Machines LP1

What are the 8 constructional parts of a DC machine?

Yoke, Poles and pole shoes, Field winding, Armature core, Armature winding, Commutator, Brushes, Air gap

Two major Parts of DC machine:

Rotor and Stator

ELECTRICAL CIRCUIT part of dc machine:

Commutator, Field winding, Armature winding, Brushes

MAGNETIC CIRCUIT part of dc machine:

Magnetic frame or yoke, Poles and pole shoes, Armature Core, Air gap

Yoke or Magnetic Frame

The outer frame of a dc machine is called as yoke. It is made up of cast iron or steel. It not only provides mechanical strength to the whole assembly but also carries the magnetic flux produced by the field winding.

Poles and pole shoes

_______ are joined to the yoke with the help of bolts or welding.

Pole shoes

They support field coils and spread out the flux in air gap uniformly.

Brushes

Are usually made from carbon or graphite. They rest on commutator segments and slide on the segments when the commutator rotates keeping the physical contact to collect or supply the current.

Air gap

The space between armature and pole shoe (from top of teeth to pole face)

Rotor

houses the field windings

Stator

rotates in magnetic field

Field winding

They are usually made of copper. They are wound in such a way that, when energized, they form alternate North and South poles.

Field coils

are former wound and placed on each pole and are connected in series.

Armature core

It is the rotor of a dc machine. It is cylindrical in shape with slots to carry armature winding.

Armature

It is built up of thin laminated circular steel disks for reducing eddy current losses. It may be provided with air ducts for the axial air flow for cooling purposes.

Commutator

Physical connection to the armature winding is made through a commutator-brush arrangement. The function of a _____________, in a dc generator, is to collect the current generated in armature conductors. The number of segments is equal to the number of armature coils. Each segment is connected to an armature coil and the commutator is keyed to the shaft.

Commutator

It helps in providing current to the armature conductors. A commutator consists of a set of copper segments which are insulated from each other.

Armature winding

It is usually a former wound copper coil which rests in armature slots. The armature conductors are insulated from each other and also from the armature core.

Double layer

It is winding means that each armature slot will carry two different coils.

Lap winding or Wave winding

Two methods of Armature winding: