31027590 Topic 5 Ward Leonard System
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Transcript of 31027590 Topic 5 Ward Leonard System
Topic 5:
Prepared by:
Engr. ARJUN G. ANSAY, EE PhD
Professor, TUP-IRTC
At the end of the discussion, the
participants should be able to:
1. Familiarized the Ward-Leonard System
Objectives:
of speed control;
2. Identify the different components of
Ward-Leonard System and their
functions.
1. Content Principle of DC Motor Speed
Control
2. Methods of DC Motor Speed Control
Contents:
3. The Ward-Leonard System Principle
The speed “n” of a DC Motor is defined by the following equation:
Principle of DC Motor Speed
Control
n = kE – Ia ( Ra + Rb )
Ø
Where:n = speed of DC MotorØ = magnetic fluxE = impressed voltageIa = armature currentRa = armature resistanceRb = brush contact resistance
Ø
1. Field Control
� This is a method of controlling the speed by
changing the magnetic flux Ø in equation
2. Armature Resistance Control
Methods of DC Motor speed
control:
2. Armature Resistance Control
� This speed control is performed by inserting a
series resistance in the armature circuit.
3. Voltage Control
� This speed control is done by varying the
voltage across the armature circuit of the DC
Motor.
WARD-LEONARD SYSTEM
- is a method of speed control
using voltage as variable to using voltage as variable to
supply the DC Motor thru the
used of Separately Excited DC
Generator.
1. 3Ø – induction motor
2. Separately excited DC Generator
3. Separately excited DC Motor
4. Load (DC Generator)
Components of Ward-Leonard System:
4. Load (DC Generator)
Block diagram of Ward-Leonard System:
Where:
3Ø = three phase induction motorG1 = separately excited DC GeneratorM = separately excited DC MotorG = Load (DC Generator)
Schematic Diagram of Ward Leonard System
�Note:
Frequently, control of generator voltage
is combined with motor field control for
variation in speed.variation in speed.
Advantage:
1. Provide excellent step less speed
control
2. Very wide range of speed.
Disadvantage:
1. High first cost
2. Low over-all efficiency
Thank you for Thank you for
kind attention