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