Three Phase Induction Motor Dynamic Modeling and Behavior Estimation

1
Three Phase Induction Motor Dynamic Modeling and
Behavior Estimation
Lauren Atwell1, Jing Wang2, and Leon M.
Tolbert2 Auburn University1, University of
Tennessee2
Introduction
Results

• Induction motors are widely used for industrial
  applications because they are reliable, rugged,
  and very efficient.
• Rotor speed and torque characteristics of
  induction motors are usually controlled by a
  motor drive for smoother transitions, more
  accurate behavior, and stable operations.
• While testing power electronics motor drives, an
  induction motor dyno set requires a mechanical
  load for different operating points, meaning it
  requires not only the motor to be tested, but
  also a second motor mechanically coupled to the
  first. These two motors have a large footprint in
  a lab, and also do not allow for variations in
  motor parameters.
• Induction motor dynamic modeling will allow for
  much more flexible testing of motor drives.

Fig. 3. Torque of all three models (mathematical
ideal, mathematical with PWM inverter, and
MATLAB), with increased torque load at t 0.5
seconds.
Fig. 4. Rotor speed of all three models
(mathematical ideal, mathematical with PWM
inverter, and MATLAB) with increased torque load
at t 0.5 seconds.
Research Goals

• Mathematically model a three-phase squirrel-cage
  induction motor.
• Verify model with MATLAB Simulinks inherent
  integrated induction motor model.
• Test by simulating various loads to verify
  correct functionality of mathematical model.

Fig. 5. dq-axis stator voltage of MATLAB model.
Methodology
Figure 1 shows the implementation of the
induction motor model from Simulink library
driven by the inverter bridge output with motor
rated voltage and frequency.
Fig. 6. dq-axis stator voltage of mathematical
model.
 
Fig. 7. Three phase AC current of mathematical
model with increased torque load at t 0.5
seconds.
Fig. 1. MATLAB Simulink inherent integrated
induction motor model.
The mathematical model of an induction motor is
split into several sub-models, including
electrical and mechanical systems expressed
within dq0 domain. This realization in Simulink
is shown in Figure 2. The model was tested first
under ideal voltage conditions, and then powered
by a PWM inverter. Both results were then
compared to the MATLAB model.
Fig. 8. dq-axis current of mathematical model
with increased torque load at t 0.5 seconds.
Conclusions
Behaviors of the built induction motor have been
verified for torque and rotor speed
characteristics, regardless of supply (ideal
constant supply versus PWM inverter). However,
the built mathematical model allows for flexible
voltage filtering resulting in more accurate
inputs for the motor model. It produces much more
steady dq-axis voltage inputs in the per-unit
system, as evidenced by the results comparison
between Figures 5 and 6.
 
Fig. 2. Mathematical model of a three phase
squirrel-cage induction motor.
This work was supported primarily by the
Engineering Research Center Program of the
National Science Foundation and the Department of
Energy under NSF Award Number EEC-1041877 and the
CURENT Industry Partnership Program.