How to define symmetries in MANATEE?


This article shows how to define symmetries in MANATEE simulation software for the fast NVH calculation of electric powertrains.


MANATEE allows to define or calculate the symmetries of the airgap flux distribution along time and space (airgap angle), namely

  • periodicities (number of repetitions of an elementary pattern)
  • antisymmetries (if the elementary pattern is antisymmetric or not)

Note that symmetries are based on the flux waveform and not the force waveform (square of the flux). The maximum angle for flux density calculation is

\alpha_{f}= 2 \pi

The maximum time for flux density calculation is given by

T_{f}= \frac{N_{rev}p}{(1-s)f_{s}

where Nrev is the number of mechanical revolutions (Input.Simu.Nrev), p is the number of pole pairs (Input.Magnetics.p), s is the slip for induction machines (Output.Electrical.slip0) and fs is the fundamental electrical frequency (Output.Electrical.freq0).

These final simulation time and angle can be reduced to speed-up NVH calculation of electrical machines. The symmetries automatically identified by MANATEE depend on machine topology, load state, winding pattern, faults, etc.

The following picture illustrates the application of symmetries along the airgap:

PNG - 88.5 kb

GUI implementation


Scripting implementation

By default, MANATEE automatically identifies the symmetries to speed up calculation: Input.Simu.is_symmetry = 1; Symmetries can be manually desactivated with

Input.Simu.is_symmetry = 0;

Alternatively space and time symmetries can be user-defined with

Input.Simu.is_symmetry = 2;

In that case the user must specify the number of time/angle flux waveform periodicities

Input.Simu.npert0=2; Input.Simu.npera0=2;

and the presence of time/angle flux waveform antisymmetries

Input.Simu.is_antisymt0=1; Input.Simu.is_antisymt0=0;

The calculated periodicities by MANATEE are then stored in outputs as

Output.Geometry.npert Output.Geometry.npera Output.Geometry.is_antisymt Output.Geometry.is_antisyma

See also

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