PROJECT.pdf

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1 1 CHAPTER 1 CHAPTER 1

1.1 PROJECT INTRODUCTION

The proposed of this project is developed to control the speed of DC (direct The proposed of this project is developed to control the speed of DC (direct current) motor. This project is also consisting of dc converter, power control current) motor. This project is also consisting of dc converter, power control circuit and also gate circuit. The input signal from AC (alternative current) supply circuit and also gate circuit. The input signal from AC (alternative current) supply will go through the transformer for stepping down the line voltage to level

will go through the transformer for stepping down the line voltage to level

suitable for the control circuit at the dc converter and also for the dc motor itself suitable for the control circuit at the dc converter and also for the dc motor itself the power control circuit will produced the smooth without ripple signal for dc the power control circuit will produced the smooth without ripple signal for dc motor input. The power control circuit include with thyristor. The thyristor (SCR) motor input. The power control circuit include with thyristor. The thyristor (SCR) is line-commutated converter; therefore the firing angle must be delivered

is line-commutated converter; therefore the firing angle must be delivered

synchronously with the line voltage. The additional circuit called gate circuit is an synchronously with the line voltage. The additional circuit called gate circuit is an external circuit that is needed to generate the firing angle

external circuit that is needed to generate the firing angle

1.2 project

1.2 project objective

objective

The main objective of this project is to design and integrated the power control The main objective of this project is to design and integrated the power control circuit. At the same time this power control circuit also will control the dc motor circuit. At the same time this power control circuit also will control the dc motor speed.

speed.

1.3 problem statement

The main problem that can be stated here are, where we could not gate the The main problem that can be stated here are, where we could not gate the smooth input signal without ripples for the speed of dc motor and at the same smooth input signal without ripples for the speed of dc motor and at the same time it also could not control the speed range of the dc motor.

time it also could not control the speed range of the dc motor.

1.4 problem solving

The input signal from ac supply is sinusoidal as in figure1.1. After the signal go The input signal from ac supply is sinusoidal as in figure1.1. After the signal go through the dc converter the signal will be converted as in figure 1.2. If this signal through the dc converter the signal will be converted as in figure 1.2. If this signal go through the dc motor, so the speed range of dc motor will be constant. At the go through the dc motor, so the speed range of dc motor will be constant. At the same time the speed of dc motor also cannot be controlled at all.

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This situation is not good for the dc motor because it will damage the motor This situation is not good for the dc motor because it will damage the motor itself. The dc motor or any other motors need to be worm up first with a very itself. The dc motor or any other motors need to be worm up first with a very slow speed before start with heavy load or speed.

slow speed before start with heavy load or speed.

For solving this problem we need to add power control circuit to control the For solving this problem we need to add power control circuit to control the speed of dc motor and to produce a smooth input signal for dc motor. In this speed of dc motor and to produce a smooth input signal for dc motor. In this power control circuit there is a thyristor which will firing the angle of control power control circuit there is a thyristor which will firing the angle of control circuit. As we know the speed of DC motor is consists of voltage, current and also circuit. As we know the speed of DC motor is consists of voltage, current and also angle. Thyristor is the only component that provides a controllable power output angle. Thyristor is the only component that provides a controllable power output by “phase angle control”, so called because the firing angle (a point in time where by “phase angle control”, so called because the firing angle (a point in time where the thyristor is triggered in to conduction) is synchronized with the phase rotation the thyristor is triggered in to conduction) is synchronized with the phase rotation of the ac power source. If the device is triggered early in half cycle, maximum of the ac power source. If the device is triggered early in half cycle, maximum power is delivered the motor, late triggering in the half cycle provides minimum power is delivered the motor, late triggering in the half cycle provides minimum power. The effect is similar to a very high speed switch, capable of being turned power. The effect is similar to a very high speed switch, capable of being turned on and “conducted “of at an infinite number of points with in each half cycle. The on and “conducted “of at an infinite number of points with in each half cycle. The efficiency of this form of power control is extremely high since a very small

efficiency of this form of power control is extremely high since a very small amount of triggering energy can enable the thyristor to control a great deal of amount of triggering energy can enable the thyristor to control a great deal of output power in dc motor. The final signal input at d c motor speed is as in figure output power in dc motor. The final signal input at d c motor speed is as in figure 1.3.

1.3.

This power control circuit needs another additional external circuit called gate This power control circuit needs another additional external circuit called gate circuit to generate the firing angle at thyristor. This is because the thyristor itself circuit to generate the firing angle at thyristor. This is because the thyristor itself with three leads, there are anode, cathode and gate. We need the gate circuit to with three leads, there are anode, cathode and gate. We need the gate circuit to be connected to the gate lead.

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1.5 SCOPE OF STUDY

In this paper, it has been tried to control the speed of a single phase DC motor In this paper, it has been tried to control the speed of a single phase DC motor by using thyristor with the help of MATLAB simulation software. The scope is to by using thyristor with the help of MATLAB simulation software. The scope is to study the DC motor characteristic curve at the load terminal.

study the DC motor characteristic curve at the load terminal.

1.6 1.6 SIGNIFICANC

SIGNIFICANCE

E

The speed control of dc motor by using thyristor in general is very useful by The speed control of dc motor by using thyristor in general is very useful by preventing the previously mentioned problems of classical control techniques. preventing the previously mentioned problems of classical control techniques. The ultimate result of the study is to have variable speed, in terms of efficiency The ultimate result of the study is to have variable speed, in terms of efficiency and serviceability and to increase or decrease the developed torque.

and serviceability and to increase or decrease the developed torque.

1.7 Outline of project

This project consists four chapters. In first chapter, it discusses about the This project consists four chapters. In first chapter, it discusses about the introduction, objective, problem statement, problem solving and scope of this introduction, objective, problem statement, problem solving and scope of this project as long as summary of works. While Chapter 2 will discuss more on theory project as long as summary of works. While Chapter 2 will discuss more on theory and literature reviews that have been done. It well discuss about introduction of and literature reviews that have been done. It well discuss about introduction of dc motor, basics of dc motor , features, construction, principle operation,

dc motor, basics of dc motor , features, construction, principle operation, application of

application of dc motor, dc motor, dc motor dc motor control, basics of speed control, basics of speed control .control .

In Chapter 3, the discussion will be on the different speed control of dc motor In Chapter 3, the discussion will be on the different speed control of dc motor methods using field control, armature control and SCR control and also discuss methods using field control, armature control and SCR control and also discuss about matmatical model of dc motor and block diagram of dc motor speed about matmatical model of dc motor and block diagram of dc motor speed

control using thyristor. The result and discussion will be presented in Chapter 4. control using thyristor. The result and discussion will be presented in Chapter 4. Last but not least, Chapter 5 discusses the conclusion of this project and future Last but not least, Chapter 5 discusses the conclusion of this project and future work that can be done.

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CHAPTER 2

2.0 2.0 LITERATURE

LITERATURE REVIEW

REVIEW

2.1 REVIWE OF CONTROL SPEED MOTOR SYSTEM

A.T.Alexandridis (1997) proposed on the speed control on nonlinear firing A.T.Alexandridis (1997) proposed on the speed control on nonlinear firing angel control scheme, which is suitable series and shunt connected dc motor angel control scheme, which is suitable series and shunt connected dc motor drive system. The design procedure obtains an equivalent linear model of the drive system. The design procedure obtains an equivalent linear model of the system by exact state transformation and feedback rather than by linear

system by exact state transformation and feedback rather than by linear approximations about particular set points. Therefore, large change of the approximations about particular set points. Therefore, large change of the operating points through the command input or of the external load can be operating points through the command input or of the external load can be applied the successfully. In case the simulation results verify an excellent applied the successfully. In case the simulation results verify an excellent performance of the dc motor speed control.

performance of the dc motor speed control.

M.Nedelikovic (2000) created a new approach to the design of feed forward M.Nedelikovic (2000) created a new approach to the design of feed forward fast current controller for SCR is described. This type of current control has fast current controller for SCR is described. This type of current control has

excellent stability and the fastest possible limited only by the DC side inductor. As excellent stability and the fastest possible limited only by the DC side inductor. As in any type of feed forward control, there is a problem of small inaccuracy in

in any type of feed forward control, there is a problem of small inaccuracy in estimating circuit

estimating circuit parameters parameters and and especiaespecially lly in in this this case case , , due due to to setting thesetting the maximum instant value of current instead of preferable average value .

maximum instant value of current instead of preferable average value .

This problem can be solved with the outer control loop with the PI controller, This problem can be solved with the outer control loop with the PI controller, which will generate a reference value for maximum instant value of current. For which will generate a reference value for maximum instant value of current. For the sake of simplicity, in this paper, although it can easily be extended to rectifier the sake of simplicity, in this paper, although it can easily be extended to rectifier with any number of phase.

with any number of phase.

A new GTO due to converter is proposed by Khan el al. (1988).The two A new GTO due to converter is proposed by Khan el al. (1988).The two converters which Constitute the dual converter are always operated

converters which Constitute the dual converter are always operated

simultaneously permitting a free flow of current from the load of the converter. simultaneously permitting a free flow of current from the load of the converter. The getting pulse pattern is such that no circulating currents flow through the The getting pulse pattern is such that no circulating currents flow through the converters at any time.

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This disperses with the need for dc choke and avoids over-rating of the This disperses with the need for dc choke and avoids over-rating of the thyristor, two major drawbacks of circulating current dual converter, while thyristor, two major drawbacks of circulating current dual converter, while maintaining good dynamic response and continuity of the load current. maintaining good dynamic response and continuity of the load current.

2.2 SUMMRY OF REVIEW

From the above authors reviews’ , there

From the above authors reviews’ , there are a lot methods are a lot methods to control theto control the speed of DC

speed of DC the the motor ,such as dual modmotor ,such as dual mode inverter controller , microprocessor ,e inverter controller , microprocessor , SCR ,

SCR , PWM ,by PWM ,by inserting resistance inserting resistance in the in the armature and armature and field windings .In field windings .In thosethose methods we can control the speed of the DC motor but the out puts is not

methods we can control the speed of the DC motor but the out puts is not balanced.

balanced.

As a conclusion MATLAB/SIMULINK realization of the speed control of the DC As a conclusion MATLAB/SIMULINK realization of the speed control of the DC motor SCR is used to control the DC motor easily and it shows controlled wave motor SCR is used to control the DC motor easily and it shows controlled wave form and the characteristics of speed-torque, current-torque, and power-torque form and the characteristics of speed-torque, current-torque, and power-torque

2.3 REVIEW

2.3 REVIEW OF SELECTED COMPONENTES

OF SELECTED COMPONENTES

The project proposed uses of DC motor and thyristor to control the speed of dc The project proposed uses of DC motor and thyristor to control the speed of dc motor itself.

motor itself.

2.3.1 INTRODUTION OF DC MOTOR: An

electric motor converts electrical electric motor converts electrical energy into mechanical energy. Most electric motors operate through interacting energy into mechanical energy. Most electric motors operate through interacting magnetic fields and current-carrying conductors to generate force.

magnetic fields and current-carrying conductors to generate force. Motor Classification:

Motor Classification:



 Direct Current Motors (DC)Direct Current Motors (DC)



 Alternating Current Motors (AC)Alternating Current Motors (AC)



 Asynchronous Induction Motor (ACI)Asynchronous Induction Motor (ACI)



 permanent Magnet permanent Magnet Synchronous Synchronous Motor Motor (PMSM)(PMSM)



 Synchronous Brushless DC Motor (BLDC)Synchronous Brushless DC Motor (BLDC)

Electric motors are found in applications as diverse as industrial fans, blowers and Electric motors are found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives. They pumps, machine tools, household appliances, power tools, and disk drives. They

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may be powered by direct current (e.g., a battery powered portable device or may be powered by direct current (e.g., a battery powered portable device or motor vehicle), or by alternating current from a central electrical distribution grid. motor vehicle), or by alternating current from a central electrical distribution grid.

Fig. 2.1 DC Motor Fig. 2.1 DC Motor

2.3.1.2 BASICS OF DC

2.3.1.2 BASICS OF DC MOTOR

MOTOR::

A DC motor is designed to run on DC electric power. The most common DC motor A DC motor is designed to run on DC electric power. The most common DC motor types are the brushed and brushless types, which use internal and external

types are the brushed and brushless types, which use internal and external commutation respectively to periodically reverse the current in the rotor commutation respectively to periodically reverse the current in the rotor windings. The three basic types of DC motors are the series motor, the shunt windings. The three basic types of DC motors are the series motor, the shunt motor, and the compound motor.

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

 The series motor is designed to move large loads with high starting torqueThe series motor is designed to move large loads with high starting torque in applications such as a crane motor or lift hoist.

in applications such as a crane motor or lift hoist.



 The shunt motor is designed slightly differently, since it is made forThe shunt motor is designed slightly differently, since it is made for

applications such as pumping fluids, where constant-speed characteristics applications such as pumping fluids, where constant-speed characteristics are important.

are important.



 The compound motor is designed with some of the series motor'sThe compound motor is designed with some of the series motor's

characteristics and some of the shunt motor's characteristics. This allows characteristics and some of the shunt motor's characteristics. This allows the compound motor to be used in applications where high starting torque the compound motor to be used in applications where high starting torque and controlled operating speed are both required.

and controlled operating speed are both required.

2.3.1.3 FEATURES

::



 Internal commutationInternal commutation



 Speed proportionate to voltage appliedSpeed proportionate to voltage applied



 Easy to control: ON/OFF, ProportionalEasy to control: ON/OFF, Proportional



 Low CostLow Cost



 Electrical sparks due to commutatorsElectrical sparks due to commutators



 Produce significant EMI!Produce significant EMI!



 NOT suitable for deployment in combustible environmentsNOT suitable for deployment in combustible environments



 Limited speed due to commutatorsLimited speed due to commutators



 Mechanical noise due to commutatorsMechanical noise due to commutators



 Commutators Commutators limit limit life life time.time.

2.3.1.4 2.3.1.4 CONSTRUC

CONSTRUCTION:

TION:

The basic components of a DC motor include the armature assembly, which The basic components of a DC motor include the armature assembly, which includes all

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coils; and the end plates, which provide bearings for the motor shaft and a coils; and the end plates, which provide bearings for the motor shaft and a mounting point for the brush rigging. The DC motor has two basic parts: the mounting point for the brush rigging. The DC motor has two basic parts: the

rotating part that is called the armature and the stationary part that includes coils rotating part that is called the armature and the stationary part that includes coils of wire called the field coils. The stationary part is also called the stator.

of wire called the field coils. The stationary part is also called the stator.

The armature is made of coils of wire wrapped around the core, and the core has The armature is made of coils of wire wrapped around the core, and the core has an extended shaft that rotates on bearings .we can also notice that the ends of an extended shaft that rotates on bearings .we can also notice that the ends of each coil of wire on the armature are terminated at one end of the armature. The each coil of wire on the armature are terminated at one end of the armature. The termination points are called the commutator, and this is where the brushes

termination points are called the commutator, and this is where the brushes make electrical contact to bring electrical current from the stationary part to the make electrical contact to bring electrical current from the stationary part to the rotating part of the machine .The coils that are mounted inside the stator are rotating part of the machine .The coils that are mounted inside the stator are called field coils and they may be connected in series or parallel with each other called field coils and they may be connected in series or parallel with each other to create changes of torque in the motor. You will find the size of wire in these to create changes of torque in the motor. You will find the size of wire in these coils and the number of turns of wire in the coil will depend on the effect that is coils and the number of turns of wire in the coil will depend on the effect that is trying to be achieved.

trying to be achieved.

2.3.1.5 PRINCIPLE

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Fig.

Fig. 2.2. 2.2. Principle Principle of of OperationOperation A direct

A direct current (DC) current (DC) motor is motor is a fairly a fairly simple electric simple electric motor that motor that usesuses

electricity and a magnetic field to produce torque, which turns the motor. At its electricity and a magnetic field to produce torque, which turns the motor. At its most simple, a DC motor requires two magnets of opposite polarity and an

most simple, a DC motor requires two magnets of opposite polarity and an electric coil, which acts as an electromagnet. The repellent and attractive electric coil, which acts as an electromagnet. The repellent and attractive electromagnetic forces of the magnets provide the torque that causes the DC electromagnetic forces of the magnets provide the torque that causes the DC motor to turn.

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A DC motor requires at least one electromagnet. This electromagnet A DC motor requires at least one electromagnet. This electromagnet switches the current flow as the motor turns, changing its polarity to keep the switches the current flow as the motor turns, changing its polarity to keep the motor running. The other magnet or magnets can either be permanent magnets motor running. The other magnet or magnets can either be permanent magnets or

or other electromagnets. Often, other electromagnets. Often, the electromagnet is the electromagnet is located in located in the the center center ofof the motor and turns within the permanent magnets, but this arrangement the motor and turns within the permanent magnets, but this arrangement is not necessary.

is not necessary.

Electrical current is supplied to the coils of wire on the wheel within the Electrical current is supplied to the coils of wire on the wheel within the DC

DC motor. motor. This electrical current This electrical current causes a mcauses a magnetic force. To agnetic force. To make the make the DC motorDC motor turn, the wheel must have be negatively charged on the side with the negative turn, the wheel must have be negatively charged on the side with the negative permanent magnet and positively charged on the side with the permanent permanent magnet and positively charged on the side with the permanent positive magnet. Because like charges repel and opposite charges attract, the positive magnet. Because like charges repel and opposite charges attract, the wheel will turn so that its negative side rolls around to the right, where wheel will turn so that its negative side rolls around to the right, where the positive

the positive permanent magnepermanent magnet is, and the wheet is, and the wheel's positive sl's positive side will roide will roll toll to the

the left, left, where where the the negative negative permanent permanent magnet magnet is. is. The The magnetic magnetic force force causescauses the wheel to turn, and this motion can be used to do work.

the wheel to turn, and this motion can be used to do work.

When the sides of the wheel reach the place of strongest attraction, the When the sides of the wheel reach the place of strongest attraction, the electric

electric current current is is switcheswitched, d, making the making the wheel change wheel change polarity. The polarity. The side that side that waswas positive becomes negative, and the side that was negative becomes positive. The positive becomes negative, and the side that was negative becomes positive. The magnetic forces are out of alignment again, and the wheel keeps rotating. As the magnetic forces are out of alignment again, and the wheel keeps rotating. As the DC motor spins, it continually changes the flow of electricity to the inner wheel, DC motor spins, it continually changes the flow of electricity to the inner wheel, so the magnetic forces continue to cause the wheel to rotate.

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2.3.1.6 APPLICATIONS OF A DC MOTOR:



 Low power DC motors are particularly useful as speed changes from 0 to 1Low power DC motors are particularly useful as speed changes from 0 to 1 are almost instantaneous. Therefore, they can be used successfully in are almost instantaneous. Therefore, they can be used successfully in digital systems.

digital systems.



 A low speed, low power brushless DC motor can be found in mostA low speed, low power brushless DC motor can be found in most

turntable devices, particularly precision turntable devices. Devices with turntable devices, particularly precision turntable devices. Devices with such motors are things like personal computers, CD and DVD players. such motors are things like personal computers, CD and DVD players.



 Arguably the most common and useful motors are High Power DC Motors.Arguably the most common and useful motors are High Power DC Motors. These motors are generally used in open systems, and generally used in These motors are generally used in open systems, and generally used in systems were torque and power, as well as drive are paramount. Examples systems were torque and power, as well as drive are paramount. Examples of such systems include electric wheelchairs, electric scooters, Segway, of such systems include electric wheelchairs, electric scooters, Segway, hybrid cars, as well as in elevators.

hybrid cars, as well as in elevators.



 Kitchen Kitchen appliances appliances Power Power toolstools



 Door locks (example: train doors)Door locks (example: train doors)



 Automotive applications: windows lift, seat adjust, antenna retractorAutomotive applications: windows lift, seat adjust, antenna retractor

2.4 DC MOTOR CONTROL

The function of a dc motor which must be controllable for practical use are the The function of a dc motor which must be controllable for practical use are the speed, the torque delivered, and direction of rotation. Speed is proportional to speed, the torque delivered, and direction of rotation. Speed is proportional to armature back-emf and inversely proportional to field flux. Torque is proportional armature back-emf and inversely proportional to field flux. Torque is proportional to armature current and field flux. Direction of rotation is simply a matter of the to armature current and field flux. Direction of rotation is simply a matter of the relative polarities of the armature and field voltages. It follows that it is necessary relative polarities of the armature and field voltages. It follows that it is necessary to control. The armature voltage; back-emf is component of armature voltage. to control. The armature voltage; back-emf is component of armature voltage. Thus, assuming the field to be constant, control of armature voltage provides Thus, assuming the field to be constant, control of armature voltage provides complete control of speed up to the point where the voltage reaches the complete control of speed up to the point where the voltage reaches the maximum value of which the armature is designed. Armature current is also a maximum value of which the armature is designed. Armature current is also a function of armature voltage, so that with in the speed range up to maximum function of armature voltage, so that with in the speed range up to maximum voltage, torque is controlled by voltage also, provided that the field is fully – voltage, torque is controlled by voltage also, provided that the field is fully – excited, the availability of maximum torque is normally maintained from zero excited, the availability of maximum torque is normally maintained from zero speed up to armature voltage maximum (base speed).

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2.4.1 Basics of s

2.4.1 Basics of speed control

peed control

In order to investigate the modern speed control techniques for motors, we In order to investigate the modern speed control techniques for motors, we should first review what determines the speed of a motor- load system. Let as should first review what determines the speed of a motor- load system. Let as consider the situation in figure 2.1(a) and (b).it may be noted that two devices are consider the situation in figure 2.1(a) and (b).it may be noted that two devices are involved: the motor, which produces a torque Tdev, and the load, producing

involved: the motor, which produces a torque Tdev, and the load, producing acounter torque Tm.in case the motor has significant rotational loss, we shall acounter torque Tm.in case the motor has significant rotational loss, we shall combine these with the load for sake of simplicity. Using Newton’s second law, combine these with the load for sake of simplicity. Using Newton’s second law, we therefore have we therefore have Tdev = J.dw/dt Tdev = J.dw/dt Where, Where,

Tdev = Electromagnetic Torque developed by the motor, in NM. Tdev = Electromagnetic Torque developed by the motor, in NM.

Tm = Mechanical torque required by the load, plus motor rotational loss, NM. Tm = Mechanical torque required by the load, plus motor rotational loss, NM. J = Moment of inertia of all rotating parts in kg.m2.

J = Moment of inertia of all rotating parts in kg.m2. W = shaft speed in radian/sec.

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FIG 2.3 motor load system and torque speed characteristics FIG 2.3 motor load system and torque speed characteristics

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CHAPTER 3

CHAPTER 3 SPEED CONTROLOF DC MOTOR

SPEED CONTROLOF DC MOTOR

3.0 INTRODUCTION

Motors come in a variety of forms, and the speed controller’s motor drive Motors come in a variety of forms, and the speed controller’s motor drive output will be different dependent on these forms. Direct current (DC) motors output will be different dependent on these forms. Direct current (DC) motors have been widely used in many industrial applications such as electric vehicles, have been widely used in many industrial applications such as electric vehicles, steel rolling mills, electric cranes and robotic manipulators due to precise, wide, steel rolling mills, electric cranes and robotic manipulators due to precise, wide, simple and continuous control characteristics.

simple and continuous control characteristics.

Traditionally rheostatic armature control method was widely used for the Traditionally rheostatic armature control method was widely used for the speed control of low power dc motors. However the controllability, cheapness, speed control of low power dc motors. However the controllability, cheapness, higher efficiency and higher current carrying capabilities of static power

higher efficiency and higher current carrying capabilities of static power

converters brought a major change in the performance of electrical drives. The converters brought a major change in the performance of electrical drives. The desired torque – speed characteristic could be achieved by the use of

desired torque – speed characteristic could be achieved by the use of

conventional Thyristor controlled methods. The thyristor dc drive remains an conventional Thyristor controlled methods. The thyristor dc drive remains an important speed-controlled industrial drive, especially where the higher

important speed-controlled industrial drive, especially where the higher maintenance cost associated with the dc motor brushes is tolerable. The maintenance cost associated with the dc motor brushes is tolerable. The

controlled (thyristor) rectifier provides a low impedance adjustable dc voltage for controlled (thyristor) rectifier provides a low impedance adjustable dc voltage for the motor armature, thereby providing speed control. In all variable speed drive the motor armature, thereby providing speed control. In all variable speed drive systems, power electronic converter acts as an interface which accepts electric systems, power electronic converter acts as an interface which accepts electric power from the existing source and converts it in a controlled manner into a power from the existing source and converts it in a controlled manner into a suitable form compatible with the particular load or the process for which it is suitable form compatible with the particular load or the process for which it is employed. The main sources for electric power are:

employed. The main sources for electric power are:

1. Single or three phase 50Hz ac from utility system. 1. Single or three phase 50Hz ac from utility system. 2. Dc from storage batteries or solar cells.

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The modern converters are compact, cheap, reliable, flexible and completely The modern converters are compact, cheap, reliable, flexible and completely controllable. They need reduced maintenance too. For dc motor control,

controllable. They need reduced maintenance too. For dc motor control,

controlled dc power from a constant ac supply is obtained by means of controlled controlled dc power from a constant ac supply is obtained by means of controlled rectifiers (converters) using thyristors and diodes. The control of dc voltage is rectifiers (converters) using thyristors and diodes. The control of dc voltage is achieved by varying the phase angle at which the thyristors are fired relative to achieved by varying the phase angle at which the thyristors are fired relative to the applied alternating waveform. This scheme of phase control is known as the applied alternating waveform. This scheme of phase control is known as ‘phase control’.

‘phase control’. In another control system, kIn another control system, known as ‘nown as ‘integral cycle integral cycle control’, thecontrol’, the current is gated to flow from the ac supply for a number of complete cycles and is current is gated to flow from the ac supply for a number of complete cycles and is then quenched further for a few cycles, the process being repeated continuously. then quenched further for a few cycles, the process being repeated continuously. Control is applied by adjusting the ratio of on and off durations. This method is Control is applied by adjusting the ratio of on and off durations. This method is suitable for the control of fractional kW output dc motors.

suitable for the control of fractional kW output dc motors.

Phase controlled converters are simple to operate and less expensive as they Phase controlled converters are simple to operate and less expensive as they do not require additional circuitry for commutation process. In such converters do not require additional circuitry for commutation process. In such converters natural commutation is achieved, i.e., when an incoming thyristor is turned on, it natural commutation is achieved, i.e., when an incoming thyristor is turned on, it immediately reverse biases the outgoing thyristor and turns it off. Thereby

immediately reverse biases the outgoing thyristor and turns it off. Thereby

obtaining control in both half cycles of ac mains. This rectified voltage is fed to the obtaining control in both half cycles of ac mains. This rectified voltage is fed to the armature of dc motor. Hence speed of the motor can be controlled in proportion armature of dc motor. Hence speed of the motor can be controlled in proportion with the voltage.

with the voltage.

3.1 Different speed control methods of DC motor

Dc machines are generally much more adaptable to adjustable speed service. Dc machines are generally much more adaptable to adjustable speed service. The ready availability of dc motors to adjustment of their operating speed over The ready availability of dc motors to adjustment of their operating speed over wide ranges and by a variety of methods is one of the important reasons for the wide ranges and by a variety of methods is one of the important reasons for the strong competitive position of dc machinery in modern industrial applications.The strong competitive position of dc machinery in modern industrial applications.The speed of a dc motor can be expressed by the following relationship.

speed of a dc motor can be expressed by the following relationship. N α (V

N α (V-IaRa)/-IaRa)/ф,ф, wherewhere N- Speed of motor

N- Speed of motor Ia- Armature current Ia- Armature current

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17 17 Ra- Armature resistance

Ra- Armature resistance Ф

Ф- Flux per pole- Flux per pole V- Applied voltage V- Applied voltage

It is obvious that the speed can be controlled by varying It is obvious that the speed can be controlled by varying •Flux per pole

•Flux per pole

•Resistance of armature circuit and •Resistance of armature circuit and •Applied voltage

•Applied voltage In other words by In other words by •Field control and •Field control and •Armature control •Armature control

3.1.1 Field control method:

It is the most common method and forms one of the outstanding advantages of It is the most common method and forms one of the outstanding advantages of shunt motors.The method is also applicable to compound motors. Adjustment of shunt motors.The method is also applicable to compound motors. Adjustment of field current and hence the flux and speed by adjustment of the shunt field circuit field current and hence the flux and speed by adjustment of the shunt field circuit resistance or with a solid state control when the field is separately excited is

resistance or with a solid state control when the field is separately excited is

accomplished simply, inexpensively and without much change in motor losses.The accomplished simply, inexpensively and without much change in motor losses.The speed is inversely proportional to the field current.The lowest speed obtainable is speed is inversely proportional to the field current.The lowest speed obtainable is that corresponding to maximum field current. The highest speed is limited

that corresponding to maximum field current. The highest speed is limited electrically by the effects of armature reaction under weak field conditions in electrically by the effects of armature reaction under weak field conditions in causing motor instability and poor commutation.

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Merits: Merits:

•Good working efficiency. •Good working efficiency.

• Compact controlling equipment • Compact controlling equipment

• The speed is not effected by load and speed control can be performed • The speed is not effected by load and speed control can be performed effectively even at light loads.

effectively even at light loads.

•Relatively inexpensive and simple to accomplish both manually and •Relatively inexpensive and simple to accomplish both manually and automatically.

automatically.

Demerits: Demerits:

•Inability to obtain prefer below the basic speed. •Inability to obtain prefer below the basic speed.

•Instability at high speeds because of armature reaction. •Instability at high speeds because of armature reaction.

•Commutation difficulties and possible commutator damage at high speeds. •Commutation difficulties and possible commutator damage at high speeds.

3.1.2 ARMATURE CONTROL METHODS

3.1.2.1Rheost

3.1.2.1Rheostatic

atic control:

control:

This method consists of obtaining reduced speeds by the insertion of external This method consists of obtaining reduced speeds by the insertion of external series resistance in the armature circuit. It can be used with series, shunt and series resistance in the armature circuit. It can be used with series, shunt and compound motors.It is common method of speed control for series motors.This compound motors.It is common method of speed control for series motors.This method is used when speeds below the no load speed is required.

method is used when speeds below the no load speed is required. Merits:

Merits:

• The ability to achieve speeds below the basic speed. • The ability to achieve speeds below the basic speed. • Simplicity and ease of connection.

• Simplicity and ease of connection.

•The possibility of combining the functions of motor starting with speed control. •The possibility of combining the functions of motor starting with speed control.

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19 19 Demerits:

Demerits:

•The relatively high cost of large, convinously rated, variable resistors capable of •The relatively high cost of large, convinously rated, variable resistors capable of dissipating large amounts of power.

dissipating large amounts of power.

• Poor speed regulation for any given no load speed setting. • Poor speed regulation for any given no load speed setting. •Low efficiency resulting in high operating cost.

•Low efficiency resulting in high operating cost.

•Difficulty in obtaining stepless control of speed in higher power ratings. •Difficulty in obtaining stepless control of speed in higher power ratings.

3.1.2.2 Voltage control:

When the speed is controlled by regulating the motor terminal voltage while When the speed is controlled by regulating the motor terminal voltage while maintaining constant field current, it is called voltage control. With voltage maintaining constant field current, it is called voltage control. With voltage

control, the change in speed is almost proportional to the change in voltage. The control, the change in speed is almost proportional to the change in voltage. The output varies directly with speed and the torque remains constant. Since the output varies directly with speed and the torque remains constant. Since the voltage has to be regulated without affecting the field, the application of voltage voltage has to be regulated without affecting the field, the application of voltage control is limited to separately excited motors.

control is limited to separately excited motors.

Merits: Merits:

•Speed control over a wide range is possible. •Speed control over a wide range is possible.

•This method eliminates the need for series armature starting resistance. •This method eliminates the need for series armature starting resistance. •Uniform acceleration can be obtained.

•Uniform acceleration can be obtained. •Speed regulation is good.

•Speed regulation is good.

Demerits: Demerits:

•Arrangement is costly as two extra machines are required. •Arrangement is costly as two extra machines are required.

•The overall efficiency of the system is low, especially at light loads. •The overall efficiency of the system is low, especially at light loads.

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3.2 SCR POWER CONTROLLERS

Since the development of SCR power controllers in the late 1950's, the Since the development of SCR power controllers in the late 1950's, the power handling capabilities of SCR's (silicon controlled rectifiers) have advanced power handling capabilities of SCR's (silicon controlled rectifiers) have advanced from a few hundred watts to many megawatts. As a result, the use of SCR power from a few hundred watts to many megawatts. As a result, the use of SCR power controllers in industrial applications has increased dramatically and they are now controllers in industrial applications has increased dramatically and they are now used in almost every major industry.SCR power controllers provide a relatively used in almost every major industry.SCR power controllers provide a relatively economical means of power control. SCR power controllers cost less and are more economical means of power control. SCR power controllers cost less and are more efficient than saturable core reactors and variable transformers. Compared to efficient than saturable core reactors and variable transformers. Compared to contactors, SCR power controllers offer a much finer degree of control and do not contactors, SCR power controllers offer a much finer degree of control and do not suffer from the maintenance problems of mechanical devices.

suffer from the maintenance problems of mechanical devices.

3.2.1Features and benefits of SCR power controllers over other

forms of control include:

•High reliability: •High reliability:

Because the SCR power controller is a solid-state device, there are no inherent Because the SCR power controller is a solid-state device, there are no inherent wear-out modes. Thus, they provide virtually limitless and trouble free operation. wear-out modes. Thus, they provide virtually limitless and trouble free operation.

•Infinite resolution: •Infinite resolution:

Power, current or voltage can be controlled from zero to 100% with infinite Power, current or voltage can be controlled from zero to 100% with infinite resolution. This capability allows extremely accurate, step less control of the resolution. This capability allows extremely accurate, step less control of the process.

process.

•Extremely fast response: •Extremely fast response:

The SCR controller can switch load power on and off extremely fast providing The SCR controller can switch load power on and off extremely fast providing the means to respond rapidly to command changes, load changes and power the means to respond rapidly to command changes, load changes and power supply changes. This feature allows the control of fast responding loads and supply changes. This feature allows the control of fast responding loads and eliminates the negative effects of variations in load or supply voltages that can eliminates the negative effects of variations in load or supply voltages that can occur with other types of control

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21 21 •Selectable control parameters:

•Selectable control parameters:

The SCR power controller can control the average load voltage, the RMS value The SCR power controller can control the average load voltage, the RMS value of the load voltage, the RMS or the average load current or load power. It can also of the load voltage, the RMS or the average load current or load power. It can also provide useful features such as current and voltage limiting. The ability to control provide useful features such as current and voltage limiting. The ability to control the desired parameter as a function of a command signal and to incorporate the desired parameter as a function of a command signal and to incorporate limiting features is not normally available with other types of control.

limiting features is not normally available with other types of control.

•Minimum Maintenance: •Minimum Maintenance:

Because they are solid state there are no moving parts to wear out or replace. Because they are solid state there are no moving parts to wear out or replace. Therefore, the routine replacement required in some forms of control is

Therefore, the routine replacement required in some forms of control is eliminated.

eliminated.

3.3 Model of Separately Excited DC motor

Figure 3.1

Figure 3.1 shows a model shows a model of separately excited DC of separately excited DC motor. motor. When a When a separatelyseparately excited motor is excited by a field current of I f and an armature current of Ia excited motor is excited by a field current of I f and an armature current of Ia flows in the circuit, the motor develops a back EMF and a torque to balance the flows in the circuit, the motor develops a back EMF and a torque to balance the load torque

load torque at a at a particular speed. particular speed. The If The If is independent of is independent of the Ia. the Ia. Each windingEach winding are

are supplied separately. Any change supplied separately. Any change in the in the armature current harmature current has no as no effect on theeffect on the field current.

field current. The If is n

The If is normally much less than the Ia. ormally much less than the Ia. The relationship of the The relationship of the field andfield and armature are shown in Equation 3.1.

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Figure 3.1 Model of separately Figure 3.1 Model of separately excited DC motor

excited DC motor

Instantaneous field current: Instantaneous field current:

………..3.1 ………..3.1

Where Rf and Lf are the field resistor and inductor respectively. Where Rf and Lf are the field resistor and inductor respectively.

Instantaneous armature current: Instantaneous armature current:

………..3.2 ………..3.2

Where Ra and La are the armature resistor and inductor respectively. Where Ra and La are the armature resistor and inductor respectively.

The motor back EMF which is also known as speed voltage is expressed as The motor back EMF which is also known as speed voltage is expressed as

……….3.3 ……….3.3

Where Kv is the motor constant (in V/A-rad/s) and w is the motor speed (rad/s). Where Kv is the motor constant (in V/A-rad/s) and w is the motor speed (rad/s).

The torque developed by the motor is The torque developed by the motor is

……….3.4 ……….3.4

Where (K t =Kv) is the torque constant (in V/A-rad/s). Where (K t =Kv) is the torque constant (in V/A-rad/s).

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23 23 Sometimes it is written as:

Sometimes it is written as: ……….3.5 ……….3.5

For normal operation, the developed torque must be equal to the load torque For normal operation, the developed torque must be equal to the load torque plus the friction and inertia, i.e.:

plus the friction and inertia, i.e.:

………..3.6 ………..3.6

Where B = viscous friction constant (N.m/rad/s) Where B = viscous friction constant (N.m/rad/s)

T L = load torque (N.m) T L = load torque (N.m)

J = inertia of the motor (kg.m^ 2) J = inertia of the motor (kg.m^ 2) Under steady-state operations, a t

Under steady-state operations, a time derivative is zero. ime derivative is zero. Assuming the motor isAssuming the motor is not saturated.

not saturated.

For field circuit, For field circuit,

…………3.7 …………3.7

The back EMF is given by: The back EMF is given by:

……….3.8 ……….3.8 The armature circuit, The armature circuit,

………….3.9 ………….3.9 The motor speed can be easily derived: The motor speed can be easily derived:

………..3.10 ………..3.10

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If Ra is a small value (which is usual), or when the motor is lightly loaded, i.e. Ia is If Ra is a small value (which is usual), or when the motor is lightly loaded, i.e. Ia is small,

small,

………3.11 ………3.11

That is if the field current is kept constant, the speed motor speed depends on the That is if the field current is kept constant, the speed motor speed depends on the supply voltage.

supply voltage. These observation leads to These observation leads to the application of variable DC the application of variable DC voltagevoltage to control the speed and torque of DC motor.

to control the speed and torque of DC motor.

3.4 3.4 DC

DC motor

motor Speed

Speed Controller

Controller

For precise speed control of servo system, closed-loop control is normally used. For precise speed control of servo system, closed-loop control is normally used. Basically, the block diagram and the flow chart of the speed control are shown in Basically, the block diagram and the flow chart of the speed control are shown in Figure 3.2

Figure 3.2 and Figure 3.3 and Figure 3.3 respectivelrespectively. y. The speed, which is The speed, which is sensed by analogsensed by analog sensing devices (e.g., tachometer) is compared with the reference speed to sensing devices (e.g., tachometer) is compared with the reference speed to generate the error signal and to vary the armature voltage of the motor. generate the error signal and to vary the armature voltage of the motor.

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25 25

Fig 3.2 Basic block diagram for DC Motor speed control Fig 3.2 Basic block diagram for DC Motor speed control

Fig 3.3 Basic flow chart of DC motor speed control Fig 3.3 Basic flow chart of DC motor speed control

There are several controllers that can used to control the speed of the There are several controllers that can used to control the speed of the

motor such as by using thyristor, phase-locked-loop control, chopper circuit, Fuzzy motor such as by using thyristor, phase-locked-loop control, chopper circuit, Fuzzy Logic Controller and etc.

Logic Controller and etc. Here, we will discuss only at the Here, we will discuss only at the speed control system byspeed control system by using thyristor, phase-locked loop and PWM technique.

using thyristor, phase-locked loop and PWM technique.

3.4.1 Speed Control by using thyristor

Figure 3.4 shows the block diagram of DC motor speed control by using Figure 3.4 shows the block diagram of DC motor speed control by using thyristor.

thyristor. The thyristor is used to The thyristor is used to supply a variable DC voltage to motor, thus supply a variable DC voltage to motor, thus itit can control the speed of motor (Equation 3.11). The average output of voltage is can control the speed of motor (Equation 3.11). The average output of voltage is given by

given by

………..3.12 ………..3.12

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Where Vm = peak voltage of voltage supply of thyristor and Where Vm = peak voltage of voltage supply of thyristor and

α

α = = firing firing angle angle of of thyristor thyristor

Figure 3.4 Block diagram of DC Motor speed control by using thyristor Figure 3.4 Block diagram of DC Motor speed control by using thyristor From Equation 3.12

From Equation 3.12, by controlling the firing angle, α, the average of output DC, by controlling the firing angle, α, the average of output DC voltage can be varied.

voltage can be varied. If the motor speed is If the motor speed is low, the speed low, the speed sensor frequency willsensor frequency will be below the

be below the reference frequency. reference frequency. The frequency difference produces a The frequency difference produces a changechange in the firing circuit that causes the thyristor, SCR to fire sooner (firing angle, α is in the firing circuit that causes the thyristor, SCR to fire sooner (firing angle, α is reduced).

reduced). There is a There is a resulting increase in motor speed which brings the resulting increase in motor speed which brings the outputoutput speed back up to the value which is equal to the reference signal.

speed back up to the value which is equal to the reference signal.

Conversely, if the speed sensor output frequency is above the reference, then the Conversely, if the speed sensor output frequency is above the reference, then the firing circuit will be modified to allow the SCR to conduct for a shorter period of firing circuit will be modified to allow the SCR to conduct for a shorter period of time, the decrease in conduction reduces the DC motor speed.

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27 27

CHAPTER FOUR

SIMULATION AND RESULTS

4.0 INTRODUCTION

SimPowerSystems software and other products of the Physical Modeling SimPowerSystems software and other products of the Physical Modeling product family work together with Simulink software to model electrical, product family work together with Simulink software to model electrical, mechanical, and control systems. SimPowerSystems software operates in the mechanical, and control systems. SimPowerSystems software operates in the Simulink environment. Therefore, before starting this user's guide, make yourself Simulink environment. Therefore, before starting this user's guide, make yourself familiar with Simulink documentation. Or, if you perform signal processing and familiar with Simulink documentation. Or, if you perform signal processing and communications tasks (as opposed to control system design tasks), see the Signal communications tasks (as opposed to control system design tasks), see the Signal Processing Block set documentation.

Processing Block set documentation.

The Role of Simulation in

The Role of Simulation in Design

Design

Electrical power systems are combinations of electrical circuits and Electrical power systems are combinations of electrical circuits and

electromechanical devices like motors and generators. Engineers working in this electromechanical devices like motors and generators. Engineers working in this discipline are constantly improving the performance of the systems.

discipline are constantly improving the performance of the systems.

Requirements for drastically increased efficiency have forced power system Requirements for drastically increased efficiency have forced power system designers to use power electronic devices and sophisticated control system designers to use power electronic devices and sophisticated control system concepts that tax traditional analysis tools and techniques. Further complicating concepts that tax traditional analysis tools and techniques. Further complicating the analyst's role is the fact that the system is often so nonlinear that the only the analyst's role is the fact that the system is often so nonlinear that the only way to understand it is through simulation.

way to understand it is through simulation.

SimPowerSystems software is a modern design tool that allows scientists and SimPowerSystems software is a modern design tool that allows scientists and engineers to rapidly and easily build models that simulate power systems. It uses engineers to rapidly and easily build models that simulate power systems. It uses the Simulink environment, allowing you to build a model using simple click and the Simulink environment, allowing you to build a model using simple click and drag procedures. Not only can you draw the circuit topology rapidly, but your drag procedures. Not only can you draw the circuit topology rapidly, but your analysis of the circuit can include its interactions with mechanical, thermal, analysis of the circuit can include its interactions with mechanical, thermal,

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control, and other disciplines. This is possible because all the electrical parts of control, and other disciplines. This is possible because all the electrical parts of the simulation interact with the extensive Simulink modeling library. Since the simulation interact with the extensive Simulink modeling library. Since

Simulink uses the MATLAB computational engine, designers can also use MATLAB Simulink uses the MATLAB computational engine, designers can also use MATLAB toolboxes and Simulink block sets. SimPowerSystems software belongs to the toolboxes and Simulink block sets. SimPowerSystems software belongs to the Physical Modeling product family and uses similar block and connection line Physical Modeling product family and uses similar block and connection line interface.

interface.

SimPowerSyste

SimPowerSystem

m Libraries

Libraries

SimPowerSystems libraries contain models of typical power equipment such as SimPowerSystems libraries contain models of typical power equipment such as transformers, lines, machines, and power electronics. The capabilities of

transformers, lines, machines, and power electronics. The capabilities of

SimPowerSystems software for modeling a typical electrical system are illustrated SimPowerSystems software for modeling a typical electrical system are illustrated in demonstration files. And for users who want to refresh their knowledge of

in demonstration files. And for users who want to refresh their knowledge of power system theory, there are also self-learning case studies.

power system theory, there are also self-learning case studies.

The SimPowerSystems main library, powerlib, organizes its blocks into libraries The SimPowerSystems main library, powerlib, organizes its blocks into libraries according to their behavior. The powerlib library window displays the block library according to their behavior. The powerlib library window displays the block library icons and names. Double-click a library icon to open the library and access the icons and names. Double-click a library icon to open the library and access the blocks. The main powerlib library window also contains the Powergui block that blocks. The main powerlib library window also contains the Powergui block that opens a graphical user interface for the steady-state analysis of electrical circuits. opens a graphical user interface for the steady-state analysis of electrical circuits.

Nonlinear Simulink Blocks for SimPowerSystems Models Nonlinear Simulink Blocks for SimPowerSystems Models

The nonlinear Simulink blocks of the powerlib library are stored in a special The nonlinear Simulink blocks of the powerlib library are stored in a special block library named powerlib_models. These masked Simulink models are used by block library named powerlib_models. These masked Simulink models are used by SimPowerSystems software to build the equivalent Simulink model of your circuit. SimPowerSystems software to build the equivalent Simulink model of your circuit.

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29 29 fig 4.1 connection diagram

fig 4.1 connection diagram

4.1 4.1 DC

DC Machine

Machine Description

Description

The DC Machine block implements a wound-field or permanent magnet DC The DC Machine block implements a wound-field or permanent magnet DC machine. For the wound-field DC machine, an access is provided to the field machine. For the wound-field DC machine, an access is provided to the field terminals (F+, F

terminals (F+, F−) so that the machine model can be used as a shunt−) so that the machine model can be used as a shunt-connected-connected or a series-connected DC machine. The torque applied to the shaft is provided at or a series-connected DC machine. The torque applied to the shaft is provided at the Simulink input TL.

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The armature circuit (A+, A

The armature circuit (A+, A−) consists of an inductor La and resistor Ra in−) consists of an inductor La and resistor Ra in

series with a counter-electromotive force (CEMF) E.The CEMF is proportional to series with a counter-electromotive force (CEMF) E.The CEMF is proportional to the machine speed.

the machine speed.

KE is the voltage constant and ω is the machine speed. In a separately excited KE is the voltage constant and ω is the machine speed. In a separately excited

DC machine model, the voltage constant KE is proportional to the field current If DC machine model, the voltage constant KE is proportional to the field current If

Where Laf is the field-armature mutual inductance. The electromechanical Where Laf is the field-armature mutual inductance. The electromechanical

torque developed by the DC machine is proportional to the armature current Ia. torque developed by the DC machine is proportional to the armature current Ia.

Where Kt is the torque constant. The sign convention for Te and TL is Where Kt is the torque constant. The sign convention for Te and TL is

The torque constant is equal to the voltage constant. The torque constant is equal to the voltage constant.

The armature circuit is connected between the A+ and A

The armature circuit is connected between the A+ and A− ports of the DC− ports of the DC

Machine block. It is represented by a series Ra La branch in series with a Machine block. It is represented by a series Ra La branch in series with a Controlled Voltage Source and a Current Measurement block.

Controlled Voltage Source and a Current Measurement block. Mechanical part:

Mechanical part:

In the wound-field DC machine model, the field circuit is represented by an In the wound-field DC machine model, the field circuit is represented by an RL circuit. It is connected between the F+ and F

RL circuit. It is connected between the F+ and F− ports of the DC Machine block.− ports of the DC Machine block.

In the permanent magnet DC machine model, there is no field current as the In the permanent magnet DC machine model, there is no field current as the excitation flux is established by the magnets. KE and KT are constants. The excitation flux is established by the magnets. KE and KT are constants. The mechanical part computes the speed of the DC machine from the net torque mechanical part computes the speed of the DC machine from the net torque applied to the rotor. The speed is used to implement the CEMF voltage E of the applied to the rotor. The speed is used to implement the CEMF voltage E of the armature circuit.

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31 31

The mechanical part is represented by Simulink blocks that implement the The mechanical part is represented by Simulink blocks that implement the equation

equation

Where J = inertia, Where J = inertia,

Bm =

Bm = viscous friction viscous friction coefficient, and coefficient, and Tf Tf = = Coulomb friction Coulomb friction torque.torque. Preset model

Preset model

Provides a set of predetermined electrical and mechanical parameters for Provides a set of predetermined electrical and mechanical parameters for various DC machine ratings of power (HP), DC voltage (V), rated speed (rpm), various DC machine ratings of power (HP), DC voltage (V), rated speed (rpm), and field voltage (V).The preset models are only available for the wound-field and field voltage (V).The preset models are only available for the wound-field DC machine model, that is, when the Field type parameter is set to Wound. DC machine model, that is, when the Field type parameter is set to Wound. Select one of the preset models to load the corresponding electrical and Select one of the preset models to load the corresponding electrical and

mechanical parameters in the entries of the dialog box. Select No if you do not mechanical parameters in the entries of the dialog box. Select No if you do not want to use a preset model, or if you want to modify some of the parameters of want to use a preset model, or if you want to modify some of the parameters of a preset model, as described below.

a preset model, as described below.

When you select a preset model, the electrical and mechanical parameters in When you select a preset model, the electrical and mechanical parameters in the Parameters tab of the dialog box become unmodifiable (grayed out). To the Parameters tab of the dialog box become unmodifiable (grayed out). To start from a given preset model and then modify machine parameters, you have start from a given preset model and then modify machine parameters, you have to do the following:

to do the following:

Select the desired preset model to initialize the parameters. Change the Preset Select the desired preset model to initialize the parameters. Change the Preset model parameter value to No. This will not change the machine parameters. By model parameter value to No. This will not change the machine parameters. By doing so, you just break the connection with the particular preset model.

doing so, you just break the connection with the particular preset model. Modify the machine parameters as you wish, then click Apply.

Modify the machine parameters as you wish, then click Apply.

Mechanical input

Allows you to select either the torque applied to the shaft or the rotor speed Allows you to select either the torque applied to the shaft or the rotor speed as the Simulink signal applied to the block's input. Select Torque TL to specify a as the Simulink signal applied to the block's input. Select Torque TL to specify a

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torque input, in N.m, and change labeling of the block's input to TL. The torque input, in N.m, and change labeling of the block's input to TL. The machine speed is determined by the machine Inertia J and by the difference machine speed is determined by the machine Inertia J and by the difference between the applied mechanical load torque TL and the internal

between the applied mechanical load torque TL and the internal

electromagnetic torque Te. The sign convention for the mechanical torque is the electromagnetic torque Te. The sign convention for the mechanical torque is the following: when the speed is positive, a positive torque signal indicates motor following: when the speed is positive, a positive torque signal indicates motor mode and a negative signal indicates generator mode.

mode and a negative signal indicates generator mode.

Select Speed w to specify a speed input, in rad/s, and change labeling of the Select Speed w to specify a speed input, in rad/s, and change labeling of the block's input to w. The machine speed is imposed and the mechanical part of block's input to w. The machine speed is imposed and the mechanical part of the model (Inertia J) is ignored. Using the speed as the mechanical input allows the model (Inertia J) is ignored. Using the speed as the mechanical input allows modeling a mechanical coupling between two machines and interfacing with modeling a mechanical coupling between two machines and interfacing with SimMechanics and SimDriveline models.

SimMechanics and SimDriveline models. Field type

Field type

Allows you to select between the wound-field and the permanent magnet DC Allows you to select between the wound-field and the permanent magnet DC machine.

machine.

Armature resistance and inductance [Ra La] Armature resistance and inductance [Ra La]

The armature resistance Ra, in ohms, and the armature inductance La, in The armature resistance Ra, in ohms, and the armature inductance La, in henries.

henries.

Field resistance and inductance [Rf Lf] Field resistance and inductance [Rf Lf]

The field resistance Rf, in ohms, and the field inductance Lf, in henries. This The field resistance Rf, in ohms, and the field inductance Lf, in henries. This parameter is only visible when the Field type parameter on the Configuration parameter is only visible when the Field type parameter on the Configuration tab is set to Wound.