Pratica di Shadowing: How Electric Motors Work - 3 phase AC induction motors ac motor - Impara a parlare inglese con i video
Scegli una modalità di pratica
Ogni modalità apre una sala di pratica a schermo intero.
161 frasi
Se le frasi sono troppo corte o troppo lunghe, clicca su Edit per modificarle.
1
This is an electrical motor is one of the most important
2
devices ever to be invented these motors are used everywhere from pumping the water we drink to powering elevators
3
and cranes even cooling nuclear power stations
4
so we are going to look inside one
5
and learn in detail exactly how they work in this video
6
which is sponsored by the Great Courses Plus visit the link in the video description to start a free trial
7
and get access to some truly great online courses.
8
The induction motor will look something like this.
9
They turn electrical energy into mechanical energy which we can use to drive pumps,
10
fans, compressors, gears, pulleys etc. Almost all the parts are held inside the main housing.
11
At the front we find the shaft.
12
This is the part that rotates and we can connect things like pumps, gears and pulleys to this to do work for us.
13
At the back we find the fan and a protective cover.
14
The fan is connected to the shaft and so it rotates whenever the motor operates.
15
That's because the induction motor can produce a lot of heat
16
when in operation so the fan blows ambient air over the casing to cool it down.
17
If the induction motor became too hot
18
The insulation of the internal electrical coils will melt.
19
This will cause a short circuit and the motor will destroy itself.
20
The fins on the side of the enclosure help to increase the surface area and that lets us remove more unwanted heat.
21
The shaft is supported by some bearings, which sit inside the front as well as the rear shields.
22
The bearings help the shaft rotate smoothly and also hold it in position.
23
Inside the housing we find the stator.
24
The stator is stationary and does not rotate.
25
This consists of a number of copper wires which are wrapped into coils between the slots positioned around the inner perimeter.
26
The copper wires are coated with a special enamel which electrically insulates the wires from each other.
27
This means electricity has to flow through the entire coil.
28
Otherwise it would take the shortest path possible and we'll see why that's important a little later in this video.
29
Now, this is a three phase induction motor, so we have three separated sets of coils in the stator.
30
The ends of each set will connect with the terminals within the electrical terminal box.
31
We will also see how these are connected a little later in this video.
32
When connected to the electrical supply, the stator generates a rotating electromagnetic field.
33
Connected to the shaft is the rotor.
34
In this case, it's a squirrel cage type rotor.
35
It's called a squirrel cage because it has two end rings which are connected by some bars
36
and these will all rotate together.
37
This design is similar to a small cage or an exercise wheel used by a pet hamster or even a squirrel.
38
The squirrel cage is fitted with a number of laminated steel sheets.
39
These sheets will help concentrate the magnetic field into the bars.
40
Sheets are used instead of a solid piece of metal as
41
this improves the efficiency by reducing the size of the eddy currents in the rotor.
42
When the rotor is placed inside the stator and the stator is connected to an electrical power supply, the rotor will begin to rotate.
43
So how does this work?
44
work.
45
When electricity passes through a wire an electromagnetic field is generated around the wire.
46
We can see this by placing some compasses around the wire.
47
The compasses will rotate to align with this magnetic field.
48
If the direction of current is reversed the magnetic field also reverses and so the compasses will change direction.
49
The magnetic field of the wire is pulling
50
and pushing the compass dials just like
51
if we slide two bar magnets towards each other they will either be attracted or repelled.
52
We can even use one magnet to rotate another
53
or we could also rotate the magnet by changing the intensity of the magnetic field around it.
54
If we place a wire in a magnetic field
55
and pass a current through it the magnetic field of the wire will interact with the permanent magnets magnetic field
56
and the wire will therefore experience a force this force will move the wire either upwards or downwards
57
depending on the direction of current and the polarity of the magnetic fields.
58
If we wrap the wire into a coil, the electromagnetic field becomes stronger.
59
The coil will produce a north and south pole just like a permanent magnet.
60
We call these coils of wire an inductor.
61
When we pass an alternating current through the wire, the electrons will be constantly changing direction between flowing forwards
62
and backwards so the magnetic field will also expand and collapse and the polarity reverses each time.
63
When we place another separated coil in close proximity and complete the circuit,
64
the electromagnetic field will induce a current in the second coil.
65
We can connect two coils together and place them opposite each other to create a larger magnetic field field.
66
If we placed a closed loop of wire inside
67
this large magnetic field we will induce a current in the loop as we know
68
when we pass a current through a wire it generates a magnetic field
69
and we also know the magnetic fields will push or pull each other when they interact.
70
So this loop of wire will also generate a magnetic field and this will interact with the larger magnetic field.
71
Each side of the coil will experience opposing forces which causes it to rotate.
72
This loop is therefore our rotor and the coils are therefore our stator.
73
The rotor will only rotate until it aligns with the stator coils.
74
At this point it will likely get stuck as the induced current reverses with the coil.
75
To overcome this we need to introduce another set of coils in the stator and we must connect these to another phase.
76
The electrons flow in this phase at a slightly different time.
77
So the electromagnetic field will also therefore change in strength as well as polarity at a slightly different time.
78
This will force the rotor to rotate.
79
Inside the induction motor we have three separated coils which are used to produce a rotational electromagnetic field.
80
When we pass an alternating current through each coil,
81
the coils will produce an electromagnetic field which changes in intensity as well as polarity as the electrons change direction.
82
But if we were to connect each coil to a different phase, then the electrons in each coil will change direction at a different time.
83
This means the polarity and intensity of the magnetic field will also occur at a different time.
84
To distribute this magnetic field we need to rotate the coil sets 120 degrees from the previous phase.
85
We then combine these into the stator.
86
The magnetic field varies in strength and polarity between the coils which combine to produce the effect of a rotating magnetic field.
87
We saw earlier in this video that current can be induced into a second coil when in close proximity.
88
The bars of the squirrel cage are shorted at each end, which therefore creates multiple loops or coils.
89
Each bar therefore induces a current and creates a magnetic field.
90
The magnetic field of the rotor bars interacts with the magnetic field of the stator.
91
The rotor bar's magnetic field is attracted to the magnetic field of the stator.
92
As the magnetic field is rotating,
93
the rotor will therefore also rotate in the same direction as the magnetic field to try and align with it,
94
but it will never be able to fully catch up.
95
The bars of the rotor are often skewed.
96
This helps distribute the magnetic field across multiple bars and stops the motor being able to align and jam.
97
the stator contains all of the coils
98
or windings used to create the rotating electromagnetic field
99
when electricity is passed through the wires to power the coils we find an electrical terminal box on the top
100
or sometimes on the side inside this box we have six electrical terminals each terminal has a corresponding letter
101
and number we have u1 v1 and w1 then w2 u2
102
and v2 we have our phase 1 coil connected to the 2u terminals then the phase 2 coils
103
which are connected to the 2v terminals and lastly the phase 3 coil
104
which is connected to the 2w terminals notice
105
that the electrical terminals are arranged in a different configuration on one side to the other.
106
We will see why that is in just a moment.
107
We now bring in our three phase power supply and connect these to their respective terminals.
108
For the motor to run, we need to complete the circuit.
109
And there are two ways to do this.
110
The first way is the Delta configuration.
111
For this, we connect across the terminals U1 to W2, V1 to U2, and W1 to V2.
112
This will give us our delta configuration.
113
Now, when we provide AC current through the phases, we see
114
that electricity flows from one phase to another as the direction of AC power reverses in each phase at a different time.
115
That is why we have the terminals in different arrangements in the terminal box.
116
Because we can easily connect across and allow electricity to flow between the phases as the electrons reverse at different times.
117
The other way we can connect the terminals is to use the star or Y configuration.
118
In this method, we connect between W2, U2 and V2 on only one side.
119
This will give us our star or Y equivalent connection.
120
Now, when we pass electricity through the phases, we see the electrons are shared between the terminals of the phases.
121
Due to their design differences, the amount of current flowing in the star and delta configuration is very different.
122
And we're going to see some calculations for these towards the end of this video.
123
But first, I want to tell you about The Great Courses Plus.
124
All of our viewers can get a free trial right now by visiting thegreatcoursesplus .com forward slash engineering mindset.
125
The Great Courses Plus is an on -demand learning platform that lets you binge -watch lectures and courses.
126
They have over 13 ,000 videos by industry experts on everything from science, maths, history, and even cooking.
127
Personally, my favorite is their engineering lectures and their course on inventions that change the world.
128
As a fan of this channel, I'm certain you'll also find these interesting too, so do check those out.
129
They add new content every month and you can watch as many videos as you want from your TV, tablet, laptop or phone.
130
Just click the link in the video description down below to start your free trial today.
131
Let's have a look at the difference between the star and delta configurations.
132
Let's say we have the motor connected in delta with a supply voltage of 400 volts.
133
That means when we use a multimeter to measure the voltage between any two phases, we will get a reading of 400 volts.
134
We call this our line -to -line voltage.
135
Now, if we measure across the two ends of a coil, we again see the line -to -line voltage of 400 volts.
136
Let's say each coil has a resistance, or impedance as this is alternating current, of 20 ohms.
137
That means we will get a current reading on the coil of 20 amps.
138
We can calculate that from 400 volts divided by 20 ohms, which is 20 amps.
139
But the current in the line will be different.
140
It will be 34 .6 amps.
141
We get that from 20 amps multiplied by the square root of 3, which is 34 .6 amps.
142
That's because each phase is connected to two coils.
143
Now, if we look at the star or wire configuration, we again have a line -to -line voltage of 400 volts.
144
We see that if we measure between any two phases, but with the star configuration,
145
all our coils are connected together and meet at the star point or neutral point.
146
It's from this point that we can run a neutral wire if needed.
147
So this time, when we measure the voltage across the ends of any coil we get a lower voltage of 230 volts.
148
That's because the phase isn't directly connected to two coils like in the delta configuration.
149
One end of the coil is connected to a phase
150
but the other is connected to a shared point so the voltage is therefore shared.
151
The voltage is less as one phase is always in reverse.
152
We can calculate this by 400 volts divided by the square root of three, which is 230 volts.
153
As the voltage is less, the current will be two.
154
If this coil also has an impedance of 20 ohms, then 230 volts divided by 20 amps I'll see you guys equals 11 .5 amps.
155
The line current will also therefore be the same at 11 .5 amps.
156
So we can see from the Delta configuration the coil is exposed to the full 400 volts between two phases.
157
But the star configuration is only exposed to 230 volts between the phase and the neutral point.
158
So the star uses less voltage and less current compared to the Delta version.
159
Okay, that's it for this video, but to continue learning about electrical engineering,
160
check out one of the videos on screen now and I'll catch you there for the next lesson.
161
Don't forget to follow us on Facebook, Instagram, LinkedIn, as well as theengineeringmindset .com.
Scarica l'app
Tutto ciò che serve per parlare fluentemente
Pronuncia con IAVoto per ogni frase
Pratica IPAPadroneggia ogni suono
VocabolarioCostruisci il tuo lessico
Gioco di vocabolarioImpara giocando
Stesso Canale
B21
Ohms Law Explained - The basics circuit theory
Daily ConversationUniversity Students
C1Single Phase Electricity Explained - wiring diagram energy meter
Daily ConversationUniversity Students
B21
Air Conditioning System Basics hvacr how does it work
Daily ConversationWorking Adults
C1120V 240V Electricity explained - Split phase 3 wire electrician
Daily ConversationUniversity Students
B22
How ELECTRICITY works - working principle
Daily ConversationUniversity StudentsWorking Adults
C11
Diodes Explained - The basics how diodes work working principle pn junction
Daily ConversationUniversity StudentsWorking Adults
C1Centrifugal Pump Basics - How centrifugal pumps work working principle hvacr
Daily ConversationWorking Adults
FOR YOU
Video consigliato
C165 frasi
How does a Steam Turbine Work?
Daily ConversationUniversity Students
C11
19 frasi
Types of Proximity Sensors! #automation #engineering #science #robotics #electronics
Daily ConversationUniversity StudentsWorking Adults
C12
520 frasi
An Animated Introduction to Vibration Analysis by Mobius Institute
Daily ConversationUniversity Students
C11
19 frasi
I Made an EMP Device... It Actually Works
Daily ConversationUniversity StudentsWorking Adults
C11
67 frasi
How a Car Engine Works
Daily ConversationUniversity Students
C14
23 frasi
3-D Brain Scans | Pathways 2
Daily ConversationUniversity Students
C12
474 frasi
Metabolism | Electron Transport Chain: DETAILED | Part 1
Daily ConversationUniversity Students
C11
197 frasi
How I use AI to learn engineering (anti brain rot studying)
Daily ConversationUniversity Students
C136 frasi
This Machine Keeps Ship Engines Alive | Fuel Oil Purifier Explained
Daily ConversationUniversity Students
C11
95 frasi
26 - How does harmonic phase shifting work including a detailed mathematical explanation to reduce s
Daily ConversationUniversity Students
C11
118 frasi
Current | Introduction to electrical engineering | Electrical engineering | Khan Academy
Daily ConversationUniversity Students
Vocabolario e note di pronuncia per questa lezione
Questa lezione di conversazione si basa sul video “How Electric Motors Work - 3 phase AC induction motors ac motor”. Le parole che ritornano più spesso: coil, field, magnetic, phase, wire. Questo video contiene 161 frasi e 2253 parole da ripetere con lo shadowing. Il parlato dura 15:29. Chi parla mantiene un ritmo costante di circa 145 parole al minuto, comodo per lo shadowing. Solo il 75% delle parole rientra nelle 3.000 più comuni dell’inglese, quindi il lessico è impegnativo.
Vocaboli chiave di questo video
15 parole del video che vale la pena imparare, con pronuncia e significato:
| Parola | Pronuncia | Significato |
|---|---|---|
| coil sostantivo | /kɔɪl/ | spirale |
| magnetic aggettivo | /mæɡˈnɛtɪk/ | magnetico |
| connect verbo | /kəˈnɛkt/ | connettere, connettersi |
| wire sostantivo | /ˈwaɪɚ/ | filo, filo metallico |
| rotate verbo | /ˈɹoʊ.teɪt/ | ruotare |
| terminal sostantivo | /ˈtɚmɪnəl/ | terminal, terminale |
| voltage sostantivo | /ˈvəʊltɪd͡ʒ/ | voltaggio, tensione |
| configuration sostantivo | /kənˌfɪɡ.əˈɹeɪ̯.ʃən/ | configurazione |
| electromagnetic aggettivo | /ɪˌlɛk.tɹoʊ.mæɡˈnɛ.tɪk/ | elettromagnetico |
| reverse sostantivo | /ɹɪˈvɝs/ | contrario, opposto |
| loop sostantivo | /luːp/ | cappio |
| cage sostantivo | /keɪd͡ʒ/ | gabbia |
| shaft sostantivo | /ˈʃɑːft/ | lancia |
| magnet sostantivo | /ˈmæɡ.nɪt/ | magnete, calamita |
| induction sostantivo | /ɪnˈdʌkʃən/ | induzione |
I phrasal verb che sentirai
| Parola | Significato |
|---|---|
| pass through verbo | trapassare |
| check out verbo | investigare |
La grammatica di questo video
Le strutture che chi parla usa di più, con le parole esatte del video:
| Struttura | Nel video |
|---|---|
| Forma passiva be + participio passato — conta ciò che accade, non chi lo fa | be invented · is sponsored · are held |
| Frasi relative who / which + frase — un’informazione in più su una persona o una cosa | wires which are · rings which are · coils which are |
Pronuncia a cui fare attenzione
Chi parla usa 8 contrazioni e forme ridotte, come I'll, don't, I'm. Pronunciale nella forma breve, così come le senti.
- I suoni “th”: mathematics /mæθ(.ə)ˈmæt.ɪks/, smoothly /ˈsmuːðli/
- I suoni “sh” e “zh”: configuration /kənˌfɪɡ.əˈɹeɪ̯.ʃən/, shaft /ˈʃɑːft/, induction /ɪnˈdʌkʃən/, sheet /ʃit/, efficiency /ɪˈfɪʃ.ən.si/
- Parole lunghe — attenzione all’accento: configuration /kənˌfɪɡ.əˈɹeɪ̯.ʃən/, electrical /ɪˈlɛktɹɪkəl/, electromagnetic /ɪˌlɛk.tɹoʊ.mæɡˈnɛ.tɪk/, electricity /ɪˌlɛkˈtɹɪsɪti/, intensity /ɪnˈtɛnsɪti/
I suoni difficili per chi parla italiano:
- Consonante finale — senza aggiungere una vocale dopo: magnetic /mæɡˈnɛtɪk/, connect /kəˈnɛkt/, rotate /ˈɹoʊ.teɪt/, voltage /ˈvəʊltɪd͡ʒ/, amp /ˈæmp/
- /æ/ — più aperta della “e”: magnetic /mæɡˈnɛtɪk/, amp /ˈæmp/, electromagnetic /ɪˌlɛk.tɹoʊ.mæɡˈnɛ.tɪk/, magnet /ˈmæɡ.nɪt/, interact /ɪn.təˈɹækt/
- /ŋ/ finale — senza pronunciare la /g/: bearing /ˈbɛɹɪŋ/, winding /ˈwaɪndɪŋ/
Come esercitarsi con questo video
- Ascolta tutto il video una volta senza parlare e annota le parole che non conosci.
- Fai shadowing frase per frase a velocità normale, ripetendo ognuna finché il tuo ritmo coincide con quello di chi parla.
- Registrati e confronta con l’originale, facendo attenzione a parole come coil, magnetic, connect.
Cos'è la tecnica dello Shadowing?
Shadowing è una tecnica di apprendimento delle lingue supportata da studi scientifici, originariamente sviluppata per la formazione dei traduttori professionisti e resa popolare dal poliglotta Dr. Alexander Arguelles. Il metodo è semplice ma potente: ascolti un audio in inglese di madrelingua e lo ripeti immediatamente ad alta voce — come un'ombra che segue il parlante con un ritardo di solo 1–2 secondi. A differenza dell'ascolto passivo o degli esercizi di grammatica, lo shadowing costringe il tuo cervello e i muscoli della bocca a elaborare e riprodurre simultaneamente i modelli di discorso reale. La ricerca dimostra che migliora significativamente la precisione della pronuncia, l'intonazione, il ritmo, il discorso connesso, la comprensione dell'ascolto e la fluidità del parlato — rendendolo uno dei metodi più efficaci per la preparazione alla prova di speaking dell'IELTS e per la comunicazione reale in inglese.