There are a few ways to detect magnetic fields, one of the most reliable is with magnetic viewer film. This unique film suspends tiny nickel particles over a thin layer of viscous material allowing the particles to align with magnetic fields. It shows the location, as well as how many poles, a magnet has. Magnetic field lines can be drawn by moving a small compass from point to point around a magnet. At each point, draw a short line in the direction of the compass needle. Joining the points together reveals the path of the magnetic field lines.

1. Visualization of magnetic field produced by the
field winding excitation with armature winding
open , air gap flux density distribution, flux per pole,
induced EMF in an armature coil.

2. Visualizing the magnetic field produced by the field winding excitation with the
armature winding open in a DC machine, as well as air gap flux density distribution,
flux per pole, and induced EMF in an armature coil, involves understanding various
components and concepts like –
Components: The visualization should display the major components of a DC
machine, including the stator with field poles, the armature core, the commutator,
and the air gap.
Field Winding: Represent the field winding wound around the field poles with
arrows or color coding to indicate the direction of current flow and polarity of
each pole.

3. Magnetic Lines of Force:
Depict the magnetic lines of force originating from the north pole and terminating
at the south pole. These lines represent magnetic field.
Concentration at Poles:
Illustrate how the magnetic lines of force are densely concentrated near the poles
where the field winding is located, indicating the strength of the magnetic field.
Air Gap Flux Density Distribution:
Display the distribution of flux density in the air gap between the field poles and the
armature core.
The flux lines will span from the poles into the air gap and curve around.

4. Flux Per Pole: Show the quantity of magnetic flux passing through each pole. This
value is the total flux produced by the field winding divided by the number of
poles.
Armature Core: Include the stationary armature core encircling the field poles. The
core guides the magnetic lines of force and influences the flux distribution.
Commutator: If visible, depict the commutator on the rotor. The commutator
reverses the direction of current in the armature coils as the rotor turns.
Induced EMF in an Armature Coil: Indicate the armature coils in the armature core.
As the magnetic field lines pass through these coils, they will induce an
electromotive force (EMF) due to Faraday's law of electromagnetic induction. You
can represent this EMF with a voltage symbol near the coil.

5. Air Gap: Emphasize the air gap where the magnetic lines of force span between
the poles and the armature core.

6. Armature winding and commutation - Elementary armature coil and commutator,
lap and wave windings, construction of commutator, linear commutation

7. Armature winding -
What is an Armature ???
• An armature is a device through which electric current is passed for
generating torque (rotor).
• An armature can be defined as an power generating component in an
electric machine where the armature can be a rotating part in the machine.

8. Armature winding -
What is an Armature Winding ???
• Generally, an armature winding can be defined as, an electrical machine in which
emf can be generated because of the air gap field flux.
• The armature winding is supposed to carry the entire load current. Hence it is
made up of a conducting material such as copper.
• The armature winding of a dc machine is placed on the rotor to facilitate
commutation.
• Commutation is a process of converting the alternating voltage produced in the
winding into direct voltage at the brushes.

9. Basically armature winding of a DC machine is wound by one of the two
methods, lap winding or wave winding.
Lap Winding –

10. Basically armature winding of a DC machine is wound by one of the two
methods, lap winding or wave winding.
Lap Winding –
1. Lap winding is a method of connecting the armature coils in an electric
motor or generator.
2. It is a winding arrangement commonly used in direct current (DC)
machines to achieve a balance between voltage and current in the
armature winding.
3. Lap winding is particularly suited for machines that require high current
output and relatively low voltage, such as traction motors and industrial
motors.

11. Simplex Lap Winding
When the number of the parallel paths
is equal to the number of poles then
that type of winding is known as
simplex Lap winding.
4. In lap winding, the armature coils are connected in parallel, resulting in
multiple parallel paths for the current to flow.
Types of Lap Windings
There are three types of Lap winding:

12. Duplex Lap Winding
• When the parallel path is twice the number of poles then it is
known as Duplex Lap Winding.
• This type of winding is mainly used for high current applications.
Here, there are four successive coils of which two parallel paths
will be under N-pole and another two parallel paths are under S-
Pole.

13. Triplex Lap Winding
• The triplex lap winding has a number of turns and is usually used for
higher and larger currents.
• It is connected to one-third of the commutator bars. The only
problem with this type of winding is that its coil cost will be more
than other types of winding.

14. Lap winding offers several advantages:
•High Current Capacity:
Lap winding provides a high current-carrying capacity due to the parallel paths
created by the coil groups.
•Lower Voltage:
The parallel arrangement of coils in lap winding results in a lower voltage per coil,
which is suitable for applications requiring high current but lower voltage.

15. Lap winding also has some drawbacks:
•Complexity:
Lap winding can be more complex to manufacture and wind due to the intricate
connections between coils and commutator segments.
•Size:
The winding arrangement can lead to a larger physical size of the armature
compared to other winding configurations.

16. Wave Winding –

17. Wave Winding –
• Wave winding is another method of connecting the armature coils in
direct current (DC) machines, such as electric motors and generators.
• It is an alternative to lap winding and offers certain advantages and
characteristics that make it suitable for specific applications.
• In wave winding, the armature coils are connected in a wave-like pattern,
creating a single continuous path for the current to flow through the
coils.

18. Coil Layout:
The armature winding is divided into several coil groups. Each coil group
consists of two coils connected in series. The starting end of the first coil
is connected to the ending end of the second coil, creating a continuous
path.
Series Connection:
The coil groups are connected in series. The starting end of the first coil
group is connected to one terminal of the armature, and the ending end of
the last coil group is connected to the other terminal. This creates a single
path for the current to flow through the entire armature winding.

19. Commutator Connection:
• Each coil's starting point is connected to a commutator segment, and
its ending point is connected to the adjacent segment.
• As the armature rotates, the brushes make contact with the
commutator segments, reversing the direction of current flow through
the coils in a coordinated manner.

20. Wave winding offers several advantages:
•Simplicity:
Wave winding is simpler to manufacture and wind compared to lap winding, as it
involves fewer connections between coils and commutator segments.
•Higher Voltage:
The series arrangement of coils in wave winding results in a higher voltage per coil,
which is suitable for applications requiring higher voltage but potentially lower
current.
•Smaller Size:
The winding arrangement can lead to a smaller physical size of the armature
compared to lap winding.

21. Wave winding also has limitations:
•Limited Current Capacity:
Wave winding provides a single path for current, which may limit the current-
carrying capacity compared to lap winding's parallel paths.
•Greater Brush Wear:
Since the entire current flows through a single path, the brushes and commutator
segments may experience higher wear and tear due to the concentrated current.

22. • The choice between lap winding and wave winding depends on the specific
requirements of the application.
• Wave winding is often used in machines where higher voltage is required and
where simplicity of winding and manufacturing is valued.
Difference between Lap Winding and Wave Winding -

23. S.N.
Lap Winding Wave Winding
1 The lap winding can be defined as a
coil which can be lap back toward
the succeeding coil.
The wave winding can be defined as
the loop of the winding can form the
signal shape.
2 The connection of the lap winding is,
the armature coil end is connected to
the nearby section on the
commutators.
The connection of the wave winding
is, the armature coil end is connected
to commutator sections at some
distance apart.
3 The numbers of the parallel path are
equal to the total of number poles.
The number of parallel paths is equal
to two.
4 Another name of lap winding is
multiple winding otherwise Parallel
Winding
Another name of wave winding
is Series Winding otherwise Two-
circuit

24. S.N.
Lap Winding Wave Winding
5
The e.m.f of lap winding is Less
The e.m.f of wave winding is
More
6 The no. of brushes in lap winding
is Equivalent to the no. of
parallel paths.
The no. of brushes in wave
winding is Equivalent toTwo
7 The efficiency of the lap winding
is Less
The efficiency of the wave
winding is High
8
The e.m.f of lap winding is Less
The e.m.f of wave winding is
More
9 The winding cost of the lap
winding is High
The winding cost of the wave
winding is Low