1) A DC generator operates on the principle of electromagnetic induction to convert mechanical energy into electrical energy. 2) It uses Faraday's law - whenever a conductor moves through a magnetic field, an electromotive force (EMF) is induced in the conductor. 3) The direction of the induced EMF is determined by Fleming's right-hand rule.

1. DC GENERATOR

2. WORKING PRINCIPLE
• Energy can be converted form one form to another.
• It uses Faraday’s law of electromagnetic induction.
• Whenever there is change in the magnetic flux
associated with conductor, an EMF is induced in it.
Mechanical
Energy
Electrical
Generator
Electrical
Energy

3. • The direction of induced e.m.f. (and hence current) is given by
Fleming’s right hand rule
• As per Faraday's law of electromagnetic induction, whenever a
conductor moves inside a magnetic field, there will be an induced
current in it. If this conductor gets forcefully moved inside the
magnetic field, there will be a relation between the direction of
applied force, magnetic field and the current. This relation among
these three directions is determined by Fleming Right Hand rule
Cont……

4. Simple Loop DC Generator
• Consider a single turn loop ABCD rotating clockwise in a uniform
magnetic field with a constant speed as shown in Fig.(1.1). As the
loop rotates, the flux linking the coil sides AB and CD changes
continuously. Hence the e.m.f. induced in these coil sides also
changes but the e.m.f. induced in one coil side adds to that induced
in the other. E.M.F. generated in the loop is alternating one. It is
because any coil side, say AB has e.m.f. in one direction when
under the influence of N-pole and in the other direction when
under the influence of S-pole.

5. • A DC Generator operates on the principle of dynamically induced emf.
• To convert the alternating bidirectional alternating current into
unidirectional direct current split rings are used.
• Split rings are cut into two half's called segment separated by insulated
sheet mica. The ring segments are also kept insulated from the central
shaft and are connected to the ends of the coil and the carbon brushes.
• The action of split rings is called commutation
Cont……

6. Cont……

7. • Yoke of DC Generator - yoke are made of cast iron
– Yoke of DC generator serves two purposes
• It holds the magnetic pole cores of the generator and acts as
cover of the generator.
• It carries the magnetic field flux.
Construction of DC Generator

8. • Pole Cores and Pole Shoes of DC Generator- There are mainly two
types of construction available.
• One: Solid pole care, where it made of a solid single piece of cast iron or
cast steel.
• Two: Laminated pole core, where it made of numbers of thin, limitations
of annealed steel which are riveted together.
• The pole core is fixed to the inner periphery of the yoke by means of
bolts through the yoke and into the pole body.
• The pole shoes are so typically shaped, that, they spread out the
magnetic flux in the air gap and reduce the reluctance of the magnetic
path.
Construction of DC Generator

9. • Armature Core of DC Generator- The purpose of armature core is to
hold the armature winding and provide low reluctance path for the flux
through the armature from N pole to S pole. Although a DC generator
provides direct current but induced current in the armature is alternating
in nature. That is why, cylindrical or drum shaped armature core is build
up of circular laminated sheet.
• Armature Winding of DC Generator - Armature winding are
generally formed wound. These are first wound in the form of flat
rectangular coils and are then pulled into their proper shape in a coil
puller. Various conductors of the coils are insulated from each other. The
conductors are placed in the armature slots, which are lined with tough
insulating material.
Construction of DC Generator

10. • Commutator of DC Generator - The commutator plays a vital role in
dc generator. It collects current from armature and sends it to the load as
direct current. It actually takes alternating current from armature and
converts it to direct current and then send it to external load.
• Brushes of DC Generator - The brushes are made of carbon. These are
rectangular block shaped. The only function of these carbon brushes of
DC generator is to collect current from commutator segments.
• Bearing of DC Generator - For small machine, ball bearing is used and
for heavy duty dc generator, roller bearing is used
Construction of DC Generator