How does an Electric Motor work? DC Motor explained

Summary

In this educational video, Paul from engineeringmindset.com explores the fundamentals of DC motors, which convert electrical energy into mechanical energy for applications in power tools, toy cars, and cooling fans. He details the motor's components, including the stator, rotor, commutator, and brushes, and explains how they work together to create rotation. Paul also covers basic electricity concepts, the role of permanent magnets, and the significance of Fleming's left-hand rule in determining the direction of force on the coils. The video is a comprehensive guide for understanding the inner workings of DC motors and their practical applications.

Takeaways

• 🔌 DC motors convert electrical energy into mechanical energy and are used in various applications like power tools, toy cars, and cooling fans.
• 🏗️ The basic components of a DC motor include a metal casing (stator), a rotor with laminated disks and coil windings, a shaft, and a commutator.
• 🧲 The motor contains permanent magnets that create a strong magnetic field through the rotor, essential for the motor's operation.
• 🔋 The commutator is a segmented ring that helps control the timing and polarity of the magnetic field, enabling the motor to rotate.
• 🔌 The brushes and brush arms complete the electrical circuit by rubbing against the commutator segments, allowing current to flow to the coils.
• 🔋 The rotor's laminated disks reduce eddy currents, which can decrease motor efficiency, by providing electrical insulation between each disk.
• 🔧 Fleming's left-hand rule is used to determine the direction of force on a coil when it interacts with a magnetic field, crucial for understanding motor rotation.
• 🔄 The motor's rotation is achieved through the interaction of the electromagnetic fields created by the current-carrying coils and the permanent magnets.
• 🔀 Reversing the power supply or the current direction will reverse the forces acting on the coils, thus changing the direction of motor rotation.
• 📚 Understanding the fundamentals of electricity, such as electron flow, current, voltage, and magnetic fields, is essential for comprehending how DC motors work.
• 🔍 The script encourages viewers to think about where they have seen DC motors used and to share their project ideas in the comments section.

Q & A

What is the primary function of a DC motor?

The primary function of a DC motor is to convert electrical energy into mechanical energy.

What are some common applications of DC motors?

DC motors are commonly used in power tools, toy cars, and cooling fans.

What are the main components of a DC motor?

The main components of a DC motor include the stator, rotor, commutator, brushes, and permanent magnets.

What is the role of the stator in a DC motor?

The stator is the metal protective casing that houses the motor and provides a stationary structure for the rotor to spin within.

What is the purpose of the rotor in a DC motor?

The rotor is made from laminated disks with T-shaped arms and coil windings, which when energized, interact with the magnetic field to produce rotation.

How does the commutator in a DC motor work?

The commutator is a segmented ring that electrically isolates different plates and helps to switch the connections of the coil windings as the rotor turns, maintaining continuous rotation.

What are the brushes in a DC motor and what do they do?

The brushes are conductive contacts that rub against the commutator segments to complete the electrical circuit, allowing current to flow through the motor.

Why do DC motors use coils instead of straight wires to create a magnetic field?

Coils are used because when wires are wrapped into a coil, the individual electromagnetic fields combine to create a much larger and stronger magnetic field.

What is the significance of laminating the rotor disks in a DC motor?

Lamination of the rotor disks helps to reduce eddy currents, which can decrease the motor's efficiency by causing energy loss due to induced electromagnetic forces.

What is Fleming's left-hand rule and how is it used in DC motors?

Fleming's left-hand rule is a method to determine the direction of force on a current-carrying conductor in a magnetic field. It is used in DC motors to understand the interaction between the electromagnetic field of the coils and the magnetic field of the permanent magnets, which results in the motor's rotation.

How does reversing the battery in a DC motor affect its operation?

Reversing the battery changes the direction of the current flowing through the motor, which in turn reverses the forces acting on the coils and changes the direction of the motor's rotation.

Outlines

00:00

🔧 Introduction to DC Motors and Their Basic Components

In this paragraph, Paul from the 'Engineering Mindset' introduces the topic of DC motors, explaining their purpose to convert electrical energy into mechanical energy. He describes the general appearance of a DC motor, including its metal casing or stator, the protruding tip for attaching gears or fan blades, and the plastic end cap with terminals for power supply connection. The inner components such as the permanent magnets, the shaft, the rotor with laminated disks and T-shaped arms, and the coil windings are also detailed. The paragraph concludes with an explanation of the commutator's function, which is to control the timing and polarity of the magnetic field to create rotation, and the brushes that complete the circuit for electricity to flow.

05:01

🔋 Understanding Electricity and Magnetism in DC Motors

This paragraph delves into the fundamentals of electricity and magnetism that are essential for understanding DC motors. It starts with the basics of electricity, explaining the flow of electrons as current and the significance of DC electricity where electrons flow in a single direction. The concept of voltage as a driving force for electron flow and the necessity of a complete circuit are also covered. The paragraph then moves on to discuss magnets, highlighting their polarity and the interaction of their magnetic fields, which is crucial for the motor's operation. The visualization of magnetic fields using iron filings and the creation of electromagnetic fields by passing current through wires are explained. The concept of windings, which are coils of wire that enhance the magnetic field strength, is also introduced, along with the construction of the rotor and the role of the commutator in delivering electricity to the coils.

10:03

👨‍🔧 The Working Principles of DC Motors and Eddy Currents

This section of the script explains the working principles of DC motors in detail. It begins by discussing the construction of the rotor, which is made of multiple laminated iron disks to reduce eddy currents and increase efficiency. The function of the commutator and brushes in maintaining electrical contact and completing the circuit is also explained. Fleming's left-hand rule is introduced to determine the direction of force on the coils when interacting with the magnetic field. The paragraph further illustrates how the motor operates through a step-by-step analysis of the current flow and the resulting forces on the coils during rotation. It describes the continuous process of current flow through different commutator plates and the corresponding forces that lead to the motor's rotation.

15:04

🔄 Conclusion and Further Learning on DC Motors

In the concluding paragraph, the script summarizes the operation of DC motors, emphasizing how the interaction of conventional current and magnetic fields results in rotational force. It also touches on the effect of reversing the power supply, which would reverse the current and the direction of rotation. The paragraph ends with an invitation for viewers to continue their learning by watching more videos on the topic and to follow the 'Engineering Mindset' on various social media platforms for additional insights and content.

Keywords

💡DC Motor

A DC Motor, or Direct Current Motor, is a type of electrical motor that operates using direct current electricity. It is designed to convert electrical energy into mechanical energy, which can be used to power various devices such as power tools, toy cars, and cooling fans, as mentioned in the script. The video's theme revolves around understanding the basic operation of a DC motor, making this keyword central to the video's educational content.

💡Stator

The stator is the stationary part of the motor that houses the motor's components. In the context of the video, it is the metal protective casing of the DC motor. The stator provides a stable structure to which other components like gears, fan blades, or pulleys can be attached. It plays a crucial role in the motor's operation by supporting the rotor and the magnetic field generation.

💡Rotor

The rotor is the rotating part of the motor that is made from a number of laminated disks with T-shaped arms. These arms have coil windings wrapped around them, which carry the electrical current and produce an electromagnetic field. The rotor's interaction with the magnetic field generated by the stator is essential for the motor's rotation, as explained in the script.

💡Commutator

The commutator is a segmented ring that sits around the shaft of the rotor and is responsible for controlling the direction of the current flow in the motor's coils. It consists of a series of electrically isolated plates that connect to the ends of the coils, allowing the current to flow in a manner that sustains the motor's rotation. The script describes how the commutator works in conjunction with brushes to complete the electrical circuit.

💡Brushes

Brushes are conductive materials that make contact with the commutator segments to complete the electrical circuit. They are part of the brush arms and terminals, which are housed within the plastic back cover of the motor. As the commutator rotates, the brushes rub against its segments, allowing electricity to flow into the motor's coils and maintain the motor's operation, as depicted in the video script.

💡Electrical Energy

Electrical energy is the energy derived from the flow of electric charge. In the context of the video, electrical energy is converted into mechanical energy by the DC motor. The script explains that this conversion occurs when the current passes through the coils, producing an electromagnetic field that interacts with the magnetic field of the stator to cause rotation.

💡Magnetic Field

A magnetic field is a region around a magnetic material or a moving electric charge within which the force of magnetism acts. The video script describes how the permanent magnets in the stator create a strong magnetic field that interacts with the electromagnetic field produced by the rotor's coils to facilitate the motor's rotation.

💡Eddy Currents

Eddy currents are circular electric currents induced within conductors by a changing magnetic field. The script explains that engineers laminate the rotor to reduce eddy currents, which can decrease the motor's efficiency. By using insulated disks, the size and impact of eddy currents are minimized.

💡Fleming's Left Hand Rule

Fleming's Left Hand Rule is a mnemonic used to determine the direction of force on a current-carrying conductor in a magnetic field. The script uses this rule to illustrate how the forces on the coils of the motor are generated and how they contribute to the motor's rotation. The rule is applied using conventional current, not electron flow.

💡Electromagnets

Electromagnets are magnets whose magnetic field is generated by the flow of electric current. In the script, it is mentioned that the electromagnetic field around a wire can be strengthened by coiling the wire, which is a principle used in creating the coils around the rotor of a DC motor. The video also suggests a related video on making a solenoid, which is a type of electromagnet.

Highlights

DC motors convert electrical energy into mechanical energy, used in power tools, toy cars, and cooling fans.

DC motor structure includes a metal casing forming the stator, rotor with laminated disks, and coil windings.

Permanent magnets form the north and south poles within the motor, creating a magnetic field.

The rotor's T-shaped arms are wrapped with coil windings that carry electrical current, producing an electromagnetic field.

The commutator is a segmented ring that controls the timing and polarity of the magnetic field for rotation.

Brushes and brush arms complete the circuit, allowing electricity to flow through the motor.

DC electricity involves a single-direction electron flow from one battery terminal to another.

Free electrons in copper wire move randomly until influenced by an applied voltage.

Magnet poles repel like ends and attract opposite ends, creating pushing and pulling forces.

Magnetic field lines are most powerful at the ends of magnets, where they are closely packed.

Electromagnetic fields around wires can be strengthened by coiling them, creating a more effective force.

Multiple coil sets in a rotor ensure smoother rotation, especially useful for low-speed applications.

Eddy currents are reduced in rotors made of laminated disks, improving motor efficiency.

Fleming's left-hand rule determines the direction of force on a coil interacting with a magnetic field.

The commutator and brushes allow for continuous rotation by maintaining electrical contact.

DC motor operation involves the interaction of conventional current, magnetic fields, and coil forces.

Reversing the power supply or battery will reverse the current and direction of motor rotation.

Transcripts

hey there guys Paul here from the

engineering mindset calm in this video

we're going to be looking at the DC

motor to understand the basics of how it

works

DC motors look something like this

although there are quite a few

variations these are used to convert

electrical energy into mechanical energy

and we can use these for example in our

power tools our toy cars and even our

cooling fans when we look at a DC motor

we first see the metal protective casing

which forms the stator at one end we

have the tip of a sharp protruding

through the casing we can attach gears

fan blades or even pulleys onto this on

the other end we have a plastic end cap

with two terminals we can connect the

power supply to these terminals to

rotate the shark if we remove the casing

to look inside the motor we first find

two magnets inside these are permanent

magnets which form a north and south

pole running through the center of the

motor we see this rod which is called

the shaft the shaft is used to transfer

mechanical energy attached to the shaft

we have the rotor the rotor is made from

a number of disks which are laminated

together each disk has these t-shaped

arms cut into them wrapped around these

t-shaped arms of the rotor or the coil

windings which carry the electrical

current from the battery as the current

passes through the coils it produces an

electromagnetic field we control the

timing and the polarity of the magnetic

field to create rotation the ends of the

coils are connected to the commutator

the commutator is a ring which has been

segmented into a number of plates which

sit concentric lis around the shaft

these plates are separated and

electrically isolated from each other as

well as the shaft the ends of each coil

connect to a different commutator plate

they do this to create a circuit and

we'll see that in detail just shortly

sitting within the plastic back cover

are the brushes brush arms and terminals

the commutator plates sit between the

two brushes the brushes rub against the

commutator segments to complete the

circuit electricity can then flow

through a terminal through the arm into

the brush through a commutator segment

into a coil then out to another

commutator segment onto the opposite

brush and arm and back to the other

terminal these components give us our

basic DC motor

to understand how the DC motor works we

need to understand some fundamentals of

electricity as well as how the

components inside work but first where

have you seen a DC motor used or where

could you apply one let me know your

thoughts and project ideas in the

comment section down below

electricity is the flow of electrons

through a wire when lots of electrons

flow in the same direction we call this

current DC electricity means the

electrons flow in just a single

direction from one terminal of a battery

directly to the other if we reverse the

battery then the current will flow in

the opposite direction inside the copper

wire we find copper atoms orbiting each

atom we find free electrons these are

called free electrons because they are

free to move to other atoms they do

naturally move to our atoms by

themselves but this is in any and all

directions at random which is of no use

to us we need lots of electrons to flow

in the same direction and we can do that

by applying a voltage voltage is like

pressure and will force electrons to

move electrons only flow in a complete

circuit they always try to get back to

their source so when we give them a path

such as a wire they will flow through

this even if we temporarily create a

path they will take it as soon as it's

available we can place components in

this path so that they have to flow

through it and that way they do work for

us such as illuminating the lamp in

these animations we're going to be using

two terms that's electron flow and

conventional current electron flow is

what's actually occurring with the

electrons flowing from the negative

terminal to the positive terminal

conventional current moves in the

opposite direction from positive to

negative just be aware of the two terms

and which one we're using

as you probably already know magnets are

polarized with north and south ends

these types are known as permanent

magnets because their magnetic field is

always active when in proximity with

another magnet the Lycans push away and

the opposite ends attract so we get

these pushing and pulling forces caused

by the magnetic field of the magnets

magnets have these curved magnetic field

lines which run from the North Pole to

the South Pole and extend curving around

the exterior the magnetic field is most

powerful at the ends we see this because

there are more magnetic fields closely

packed together we can actually see the

magnetic field of a magnet by sprinkling

some iron filings over the top when two

magnets are in close proximity to each

other

the magnetic fields interact too alike

ends will repel each other and the

magnetic field lines will not join

however two opposite polarities will be

attracted to each other and the magnetic

field lines will converge into a highly

concentrated region therefore we place

tube magnets of opposite polarities into

the motor stator to form a strong

magnetic field through the rotor

when we connect a wire to the positive

and negative terminals of a battery a

current of electrons will flow through

the wire between the two terminals when

electrons pass through the copper wire

they generate an electromagnetic field

around the wire we can actually see that

by placing some magnets around the wire

when we pass electricity through the

wire the magnets rotate

when we reverse the direction of current

the magnets will also reverse and align

the opposite way so we can create a

magnetic field which acts just like a

permanent magnet except this type we are

able to turn off the problem with the

electromagnetic field and a wire is that

it's quite weak but we can make it much

stronger simply by wrapping the wires

into a coil each wire still creates an

electromagnetic field but they combine

into a much larger and stronger magnetic

field that's why we use these to create

the coils around the rotor if you find

electromagnets interesting then check

out our video on how to make a solenoid

you can find links to that in the video

description down below

the coils of wire are known as windings

the simplest DC motor has just a single

coil these are a much simpler design the

problem though is that they can align

magnetically with jams the motor and

stops it from rotating the more sets of

coils we have the smoother the rotation

will be this is especially useful for

low-speed applications therefore we

normally find at least three coils in a

rotor to ensure smooth rotation each

coil is positioned 120 degrees from

previous between each coil we find a

commutator plate

each coil is connected with two

commutator plates the plates are

electrically isolated from each other

except that they are now connected via

the coils so if we connect the positive

and negative terminals to two of the

commutator plates we can complete the

circuit current will now flow and a

magnetic field will generate in the

coils

the rotor or armature is made from

multiple disks of iron which are

laminated together each disk is

electrically insulated from one another

with a lacquer coating if the armature

was a single piece of solid metal large

eddy currents would swirl around inside

these are caused by induced

electro-motive force or EMF s-- the eddy

currents affect the efficiency of the

motor to reduce the eddy currents

engineers segment the rotor into

insulated disks this way the eddy

currents will still flow but they will

be much smaller

the thinner the disc the smaller the

eddy currents will be

the commutator consists of small copper

plates which are mounted to the shaft

each plate is electrically isolated from

one another as well as the shaft the end

of each coil is connected to a different

commutator plate in this design each

commutator plate is connected with two

coils the plates deliver electricity to

the coils to get the electricity from

the battery and into the plates we have

some brushes which rub against the place

the brush arms hold these in place when

we complete the circuit electricity will

flow into the commutator segments by the

brushes and then it will flow into one

or two coils as a path becomes available

at certain points in the rotation the

brushes will come into contact with two

plates this will create an arc and we

get these small bursts of blue light as

this occurs these arcs as well as

friction will eventually destroy the

brushes over time

something we must understand is

Fleming's left hand rule and for this we

need to use our left hand in this funny

shape you need to remember that

Fleming's rule uses conventional current

and does not use electron flow

conventional current is from positive to

negative we use Fleming's left hand rule

to work out which direction the coil

will push and pull as electromagnetic

field interacts with the magnetic field

of the permanent magnet if we looks a

wire and visualize which end is

connected to the positive or negative we

can work out the direction of force to

do that stick your left hand out flat

with your palm facing you think of these

as being your thumb then fingers one two

three and four first of all close

fingers three and four point finger two

to the right so it's perpendicular to

your palm then point finger one straight

ahead and point your thumb upwards your

second finger points in the direction of

conventional current from positive to

negative your first finger points in the

direction of the permanent magnetic

field from north to south your second

finger will point in the direction of

conventional current from positive to

negative your farm will then point in

the direction of force now I've made a

PDF guide for this which includes some

worked examples to help you remember it

you can find links in the video

description down below for how to get

your copy so if we look at this example

the conventional current is coming

towards us and the magnetic field is

going from left to right so we point our

second finger towards us and the first

finger in the direction of the magnetic

field our farm is therefore pointing

upwards which means the force on the

wire will move it upwards in this

example we have the conventional current

reversed in the wire so it's moving away

from us

therefore we flip our hand over so our

second finger is pointing away from us

our first finger still points in the

direction of the magnetic field and our

thumb points downward this means the

force on the wire will move it downwards

if we wrap the wire into a coil

how will the forces act now well we need

to consider the coil as two halves on

the left half the conventional current

is flowing away from us so our hand

flips and we see we get a downward force

on the right side the conventional

current is flowing towards us so the

force is upward therefore we have a

combined upward and downward force so

the coil will rotate so now we can see

how the motor rotates so let's have a

look in detail

okay let's consider the operation of a

DC motor in slow motion I'll just point

out the main parts

there's the north and south magnets

which concentrate a magnetic field

through the center in the center we find

the shark

attached to the shaft we have the rotor

wrapped around the rotor we have the

coils connecting the coils we have the

commutator and providing power to the

commutator we have the brushes and brush

arms and finally we have a power supply

the rotor coils and commutator are going

to rotate everything else will remain

stationary we are going to be

considering the flow of conventional

current and the forces which are

occurring in the long sides of each coil

that's this side and this side will also

label these coils one two and three and

the commutator plates a b and c in this

first position the conventional current

will flow from the positive of the

battery into plate a then through both

coils one and three through plates b and

c into the right brush and back to the

battery the right side of coil one has a

downward force and the left side has an

upward force coil three has an upward

force on this side and a downward force

on this side and therefore it rotates

the current now flows through plate a

and into coil one only then exits via

plate B this creates an upward force on

the left and a downward force on the

right the current now flows through

plates-a and c through coils one and two

and into plate B coil one has an upward

force on the left and a downward force

on the right coil two has an upward

force on the left and the downward on

the right

the current now flows through plates II

into coil to and into plate B the left

side of coil 2 has an upward force and

the right side has a downward force the

current now flows through plate C into

coil three and two and it exits wire

plates a and B this gives us our upward

and downward forces on the coils the

current now flows through plate C into

coil three then out through plate a

creating our upward and downward forces

the current now flows through plate C

and B through coils two three and one

and out through plate a giving us our

forces on each side the current now

flows through plate B into coil one and

out through plate a which creates our

forces the current now flows through

plate B and in two coils two and one it

then exits via plate C and a the current

now flows through plate B into quill -

and then out through plate see the

current now flows through plates B and a

in into coils two and three and then out

through plate see this then repeats

again and again like so which gives us

our rotating force which we can use to

drive things such as fans gears wheels

and pulleys if we were to reverse the

power supplier then we reverse the

current and that will also reverse the

forces and thus the direction of

rotation okay guys that's it for this

video but to continue your learning then

check out one of the videos on screen

now and I'll catch you there for the

next lesson

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