Lap Winding vs Wave Winding
Construction, Working, Parallel Paths, Brushes, Applications, Advantages, Disadvantages and Differences
⚡ Introduction to DC Machine Winding
The winding placed on the armature of a DC machine is one of the most important parts of the electrical machine. The armature winding consists of insulated conductors arranged in slots on the armature core. When the armature rotates inside the magnetic field, an electromotive force (EMF) is induced in these conductors according to Faraday's law of electromagnetic induction.
The armature winding also provides the path through which the generated current flows to the commutator and brushes. The two important types of armature windings used in DC machines are Lap Winding and Wave Winding.
Although both windings perform the same basic function, their connections, number of parallel paths, number of brushes, voltage-current characteristics and applications are different.
💡 Important Concept
The choice between lap winding and wave winding mainly depends on the required voltage, current, number of poles and number of parallel paths of the DC machine.
🧲 DC Generator Armature Winding
🔵 1. Lap Winding
What is Lap Winding?
Lap winding is a type of DC armature winding in which the end of one armature coil is connected to the adjacent commutator segment. The winding progresses from one coil to the next in such a manner that the coils overlap or "lap" over one another.
In a simplex lap winding, the ends of each armature coil are connected to adjacent commutator segments. For duplex winding, the connection extends by two commutator segments, while in triplex winding it extends by three segments.
Lap winding is particularly suitable for DC machines that require high current and comparatively low voltage.
A = P × m
Where P = number of poles and m = plex of winding
Example of Lap Winding
Suppose a DC generator has 4 poles and uses simplex lap winding.
A = 4 × 1
A = 4 parallel paths
Therefore, the armature current is divided among four parallel paths. This makes lap winding suitable for low-voltage, high-current DC generators and motors.
🔧 Main Features of Lap Winding
The coil ends are generally connected to adjacent commutator segments in simplex lap winding.
The number of parallel paths is related directly to the number of poles.
The number of brush positions is normally equal to the number of poles.
It is suitable where large armature current is required.
🔴 2. Wave Winding
What is Wave Winding?
Wave winding is another important type of DC armature winding. The winding is called "wave winding" because the coil connection progresses around the armature in a wave-like manner.
The two ends of each armature coil are connected to commutator segments that are separated by a suitable distance. In simplex wave winding, the connection generally moves to another coil under a pole of the same polarity.
Unlike lap winding, the number of parallel paths in simplex wave winding is normally independent of the number of poles.
Wave winding is therefore especially suitable for machines requiring higher voltage and lower current.
A = 2m
For simplex: m = 1
A = 2
Example of Wave Winding
Consider a DC generator using simplex wave winding. Regardless of whether the machine has 2, 4, 6 or more poles, the number of parallel paths is normally:
A = 2 parallel paths
This makes wave winding useful for high-voltage and comparatively low-current DC machines.
🔧 Main Features of Wave Winding
The winding progresses around the armature in a wave-like pattern.
Simplex wave winding normally has two parallel paths.
Only two brush positions are required in the simplex wave winding.
Suitable for machines requiring higher voltage and lower current.
📐 Simplex, Duplex and Triplex Winding
The terms simplex, duplex and triplex indicate the number of sets of winding circuits. The plex value affects the number of parallel paths.
- Simplex: m = 1
- Duplex: m = 2
- Triplex: m = 3
A = P × m
Wave Winding:
A = 2 × m
📊 Lap Winding vs Wave Winding
| Parameter | Lap Winding | Wave Winding |
|---|---|---|
| Basic connection | Coils are connected to adjacent commutator segments in simplex lap winding. | Coils progress in a wave-like manner and connect to suitably separated commutator segments. |
| Parallel paths | A = P × m | A = 2 × m |
| Simplex winding | A = P | A = 2 |
| Dependence on poles | Parallel paths increase with number of poles. | Simplex parallel paths do not normally depend on number of poles. |
| Brush positions | Normally equal to the number of poles. | Normally two brush positions. |
| Voltage | Suitable for relatively low voltage. | Suitable for relatively high voltage. |
| Current | Suitable for high current. | Suitable for comparatively low current. |
| Typical application | High-current, low-voltage DC machines. | High-voltage, low-current DC machines. |
✅ Advantages of Lap Winding
Why is Lap Winding Used?
- Provides multiple parallel paths.
- Suitable for high-current applications.
- Useful for low-voltage DC generators and motors.
- Parallel paths increase with the number of poles.
- Suitable for heavy-current electrical machines.
✅ Advantages of Wave Winding
Why is Wave Winding Used?
- Simplex wave winding provides two parallel paths.
- Suitable for high-voltage applications.
- Requires only two brush positions in the normal simplex arrangement.
- Parallel paths are not directly dependent on the number of poles.
- Suitable for relatively low-current machines.
⚠️ Disadvantages and Limitations
Lap Winding
- Requires more brush positions for multipole machines.
- Equalizer connections may be required in practical multipole machines.
- More parallel paths make it suitable mainly for high-current applications.
Wave Winding
- Not preferred where extremely high armature current is required.
- Winding design is more complicated.
- Dummy coils may sometimes be required depending on the number of coils and poles.
🏭 Applications
Lap Winding Applications
Lap winding is commonly selected when the DC machine must deliver high current at comparatively low voltage. It is therefore associated with heavy-current DC machines.
Wave Winding Applications
Wave winding is suitable when a comparatively high generated voltage is required with lower armature current. It is useful for machines where only a small number of parallel paths are desired.
🎯 Important ITI / Diploma / BTech Exam Points
Remember These Points
- In simplex lap winding: A = P
- In simplex wave winding: A = 2
- Lap winding is suitable for low voltage and high current.
- Wave winding is suitable for high voltage and low current.
- Lap winding parallel paths depend on the number of poles.
- Simplex wave winding normally has two parallel paths.
- The number of brush positions in lap winding is normally related to the number of poles.
- Simplex wave winding normally uses two brush positions.
🧠 Easy Memory Trick
Remember: LAP = LOW Voltage / HIGH Current
LAP → Low voltage + High current
WAVE → High voltage + Low current
Another important memory point:
Wave → A = 2 × m
📚 Conclusion
Lap winding and wave winding are two important armature winding arrangements used in DC generators and motors. The main difference between them is the manner in which armature coils are connected to the commutator and the resulting number of parallel paths.
Lap winding provides a number of parallel paths related to the number of poles and is therefore suitable for low-voltage, high-current machines.
Wave winding, on the other hand, normally provides two parallel paths in simplex form and is therefore suitable for high-voltage, low-current machines.
For examination purposes, remember the two most important relations:
Wave Winding: A = 2 × m
Understanding these relationships makes it much easier to select the appropriate armature winding for a DC machine and to solve numerical problems involving generated EMF, armature current and parallel paths.