advanced inputs, depending on whether a machine is skewed or not.

Standard inputs

Convention

There are two conventions to choose from: “generator” and “motor”.

The “generator” convention is considered the default. In this convention, the machine operates as a generator from an electrical perspective. It receives mechanical power through the shaft (input) and outputs electrical power via the stator winding.

The “motor” convention is used when viewing the machine as a motor from an electrical perspective. It receives electrical power through the stator winding (input) and outputs mechanical power via the shaft.

Note: The sign of the power terms will vary based on the chosen convention and the machine's operating mode. For further details, refer to the document: MotorFactory_SMWF_ISP_IR_3PH_Test_Introduction – section “Test generic information”.

Note: Only the “generator” convention in FluxMotor 2024.1.

Operating mode

There are two operating modes to choose from: “generator” and “motor”.

It is intuitive to say that an electrical machine operates as a motor in the motor convention and vice versa as a generator in the generator convention. However, in any convention, an electrical machine can be regulated to operate in both generator and motor modes. This is because the machine can function in all the four quadrants of the d-q plane.

Note: It is advised to choose the “motor” operating mode when the “motor” convention has been selected previously. And vice versa, the “generator” operating mode should be chosen for the “generator” convention. The other couple of selections are less common but very useful for applications in which the machine can switch between the two operating modes such as in the traction application.

Note: Only “generator” operating mode in the FluxMotor 2024.1.

Power definition mode

Depending on the user’s habit, the working point can be defined either by output power of the machine or by its apparent electrical power.

Note: When the generator mode is selected, both apparent power and output power options are available for defining the working point. When the motor mode is selected, only the output power option is available. Defining the working point using apparent power is not applicable for motor operation.

Output power

If the generator operating mode is selected, the output power corresponds to the machine's active power, labeled “Stator Electrical Power” in the “Machine Performance – Working Point” result table.

If the motor operating mode is selected, the output power refers to the mechanical power exerted on the machine's shaft, labeled “Mechanical Power” in the “Machine Performance – Working Point” result table.

Apparent power

This option is only available if the generator operating mode is selected. It is also the default selection for the user. The apparent power is labeled “Apparent power” in the “Machine Performance – Working Point” result table.

Note: It is recommended to use apparent power to define the test if the user intends to evaluate different power factors at the same apparent power value. This approach allows the backend of FluxMotor to run the Flux simulation only once for the initial power factor value and then use the simulated data for subsequent power factor values. Since the Flux simulation constitutes most of the computing time for the test, this method can significantly reduce the computing time for evaluating later power factor values.

Power factor definition mode

The power factor itself is not sufficient to determine if a machine supplies or consumes reactive power from the electrical network. Therefore, the user is provided with two options for the power factor.

The power factor lag means that the phase current vector is behind the phase voltage vector and the reactive power is positive, or the machine supplies reactive power in the generator convention and consumes reactive power in the motor convention.

The power factor lead means that the phase current vector is in advance compared to the phase voltage vector and the reactive power is negative, or the machine consumes reactive power in the generator convention and supplies reactive power in the motor convention.

Power factor lag

The power factor lag takes values from 0 to 1. If the user chooses this option, the phase current vector is behind the phase voltage vector. Hence, the phase angle and reactive power must be positive in the “Machine Performance – Working Point” result table.

Power factor lead

The power factor lead takes values from 0 to 1. If the user chooses this option, the phase current vector is in advance compared to the phase voltage vector. Hence, the phase angle and reactive power must be negative in the “Machine Performance – Working Point” result table.

Field current definition mode

In the backend of FluxMotor, machine performance is analyzed within a research zone defined by the field current and the control angle. The goal is to identify the combination of field current and control angle that allows achieving the desired working point characterized by P-P_f-U-N. The maximum field current sets the upper limit for the field current.

There are two common ways to define the maximum field current:

by the current density in electric conductors, in this case, the field current definition mode should be « Density ».
by indicating the value of the field current (DC value), in this case, the field current definition mode should be « Current ».

Maximum Field current

When the choice of current definition mode is “Current”, the DC value of the maximum current supplied to the field winding: “Maximum Field current” (Current in Field conductors) must be provided.

Maximum Field current density

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

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

Speed

The imposed “Speed” (Speed) of the machine must be set.

Line-line voltage, rms

The imposed “Line-line voltage” (Line-line voltage, rms) of the machine must be set.

Ripple torque analysis

The “Ripple torque analysis” (Additional analysis on ripple torque period: Yes / No) allows to compute or not the value of the ripple torque and to display the corresponding torque versus the angular position over the ripple torque period.

The default value is “No”.

Note:

This choice influences the accuracy of results and the computation time. The magnitude of the ripple torque is calculated.

This additional computation needs additional computation time.
In the case of “Yes”, the ripple torque is computed. Then, the flux density in regions is evaluated through the ripple torque computation.
In the case of “No”, the ripple torque is not computed.

Then, the flux density in regions is evaluated by considering the Park’s model computation.

Advanced inputs

Number of computations for field current

In the backend of FluxMotor, the field current is varied within a research zone from 0 to the maximum field current defined previously to find the value allows achieving the desired working point P-P_f-U-N. This research zone is discretized linearly based on the “Number of computations for field current.”

The machine's performance is represented by the response surfaces of field current and control angle. An optimization algorithm uses these response surfaces to determine the field current and control angle that provide the required P-P_f-U-N performance. Thus, the “Number of computations for field current” is crucial for the optimizer's accuracy.

Note: For the best compromise between computing time and accuracy, set the “Number of computations for field current” to 6. If higher accuracy is needed, increase this value accordingly, keeping in mind that higher values will require more computing time.

Number of computations for control angle

Considering the vector diagram shown below, the “Control angle” is the angle between the electromotive force (E) and the electrical current (J) (Ψ= angle (E, J)).



Definition of the control angle Ψ

In the backend of FluxMotor, the control angle is varied within a research zone to find the value allows achieving the desired working point P-P_f-U-N. This research zone is discretized linearly based on the “Number of computations for control angle.”

The machine's performance is represented by the response surfaces of field current and control angle. An optimization algorithm uses these response surfaces to determine the field current and control angle that provide the required P-P_f-U-N performance. Thus, the “Number of computations for control angle” is crucial for the optimizer's accuracy.

Note: For the best compromise between computing time and accuracy, set the “Number of computations for control angle” to 13.

If higher accuracy is needed, increase this value accordingly, keeping in mind that higher values will require more computing time.

Number of computations per ripple torque period

The number of computations per ripple torque period is considered when the user has chosen to perform a “Ripple torque analysis” (i.e., answered “Yes” to the standard input “Ripple torque analysis” required only with “Fast” computation mode).

The user input “No. comp. / ripple period” (Number of computations per ripple torque period) influences the accuracy of the results (computation of the peak-peak ripple torque) and the computation time.

The default value is equal to 30. The minimum allowed value is 25. The default value provides a good balance between the accuracy of results and computation time.



Definition of the number of computations per ripple torque period

Skew model – Number of layers

When the rotor magnets or the armature 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).

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 of FluxMotor®. The resulting relative angular position corresponds to the alignment between the axis of armature phase 1 (reference phase) and the direct axis of the salient pole.

When the “Rotor initial position” is set to “User input” (i.e., the toggle button on the right), the initial position of the rotor to be 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 armature relative position”.

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, a second order mesh is used.

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 the “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 the points of the geometry) inside the Flux® software is described as:

Mesh Point = (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 the formation of 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.