DC Machine_Session 1 - out of four sessions

DC Machine session-1

1. Electrical Machines-1
Unit 3: DCMachines
Dr.Mrs. Haripriya H. Kulkarni.

2. Review of previous Lecture







•Transformer-1 phase and 3 phase

3. Learning Objectives
Comparison between Motor and Generator
Study of D.C. Machine
Basics of Machine
Operating principle of Motor and Generator
Different parts and its function

4. Learning Outcomes
Students will be able to :
Compare Motor and Generator
Study of D.C. Machine
Explain basics of Machine
Demonstrate operating principle of Motor and Generator
Different parts and its function

5. Generating and Motoring Action
DIFFERENCE BETWEEN MOTOR AND GENERATOR
+
MOTOR GENERATOR

6. BASIS MOTOR GENERATOR
Function The Motor converts Electrical energy into
Mechanical energy
The Generator converts Mechanical energy to
Electrical Energy
Electricity It uses electricity. It generates electricity
Driven
element
The Shaft of the motor is driven by the
magnetic force developed between
armature and field.
The Shaft is attached to the rotor and is driven
by mechanical force.
Current Current is to be supplied to the armature
of the motor
In the generator current is produced in the
armature windings.
Rule
Followed
Motor follows Fleming·s Left hand rule. GeneratorfollowsFlcming's Right hand rule.
Example An electric car or bike is an example
of electric motor.
Energy in the form of electricity is generated at
the power stations.
Generating and Motoring Action

7. Left Hand-Motor
principle
Right Hand-
Generator principle

8. DC Generator Construction
A DC Generator is an electrical device which converts mechanical energy intoelectrical energy.
libdkiH:IHI
Itmainlyconsists of three main pa1ts,i.e.magneticfieldsystem,armatm-eandcommutator andbrush gear.

The other partsofa DCGenerator are magnetic fn1n1e and yoke, pole coreand poleshoes, field orexciting
coils, armature core and windings, brushes, end housings, bea,ings andshafts.

9. DC Generator Construction
Arm;nure
CommuUitor
8ru hi,s

10. DC Generator Construction
-
Field winding/ Pole coils:
They are usually made ofcopper.
Field coils are former wound and placed on each
pole and are connected inseries.
They are wound in such a way that, when energized,
they form alternate North and South poles.

11. DC Generator Construction
Pole s h o e s function:
Poles arejoined to the yoke with the help of bolts or welding.
It carries and support the field winding.
To support the filed winding: Pole Core provides this area to
wound the field winding.
To spread out the flux in air gap:Pole core direct the magnetic flux
to the air gap, armature, and to the next pole.
0

12. DC Generator Construction
Armature core/ rotor:
Armature core is the rotor of a de machine.
It is cylintlrical in shape with slots tocarryarmature winding.
11,e armature is built up of thin luminated circular steel disks for reducing eddy current losses.
It may be provided with air ducts for the axialair flow for cooling purposes.
Armature is keyed to theshaft.

13. DC Generator Construction
Armatvr• Windmgl
Armature winding:
The armature core slots are mainly used for holding the armature winding and it is connected in series
to parallel for enhancing the sum of produced current.

14. DC Generator Construction
Commutator:
The working of the commutator is like a rectifier for changing AC voltage to the DC voltage within the
armature ,winding to across the brushes.
It is designed ,with a copper segment, and each copper segment is protected from each other,with the
help of mica sheets. It is located on the shaft of the machine.

15. DC Generator Construction
Brushes:
The electrical connections can be ensured between the commutator as well as the external load circuit
with the help of brushes
They collect current from commutator. Made up of carbon or graphite.

16. Student’s Evaluation
Name the parts of D.C.Machine
Flemings left hand rule? Application?
Flemings right hand rule? Application?

17. Assignment
1. Draw constructional diagram of D.C. machine. State functions of different parts along with
the material used.

18. Wrap up
1. Principle of operation of D.C. Machine
2. As a motor, as a generator
3. Different parts of machine
4. Function of each part and construction , significance.