BÁO cáo CHUYÊN đề tiếng anh chuyên ngành

Ohm’s law of an electrical circuit regarding power sources The current through a resistor is in direct proportion to the voltage across the resistor's terminals.. Synchronous motors cont

BÁO CÁO CHUYÊN ĐỀ

NGÀNH: Công nghệ kỹ thuật điều khiển và tự động hóa

CHUYÊN NGÀNH: Tự động hóa và điều khiển thiết bị công nghiệp HỌC PHẦN: Tiếng Anh chuyên ngành

Giảng viên hướng dẫn: Nguyễn Ngọc Khoát

Nhóm sinh viên/ sinh viên thực hiện – Mã sinh viên:

Nhóm 3 : Nguyễn Khánh Hùng Khôi - 19810430152

Trần Lâm Hải Long - 19810430211

Lê Hoàng Minh - 19810430138

Trần Anh Thắng - 19810430273

Lớp : D14TDH&DKTBCN3

HÀ NỘI, 2/2022

Đề tài nhóm 3:

Chương 1: Introduction to power sources (DC and AC power)

1.1 Definition

1.2 How to use power sources in an electrical circuit?

1.3 How to produce power sources?

1.4 How internal resistance of power sources affects operation of an electrical circuit? 1.5 Ohm’s law of an electrical circuit regarding power sources

1.6 Applications of power sources

Chương 2: Synchronous AC motors

2.1 Concept

2.2 Classification

2.3 Structure

2.4 Working principle

2.5 Speed control methods for the synchronous AC motors

2.6 Applications

Chương 3: Introduction to PLC Mitsubishi

3.1 What is PLC?

3.2 What are differences between PLC and traditional relay circuits?

3.3 Select and present briefly a PLC of Mitsubishi

LỜI CẢM ƠN

Trong thời gian làm báo cáo chuyên đề, em đã nhận được nhiều sự giúp đỡ, đóng góp ý kiến và chỉ bảo nhiệt tình của thầy cô và bạn bè Em xin gửi lời cảm ơn chân thành đến thầy Nguyễn Ngọc Khoát, giảng vên người đã tận tình hướng dẫn, chỉ bảo em trong suốt quá trình làm chuyên đề điều khiển số Em cũng xin chân thành cảm ơn thầy cô giáo trường Đại học Điện Lực nói chung, các thầy cô bộ môn điện tử công suất nói riêng đã hướng dẫn cho em kiến thức về cách trình bày và nội dung đồ án, giúp em có được cơ sở lý thuyêt và tạo điều kiện gúp đỡ em trong quá trình làm báo cáo chuyên đề Tuy vậy, với kinh nghiệm và kiến thức còn thiếu sót nên bản báo cáo chuyên đề của em còn chưa được hoàn thiện lắm, em mong được sử chỉ dẫn chân thành của các thầy cô

Cuối cùng, em xin chân thành cảm ơn thầy cô và bạn bè đã luôn tạo đều kiện, quan tâm, giúp đỡ em trong suốt quá trình học tập và hoàn thành báo cáo

Chương 1: Introduction to power sources (DC and AC power)

1.1 Definition

Alternating current power is the standard electricity that comes out of power outlets and is defined as a flow of charge that exhibits a periodic change in direction AC's current flow changes between positive and negative because of electrons-electrical currents come from the flow of these electrons, which can move in either a positive (upward) or negative (downward) direction This is known as the sinusoidal

AC wave, and this wave is caused when alternators at power plants create AC power Alternators create AC power by spinning a wire loop inside a magnetic field Waves of alternating current are made when the wire moves into areas of different magnetic polarity—for example, the current changes direction when the wire spins from one of the magnetic field's poles to the other This wave-like motion means that AC power can travel farther than DC power, a huge advantage when it comes to delivering power

to consumers via power outlets

Direct current (DC) power, as you may guess from the name, is a linear electrical current—it moves in a straight line

Direct current can come from multiple sources, including batteries, solar cells, fuel cells, and some modified alternators DC power can also be "made" from AC power by using a rectifier that converts AC to DC DC power is far more consistent in terms of voltage delivery, meaning that most electronics rely on it and use DC power sources such as batteries Electronic devices can also convert AC power from outlets to DC power by using a rectifier, often built into a device's power supply A transformer will also be used to raise or lower the voltage to a level appropriate for the device in question

1.2 How to use power sources in an electrical circuit?

Power sources do two important things:

+) They supply energy to the circuit in the form of an electric potential difference +) They provide a source and sink for electrons in a circuit

As a simple analogy, you can think of a power source as the heart of a circuit; just as our heart circulates blood to enable our bodies to function, electric power sources pump or circulate electrons, enabling electric circuits to function

You can think of a power source as a ‘pump’ that keeps electrons flowing in a circuit Without a power source, a circuit will quickly lose energy due to the electrical resistance of its components

Power sources are known as active components because they supply energy to the electric circuit

Power sources supply electric power by pushing and pulling the electrons in a circuit Without a power source, circuits quickly stop working due to energy losses Think about the battery in your phone or tablet When the battery runs out of charge, it stops functioning as a power source and your device quickly shuts down Power sources are really important because every circuit and component relies on them in order to function We start our discussion on circuits with power sources because they are the beating heart of every circuit

1.3 How to produce power sources?

The three major categories of energy for electricity generation are fossil fuels (coal, natural gas, and petroleum), nuclear energy, and renewable energy sources Most electricity is generated with steam turbines using fossil fuels, nuclear, biomass, geothermal, and solar thermal energy Other major electricity generation technologies include gas turbines, hydro turbines, wind turbines, and solar photovoltaics

1.4 How internal resistance of power sources affects operation of an electrical circuit?

In the case of circuits, the equivalent of ‘friction’ is something called electric resistance Every electric component has some amount of electric resistance Even conductors like wires have some resistance to the movement of electrons That’s because conductors don’t conduct electricity perfectly, and they lose some energy as heat as a result The energy loss quickly causes all the electrons in the circuit to stop moving when disconnected from the power source, even if the circuit remains closed

In AC circuits, resistance is called impedance That’s because the total

‘resistance’ to current flow in an AC circuit doesn’t just come from electric resistance Capacitance and inductance also contribute to the overall opposition to current flow in

an AC circuit The total opposition to current flow, caused by resistance, capacitance and inductance is called impedance

1.5 Ohm’s law of an electrical circuit regarding power sources

The current through a resistor is in direct proportion to the voltage across the resistor's terminals This relationship is represented by Ohm's law:

Where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms (symbol: Ω)

1.6 Applications of power sources

For DC

 DC current limited by a resistor causes light-emitting diodes (LEDs) to produce light

 Mechanical and electronic switches can deliver large amounts of DC control current to motors, solenoids, and resistive heaters

 DC currents and voltages establish the electrical conditions that allow transistors to amplify AC signals

For AC

 Cell phones

 Flashlights\

 The Lilypad-based D&D Dice Gauntlet

 Flat-screen TVs (AC goes into the TV, which is converted to DC)

 Hybrid and electric vehicles

Chương 2: Synchronous AC motors

2.1 Concept

A synchronous electric motor is an AC electric motor in which, at steady state, the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles Synchronous motors contain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with the oscillations of the line current The rotor with permanent magnets or electromagnets turns in step with the stator field at the same rate and as a result, provides the second synchronized rotating magnet field of any AC motor A synchronous motor is termed doubly fed if it is supplied with

independently excited multiphase AC electromagnets on both the rotor and stator

The synchronous motor and the induction motor are the most widely used types

of AC motors The difference between the two types is that the synchronous motor rotates at a rate locked to the line frequency since it does not rely on current induction

to produce the rotor's magnetic field By contrast, the induction motor requires slip: the rotor must rotate slightly slower than the AC alternations in order to induce current in the rotor winding Small synchronous motors are used in timing applications such as in synchronous clocks, timers in appliances, tape recorders and precision

servomechanisms in which the motor must operate at a precise speed; speed accuracy

is that of the power line frequency, which is carefully controlled in large

interconnected grid systems

Synchronous motors are available in self-excited sub-fractional horsepower sizes to high power industrial sizes In the fractional horsepower range, most

synchronous motors are used where precise constant speed is required These

machines are commonly used in analog electric clocks, timers and other devices where correct time is required In higher power industrial sizes, the synchronous motor provides two important functions First, it is a highly efficient means of converting AC energy to work Second, it can operate at leading or unity power factor and thereby provide power-factor correction

2.2 Classification

Synchronous motors are classified according to their speed They are either high-speed or low-speed machines Those operating over 500 RPM are designated high-speed motors

Beside speed, synchronous motors can be classified by type There are different types of synchronous motors based on the way they are excited

 Non Excited Synchronous Motors

 Current Excited Synchronous Motors

Non Excited Synchronous Motor

The rotor is made up of steel The external magnetic field magnetizes the rotor, and it rotates in synchronism with it The rotor is generally made of high retentivity steel such as cobalt steel

Non-excited motors are available in three designs:

+) Hysteresis Motor

Hysteresis motors are single phase motors in which the rotor is made up of ferromagnetic material The rotors are cylindrical in shape and have high hysteresis loss property They are generally made up of chrome, cobalt steel or alnico The stator

is fed by single phase AC supply The stator has two windings:

1 main windings and

2 auxiliary windings

The combination of the two produces a revolving magnetic field from a single phase supply They are self-starting and do not need additional windings When single phase AC supply is given, a rotating magnetic field is produced This rotating

magnetic field induces eddy currents in the rotor The rotor starts to move initially with a slip When the rotor reaches synchronous speed, the stator pulls the rotor into synchronism So initially the motor starts as an induction motor and later runs as a synchronous motor

+) Reluctance Motor

The reluctance motor is based on the principle that an unrestrained piece of iron will move to complete a magnetic flux path where the reluctance is minimum The stator has the main winding and the auxiliary windings just like the hysteresis motor These help to create a rotating magnetic field The rotor of a reluctance motor is a squirrel cage rotor with some teeth removed to provide the desired number of salient

poles The reluctance becomes minimum when the rotor is aligned with the magnetic field of the stator

When single phase AC supply is given, the motor starts as an induction motor The rotor tries to align itself with the magnetic field of the stator and experiences reluctance torque But due to inertia, it exceeds the position and again tries to align itself during the next revolution In this manner, it starts to rotate Once it reaches 75%

of synchronous speed, the auxiliary windings are cut off When the speed reaches synchronous speed, the reluctance torque pulls it into synchronism The motor remains

in synchronism due to synchronous reluctance torque

+) Permanent Magnet Synchronous Motors

The rotor is made up of permanent magnets They create a constant magnetic flux The rotor locks in synchronism when the speed is near synchronous speed They are not self-starting and need electronically controlled variable frequency stator drive

Direct Current Excited Motor

Direct current excited synchronous motors need a DC supply to the rotor to generate rotor magnetic field A direct current excited motor has both stator windings

as well as rotor windings They can either have cylindrical rotors or salient pole rotors They are not self-starting and need damper windings to start Initially, they start as an induction motor and later attains synchronous speed

2.3 Structure

The construction of synchronous motor is similar to that of a synchronous alternator Most of the synchronous motors construction uses the stationary armature and rotating field winding This type of construction as an advantage than DC motor type where the armature used is of rotating type

2.4 Working principle

The principle of operation of a synchronous motor can be understood by

considering the stator windings to be connected to a three-phase alternating-current supply The effect of the stator current is to establish a magnetic field rotating at

120 f/p revolutions per minute for a frequency of f hertz and for p poles A direct current in a p-pole field winding on the rotor will also produce a magnetic field

rotating at rotor speed If the rotor speed is made equal to that of the stator field and there is no load torque, these two magnetic fields will tend to align with each other As mechanical load is applied, the rotor slips back a number of degrees with respect to the rotating field of the stator, developing torque and continuing to be drawn around by this rotating field The angle between the fields increases as load torque is increased The maximum available torque is achieved when the angle by which the rotor field lags the stator field is 90° Application of more load torque will stall the motor

One advantage of the synchronous motor is that the magnetic field of the

machine can be produced by the direct current in the field winding, so that the stator windings need to provide only a power component of current in phase with the applied stator voltage—i.e., the motor can operate at unity power factor This condition

minimizes the losses and heating in the stator windings

The power factor of the stator electrical input can be directly controlled by adjustment of the field current If the field current is increased beyond

the value required to provide the magnetic field, the stator current changes to include a component to compensate for this overmagnetization The result will be a total stator current that leads the stator voltage in phase, thus providing to the power system reactive volt-amperes needed to magnetize other apparatuses connected to the system such as transformers and induction motors Operation of a large synchronous motor at such a leading power factor may be an effective way of improving the overall power factor of the electrical loads in a manufacturing plant to avoid additional electric supply rates that may otherwise be charged for low power-factor loads

2.5 Speed control methods for the synchronous AC motors

Synchronous motors are constant speed motors They run at the synchronous speed of the supply They are generally used for constant speed operation under no load conditions such as to improve the power factor Synchronous motors have fewer losses than induction motors at a given rating

The speed of a synchronous motor is given by

N= 120 f p

As you can see, the synchronous speed depends on the frequency of the supply and the number of poles of the rotor Changing the number of poles is not easy, so we