After completing the following series of exercises, the student will understand the design of controllers for a squirrel-cage induction motor.
Real-time simulation results are shown in the laboratory panel.

Flux Control

• Open the model with the default settings.
• Gradually apply a field voltage of 460 V for the DC machine.
• Go to “Flux Control” tab under Command (see figure 9).
• Switch the Flux Control to Predefine.
• Activate the flux control by pressing the “ACTIVATE” button (see figure 9).

Figure 9: Activation of Predefined Flux Control

• Observe the waveforms under “Flux Control” panel.
• What is the rotor nominal flux?
• Does the measured rotor nominal flux match the value of table 3?
  Explain your observation.

Torque Control

• Keep the flux control activated.
• Go to “Torque Control” tab under Command (see figure 10).
• Switch the Torque Control to Predefine and press on the “enable” button (see figure 10).

Figure 10: Activation of Predefined Torque Control

• Apply a reference torque of 25 N.m.
  1. Observe the results under the “Torque Control” and “Triggering Scopes” panels.
  2. Does the measured torque follow the reference torque?
     Explain your observation.
• From the reference torque of 25 N.m., apply a new value of 50 N.m.
  1. Again, observe the results under the “Torque Control” and “Triggering Scopes” panels.
  2. Does the measured torque follow the reference torque?
     Show your results.
• How do the stator currents and voltages differ for reference torques of 25 and 50 N.m?

Speed Control

• Keep the flux and torque controls activated.
• Reset the torque reference to a value of 0 N.m.
• Go to “Speed Control” tab under Command (see figure 11).
• Switch the Speed Control to Predefine and press on the “ENABLE” button (see figure 11).

Figure 11: Activation of Predefined Speed Control

• Apply a reference speed of 500 rpm.
• Observe the results under “Triggering Scopes” panel.
  1. Does the measured speed follow the reference speed?
  2. Does the measured torque follow the reference torque?
  3. What is the rotor flux in q-axis?
• From the reference speed of 500 rpm, apply a reference speed of 1000 rpm.
  • Repeat questions 1 to 3 above.
• From the reference speed of 1000 rpm, apply a reference speed of 1500 rpm.
  • Repeat questions 1 to 3 above.
• Increase the DCM variable load to a value of 12 ohms.
• From the reference speed of 1500 rpm, apply a reference speed of 2000 rpm.
  • Repeat questions 1 to 3 above.
• From the reference speed of 2000 rpm, apply a reference speed of 2500 rpm.
  • Repeat questions 1 to 3 above.
• How does the increase in speed value impact the rotor flux and the torque of the induction motor? Explain your observations.

V/F Control

• Open the model with the default settings.
• Gradually apply a field voltage of 460 V for the DC machine.
• Go to “V/F” tab under Command (see figure 12).
• Press on the “v/f control” button to activate the command (see figure 12).

Figure 12: Activation of V/F Control

•  Increase the inverter frequency by steps of 10 Hz and fill out table 9.

Table 9: Effect of Varying Inverter Frequency

• Plot the frequency versus the speed N.
• How does the speed change with frequency?
  Explain.
• How does the ratio v/f change with frequency?
  Explain what you observe.
• How does the active power Ps change with frequency?
  Explain your observation.
• What are the voltage output levels of the inverter?
  Show your results.
• Do the voltage output levels of the inverter change with frequency?