## Lab 4: DC Chopper fed DC Motor Speed Control

### MATLAB Simulink LAB 1 file

Matlab v2018a or above is required to run this file. Click the link below to download the file.

#### Note - ملاحظة :

عند تنزيل الملف تاكد من ان يكون اسم الملف خالي من الفراغات و الاقواس وعلامة الناقص

• Uncompress 'LAB4_FOUR_QUAD_CHOPPER.zip' into the MATLAB document folder.
• Ensure to save the Lab 4 folder in the MATLAB folder and verify that the name of the folder does not contain invalid characters.

### Introduction

In Lab 3 experiment, motor speed control was achieved via a single-phase fully-controlled thyristor-based fullwave rectifier and speed control was demonstrated. In this Lab, the objectives are:
1) Observe the four-quadrant speed operation of a DC motor.
2) Control the speed of the DC motor and observe the effect of a stepped torque.

1) Save the waveform for the speed, torque, armature current and armature voltage label the quadrant of operation. [D_ref: 0.3, 0.6, 0.9; Torque: 20 N.m, -20 N.m]
2) Give a step change in load torque from 0 to 20 N.m (TL) at t = 1 s and note the resultant speed for each D_ref setting. Elaborate on the effect of changing D_ref.
3) Theoretically estimate the no-load speed value in rpm for each case
4) What is the net power supplied by the motor? What is the quadrant of operation for all the scenarios?

1) Save the waveform for the speed, reference speed, torque, armature current and armature voltage label the quadrant of operation.
2) Give a step change in load torque from 0 to 20 N.m (TL) at t = 1 s and note the resultant speed.
3) Theoretically estimate the no-load speed value in rpm.
4) What is the net power supplied by the motor? What is the quadrant of operation?
5) repeat tasks 1-4 for all of the combinations of step torque and reference speed. [speed: 1000 rpm, -1000 rpm; Torque: 20 N.m, -20 N.m]

### Speed control of DC motor

• Explaint the controller of the motor in more details and elaborate on control strategy structure flow and investigate the advantages and disadvantages of the PI controller method.
• What is the power factor at rated speed? use the motor parameters and verify using the output mechanical power considering losses.
• When changing D_ref from 0.3, 0.6, 0.9 record the speed of the motor for each case and calculate the related armature voltage and current assuming constant load.
• Compare the results of this experiment with the results from Lab 3 experiment, What are your observations and findings egarding the two methods?
• Describe the advantages of this method of speed control.

### Conclusion

In yout own words, write the advantages and benefits for adapting this speed controller. What are the limitations, if any, when implementing a four quadrant DC chopper for DC motor speed control?