Induction motor model

An induction motor is used all over the world to drive mechanical load. I am presenting a mathematical model which plots its performance at various frequencies.
Equivalent circuit of the induction motor is as shown below:

indmotckt

  • r1 is resistance of the stator winding.
  • r2 is resistance of the rotor winding.
  • X1 is inductive reactance of stator. It can be calculated from the stator inductance and power frequency.
  • X2 is inductive reactance of rotor.  It can be calculated from the rotor inductance and power frequency.
  • The above circuit shows the parameters from the stator side. So rotor resistance appears to be r2/slip.

You can download the script in the pdf format here .

You can download the script in the zip format here.

When we run the above script on GNU Octave prompt, we get the following plots:

indmot

The above plots are seen as the result of running the script on octave prompt. You can zoom any of them, while in octave, to see exact values of parameters at various frequencies.

The 45KW motor for which the plots are generated has following specifications:

  1. Line to line voltage: 400V
  2. Rated frequency: 50Hz
  3. r1=0.15 ohm
  4. r2=0.12 ohm
  5. L1=0.001432 H
  6. L2= 0.001432 H
  7. Lm=0.09072 H
  8. Fixed losses= 400W
  9. Slip=.04 at full load (4% slip)