1. Electronic Speed Control Method for DC Motors
Lecture
Electronic Speed Control Method for DC Motors
Engr. Zahoor Ahmed Maharvi

2. Engr. Zahoor Ahmed Maharvi
Introduction
Solid state circuits using semiconductor diodes and thyristors have become very popular for controlling the speed of d.c. motors.
Solid state circuits are progressively replacing the traditional electric power control circuits based on thyratrons, ignitrons, mercury arc rectifiers, magnetic amplifiers and motor-generator sets etc.
Engr. Zahoor Ahmed Maharvi

3. Merits of Electronic Control Circuits
As compared to the electric power control circuits, the electronic control methods have
Higher accuracy
Greater reliability
Quick response
Higher efficiency as there are no I2R losses and moving parts.
Full 4-quadrant speed control is possible to meet precise high speed standards.
Engr. Zahoor Ahmed Maharvi

4. Electronic Speed Control Methods
All electronic control circuits control the motor speed by adjusting either
the voltage applied to the motor armature
the field current, or
both
Engr. Zahoor Ahmed Maharvi

5. Engr. Zahoor Ahmed Maharvi
D.C. Motors Power Supply
D.C. motors can be run from d.c. supply if available or from a.c. supply after it has been converted into d.c. supply with the help of rectifiers which can be either half-wave or full-wave and either controlled (by varying the conduction angles of the thyristors used) or uncontrolled.
Engr. Zahoor Ahmed Maharvi

6. Motor Speed Control using Thyristor Controlled Rectifier
The average output voltage of a thyristor-controlled rectifier can be changed by changing its conduction angle and hence the armature voltage of the d.c. motor can be adjusted to control its speed.
Engr. Zahoor Ahmed Maharvi

7. Motor Speed Control using Thyristor Chopper Circuit
When run on a d.c. supply, the armature d.c. voltage can be changed with the help of a thyristor chopper circuit which can be made to interrupt d.c. supply at different rates to give different average values of the d.c. voltage.
If d.c. supply is not available, it can be obtained from the available a.c. supply with the help of uncontrolled rectifiers (using only diodes and not thyristors). The d.c voltages so obtained can be then chopped with the help of a thyristor chopper circuit.
Engr. Zahoor Ahmed Maharvi

8. Uncontrolled Rectifiers
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9. Controlled Rectifiers
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10. Controlled Rectifiers (contd..)
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11. Engr. Zahoor Ahmed Maharvi
Thyristor Choppers
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12. Thyristor Choppers (Contd..)
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13. Thyristor Speed Control of a Separately Excited D.C. Motor
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14. Thyristor Speed Control of a D.C. Series Motor
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15. Full-Wave Speed Control of a Shunt Motor
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16. Thyristor Speed Control of a Shunt Motor
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17. Thyristor Speed Control of a D.C. Series Motor
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18. ? Reference Chapter # 30 Electrical Technology By B.L.Theraja
Engr. Zahoor Ahmed Maharvi