This course is an introduction about electrical control system in general and classic control system elements

1. Prepared By : Eng. Ahmed Hegab
( 9 : 10 Oct. 2019)
ELECTRICAL CONTROL
(BASICS)

2. Eng. AHMED M. HEGAB
Oct. 2019
Contents
 Part One :
INTRODUCTION TO CONTROL SYSTEMS
 Part Two :
ELEMENTS OF ELECTRICAL CONTROL
 Part Three :
CONTROL CIRCUIT TROUBLESHOOTING

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INTRODUCTION TO CONTROL
SYSTEMS
PART ONE :

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1. Introduction and Background
2. Open Loop and Closed Loop
3. Control Systems Classifications
4. Basics Electrical Relations
Main Headlines
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1. Introduction and Background
2. Open Loop and Closed Loop
3. Control Systems Classifications
4. Basics Electrical Relations
Main Headlines
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Introduction and Background
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• Electrical control systems are a product of the twenty century.
• A control system is a collection of components working
together under the direction of some system intelligence.
• A control system manages, commands, directs, or regulates
the behavior of other devices or systems using control loops.
• In most cases, electronic circuits provide the intelligence, and
electromechanical components such as sensors and motors
provide the interface to the physical world.

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Introduction and Background
Working without
Control System

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Applications
• Home (Smart Home).
• Vehicles.
• Industry.
• Electrical Power System
Introduction and Background

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Three – Layered Structure of Power System
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Introduction and Background

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Introduction and Background
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• Electromechanical relays were developed and used for
remote control of motors and devices.
• Control systems are the “automatic” in such things because
the machine itself is making the routine decisions, the
operator is freed to do other things.
• In many cases, machine intelligence is better than direct
human control because it can react faster, respond more
precisely, and maintain an accurate log of the system’s
performance.
Stage #1
Stage #2

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1. Introduction and Background
2. Open Loop and Closed Loop
3. Control Systems Classifications
4. Basics Electrical Relations
Main Headlines
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Open Loop and Closed Loop
• Control action from the controller is independent of the process
variable (No Feedback).
• This system absolutely depends on the controller knowing the
operating characteristics of the system
• An example of this is a central heating boiler controlled only by a
timer (switching on/off regardless boiler temperature).
More
Examples !!
I- Open Loop Control System

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Open Loop and Closed Loop
• Control action from the controller is dependent on the desired and
actual process variable (Feedback).
• Feedback loop will ensure the controller provides a control action to
control a process variable at the same value as the set-point
II- Closed Loop Control System

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Open Loop and Closed Loop
• For this reason, closed-loop controllers are also called feedback
controllers.
• Feedback systems, a control loop including sensors, control
algorithms, and actuators is arranged in an attempt to regulate a
variable at a set-point
• Boiler example too, utilizing a thermostat to monitor the
temperature, and feed back a signal to ensure the controller output
maintains the temperature close to that set on the thermostat.
II- Closed Loop Control System
More
Examples !!

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1. Introduction and Background
2. Open Loop and Closed Loop
3. Control Systems Classifications
4. Basics Electrical Relations
Main Headlines
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Control Systems Classifications
Loop (Open / Closed)
Digital / Analog
Application
Control Systems Classifications
Industrial
Applications

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Control Systems Classifications
• The first control systems were analog because it was the only
available technology.
• Controller consists of traditional analog devices and circuits, that is,
amplifiers.
• Any change in either set point or feedback is sensed immediately,
and the amplifiers adjust their output accordingly.
• Analog control system has another name which is Continuous
Control System (in time and magnitude)
Analog Control System

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Control Systems Classifications
Analog Control System

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Control Systems Classifications
• Controller uses a digital circuit. In most cases, a computer,
microprocessor- or microcontroller-based.
• The computer executes a program that repeats over-and-over.
• The program instructs the computer to read the set point and sensor
data and then use these numbers to calculate the controller output.
• The digital system only “looks” at the inputs at a certain time (scan
cycle) and gives the updated output later.
• The total time for one pass through the program may be less than 1
millisecond (ms)
Digital Control System

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Control Systems Classifications
Digital Control System
• If an input changes just after the computer looked at it, that change
will remain undetected until the next scan.
• This is fundamentally different than the analog system, which is
continuous and responds immediately to any changes.

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Control Systems Classifications
Control Systems Applications
Process
Control
Sequential
Control
Motion
Control

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Control Systems Classifications
1- Process Control
• Process control refers to a control system that oversees some
industrial process so that a uniform, correct output is maintained.
• It does this by monitoring and adjusting the control parameters
(such as temperature or flow rate) to ensure that the output
product remains as it should.

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Control Systems Classifications
1- Process Control
Types of Process
Control
Continuous
Process
Batch
Process

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Control Systems Classifications
2- Sequential Control
• A sequentially controlled system controls a process that is defined as a
series of tasks to be performed in order.
• Each operation in the sequence is performed either for a certain amount of
time, in which case it is time-driven, or until the task is finished (as
indicated by, say, a limit switch), in which case it is event-driven.

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Control Systems Classifications
2- Sequential Control

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Control Systems Classifications
3- Motion Control
• This system typically includes a motor, mechanical parts that move, and
(in many cases) feedback sensor(s).
• Automatic assembling machines, industrial robots, and numerical
control machines are examples

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Control Systems Classifications
3- Motion Control

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1. Introduction and Background
2. Open Loop and Closed Loop
3. Control Systems Classifications
4. Basics Electrical Relations
Main Headlines
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Basics Electrical Relations
I- Units and Symbols
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 Ampere, I (A)
 Voltage, V (V).
 Resistance, R (Ω)
II- Ohm’s Law
V = I * R
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Basics Electrical Relations

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III- Electro Magnetic
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Basics Electrical Relations

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III- Electro Magnetic
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Basics Electrical Relations

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III- Electro Magnetic
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Basics Electrical Relations

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III- Electro Magnetic
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Basics Electrical Relations

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ELEMENTS OF ELECTRICAL
CONTROL
PART TWO:

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Control
Elements
Relay
Contactor
Switch
Timer
Lamp
Transducer
Sensor
Semi-
Conductors
Electrical Control Circuit Elements
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Control Cables
Control Cable
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1. Control Switches
• Toggle switch
• Push Button switch (momentary or not )
• Single way switches
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Control Switches

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1. Control Switches
• Double way switch (till 4 ways and more)
• Dip switch
• Selector switch
• Key switch
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Control Switches

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2. Control Relays
Auxiliary Lockout Supervision
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Control Relays

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2. Control Relays
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Control Relays

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2. Control Relays
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Control Relays

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3. Timer Relays
Types of Timer
On delay Off delay
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Timers Relays

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• ON Delay
• OFF Delay
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Timers Relays

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3. Timer Relays (Characteristics)
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Timers Relays
T-OFF
T-ON

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4. Contactor
A Contactor is a control device that uses a small control
current to energize or de-energize the load connected to it.
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Contactor

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4. Contactor
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Contactor

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• A contactor has a frame,
plunger, and a solenoid coil.
• The action of the plunger is
used to close (or open) sets of
contacts.
• A contactor does not include
overload protection.
• The closing of the contacts
allows electrical devices to be
controlled from remote
locations.
4. Contactor
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Contactor

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Transducers
5. Transducers (Power)
Types of Power Transducers
Power Current Voltage Frequency
Power
Factor
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Transducers
5. Transducers (Power)
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• A circuit breaker (CB) is designed to open an electric circuit under
any fault conditions in addition to normal close/open conditions.
• Trip usually occur upon a trip signal from a protection relay.
• Main selection parameter :
- Current
- Voltage
- Number of poles
- Method of Insulation
- Short Circuit Capacity
6. Circuit Breaker
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Circuit Breaker

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Circuit Breaker OC Tripping
Characteristics
Thermal Tripping Magnetic Tripping
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Circuit Breaker

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Thermal
Trip
Magnetic
Trip
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Circuit Breaker

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Circuit Breaker

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Magnetic
Trip
Thermal
Trip
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Circuit Breaker

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Circuit Breaker Setting
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Circuit Breaker

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Circuit Breaker Setting
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Circuit Breaker

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• A fuse is a short piece of wire or thin strip which melts when
excessive current flows through it for sufficient time.
• It is inserted in series with the circuit to be protected like ( Over
load or Short Circuit ).
• Fuses are also not classified as ‘switchgear’, but rather as
protection devices.
• Choosing parameter are current ,voltage and purpose like (General
‘g’ – Associated ‘a’ )
Control Fuses
7. Fuses
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• Type : Glass or Silicon
7. Fuses
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Control Fuses

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7. Fuses
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Control Fuses

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Sensors
8. Sensors
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Sensors Applications
Position
Sensor
Velocity
Sensor
Temperature
Sensor
Level Sensor
Flow Sensor Load Sensor Proximity
Sensor
Pressure
Sensor
• The devices that inform the control system about what is actually occurring
are called sensors (also known as signal transducers)

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Sensors
8. Sensors (Light Sensors)
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Speed Sensor
Speed and
Position Sensor

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Sensors
8. Sensors (Light Sensors)
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Proximity
Sensor

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Sensors
8. Sensors (Electrical Sensors)
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Position or Load
Sensor

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Sensors
8. Sensors (Electrical Sensors)
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Load Sensor

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Sensors
8. Sensors (Electrical Sensors)
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Speed Sensor

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Sensors
8. Sensors (Electrical Sensors)
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Temperature
Sensor (PT100)

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Sensors
8. Sensors (Level Sensors)
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Semi-Conductors
9. Semi-Conductors
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9. Semi-Conductors
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Semi-Conductors

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9. Semi-Conductors
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Semi-Conductors

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9. Semi-Conductors
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Semi-Conductors

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CONTROL CIRCUIT
TROUBLESHOOTING
PART THREE:

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Main Headlines
1. Introduction
2. Aids for Prober Troubleshooting
3. Basic Tests for Troubleshooting
4. Electrical Testing Devices
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Main Headlines
1. Introduction
2. Aids for Prober Troubleshooting
3. Basic Tests for Troubleshooting
4. Electrical Testing Devices
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Introduction
• The main task of troubleshooting is to define the abnormal
condition and correct it.
• This can be done properly using the following steps in order :
 Review the system operation and components.
 Analyze the symptom.
 Detect and Isolate the trouble.
 Correct the trouble and test the work.
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Introduction
Trouble or Fail Reasons
• Failure of power supply
• Failure in equipment (relay – CB – contactor ..etc)
• Failure in the wiring (loos – cut )
• Miss operation
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Main Headlines
1. Introduction
2. Aids for Prober Troubleshooting
3. Basic Tests for Troubleshooting
4. Electrical Testing Devices
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Aids for Prober Troubleshooting
1
• All drawing related to the trouble
2
• Records on the equipment
3
• Testing equipment
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Main Headlines
1. Introduction
2. Aids for Prober Troubleshooting
3. Basic Tests for Troubleshooting
4. Electrical Testing Devices
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Basic Tests for Troubleshooting
Failure Root Causes
1. A connection does not exist where it should.
2. A connection exists where none should.
3. Power Supply Fail
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Checklists of Troubleshooting
Power Circuit Checklist
Control Circuit Checklist
Basic Tests for Troubleshooting
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Power Checklist
• Incoming power to circuit and
its integrity.
• Check for correct functioning
of protection devices.
• Check cable continuity.
• Check for any signs of flash or
burning smell of devices.
Control Checklist
• Control circuit power first.
• Check for proper functioning of
relays, timers, and switches.
• Check cable continuity.
• Check for wire interconnections
and terminal connections of
circuit
• .Check logical operational
sequence of contactor switching
Basic Tests for Troubleshooting
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Continuity
Test
1
Insulation
Test
2
Voltage
Test
3
Current
Test
4
Basic Tests for Troubleshooting
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Main Headlines
1. Introduction
2. Aids for Prober Troubleshooting
3. Basic Tests for Troubleshooting
4. Electrical Testing Devices
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Electrical Testing Devices
Digital
Multimeter
Insulation
Tester
Clamp
Ampere
Oscilloscope
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