Re: [femm] Induction Motor Tourqe Calculation

[David Meeker <dmeeker@xxxxxxxx>]

Remember that FEMM doesn't take into account the impedance of the rotor
end rings.  The decreased rotor resistance makes the operating point
occur at a lower value of slip.  Since the operating point of a typical
induction motor is on the unstable side of the constant current
torque vs. slip frequency curve, the reduction in resistance due to
ignoring the end turns decreases the torque predicted by the model when
you run the model at the rated slip frequency of the real machine. 
(Note, however, that the operating point of a typical induction motor
is on the stable side of the constant volts/hz torque vs. slip
frequency curve...)

Dave.

ihsan canakoglu wrote:

Length of machine is 0.09 m. In our model, we obtained the 80 Nm value for 1 m length. Now, nominal torque is 80*0.09=7.2 Nm<10.07 Nm.

riad kechrpud <r_kechroud@xxxxxxxx> wrote:

What is the length of your machine. Don t forget that FEMM gives you the torque per unit length so you must multiply the obtained torque by your machne length (in meter).

 

ihsan canakoglu <acembuselik@xxxxxxxxx> wrote:

Hi All,
We have studied an induction motor which parameters are as follows:

 

Pf=3 kW
2p=2 (p=1)
nr (nominal)=2844 d/d
f=50 Hz
U=380 V (Star connected)
Stator Current (nominal)=6.6 A and stator winding turn=42

 

In "Problem" definition, to obtain nominal operating point values, we
have given the frequency 2.6 Hz (ws=s*w => ws=(3000-2844)/3000*50=2.6
Hz).
Motor nominal tourqe, Tn=3000*60/(2*pi*2844)=10.07 Nm.
In FEMM model, the tourqe for this operating point has obtained ~80
Nm, ie 8 times of nominal tourqe.
All of other values, such as leakage inductance, stator and rotor
resistance are very close to obtained from experimental results.
Why the tourqe values are not close?

The fem file of our model is attached.

Best regards.

 

A. Ihsan Canakoglu

-- 
David Meeker
dmeeker@xxxxxxxx
http://femm.berlios.de/dmeeker