Dc gen

No. 1
KGTTI PRESENTATION
DC generators
The dc generator Converts the mechanical
energy to electrical energy

No. 2
KGTTI PRESENTATION
GENARATOR PRINCIPLE
The energy conversion is based on the principle of the production of
motionally induced e.m.f. As seen from fig above whenever a conductor cuts
magnetic flux, induced e.m.f. is produced in it according to Faraday’s Laws of
Electromagnetic Induction which circulates a current if the conductor circuit
is closed and the direction of induced current can be obtained by using
Fleming Right Hand Rule

No. 3
KGTTI PRESENTATION
FLEMINGS RIGHT HAND RULE
This rule states : "Hold out the right hand with the fore finger, middle finger and
thumb at right angle to each other.
 The forefinger represents the direction of field,
 The thumb points in the direction of motion or applied force,
 Then the middle finger points in the direction of the induced current

No. 4
KGTTI PRESENTATION
WORKING PRINCIPLE – DC GENERATOR

No. 5
KGTTI PRESENTATION
• Rectangular loop of conductor is ABCD which rotates inside the magnetic
field about its own axis ab.
• When the loop rotates from its vertical position to its horizontal position, it
cuts the flux lines of the field
• AB and CD of the loop cut the flux lines there will be an e.m.f induced in
these both of the sides (AB & BC) of the loop
• The direction of the current can be determined by Fleming's right hand Rule

No. 6
KGTTI PRESENTATION
• if we apply this right hand rule, we will see at this horizontal position of the
loop, electric current will flow from point A to B and on the other side of
the loop current will flow from point C to D
• If we allow the loop to move further, it will come again to its vertical
position
• Now upper side of the loop will be CD and lower side will be AB (just
opposite of the previous vertical position)
• At this position the tangential motion of the sides of the loop is parallel to
the flux lines of the field

No. 7
KGTTI PRESENTATION
• Hence there will be no question of flux cutting and consequently there will
be no current in the loop
• If the loop rotates further, it comes to again in horizontal position
• AB side of the loop comes in front of N pole and CD comes in front of S
pole, i.e. just opposite to the previous horizontal position as shown in the
figure beside
• Here the tangential motion of the side of the loop is perpendicular to the
flux lines, hence rate of flux cutting is maximum here and according to
Fleming’s right hand rule, at this position current flows from B to A and on
other side from D to C

No. 8
KGTTI PRESENTATION
COMMUTATOR

No. 9
KGTTI PRESENTATION
• It is seen that in the first half of the revolution current flows always along
ABLMCD i.e. brush no 1 in contact with segment a
• In the next half revolution, in the figure the direction of the induced
current in the coil is reversed
• But at the same time the position of the segments a and b are also
reversed which results that brush no 1 comes in touch with that segment b
• Hence, the current in the load resistance again flows from L to M
• The wave form of the current through the load circuit is as shown in the
figure. This current is unidirectional
COMMUTATOR

Dc gen

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