The document discusses speed control methods for DC motors. It describes various types of speed control for DC series and shunt motors, including flux control, armature voltage control, potential divider control, and applied voltage control. It also discusses the Ward-Leonard system of speed control, which uses a motor-generator set to provide smooth and rapid variable speed control and is commonly used for elevators and industrial machinery. The document outlines advantages like smooth wide range speed variation but also disadvantages like low efficiency and high initial cost.

1. SPEED CONTROL of DC MOTORS
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Speed control of DC motors kongunadu college of engineering & technology
Content:
 Factors affecting the speed control of DC MOTORS.
 Different Types of Speed Control Of DC SERIES and SHUNT motors.
 Ward-Leonard System of Speed Control.
 References
S.RAGUL,
ASSISTANT PROFESSOR,
DEPARTMENT OF EEE,
KNCET

2. Factors affecting the speed of D.C
Motor
 Flux
 Voltage across the armature
 Applied voltage
 Depending upon these factors the various methods of speed
control
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Speed control of DC motors kongunadu college of engineering & technology

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Speed control of DC motors kongunadu college of engineering & technology

4. Speed Control of DC Shunt Motor
FLUX CONTROL
METHOD
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Speed control of DC motors kongunadu college of engineering & technology

5. Armature Voltage Control
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6. Potential Divider Control
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Speed control of DC motors kongunadu college of engineering & technology

7. Applied Voltage Control
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Speed control of DC motors kongunadu college of engineering & technology

8. Speed Control of DC Series Motor
Flux Control – Field Divertor Method
Series field winding is shunted by a variable resistance (Rx) known
as field divertor
Speed control above rated value
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Speed control of DC motors kongunadu college of engineering & technology

9. Motor which require constant load torque
Armature of the motor is shunted by a variable resistance (Rx)
known as armature divertor
Speed control below rated value
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Speed control of DC motors kongunadu college of engineering & technology

10. Flux change is achieved by changing the number of turns of the field winding
Speed control above rated value
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Speed control of DC motors kongunadu college of engineering & technology

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Speed control of DC motors kongunadu college of engineering & technology

12. Rheostatic Control
Variable resistance (Rx) is inserted in series with the motor, the
voltage drop across this resistance (IaRx) occurs. This reduces
the voltage across the armature.
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Speed control of DC motors kongunadu college of engineering & technology

13. Applied Voltage Control
The voltage obtained from the generator is controlled by a field
divertor resistance connected across the series field winding of the
generator
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Speed control of DC motors kongunadu college of engineering & technology

14. Ward-Leonard System of Speed Control
This system is commonly employed for elevators, hoists and main drive in steel mills
The modifiedWard-Leonard system is called Ward-Leonard – Ilgner system in which a
flywheel is used in addition to motor generator set.
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Speed control of DC motors kongunadu college of engineering & technology

15. ADVANTAGES AND DISADVANTAGES
 Smooth variation of speed over wide range.
 Rapid and instant speed reversed.
 Speed control above and below rated is possible.
 Good speed regulation.
 Efficiency is low
 Initial cost of setup is very high.
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Speed control of DC motors kongunadu college of engineering & technology

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Speed control of DC motors kongunadu college of engineering & technology
Conclusion:
The factors affecting speed control of dc machines, different methods
advantage and disadvantages is explained in detail with suitable
diagrams.
 Ward-Leonard System of Speed Control also discussed.
References: