Electric Generator.ppt

1. Electric Generator
generators – which convert
mechanical energy into electrical
energy
motors – which convert electrical
energy into mechanical energy
Both types operate through the interaction
between a magnetic field and a set of windings

2. In September of 1831, Michael Faraday
made the discovery of Electromagnetic Induction.
Faraday attached two wires to a disc and
rotated the disc between the opposing
poles of a horseshoe magnet creating
an electric current.

3. An electric current is not generated unless the magnetic field is moving
relative to the copper wire, or the copper wire is moving relative to the
magnetic field.
If you place a magnet and a conductor (copper wire), in a room together
there will be no electric current generated.
This is because motion, from our equation for electricity, is missing!

5. Working
We noted earlier that Faraday’s law
describe that if a coil of N turns
experiences a change in magnetic flux,
then the induced voltage V is given by
If a coil of area A rotates with respect to a
field B, and if at a particular time it is at an
angle  to the field, then the flux linking
the coil is BAcos, and the rate of change
of flux is given by
t
Φ
N
V
d
d

  




cos
cos
d
d
d
sin
d



t
t
BA
dt
dΦ

6. Thus for the arrangement shown
below
  


cos
d
sin
d
d
d
NBA
t
NBA
t
Φ
N
V 



7. Wires connected to
the rotating coil
would get twisted
Therefore we use
circular slip rings
with sliding
contacts called
brushes

8. Therefore this arrangement produces a
sinusoidal output as shown below

9. The alternating signal from the earlier AC
generator could be converted to DC using a
rectifier
A more efficient approach is to replace the two
slip rings with a single split slip ring called a
commutator

10. Use of a
commutator