What is Wave Winding?
In wave winding, the armature coils are connected in such a way that the finishing end of one coil is connected to the starting end of the other coil, with a certain distance between them. This results in only two parallel paths being created between the positive and negative brushes, regardless of the number of poles in the machine. The number of brushes used in this type of winding is equal to the number of parallel paths.
This type of winding is mainly used in high voltage, low current machines because it allows for a greater number of turns of wire to be used in the armature coils, which increases the voltage output of the machine. This is beneficial in applications where a high voltage is required but a low current is sufficient, such as in generators. However, it is worth noting that wave winding may result in increased losses due to the increased resistance of the armature coils.
Types of Wave winding:
The Wave winding further classifies as:
- Simplex wave windings
- Duplex wave windings
- Retrogressive wave windings
- Progressive wave windings
1. Simplex Wave Windings:
In simplex wave winding, the conductors of all the coils are connected in series, resulting in only one path between the positive and negative brushes. This type of winding is mainly used in high voltage, low-current generators.
2. Duplex wave windings:
In duplex wave winding, the conductors of the coils are divided into two equal groups and connected in series, resulting in two parallel paths between the positive and negative brushes. This type of winding is mainly used in machines that require high voltage and high current, such as in some types of motors.
3. Retrogressive wave winding:
Retrogressive wave winding is a type of wave winding in which the conductors of the coils are connected in a specific way that causes the current to flow in the opposite direction in one of the parallel paths. This is achieved by connecting the finishing end of one coil to the starting end of the next coil in a manner such that after one complete rotation of the armature, the coil falls into a slot that is left of its starting slot.
This type of winding is mainly used in machines that require a high voltage and a high current, such as in some types of motors. The retrogressive connection ensures that the current flows in the opposite direction in one of the parallel paths, which can result in more efficient operation of the machine.
4. Progressive wave windings:
Progressive wave winding is a type of wave winding in which the conductors of the coils are connected in a specific way that causes the current to flow in the same direction in both parallel paths. This is achieved by connecting the finishing end of one coil to the starting end of the next coil in a manner such that after one complete rotation of the armature, the coil falls into a slot that is right of its starting slot.
This type of winding is mainly used in machines that require a high voltage and a high current, such as in some types of motors. The progressive connection ensures that the current flows in the same direction in both parallel paths, which can result in more efficient operation of the machine.
Advantages of wave winding:
- It requires fewer brushes than lap winding, which simplifies the design and reduces cost.
- In case of poor contact with the commutator, wave winding machines continue to operate satisfactorily.
- Wave winding does not require an equalizer ring, simplifying the design and reducing cost.
- Wave winding is less costly and requires less maintenance compared to lap winding machines
- Wave winding is well-suited for high voltage and low power machines.
- Wave winding is better suited for machines with power rating less than 50 KW.
- Wave winding is more efficient in terms of commutation as it does not require equalizer ring.
- It is less complex and cheaper to manufacture than lap windings.
- Wave windings are suitable for low power, high voltage machines.
- As there are only two parallel paths in wave wound machine, it is less prone to commutation issues and less likely to damage the machine.
- As wave winding does not require equalizer ring, commutation is more consistent in wave winding machine.
- The maintenance requirement for wave winding machine is less as compared to lap winding machine.
- The design of wave winding machine is simpler and more robust.
Disadvantages of wave winding:
- It cannot be used in machines having higher current rating because it has only two parallel paths.
- Wave winding may result in increased losses due to the increased resistance of the armature coils.
- It is not suitable for high current machines as the current density is high and it can cause commutation problems.
- The wave winding is less efficient than other types of winding such as lap winding, at high current.
- As wave winding has only two parallel paths, if one of the brushes develops poor contact with the commutator, the machine will not operate satisfactorily.
- The cost of wave winding machines is generally higher than that of lap winding machines.
- Wave winding is less suitable for high power machines, such as large motors, as they require large current and wave winding is not efficient to handle such large currents.
- Wave winding machines are less reliable and have a shorter lifespan than lap winding machines.
- Wave winding machines are less robust and more prone to wear and tear.
- Wave winding machines are less efficient in terms of energy consumption as compared to lap winding machines.
Applications of wave winding include:
- The applications of wave winding include low current and high voltage machines because wave winding is specifically designed to provide high voltage output with low current. It is accomplished by connecting the armature coils in a specific way that creates only two parallel paths between the positive and negative brushes. This allows for a greater number of turns of wire to be used in the armature coils, which increases the voltage output of the machine. This makes wave winding suitable for applications where a high voltage is required but a low current is sufficient.
Terms related to Armature Winding:
1. Conductor:
A conductor is a length of wire used in armature winding that is placed in the armature slots. It is typically made of copper and can have one or more parallel strands. It lies in the magnetic field produced by the field winding.
2. Turn:
Two conductors connected in series are known as a turn. The other end of the two conductors is connected to the commutator segments or connected to the other turns. The emf induced in the two conductors will help each other.
3. Coil:
A coil is the formation of one or more turns made up of a conductor. A coil consisting of one turn (two conductors) is known as a single-turn coil and more than two turns (many conductors) is known as a multi-turn coil. In a multi-turn coil, the group of wires or conductors are wrapped together with tape.
4. Coil Span or Coil Pitch:
The distance between the two sides of a coil or distance between the two conductors of a turn in a coil is known as coil span or coil pitch.
5. Pole Pitch:
The distance between the two adjacent pole centers is known as the pole pitch of the machine.
6. Full-Pitch Coil:
A coil is said to be fully pitched when the coil span is made equal to the pole pitch of the machine. In other words, the distance between the two coil sides of a coil will be equal to the distance between the centers of two adjacent poles. A pole can be of many coils but there will be maximum emf induced in the full-pitched coil since the coil sides of a coil lie under opposite poles.
7. Front Pitch:
The distance between the second conductor and the first conductor of two adjacent armature coils connected in series is called front pitch. It is denoted by Yf.
8. Back Pitch:
The back pitch is similar to that of coil span or coil pitch i.e., the distance between the two coil sides of a coil. It is the distance between the armature conductors, which a coil advances on the back of the armature. It is denoted by Yb.
9. Commutator Pitch:
It is the distance measured between two commutator segments to which starting and ending terminals of a coil are connected. It is denoted by Yc and measured in terms of commutator bars or segments.
10. Single-layer Winding:
In single-layer winding, each armature slot occupies only one coil side.
11. Double-layer Winding:
In double-layer winding, two coil sides (two conductors) of different coils are placed in the same armature slot. Here, the two coil sides are placed one upon another with an equal portion of the armature slot occupied by them.