Inputs
Standard inputs ––––--
I-Ψ-N description
The “I-Ψ-N description” allows to define several working points.
The description must be defined by clicking on the button “Set values”.
Then, two ways are possible to fill in the table: either filling the table line per line or by importing an Excel file in which all the working points to be considered are defined.
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The line current, h1 rms
The first harmonic rms value of the line current supplied to the machine: “Line current, h1 rms” (Line current, first harmonic rms value) must be provided.
Note: The number of parallel paths and the winding connection are automatically considered in the results. - 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 = (E, J)). It is an electrical angle. It must be set in a range of -90 to 90 degrees.
This range of values covers all the possible working point in motor convention.
Figure 1. Definition of the control angle Ψ - Motor convention 
- Speed
The imposed “Speed” (Speed) of the machine must be set. The speed column must contain increasing speeds.
- Process to define the list of working points
Table 1. User working point analysis = Duty cycle 
1 lick on the button “Set values” of the field “ I, Ψ, N description” to define the working points in a dialog box. Refer to the next illustration which shows how to fill the working point table. 1.1 Dialog box opened after having clicked on the button “Set values” in the field “Cycle description” 1.2 Browse the folder to select an Excel file which describes the duty cycle. 1.3 Button to refresh the table data when the considered Excel file has been modified. 1.4 Fields to be filled with data to describe the duty cycle to be considered. 1.5 Excel file template to define the duty cycle
Advanced inputs ––––--
Max. engine order
Two kinds of inputs are possible: either set an engine order or a number of points per electrical period. Define the Max. engine order (Maximum engine order) or the No. points / elec. period (Number of points per electric period).
When decomposing the Maxwell pressure, applied on the stator, to get its harmonic contributions, the “max. engine order” (Maximum engine order) is required to compute its decomposition in function of the time.
"Engine order" refers to a mechanical revolution period of the motor whereas frequency refers to the considered electrical period.
Obviously, both are linked with speed.
For instance, radiated sound power can be displayed either by considering frequency or engine order.
No. points / elec. period
The second possibility is to set a “No. points / elec. Period” meaning a number of points per electrical period.
For transient computations the minimum needed number of points per electrical period is 40.
So, when the engine order is not high enough to reach this constraint, It is automatically modified to get 40 computation points per electrical period.
Max. mode / spatial order
The “max. mode / spatial order” (Maximum mode / spatial order) input allows the user to define the number of modes to be considered for the acoustic structural analysis. If the user selects 25, it means that the highest number of lobes in the stator deformation will be equal to 25 lobes. All deformations corresponding to more than 25 lobes will be dismissed.
No. points / tooth pitch
The “No. comp. / tooth pitch” (Number of computations per tooth pitch) allows to choose the number of Maxwell pressure evaluations per tooth. The more points selected, the more accurate the Maxwell pressure harmonic decomposition will be.
No. points for speed interpolation
The “No. points for speed interpolation” (Number of points for speed interpolation) allows to manage the computation of the radiated sound power per engine order. It allows to manage the data interpolation between the speeds indicated as inputs. Thanks to that, the curves “Radiated sound power per engine order versus speed” and “weighted radiated sound power versus speed” can have a better discretization which leads to a better displaying of the local peaks.
The default value is equal to 100. The range of possible values is [50,300]
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].
The impact of the airgap mesh coefficient on resultant meshing is illustrated bellow:
Advice for use
The modal analysis as well as the radiation efficiency are based on an analytical computation where the stator of the machine is considered as a vibrating cylinder.
The considered cylinder behavior is weighted by the additional masses like the fins or the winding and the subtractive masses like the slots and the cooling circuit holes.
This assumption allows to get fast evaluation of the behavior of machine in connection to NVH. In no way this can replace a mechanical Finite Element modeling and simulation.
- The limits of the analytical model are reached or overpassed
- Unusual topology and/or dimensions of the teeth/slots
- Complexity of the stator-frame structure when it is composed with several components for instance
- The ratio between the total length of the frame Lframe and the stack length
of the machine Lstk in any case, this ratio must be lower than 1.5:
