Dave Meekers Induction Motor in FEMM example: a question

["Douglas Stevenson" <Douglas@xxxxxxxxxxxxx>]

I have a few conceptual questions regarding this model.

The example clearly demonstrates the "deep bar" effect on the rotor at
different frequencies. The current density in the rotor bars is clearly
redistributed towards the outer edge of the rotor at reasonable starting
frequencies of 50-60 Hz. 

However, how would one assess the so-called "Proximity effect" in the
stator windings? At higher frequencies of applied current (say a few Khz
caused by a current source with severe distortion), the presence of a
winding with parallel turns or conductors that are large w.r.t the skin
depth, would create an effect similar to the deep bar situation. The
ferromagnetic slot would cause the current density to be "redistributed"
in those stator windings, once again producing an effective AC
resistance far greater than the DC resistance, and a corresponding
increase in undesirable losses.

One would cleary need to define a large number of conductors/turns with
their own circuit properties in FEMM, but how would one assess which
regions of the individual conductors/turns have higher and lower
resultant current densities? Each condcutor /turn has both its self
inductance, causing the skin effect, and the mutual inductances with all
the surrounding conductors/turns as well as with the eddy currents in
the core causing the proximity effect. How and which would one define
boundary conditions for the individual turns/conductors?

Douglas Stevenson 


 
-----Original Message-----
From: David Meeker [mailto:dcm3c@xxxxxxxxxxxxx]
Sent: 27 September 2002 06:18
To: femm@xxxxxxxxxxxxxxx
Subject: [femm] Re: Induction Motor in FEMM


Ok--I've been threatening to make an example of how one might go about
analyzing an induction motor using FEMM, and now I've done it. Well,
at least I've got a draft of an example anyhow...

If you're interested checking out this example, I've put it at:
http://femm.berlios.de/2horse.zip

This example goes through the identification of parameters in an
induction motor model with FEMM. Torque results from the circuit
model are then compared to torques predicted via stress tensor
integrations. Some additional issues are also presented that are
important to consider for the purposes of design and comparison to
experimental results.

If I've made a mistake in the example, please point it out to me--I
don't usually do "normal" induction motors...

Dave.



--- In femm@xxxx, Lindolfo Marra <lindolfomcneto@xxxx> wrote:
> I am work with simulation in the induction motor. Simulation lf
loked rotor conditions and running conditions.The simulation is not
good. Femm(groups), you make this simulation, please you can send the
simulation(rotor conditions and running conditions) in the FEMM. thank
you 
> 
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