Understanding electric motor Windings!

Summary

This video script explores the automated process of fabricating three-phase windings, essential for generating a rotating magnetic field (RMF) in electric motors. It explains the principles behind creating a smooth, undistorted RMF, credits Nikola Tesla for the phase shift concept, and demonstrates how varying the number of slots in the winding design impacts the RMF's uniformity and speed. The script concludes with the application of these windings in everyday appliances, highlighting the importance of engineering in motor performance.

Takeaways

• 🔧 The video script describes the fully automatic process of fabricating three-phase windings in factories, which are crucial for creating a rotating magnetic field (RMF) in electric motors.
• 🌀 The RMF is generated by the three-phase windings taking in electric current, and it is responsible for the motor's rotation.
• 🤔 The script poses a question about how a stationary winding can create a rotating magnetic field, which is then explained through the principles of electrical engineering.
• 🛠️ The design of the windings is the result of years of effort, including design iterations, analysis, and the application of fundamental electrical engineering principles.
• 🧲 The script outlines the qualities of a good RMF, which should have a smooth shape, not distort during rotation, and have perfectly radial central flux lines.
• 🔄 Nikola Tesla's concept of phase shift is introduced as the key to creating a rotating magnetic field with stationary coils.
• 📈 The script explains the development of a winding design that generates a rotating magnetic field, starting with a simple coil and progressing to a six-slot design.
• 🔌 The use of multiple turns of thin cable in the industry increases the magnetic flux strength, with each turn insulated to prevent short circuits.
• 💻 The quality of the RMF is checked using FEA (Finite Element Analysis) results from em Works 2D software by SolidWorks.
• 🔄 The script discusses modifications to the winding design to achieve a more uniform RMF, including increasing the number of conductors and adjusting the coil connections.
• 🔗 The difference in speed and torque between two-pole and four-pole RMFs is highlighted, with the two-pole RMF rotating faster but providing less torque.
• 🔄 As the number of poles increases, the relationship between speed and torque remains consistent, with higher pole counts providing more torque but less speed.
• 🛠️ The script concludes with the preference for 24-slot windings for a smoother and more uniform RMF, and the application of these windings in various motor uses.

Q & A

What is the purpose of three-phase windings in a motor?

Three-phase windings are designed to take in electric current and create a rotating magnetic field (RMF), which is responsible for the motor's rotation.

How does the rotating magnetic field (RMF) rotate even though the windings are stationary?

The RMF rotates due to the phase shift concept introduced by Nikola Tesla, which involves keeping the maximum values of the three fields at different instances to avoid fluctuating behavior and create a uniform rotating field.

What are the fundamental qualities of a good RMF?

A good RMF should have a smooth shape, not get distorted during rotation, and have perfectly radial central flux lines.

Why was the initial design with three coils apart by 120 degrees a failure?

The initial design failed because all three magnetic fields had their maximum or minimum values at the same instance, causing the resultant field to fluctuate and not rotate smoothly.

Who is credited with the concept of phase shift in electrical engineering, and how does it help in creating a rotating magnetic field?

Nikola Tesla is credited with the concept of phase shift. It helps in creating a rotating magnetic field by ensuring that the maximum values of the three fields occur at different instances, thus avoiding a fluctuating behavior.

What is the significance of the number of slots in a winding design?

The number of slots in a winding design affects the uniformity and strength of the RMF. More slots result in a more uniform and constant strength RMF.

How does the number of poles in an RMF affect its speed and torque?

The number of poles influences the speed and torque of the RMF. A two-pole RMF rotates at double the speed of a four-pole RMF but provides less torque, while a four-pole RMF provides more torque but rotates at a slower speed.

What is the role of FEA results in checking the quality of the RMF?

FEA (Finite Element Analysis) results, produced with software like SolidWorks, are used to visualize and analyze the shape, uniformity, and consistency of the RMF during rotation, ensuring it meets the design criteria.

How are the windings supported inside the motor?

The windings are generally supported inside an iron structure, which also carries the magnetic flux lines, enhancing the magnetic field strength.

What is the process of winding the coils in the industry?

In the industry, the coils are wound on a Pharma, with two to three sets wound on each side. The Pharma loaded with coil groups is then inserted into the stator core by hydraulic pressure, followed by precise connections and testing before operation.

Why are more complex windings preferred for a smoother experience of the RMF?

More complex windings, such as a 24 slots design, provide a smoother and more uniform RMF with constant strength throughout its rotation, which is preferred for better performance in various applications.

Outlines

00:00

🔧 The Fascinating Process of Fabricating Three-Phase Windings

This section describes the automatic fabrication process of three-phase windings in factories. It explains how these windings take in electric current to create a rotating magnetic field (RMF) responsible for motor rotation. The text then delves into the fundamentals of a good RMF, highlighting that it should have a smooth shape, not get distorted during rotation, and have perfectly radial central flux lines. The section sets the stage for exploring the winding design by understanding these fundamentals.

05:01

⚡ Creating a Rotating Magnetic Field: Nikola Tesla's Contribution

The narrative continues by introducing the concept of alternating current passed through coils and the resulting magnetic flux fluctuation. By adding two more coils 120 degrees apart, an attempt to create a rotating magnetic field is made, but it initially fails. Nikola Tesla's phase shift concept is then introduced as a solution to this problem, explaining how different instances of maximum values in the fields prevent the fluctuating behavior. This section details the development of a winding that generates a rotating magnetic field using Tesla's insights.

🔄 Achieving Uniform Rotating Magnetic Fields with Six Slot Design

The text explains the creation of a rotating magnetic field with a six-slot winding design, generating two-pole rotating magnetic fields. It highlights the importance of using hundreds of thin cable turns in industrial applications to increase magnetic flux strength. The section also introduces the need for checking the quality of the RMF using FEA results, pointing out issues like non-radial central flux lines and non-uniformity due to the gap between adjacent conductors. To address these issues, the number of conductors is increased to 12, improving the RMF shape and uniformity.

🔄 Enhancing RMF with 12 Slot Design and 4-Pole Magnetic Fields

This section explores the 12-slot winding design, explaining how connecting coils in series with each phase coil creates a more uniform RMF. The design produces a two-pole RMF with better shape and uniformity, as confirmed by FEA results. The text then describes modifying this winding to generate a 4-pole RMF by removing coil overlap, resulting in a different RMF speed and torque characteristics. It emphasizes the trade-off between speed and torque in two-pole versus four-pole RMFs and concludes that increasing the number of slots leads to a more uniform and constant strength rotating magnetic field.

🏭 Complex Windings in Industrial Applications

The final section showcases complex windings wound on stators, tailored to specific motor applications. It describes the industrial process of winding coils on a Pharma, inserting them into stator cores using hydraulic pressure, and the precise human intervention required for coil connections. The section concludes by noting the testing of windings and their eventual use in various household and industrial appliances, thanking the audience and signaling the end of the video.

Keywords

💡Three-phase windings

Three-phase windings refer to the arrangement of coils in an electric motor that generates a rotating magnetic field (RMF). These windings are designed to take in electric current and create a magnetic field that rotates, which is essential for the motor's operation. In the video, it is explained that these windings are fabricated automatically in factories, highlighting their importance in the motor's functionality.

💡Rotating magnetic field (RMF)

A rotating magnetic field (RMF) is a magnetic field that rotates in space within an electric motor, causing the rotor to turn. The RMF is generated by the three-phase windings and is crucial for the motor's rotation. The video details how the RMF is produced and maintained, emphasizing its role in the motor's performance.

💡Alternating current (AC)

Alternating current (AC) is an electric current that periodically reverses direction. In the context of the video, AC is passed through the coils to produce fluctuating magnetic fields, which combine to form the RMF. AC's role is fundamental in the generation of a rotating magnetic field necessary for the motor's operation.

💡Nikola Tesla

Nikola Tesla was a pioneering electrical engineer who developed the concept of the rotating magnetic field and the use of phase shifts in AC currents. The video credits Tesla for the idea of keeping the maximum values of the three magnetic fields at different instances to avoid field fluctuation, thus enabling the generation of a consistent RMF.

💡Winding design

Winding design refers to the specific arrangement of coils within the stator of an electric motor. The video illustrates the process of designing windings to achieve a smooth and uniform RMF. Various designs, such as six-slot and twelve-slot windings, are discussed to show how the number and arrangement of coils affect the RMF's shape and stability.

💡Finite Element Analysis (FEA)

Finite Element Analysis (FEA) is a computational method used to predict how structures behave under various physical conditions. In the video, FEA is used to analyze the quality of the RMF produced by different winding designs, helping engineers refine their designs to achieve the desired magnetic field characteristics.

💡Two-pole and four-pole RMF

Two-pole and four-pole RMF refer to the number of magnetic poles created by the winding design, affecting the speed and torque of the motor. The video explains that a two-pole RMF rotates faster but produces less torque, while a four-pole RMF rotates slower but generates more torque. This relationship is crucial for determining the motor's performance characteristics.

💡Iron structure

The iron structure, or stator core, supports the windings and helps carry the magnetic flux lines. The video shows how the windings are embedded in the iron structure to enhance the magnetic field's strength and uniformity. The iron core's role is pivotal in achieving an efficient RMF.

💡Liquid varnish lamination

Liquid varnish lamination is a process used to insulate individual turns of wire within the windings. The video mentions that this insulation is crucial for preventing electrical shorts and increasing the magnetic flux strength. This step ensures the durability and reliability of the windings in industrial applications.

💡Hydraulic pressure

Hydraulic pressure is used to insert the pre-wound coils into the stator core. The video describes how hydraulic pressure facilitates the precise placement of coils within the iron structure, ensuring that the windings are correctly positioned to produce the desired RMF. This step is essential for maintaining the motor's efficiency and performance.

Highlights

The video showcases the fully automatic fabrication process of three-phase windings in factories.

Three-phase windings are essential for creating a rotating magnetic field (RMF) from electric current.

The RMF is responsible for the motor's rotation, and its creation involves complex engineering principles.

The winding design process involves years of effort, design iterations, and the use of electric engineering fundamentals.

A good RMF should have a smooth shape, not distort during rotation, and have perfectly radial central flux lines.

The initial simple coil design fails to create a rotating magnetic field due to simultaneous maximum or minimum fields.

Nikola Tesla's concept of phase shift is key to developing a winding that generates a rotating magnetic field.

A six-slot design with two pole RMF is created using the phase shift concept, but with stationary coils.

Industry practices involve using hundreds of thin cable turns to increase magnetic flux strength.

Winding turns are insulated from each other using liquid varnish lamination.

FEA results from SolidWorks' em Works 2D software are used to check the quality of the RMF.

Increasing the number of conductors adjacent to each other improves the uniformity of the RMF shape during rotation.

A 12-slot design is introduced to achieve a more uniform and consistent RMF shape.

Modifications to the 12-slot design can result in a 4-pole RMF, demonstrating flexibility in design.

The speed and torque of the RMF are inversely related, with more poles resulting in less speed but more torque.

A 24-slot winding is preferred for an even smoother and more uniform RMF experience.

Complex windings are wound on the stator according to specific applications, demonstrating the customization in motor design.

The coil winding process in factories involves precise mechanical and human interventions for quality assurance.

The video concludes by emphasizing the importance of winding design in everyday appliances like mixer grinders and air compressors.

Transcripts

it's a pleasure to watch how these

three-phase windings are getting

fabricated in the factories

what you see here is a fully automatic

winding process the windings take in

electric current and create a rotating

magnet field out of it

this RMF is responsible for the motor's

rotation

you might be curious about how this

magnetic field rotates even when the

windings are stationary

let's unveil its working come along

the winding design is not so obvious it

is clear from these visuals Engineers

Reach This winding design with years of

effort with design iterations analysis

and the use of fundamentals of electric

engineering so let's start with the

fundamentals and we will reach this

design towards the end of this video

before starting a winding design we

should first understand the qualities of

a good RMF

an RMF should have a smooth shape as

shown

it should not get distorted during its

rotation and third the central flux

lines should be perfectly radial

let's start the design journey to

achieve this perfect RMF using a simple

coil

when an alternating current is passed

through a coil the magnetic flux will

fluctuate as shown

now let's add two more coils which are

apart by 120 degrees

here each coil produces its own magnetic

field fluctuating in nature

when we add these magnetic fields we get

the combined magnetic field as shown

this design is a failure the magnetic

field is not rotating

this is where one of the Godfathers of

electrical engineering Nikola Tesla

comes into picture

he observed this disappointing behavior

of magnetic fields fluctuation

this field fluctuation happens because

all the three Fields maximum or minimum

happen at the same instance

Tesla while walking in a park

brainstorming ideas to create rotating

magnetic fields wondered what if he

keeps maximum values at these three

fields at different instances then there

will be no instant when all three

currents are zero or maximum at the same

time

eventually the resultant field will not

become zero at any instant in short he

can avoid the fluctuating Behavior

using the phase shift concept of Nikola

Tesla let's develop a winding which can

generate a rotating magnetic field

at the instance to time 0 the resultant

of these individual magnetic fields is

as shown

let's save this position for future

reference

with variations in AC currents the

magnetic fields take different

orientations if you compare these three

instances you can see that it is like a

magnetic field of uniform strength

rotating

this winding Arrangement is a six slot

design and generates two pole rotating

magnetic fields

there you have it we have just made the

magnetic field rotate with stationary

coils

here we used a single turn for the

winding however in the industries they

use hundreds of thin cable turns this

will obviously increase the magnetic

flux strength

each of these turns is insulated from

the other turns with the help of a

liquid varnish lamination

however the story is not over yet for

the winding design

these windings are generally supported

inside an iron structure

which also carries the magnetic flux

lines

to check the quality of the RMF we have

to rely on FEA results produced with the

help of em Works 2D software by

SolidWorks

you can see that this RMF has two poles

but the central flux lines are not

radial to the rotor

you can also see that during the

rotation of the RMF the shape is not

consistent

this non-uniformity arises because of

the huge gap between adjacent conductors

so to achieve the first Criterion a more

uniform shape during the rotation we

have to increase the number of

conductors adjacent to each other let's

make it 12 this time

the winding of this 12 slots design is

made by connecting one more coil in

series with each phase coil

here observe the current direction well

this straightforward connection won't

produce a two-pole magnetic field

let's overlap this pair of coils

what you get is a two pole field perfect

now let's do the same for the other two

phases

if you combine all three of these coils

around a circle

the left sides of these coils carry

current in One Direction and right sides

carry current in another Direction

this gives the resultant magnetic field

as shown here

this beautiful winding produces a

two-pole RMF with better shape and

uniformity it is clear from this FEA

result this winding is able to keep a

uniform shape throughout its rotation

interestingly just by doing a few more

modifications in this winding we can get

a 4-pole RMF if you remove the overlap

we did earlier in the coils we can get

the 4-pole RMF very easily

here each conductor of the r phase

creates individual poles

thus all three of the phases combined

create a four-pole rotating magnetic

field

let's arrange this design also in a

circular core

apart from the difference in number of

poles can you predict any other

difference in these rotating magnetic

fields

the speed at which both the RMF are

rotating is different

this is because the end pole of a

two-pole RMF reaches 180 degrees after a

half cycle of sinusoidal current wave

however in the four pole winding the end

pole reaches just 90 degrees

thus the two pole RMF has double the

speed to that of 4-pole RMF

eventually the two-pole winding gives

more speed yet lesser torque and the

exact opposite is the case with four

pole winding RMF

as you go on increasing the poles the

relation of speed and torque stays the

same

for an even better and smoother

experience of rotating magnetic field a

24 slots winding is preferred these

slots are nearer and uniformly placed

over the stator periphery

so here you can see the rotating

magnetic field how it rotates uniformly

having constant strength of magnetic

field throughout its rotation

from this we made the conclusion that as

we increase the number of slots the more

uniform and constant strength rotating

magnetic field we achieve this is the

beauty of windings

here you can see the more complex

windings wound on the stator

these winding types are selected

according to the applications you want

to use the motor in

in the factories these coils are wound

on a Pharma at a time two to three sets

are wound on each side

this Pharma loaded with coil groups is

inserted into the stator core by

hydraulic pressure

then comes the human intervention to

make precise connections between these

coils

then the windings are tested and sent to

operate your mixer grinder washing

machine or your air compressor

we hope you have enjoyed the video we

will see you next time thank you