Types of Armature Winding: lap, wave, Duplex, and Triplex Windings

Types of Armature Winding

When we talk about armature winding in electric machines (like motors or generators), we’re simply talking about how the wires are arranged inside the machine to carry current. These wires connect at a part called the commutator.

Now, depending on how these wires are connected at the ends, armature winding is mainly of two types:

1. Lap Winding
2. Wave Winding

🌟 What’s the difference?

It’s like choosing how to connect the roads in a city. In Lap winding, the wires “lap” back near where they started, making it good for machines that carry high current. In Wave winding, the wires go further, connecting in a wave-like pattern — this is better for higher voltage machines.

🧠 How do we choose between them?

The choice depends on many things, such as:

• How much current is needed
• What voltage the machine should handle
• How big the machine is
• How much space we have inside
• And of course, cost

📚 Types of Armature Winding Based on Layers

Lap and wave windings can be made in two ways:

1. Single Layer Winding – Only one wire is placed in each slot (like one book in each shelf).
2. Double Layer Winding – Two wires (from two different coils) share the same slot (like keeping two books in one shelf).

Usually, double layer winding is used because it makes it easier to connect the ends neatly.

Types of Armature Winding based on repeated:

These windings can also be grouped based on how many times the pattern is repeated:

1. Simplex – Normal winding, used in most machines
2. Duplex – Double pattern for heavier work
3. Triplex – Triple pattern for even more power

So, we can have:

• Simplex Lap or Simplex Wave
• Duplex Lap or Duplex Wave
• Triplex Lap or Triplex Wave

🎯 Summary

To sum it up:

• There are two main types: Lap and Wave
• Each can be single or double layer
• And they can be simplex, duplex, or triplex
• The best choice depends on how much current, voltage, and space we need

This is how we decide which armature winding to use in a machine!

Explanation of Duplex and Triplex Windings

In an electric motor or generator, we use something called a winding to help make or use electricity. You can think of windings like wires that are carefully placed inside the machine.

There are different types of windings. The most common one is called a simplex winding. It’s like a single path for electricity to flow.

But sometimes, to carry more current or to improve performance, we use duplex or triplex windings:

• A duplex winding is made by joining two simplex windings side by side. They work together like two friends walking together.
• A triplex winding has three simplex windings in parallel, like three friends helping each other at the same time.

Even though duplex and triplex windings are useful, we usually prefer the simplex winding because it’s easier to handle and works well in most cases.

Placing the Coil Sides in the Right Slots

Every coil has two sides, just like a magnet has a North and South pole. When we put these coil sides into the slots of the stator (the part of the motor that stays still), we must be careful.

Why? Because we want the electric push (emf) in both sides of the coil to help each other. This only happens when one side is under the North pole and the other is under the South pole. Then, they work together and make the coil stronger.

Making a Proper Winding Loop

There are two common ways to connect windings:

• Lap winding
• Wave winding

No matter which one we choose, one important thing must happen:

If we start at any point in the winding and follow the path through all the wires and coils, we must be able to come back to the same starting point, without any gap or break. This is called a closed loop. A closed loop helps electricity flow smoothly without stopping.

Simplex Lap Winding

Simplex lap winding is a special way of connecting the wires inside a DC machine like a generator or a motor. This type of winding is best when we want low voltage and high current. That means we don’t want a big spark of electricity, but we do want a strong flow of current.

You’ll mostly find lap winding in machines that give power to other big machines — like in alternators or motors that need a lot of help to start. Even DC motors that run on batteries can have lap winding inside.

⚙️ How does lap winding work?

Imagine many small wire coils inside a machine. In lap winding, each coil is connected to the next one very neatly:

• The end of one coil connects to the start of the next one.
• These connections are made on small metal pieces called commutator segments, which help in controlling the direction of the current.

This creates a circular path, like one coil sitting over another — just like the way we lap our hands while praying. That’s why it’s called lap winding!

🔄 Two types of Lap Winding:

There are two ways to arrange these coils:

1. Progressive Lap Winding
2. Retrogressive Lap Winding

The main difference is how far the wire jumps while connecting from one coil to the next:

• In progressive, the wire goes forward a bit more.
• In retrogressive, it jumps backward, which makes the coil a bit shorter and saves wire. So, retrogressive lap winding is often used more because it costs less and is easier to make.

🔢 Some Simple Rules to Remember:

• The number of slots (Z) and poles (P) are odd numbers and they are never the same. One will always be at least 2 more or less than the other.
• If Z > P, then it’s called Retrogressive Lap Winding
  (Here, Coil pitch YB = YF – 2)
• If Z < P, then it’s called Progressive Lap Winding
  (Here, Coil pitch YB = YF + 2)
• The average pitch of coils (YF and YB) should be equal to one pole pitch
  (That means: (YF + YB)/2 = pole pitch)
• Resultant pitch = YF – YB
  (This tells us how the coils are spaced)
• Commutator pitch is always +1 or -1
  (Very small jump between connections)
• The number of parallel paths (A) inside the machine = number of poles (P)
• The number of brushes used = number of poles
• And the number of commutator segments = number of coils
  
  

Parallel Paths (Lap Winding Made Simple)

Let’s understand this in a very easy way.

Imagine you have 12 small coils. These coils are connected in a special way called lap winding.

Now, in lap winding, something interesting happens.

If your motor or generator has 4 poles (think of these as 4 magnetic arms), then the number of parallel paths will also be 4. That means, the 12 coils are divided into 4 separate paths, with 3 coils in each path.

So, the rule is simple:
👉 In lap winding, the number of parallel paths is always equal to the number of poles.

What Happens to Voltage and Current?

Let’s say each coil creates an electric push, which we call E (emf), and carries a current I.

Now, in every path, there are 3 coils connected. The voltage adds up in a certain way:

• In one complete loop or coil, the voltage becomes 2E, because each side gives E.
• Since there are 3 coils in one path, the total emf (voltage) in one path becomes 6E.
• But the current in each path stays the same, I.

So:

• Emf in one path = 6E
• Current in one path = I

What About the Whole Armature?

The total voltage you get from the armature (the spinning part of the machine) is the same as one path — so, 6E.

But the total current is shared between all the paths.

Since there are 4 paths, and each path carries current I, the total current becomes:

👉 Total current = I + I + I + I = 4I

In Simple Words:

• Number of parallel paths = Number of poles
• Voltage stays the same across each path
• Total current = Sum of currents in all paths

That’s how lap winding works. It’s just like dividing a job among four friends — each one does a part, and together they complete the task faster and better!

Simplex Wave Winding

Simplex Wave Winding is a special way of connecting wires in an electric machine. It’s called a “wave” winding because the wire goes around the armature core in one single direction, just like a wave moves forward in water.

Think of it like this – imagine a wave going across the sea. It doesn’t turn back. In the same way, this winding also keeps moving forward from one coil to the next, around and around the armature.

Each coil has two ends. These two ends are connected to two parts of a device called a commutator. But here’s something cool – the ends are not side by side. They are connected a bit far apart. The space between them is based on something called the average pitch (just a fancy word for distance between coil connections).

Just like we have two sides of a coin, wave winding also comes in two types of Armature Winding.

1. ✅ Progressive Type – The winding keeps moving forward around the armature in the same direction.
2. 🔁 Retrogressive Type – The winding still moves like a wave, but it loops a little backward.

Wave Winding Made Easy

In Wave Winding, there are some simple rules we follow:

• The back pitch and front pitch are both odd numbers, and they must have the same sign.
  That means either both are positive or both are negative.
  They can be equal or can differ by 2.

What is Average Pitch?

We use this formula to find the average pitch:

Yav = Yb+Yf/2 = ± Z±2/P

• The (+) sign is used when winding is Progressive.
• The (-) sign is used when winding is Retrogressive.

✅ Very important: The value of Yav must always be a whole number (an integer).
If it’s not an integer, wave winding is not possible for that combination.

How to Decide Back Pitch and Front Pitch?

Once we get a valid integer value for average pitch (Yav), we choose back pitch (Yb) and front pitch (Yf) based on whether Yav is even or odd:

• If Yav is even:
  • Back Pitch (Yb) = Yav – 1
  • Front Pitch (Yf) = Yav + 1
• If Yav is odd:
  • Yb = Yf = Yav

Other Key Points to Remember

• Resultant Pitch (Yr) = Yb + Yf
• Commutator Pitch = Yav
• Number of parallel paths (A) = 2 (always, no matter how many poles there are)
• Number of brushes = 2 (can be 4 if you want to divide the current evenly)
• Number of commutator segments = same as the number of coils

Let’s Take an Example

Suppose we have:

• Number of Coils = 12
• Poles (P) = 4
• So, Total Conductors (Z) = 24

Let’s check if wave winding is possible.

Use the formula:

Yav=Z±2/P = 24±2/4

That gives us:

• 26/4=6.5
• 22/4=5.5

Both are not integers, so wave winding is not possible here.

✅ This means, for Z = 24 and P = 4, Lap winding is okay, but Wave winding won’t work.

But for Z = 30, 34, or 42, you can use Wave Winding with P = 4, because in those cases, Yav comes out as an integer.

Important Takeaway

Wave winding has some limits.
You can’t just use it with any number of conductors and poles.
You must always check if the average pitch is an integer.
If it’s not, wave winding can’t be used.

Dummy or Idle Coil

Sometimes, when we make a wave winding in a DC machine, we face a small problem. There is a special rule we must follow:
To make wave winding work properly, a certain number (Z) must come out as a whole number (an integer).

But not all numbers of coils can follow this rule.

For example:
If we use 4 poles (P = 4), the wave winding works best when the number of coils is odd — like 15, 17, or 21.
That gives us Z = 30, 34, or 42, which are okay.

Now, here’s where it gets tricky:
In double-layer winding, the number of slots in the machine must be the same as the number of coils.

Also, for the machine to run smoothly, the number of slots on both sides of the brush (which touches the commutator) must be equal.
That means the total number of slots should be even, not odd.

But sometimes, we don’t get this perfect even number because we’re using standard parts (called standard laminations), which come in fixed sizes. So, what do we do?

We use a Dummy Coil.

A dummy coil is a coil that we put into one extra slot — just to keep the machine balanced.
It looks like a real coil, but it is not connected to anything.
It does not carry current, and it doesn’t help in making electricity.

It is there only for mechanical balance — to keep the machine from shaking or wearing out unevenly.

Dummy coils are usually used in small machines, where it’s hard to make custom changes.
But in large machines, dummy coils are not used because they might cause problems in commutation (the switching of current).

EMF Equation

Imagine you have a DC generator. It’s a machine that changes motion into electricity. But how does this happen? Let’s break it down into simple steps.

🔄 What is EMF?

EMF stands for Electromotive Force. It’s the voltage (or push) created inside the generator when it rotates. This voltage is what makes electricity flow.

📘 Let’s Understand the Main Characters:

• Φ (Phi) – This is the magnetic flux coming from the stator (the part that doesn’t move). Think of it like invisible lines of magnetic force.
• Z – Total number of conductors (wires where current flows).
• P – Number of poles in the stator (these are the magnetic parts).
• A – Number of parallel paths in the winding (how the wires are grouped).
• N – Speed of the rotor (the rotating part) in revolutions per minute (RPM).
• E – The EMF or voltage generated.

⚙️ What Happens Inside?

When the rotor spins, the conductors inside it move through the magnetic lines (Φ). This motion creates electricity—this is called electromagnetic induction.

Now, each time a conductor goes around once, it cuts through the magnetic field completely.

• So, Total flux linked in one revolution = P × Φ
• Time for one full rotation = 60 / N seconds (since N is RPM)

🧮 So, What’s the EMF Equation?

The average EMF per conductor is: EMF per conductor =

P×Φ×N/60

Now, total EMF depends on how conductors are grouped:

• Total EMF across the machine =

E=P×Φ×Z×N/60×A​

This is the most important equation in a DC generator. It tells us how much voltage we’ll get when the machine runs.

🧠 Remember This:

• More speed → More EMF
• Stronger magnetic field (Φ) → More EMF
• More conductors (Z) → More EMF
• More poles (P) → More EMF
• More parallel paths (A) → EMF is divided (shared)

📝 For Different Windings:

• In Lap Winding: A = P
• In Wave Winding: A = 2

So always use the right value of A when using the formula.

✨ Final Touch

Let’s keep it simple:

E=P×Φ×Z×N/60×A

That’s your EMF Equation — the heart of every DC generator.

Lap Winding vs. Wave Winding – Easy Comparison

When we build electric machines like motors or generators, the way the wire is wrapped inside matters a lot. Two common ways of winding the wire are called Lap Winding and Wave Winding. Let’s understand the difference between them in a very simple way.

🌀 Lap Winding

• The wires are looped one over the other, like climbing a ladder step by step.
• It uses less copper, so it saves cost.
• It gives lower voltage, but controls speed better.
• It’s good when we need stable and smooth control, like in machines in factories.
• But it makes the machine shake a little more while working, because the power goes up and down quickly.
• It’s a bit harder to make, as the coils are not all the same.

🌊 Wave Winding

• The wires move forward in a wave-like shape, like ripples on water.
• It gives higher voltage, which is useful for heavy work.
• It needs more copper as there are always two paths for current to flow.
• It’s very smooth in rotation, with less shaking.
• But, its speed control is not as good as lap winding.
• All coils are the same, which makes mass production easier and faster.
• It’s mostly used in machines that need high starting power, like trains and cranes.

📊 Easy Comparison Table

FAQ