Definition of the simulation

Objectives

To run a MANATEE electromagnetic or vibroacoustic simulation, after having defined an electrical machine a simulation project must now be defined. This first simulation consists in using fast electromagnetic and vibroacoustic models to be used during pre-sizing of electric motors.

The new simulation project is named tuto_IPMSM_01_test to avoid confusion with the tuto_IPMSM_01 project provided in MANATEE demo version. All MANATEE inputs and outputs are expressed in the International Unit System (m, kg, etc).

GUI implementation

Machine selection

In the GUI, you can set the machine by clicking on "Select Machine".

GUI main window buttons
GUI main window buttons
Workflow/Operational parameters

In the Workflow group of the GUI, one can define the main purpose of the simulation (Input, Output, multi-simulation). In our case, we want to start the simulation by imposing currents (more especially null current for open circuit conditions) and we want to obtain acoustic calculation.

Besides instead of using fixed speed mode, the synthesized spectrogram calculation is activated to obtain the variable speed vibroacoustic behaviour of the machine with a shorter calculation time compared to variable speed. In the GUI we set (in the workflow group):

Workflow group (Variable speed tab)
Workflow group (Variable speed tab)

In the "Simulation" tab of workflow group, we also set the nominal speed at 1000 rpm and the speed variation is set from 500 to 7000 rpm.

Electrical model

The electrical model parameters define how to calculate the currents and the equivalent circuit parameters. This first simulation is an open-circuit case therefore it is not used and all parameters can be left as default.

Electromagnetic model

The electromagnetic model parameters define how to calculate the airgap flux distribution (e.g. with FEMM, with subdomain model, or with permeance/mmf model) and how to account for non-linearities.

For this first simulation, the subdomain electromagnetic model is chosen as it is the one recommended for interior PMSM:

130. Electromagnetic group (Method panel)
Electromagnetic group (Method panel)

As it is an open circuit simulation, the effect of stator field is ignored. This means that the armature field is not calculated, only the magnetic field due to rotor magnets is calculated.

40. Electromagnetic group (Assumption tab)
Electromagnetic group (Assumption tab)
Fault parameters

The fault simulation includes the definition of short circuits, broken bars, eccentricities etc. Most of these faults are modeled using the permeance/mmf electromagnetic model.
The default project does not include any fault so this part can be skipped.

Mechanical model

The Mechanical model parameters define how to calculate the dynamic deflection of the stator or rotor structure (e.g. with FEA or with experimental modal parameters). The default 2D analytical model for the calculation of natural frequencies is chosen with:

40. Mechanical group (Method tab)
Mechanical group (Method tab)

A constant damping is applied to all structural modes. The circumferential modes of electrical machine usually lie between 0.8% and 2.5%, here a 2% value is set.

40. Mechanical group (Assumption tab)
Mechanical group (Assumption tab)

The maximum number of circumferential vibration wavenumbers is set to 9 in Numerical group/Vibro-acoustic tab, meaning that the magnetic excitation wavenumbers 0, 1, 2 … until 8 are taken into account by the structural simulation. Depending on the yoke stiffness and slot numbers, one may have to include up to 20 wavenumbers (example of a large multi-pole synchronous generator) to correctly model main vibration waves. To include the largest vibration wave with a spatial frequency of the pole pair number, this parameter should be at least 2p+1 as a rule of thumb; a warning message is given if it is not the case.

The FEA structural model parameters are here ignored as an analytical calculation is run.

Acoustic model

The acoustic model parameters define how the sound pressure level is calculated. Here default options are left which means that the motor is assumed to lie on the floor and the sound pressure level is calculated 1m away from motor frame.

Numerical parameters

This part contains all the numerical parameters of the simulation. MANATEE contains several checks and warnings to ensure that the simulation results are numerically sound.

An important input variable is the maximum vibroacoustic frequency to be taken into account during vibroacoustic calculations. It should be chosen depending on the highest “dangerous” natural frequency observed in the machine, and the highest significant magnetic excitation frequency (e.g. twice the switching frequency for PWM operation, and 4 times the slot passing frequency for sinusoidal operation). Small power machines will have high frequency modes, thus requiring high time sampling frequency. In case the specified maximum frequency is not aligned with theoretical magnetic excitations, a warning message appears in console output.

Numerical group (Vibro-acoustics tab)
Numerical group (Vibro-acoustics tab)

One should be sure that the numerical discretization is high enough, taking here 2^11 points along one rotor mechanical period and 2^11 points along the airgap.

Numerical group (Magnetics tab)
Numerical group (Magnetics tab)

The text output of MANATEE gives an indication of the discretization quality. Multiples of the number of pole pairs generally lead to lower computing time when applying symmetries. During the calculation some recommendations are done on how to choose the number of time steps and angular steps.

Once the simulation project is defined you can save it with the save button.

Scripting implementation

Machine selection

To create a new machine, a new file (named tuto_IPMSM_01_test.m for instance) has to be created inside the Project folder (for instance in MyProject subfolder). Instead of creating an empty script, you can copy the default_project.m script that containes every simulation input variable with its description and unit.

You don’t need to review all the input variables of the project file. In particular, the variables whose description starts with "advanced" should only be accessed for research purposes. To ease navigation through the different types of input variables (Electrical, Electromagnetic, Structural, Acoustic etc) you can use the "GoTo" feature of Matlab GUI:

Illustration of Matlab GoTo feature in MANATEE default simulation project
Illustration of Matlab GoTo feature in MANATEE default simulation project

Some of the input parameters might refer to other machine topologies (e.g. squirrel cage induction machines), these parameters should then be simply ignored.

The name file of the electrical machine to be simulated is specified in the simulation project with:

Input.Simu.machine_name = 'machine_IPMSM_A';
Workflow/Operational parameters

The corresponding script syntax to activate the (spectrogram synthesis->563] mode is:

Input.Simu.is_varspeed =0;
Input.Simu.is_spectro_synthesis =1;

Input.Simu.N0_min=500;
Input.Simu.N0_max=7000;
Input.Simu.N0 = 1000;

All other fields can be ignored.

Electromagnetic model

The electromagnetic subdomain model is selected with

Input.Simu.type_Bmodel = 1;

To calculate the rotor excitation field with FEMM (necessary when using subdomain model on IPMSM) one must also specify:

Input.Simu.type_rmmf_mode = 1;

To avoid the armature field calculation (open circuit case) one can put

Input.Simu.is_mmfs = 0;
Input.Simu.is_mmfr = 1;
Mechanical model

The default 2D analytical model for the calculation of the stator dynamic vibrations is given by

Input.Simu.type_natfreq = 0;
Input.Simu.type_mech_workflow = 2;

The 2% constant damping is defined with

Input.Simu.type_damping = 0;
Input.Simu.ksi_damp = 0.02;

The maximum number of circumferential spatial orders is defined with Input.Simu.Nmax_fft_orders_circ = 9;

Thermal model

In the script you can also find the thermal model parameters. Here it only consists in specifying the average stator and rotor winding temperatures. These values will affect in particular the effective resistance of the equivalent circuit, and therefore the current values.

Numerical parameters

Max frequency of study is defined with Input.Simu.freq_max_spec = 6400 Angular and time discretization steps are defined with

Input.Simu.Na_tot = 2^11;
Input.Simu.Nt_tot = 2^11
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