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Electrical stepless regulation of speed and feed rates
Presented byPratyush ranjan karRoll no-163510
Brief idea
Stepped drive Stepless drive
Various electrical stepless speed control process
For ac motor the speed is given by- Rotor RPM can be
regulated by
Changing frequencyChanging poles
Therefore ,only one option left for controlling speed i.e dc motor
DC motor
PRINCIPLE OF DC MOTORS• When a current-carrying
conductor is placed in an external magnetic field, it will experience a force i.e. Lorentz force.
• Due to this force torque is produced which rotates the rotor of motor and hence a motor runs
DC motor typesDC SHUNT MOTOR
DC SERIES MOTOR
DC COMPOUND MOTOR Short shunt Long shunt
Speed Of A DC Motor
Back emf can be given by the EMF equation
Eb = PØNZ/60A
where, P= no. of poles, Ø=flux/pole, N=speed in rpm, Z=no. of armature conductors, A=parallel paths
Eb can also be given as,
Eb = V- IaRa
thus from above equations
N = Eb
60A/PØZ
but, for a DC motor A, P and Z are constant
N α K Eb/Ø (where,
K=constant)thus, it shows speed is directly proportional to back emf and inversely proportional to the flux per pole
Speed Control Methods Of DC Motor
Speed Control Of Shunt Motor
Speed Control Of Series Motor
Flux Control MethodArmature Control Method
Voltage Control Method
Flux Control MethodVariable Resistance In Series With Armature
Series-Parallel Control
Speed Control Of Shunt Motor
Flux Control Method Speed of the motor is inversely
proportional to flux. Thus by decreasing flux speed can be
increased and vice versa.
Armature Control Method
Speed of the motor is directly proportional to the back emf
Eb and Eb = V- IaRa.
Contd….
Voltage Control Method (Ward-Leonard System)
M2M1
M2M1
Output from the generator G is fed to the armature of the motor M2.
The output voltage of the generator G can be varied from zero to its maximum value
Speed Control Of Series Motor
Flux Control Method
A) Field divertor :
B) Armature divertor:
Contd…Variable Resistance In Series With Armature
Series-Parallel Control
Reference
http://www.electricaleasy.com/2014/01/speed-control-methods-of-dc-motor.html
https://www.google.com/search?client=opera&q=speed+control+of+dc+motor&sourceid=opera&ie=UTF-8&oe=UTF-8
http://www.electrical4u.com/speed-control-of-dc-motor/
“machine tool design and numerical control” –By N K Mehta
Any questions
Thank you