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- 1. Speed control of dc motor using chopper Presented by: Under the guidance of: Ajeeta Srivastava (1473720005) Assi. Prof. Nikhil Chowdhary Akansha (1473720006) DEPARTMENT OF ELECTRICAL ENGINEERING RAJKIYA ENGINEERING COLLEGE AMBEDKAR NAGAR-224122(U.P.)
- 2. Abstract The speed of a d.c. motor is given by relationship N= ( V- Ia Ra)/kΦ Speed of dc motor can be varied by following methods Armature voltage control (for below base speed) Field flux control (for above base speed) Armature resistance control Here, we are using armature voltage control method for speed control. In this method, the voltage applied to armature circuit, V is varied using DC-DC converter, a power electronics device which converts fixed dc input voltage to a variable dc output voltage.
- 3. Introduction Chopper are static power electronics device which converts fixed dc input voltage to a variable dc output voltage. It can be step-up or step-down. Separately excited dc motor has field winding and armature winding with separate supply voltage. Field winding supplies field flux to armature. When dc voltage is supplied to motor, current is fed to the armature winding through brushes and commutator .
- 4. Choppers Choppers are DC-DC converters that converts fixed DC input voltage to a variable DC output voltage. These are widely used in regulated switching power supplies and dc motor drives application.
- 5. Types of Choppers There are two types of choppers: Step-up chopper: In this the output voltage is more than input voltage. Step-down chopper: In this the output voltage is less than input voltage.
- 6. Principle of Chopper operation There are basically two time periods in chopper operation, one is the “on” time denoted as TON and other is the “off” time denoted as TOFF. During TON we get the constant source voltage VS across the load and during TOFF we get zero voltage across the load. In this way we obtain a chopped dc voltage at the load terminals.
- 7. WORKING Average Voltage, Vo= (Ton/ (Ton+Toff))*Vs = (Ton/T)*Vs =αVs
- 8. Working Of Separately Excited DC Motor Separately excited dc motor has field and armature winding with separate supply voltage. Field winding supplies field flux to armature. When dc voltage is applied to motor , current is fed to armature winding through brushes and commutator. Since rotor is placed in magnetic field and it is carrying current also. So motor will develop the back e.m.f. and torque to balance load torque at particular speed.
- 9. Block Diagram INPUT DC CHOPPER OUTPUT (variable dc voltage) Separatel y excited dc motor DISPLAY (current ,voltage , speed) PI Controller Reference speed
- 10. Application of chopper in DC Motor 1) For regenerative braking of DC motor 2) Power control or motoring control 3) Choppers are used in electric cars, airplanes and spaceships, where onboard-regulated DC power supplies are required.
- 11. Simulation Result The simulink model of speed control of DC motor is shown in figure 4. It consists of speed controller , current controller, filter , chopper and a motor . Now the simulation of model is done and analyzed in MATLAB (Simulink) under varying speed and torque condition. The result from the simulation of the motor model in SIMULINK is shown in figure 5(a),5(b),5(c),6(a),6(b) and 6(c).
- 12. Fig 4. Chopper fed separately excited dc motor
- 13. Fig 5 (a) output voltage (b) output current (c) speed of dc motor for step torque
- 14. Fig 6 (a) output voltage (b) output current (c) speed of dc motor for constant torque
- 15. Conclusion The speed of a DC motor has been successfully controlled by using chopper as converter and proportional-integral type speed and current controller based on closed loop model of dc motor. The simulation is done in MATLAB under varying load condition and varying reference speed condition .We can also implement it in hardware to observe actual feasibility.
- 16. References Websites: www.wikipedia.com/chopper www.electrical4u.com/speed-control-of-dc-motor Books: (1)Dr. P.S. Bimbhra “Power Electronics” ,Khanna Publishers. (2) Dr. P.S. Bimbhra “Electrical Machinery” ,Khanna Publishers. (3)Ashfaq Hussain “Electric Machine”,Dhanpat Rai & Co. (4)Muhammad H. Rashid “Power Electronics” Pearson
- 17. THANK YOU….

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