Re: Flux calculation

["David Meeker" <dmeeker@xxxxxxxx>]

Mihai Priboianu wrote:

> Hello !!!
> 
> I am trying to calculate the flux for a permanent magnet synchronous
machine. So I use a Lua script which evaluates the magnetic vector
potential A in each stator slot for a different position of the rotor.
For example I have the phases A1, A2, X1 and X2 and I am using the
following relation to calculate the flux for phase A:
> 
> fluxA=(AA1-AX1+AA2-AX2)*w1*L
> 
> fluxB=(AB1-AY1+AB2-AY2)*w1*L
> 
> fluxC=(AC1-AZ1+AC2-AZ2)*w1*L
> 
> where: AA1, AA2, AX1 and AX2 are the magnetic vector potentials for
the slots A1, A2, X1 and, rspectively, X2;
> w1-number of turns in each slot, in my case w1=15 turns
> L - the length of the machine, in my case L=57 mm
> 

To find the instantaneous flux linkage for a given phase, integrate
A.J over a given phase and divide by the instantaneous phase current.

> Also, I need to calculate the inductances for each phase. For that I
am using the following relations:
> 
> LA=fluxA/iA
> 
> where iA is the curent of the phase A.
> 
> Are all these correct?
> 

With a PM synchronous machine, your flux linkage could include flux
contributions from the permanent magnets--you don't want to count this
flux linkage in the computation of self inductance. If you want the
inductance of a phase, you can either "turn off" the magnets (OK if
saturation isn't really an issue) or by perturbing the phase current
slightly and computing the change in flux linkage/change in current
(which gives you the incremental inductance about some operating point).

Dave.
--
David Meeker
http://femm.berlios.de/dmeeker