The document provides an overview of electrical control systems, detailing their structure, classifications, and applications. It explains the differences between open-loop and closed-loop control systems, along with relevant components like relays, sensors, and circuit breakers. Troubleshooting techniques for control circuits and electrical testing devices are also discussed, emphasizing systematic approaches to identifying and correcting faults.

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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