Following are three types of dc machines:

1) DC generator:

“Energy can be converted from one form to other form”

It is rotated by prime mover and produces a dc voltage. i.e. Convert mechanical energy into electrical energy.

2) DC Motor :

It receives energy from a dc voltage source and rotates at Speed proportional to the applied voltage i.e .converts electrical energy into a mechanical energy.

3) Windings :

In DC machine there are two windings :

• Field Winding : It is Stationary Which does not move.
• Armature Winding :It placed in rotor and it is movable (Simple Loop Generator).

Draw wave of DC generator in following Case.

Emf Induced in side Armature

Construction:

• A single turn copper Coil is made from two Conductors A & B
• Its turn coil is rotating about its own axis in a magnetic field provided by permanent magnet with two poles N and S .
• The ends of coil are joined in two silpring C1 and C2.
• The slip ring rotate along with shaft the brushes do not rotate induce .
• Brushes Collect the current in the coil and convert into external lead resistances ’R’

Working:

• as coil rotates flux limned with it changes Hence an emf is induced magnetic Induction .
• The induced emf is zero when plane of Contactor motion is parallel top lane of magnetic flux.
• this induced emf maximum when the perpendicular to the plane of magnetic flux.
• the induced emf in single turn coil is given by,
  e=blvsin?. Here, B, l and u are magnetic flax density, length of conductor and velocity of moving conductor which are constant.
  .’. e =k sin?.
  Hence e is directly proportional to sin? .’. shape of induced emf is sine wave.
• It was single than alternator produce sine wave.