How to use flux lookup tables (airgap flux interpolation)?


This article shows how to speed-up MANATEE software electromagnetic calculations in case of skewing or variable speed operation. This feature is especially useful when working with non-linear electromagnetic model of MANATEE (coupling with FEMM).


The idea consists in building a flux distribution lookup table for different Id/Iq combination and interpolating this table when flux distribution is needed, in particular during variable speed operation or skewed operation. The calculation of the flux at different slices in case of skew can be indeed interpreted as a local change of current angle and time reference.

The flux lookup table is saved in Results folder under the name [machine_name,’_FluxTableIdIq.mat’].

Note that the flux lookup table can be built with third party electromagnetic software as long as the following format is respected. The .mat file should contain

  • TableId vector of Id current of size [1 ,nid]
  • TableIq vector of Iq current of size [1 ,niq]
  • FluxTableIdIq matrix of complex (radial + 1j*tangential) flux waveform of size [nid,niq,nt,na] where the flux is taken in the middle of the airgap at Output.Geometry.Rag_min radius, nt is the number of time steps and na is the number of angles along the airgap

GUI implementation

To be completed

Scripting implementation

The flux table is built when specifying Input.Simu.is_build_flux_table = 1; In this case the flux table is built, saved and loaded each time the airgap flux needs to be calculated. To avoid loading the flux table when available and enforcing the build of the table one can use Input.Simu.is_build_flux_table = 2; The Id/Iq current values are linear spaced in boundaries defined by

  • Input.Simu.idmin
  • Input.Simu.idmax
  • Input.Simu.Nb_id
  • Input.Simu.iqmax
  • Input.Simu.iqmin
  • Input.Simu.Nb_iq

WARNING: in case of skew make sure that you go above the current limits defined by the mid-slice of the motor (reference slice for the definition of the current angle). The effective current angle seen by first and last axial motor slice are Phi0+/-p*alpha_skew/2 where Phi0 is the current angle and alpha_skew is the total mechanical skew angle. Besides, the skew should not be activated when generating the flux table.

This table can then be used inside the skew optimization environment or at variable speed.

Validation cases

Validation cases ALG_027, ALG_028, ALG_029, ALG_031, ALG_032, ALG_033 deal with the validation of the flux lookup table.

See also

The skew optimization environment of MANATEE uses the flux lookup table feature.

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