1

ELECTRIC MOTOR
CONTROL MANUAL

PREFACE

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Upon selecting the proper motor, understanding the many various control devices available
and their uses, limitations and connections, becomes an essential part related to reliable
operation and protection of the motor and the personnel using it.

Every electric motor has to have some sort of controller. The motor controller will have
different features and complexity depending on the task that the motor will be performing. A
motor controller is a device or group of devices that serves to govern in some
predetermined manner the performance of an electric motor. A motor controller might
include a manual or automatic means for starting and stopping the motor, selecting forward
or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and
protecting against overloads and faults.

This manual introduces the students to the basics of motor control, explains its importance,
applications and components and identifies various ways in which motor control can be
accomplished.

Upon completion of this manual, the student should be able to:

o Explain the role of motor control in an electrical system.

o Identify various components of a motor control system.
o Explain the difference between the various classifications and types of motor control
wiring.
o Draw motor control ladder diagrams.
o Connect various motor control circuits.
o Test and troubleshoot motor control components and circuits.
o Apply safety precautions while connecting motor control circuits.

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TABLE OF CONTENTS

LABORATORY ACTIVITY PAGE NO.

ELECTRICAL SAFETY 4

INTRODUCTION TO MOTOR CONTROL 7

MOTOR CONTROL SYSTEM SYMBOLS 11

MOTOR CONTROL CIRCUIT 17

MOTOR CONTROL COMPONENTS FAMILIARIZATION AND TESTING 22

ACROSS THE LINE MAGNETIC MOTOR STARTER (Non- Reversing) 28

TWO STATION MOTOR CONTROL (Non- Reversing) 32

FULL VOLTAGE NON-REVERSING MOTOR CONTROL WITH JOG 36

FORWARD – REVERSE MOTOR CONTROL 41

(No Immediate Reversal)

FORWARD – REVERSE MOTOR CONTROL 47

(Immediate Reversal)

SEQUENTIAL MOTOR CONTROL 53

(Manual: Using Pushbutton)

SEQUENTIAL MOTOR CONTROL 56

(Automatic using Timer)

REDUCED VOLTAGE STARTER CIRCUITS 60

REDUCED VOLTAGE STARTER 62

(Wye-Delta Starter)

APPLICATION OF FORWARD-REVERSE MOTOR CONTROL 65

MOTOR CONTROL ACTIVITIES 67

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Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No. 1

ELECTRICAL
SAFETY
I. Objectives:
At the end of the activity, students should be able to:

1. Be aware of the hazards of electricity to the human body.

2. Observe electrical precautions and guidelines to ensure safety.
3. Appreciate the importance of practicing safety in various conditions and situations.

II. Technical Information:

Physiological Effects of Electricity

 Threshold of perception: The minimal current that an individual can detect. For AC (with wet
hands) can be as small as 0.5 mA at 60 Hz. For DC, 2 ~10 mA

 Let-go current: The maximal current at which the subject can voluntarily withdraw. 6 ~ 100
mA, at which involuntary muscle contractions, reflex withdrawals, secondary physical effects
(falling, hitting head) may also occur.

 Respiratory Paralysis / Pain / Fatigue At as low as 20 mA, involuntary contractions of

respiratory muscles can cause asphyxiation / respiratory arrest, if the current is not
interrupted. Strong involuntary contraction of other muscles can cause pain and fatigue

 Ventricular fibrillation 75 ~ 400 mA can cause heart muscles to contract uncontrollably,

altering the normal propagation of the electrical activity of the heart. Heart rate can raise up
to 300 bpm, rapid, disorganized and too high to pump any meaningful amount of blood
ventricular fibrillation. Normal rhythm can only return using a defibrillator

 Sustained myocardial contraction / Burns and physical injury At 1 ~6 A, the entire heart
muscle contracts and heart stops beating. This will not cause irreversible tissue damage;
however, as normal rhythm will return once the current is removed. At or after 10A, however,
burns can occur, particularly at points of entry and e

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III. Reflection/Evaluation:

1. In your own words, define safety and explain why it is important to your field of
specialization.

2. List unsafe practices you have done or you have observed from others that involve
electricity, electrical appliances or devices? Cite specific examples to clarify your answer.

3. Why is it important to understand the nature of electricity e.g. how it is generated,

transmitted and utilized, to avoid any electrical related accidents?

4. Write at least fifteen (15) safety guidelines that can be adapted in your electrical
laboratory rooms, residence or any location that utilizes electricity.

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IV. Conclusion (How will you ensure safety in your motor control subject?):

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Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

INTRODUCTION TO MOTOR CONTROL

I. Objectives:
At the end of the activity, students should be able to:

1. Appreciate the importance of a reliable motor control system.

2. Understand basic operating principles of various motor control components.
3. Familiarized themselves with motor control terminologies.

II. Technical Information:

Motor control systems control the electrical energy used to run a motor. Many of the
components used to control that energy are in the motor controller, protected by a motor control
enclosure. Inside the enclosure, at the heart of every motor controller, is the motor starter. The
starter has two parts: the contactor and the overload relay. It is easier to understand the motor
control system if you think of them as divided into two kinds of circuits: the power circuit and
the control circuit.

The power circuit contains all of the components that carry the full voltage and current
to operate the motor. Besides the contactor, these commonly include disconnects, fuses, breakers
and overload heaters.

The control circuit is usually operated at a lower voltage and contains all of the
components necessary to switch power to the motor on and off under the proper conditions and
at the proper time. These commonly include devices like relays, usually inside the enclosure;
field devices like start and stop buttons, limit switches and pressure switches; and indicating
devices like lights and alarms to help monitor the operation of the system.

Three-Wire Control: The Seal-In Circuit

All the components of motor control systems are linked together in circuits which
determine what function can be accomplished: starting, stopping, reversing, jogging and so on.
The seal-in circuit is one of the most common. It's also called the maintaining circuit or
holding circuit because it maintains or holds-in the power to a component - like a contactor or a
relay - even after a pushbutton or other momentary switch no longer supplies power. The circuit
is maintained until power is interrupted.
Pushing the start button energizes M, the coil of the contactor. A normally open set of
contacts on the contactor are wired in parallel with the start button. When the armature on the
contactor closes, these seal-in contacts close, and remain closed until the stop button is pushed.

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This de-energizes the M coil and returns the seal-in contacts to their normally-open condition
until the coil is energized again.

Motor starters may also be wired for two-wire control. This requires the use of a
maintained-contact switch to keep the coil of the contactor energized after the run button is
released. However, if power is restored following a shut-down, the motor starter will be re-
energized automatically.

Three-wire control is often used because it provides protection for personnel from such
unexpected start-ups. The motor will not automatically re-start after it's stopped due to a no-
voltage or low-voltage condition.

The Seal-in Circuit

III. Evaluation:

1. What are the basic components of a motor starter?

2. How important is the ladder or schematic diagram of a motor control circuit?

3. What is the function of the disconnect switch?

4. What provides short circuit protection for the motor?

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5. How does the overload relays protect the motor?

6. How does the auxiliary contact connected to a normally open pushbutton in a seal –
in circuit?

7. Why is a two – wire control unsafe to be used in a motor control circuit?

8. Differentiate instantaneous, latching and timed delay relay.

9. Differentiate an ON DELAY time relay from an OFF delay time relay.

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10. What is the role of limit switches in a motor control circuit? Explain your answer.

11. Enumerate the motor components being asked on each item:

a. Types of Control Switches ( 5 )

b. Functions of Motor Control (3)

12. Write the meaning of the following acronym:

a. TDOD
b. TDOE
c. NO
d. NC
e. CR
f. TR

IV. Conclusion:

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Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

MOTOR CONTROL SYSTEM SYMBOLS

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Develop skills in identifying the commonly used components or parts and be able
to describe and interpret correctly the standard symbols for each component used
in motor control systems.
2. Develop skills in circuit tracing using the schematic symbols or diagrams.
3. Become familiar with the different components commonly used in motor control
systems.
4. Draw the different control symbols.

II. TECHNICAL INFORMATION:

In every trade or profession, there is a certain language, which must be

understood in order to transfer information and ideas rapidly and efficiently. This
language may include words and phrases as well as symbols.

Industrial electrical symbols and line (ladder) diagrams provide the information
necessary to understand the operation of any electrical control system. Industrial
electrical symbols identify electrical devices within a circuit.

The operation of a circuit is determined by the location of electrical devices. The

line diagram indicates the location of electrical devices within a circuit. Circuit
arrangement and modifications to existing circuits is possible using line diagrams. To
read and troubleshoot an electrical control system, the engineer or electrician must have a
working knowledge of line diagrams.

III. MATERIALS NEEDED:

Drawing Materials

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III. PROCEDURE:
Draw the appropriate symbol for each electrical control component in the space provided.

CONTROL COMPONENT DIN(EUROPEAN

DESCRIPTION ANSI (AMERICAN STANDARD)
STANDARD) Deutsches Institut für Normung

Knife Switch
(Disconnect Switch)

Push Button Switch (Normally

Open)

Push Button Switch (Normally

Close)

Push Button Switch (Double

Circuit)

Push Button (Mushroom

Head)

Foot Switches (NO /NC)

Limit Switches (NO/NC)

Liquid Level Switches

Temperature Actuated
Switches

Pressure and Vacuum

Switches

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CONTROL COMPONENT DIN(EUROPEAN

DESCRIPTION ANSI (AMERICAN STANDARD)
STANDARD)

Selector Switch
Two Positions

Selector Switch
Three Positions

Time Delay Relay (TR)

Toggle Switch

Auxiliary Contacts

Overload Relay

Pilot Light

Overload Heater

Solenoid

Coil

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CONTROL COMPONENT DIN(EUROPEAN

DESCRIPTION ANSI (AMERICAN STANDARD)
STANDARD)

Control Transformer

Three Phase Motor

Fixed Resistor

Tapped Resistor

Bell

Buzzer

Battery

Rectifier

Armature

Time Delay Relay Contact

(NO TDOE)

Time Delay Relay Contact

(NC TDOE)

Proximity Switch

Switch with Neon Pilot Light

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CONTROL COMPONENT DIN(EUROPEAN

DESCRIPTION ANSI (AMERICAN STANDARD)
STANDARD)

Normally Open Contact

Normally Closed Contact

Motor

Ground

Overload Relay (Magnetic)

Alarm

Circuit Breaker Interrupter

( Three Phase)

Time Delay Relay Contact

(NO TDOD)

Time Delay Relay Contact

(NC TDOD)

V. CONCLUSION (Discuss the importance of electrical symbols in motor control

systems):

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VI. EVALUATION:

1. How are motor control symbols represented?

2. In what ways are electrical symbols compared to a certain language?

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Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

MOTOR CONTROL CIRCUIT

I. Objectives:
At the end of the activity, students should be able to:

1. Interpret a simple ladder diagram.

2. Draw a simple motor control circuit using various types of switches.
3. Appreciate the importance of gaining skills in drawing and interpreting a ladder
diagram

II. Technical Information:

Understanding motor control systems requires the ability to read and work with relay
ladder diagrams. These diagrams show the relationship among the components in the
control circuit.

o A single load (such as a contactor coil, a relay coil, a light, or an alarm) is placed on
each rung of the ladder. All loads are wired in parallel with each other, never is
series. To understand the diagram, imagine voltage flowing from left to right across
the rung. When all contacts leading to a load are closed, voltage will energize it.

o Contacts on switches are indicated by the symbol for the switch. Most switches can
be wired as normally-open or normally-closed. Switch contacts that are wired
normally-open are drawn as open, and normally-closed contacts are drawn as closed.
When contacts on contactors or relays are normally-open, they are indicated by two
vertical lines. When normally-closed, a diagonal line is added.

o When a switch is not actuated or a contactor or relay is not energized, all its contacts
are in their normal state. Normally-open contacts are open and normally-closed
contacts are closed. When the component is actuated or energized, its contacts
change their state: normally-open contacts close and normally-closed contacts open.

o Numbers are often added along the left-hand rail of relay ladder diagrams when the
diagrams have many rungs. Numbers at the right-hand rail indicate the location of
contacts controlled by the load. Comments about the components on a rung are often
written along the right-hand rail.

o For example, the rungs of the relay ladder diagram on the previous page are
numbered 1 through 5. Along the right-hand rail, the load in Rung 3 is referenced to
both Rung 1 and Rung 4 because the time-delay relay has a contact in each of those

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rungs. The contact in Rung 4 turns the alarm off when it completes its timing
sequence. The contact in Rung 1 turns the motor on. Rung references to normally-
closed contacts are underlined while normally-open contacts are not.

Power Circuit

Control Circuit

Figure 1Motor Control Ladder Diagram

o Wire numbers are sometimes added to aid in locating the proper connections in the
control system. The numbers on the diagram match real numbers affixed to the wires
in the system.

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III. Evaluation:

1. This is a ladder diagram of the control circuit for a large ventilation fan started with a
maintained – contact selector switch. In this circuit, if the power of the fan is lost, it will
automatically restart when power is restored. Modify the circuit so that the new circuit
will not permit fan to restart if power is restored after an outage.

Answer

2. Modify the given circuit so that it can be started from three other locations by using
pushbuttons. Draw your diagram and label each part.

Answer

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3. Modify the circuit you have drawn in No. 2 by adding a temperature switch that will
automatically turn the fan ON when the temperature rises to 110 ° F. The circuit must
allow each pushbuttons to ON the fan independent of the temperature switch.

Answer

4. Lastly, modify the circuit in a way that the three pushbuttons can not turn ON the fan
until the temperature reaches 110 ° F

Answer

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5. In Figure 1, what is the function of the control relay CR for the proper operation of the
motor?

6. What is the purpose of connecting a normally closed time relay contact (TDOE) in series with
the alarm? Why a normally open time relay contact (TDOE) in series with the motor contactor
coil M?

IV. Conclusion

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Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

MOTOR CONTROL COMPONENTS FAMILIARIZATION AND TESTING

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Discuss the principle of operation of basic motor control components.

2. Check the condition of basic motor components using VOM and/or CLT.
3. Recognize the importance of gaining skills in testing motor control equipments.

II. TECHNICAL INFORMATION:

MAJOR COMPONENTS OF AC MOTOR STARTERS

Alternating current (AC) motor starters have five major functional components, these include:
• Components that provide motor overload protection.
• Components that perform the motor controller function.
• Components that protect against short-circuit and ground faults.
• Components that provide motor circuit-disconnecting means.
• An enclosure suitable to meet the requirements of the motor starter application.

Overload Protection

The function of the overload device is to monitor motor line current and to open the
motor circuit when predetermined safe levels are exceeded. In accordance with the National
Electric Code and based on specific circuit conditions, continuous duty motors rated more than
one horsepower may be protected for overloads using overload relays, integral thermal
protectors, fuses or circuit breakers. The most commonly used overload device is the overload
relay.

Two types of overload relays that respond to the heating effect of the motor line current
are the thermal and the solid-state overload relays. The thermal overload relay uses the motor
line current to produce heat within itself at a designated rate that simulates load and conductor
heating. On the other hand, the solid-state overload relay monitors motor line current and uses
semiconductor circuits to determine the heating effects that the level of current will have on the
motor and conductors.

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Controller

A major component common to all AC motor starters is the controller. The controller is
consists of the contactor that carries the motor line current and the control circuit for the
contactor. When the overload relays are added to the controller, the assembly is referred to as a
basic magnetic motor starter. The contactor portion of the controller is essentially an on-off
device operated by electromagnetic means. When the controller coil is energized through a
control circuit, the resulting magnetic field mechanically forces the main contacts to close, thus
starting the motor. The coil is then continuously energized to hold the contacts closed and keep
the motor running. When the coil is de-energized, the main controller contacts are forced open
by either spring pressure or gravity, thus stopping the motor.

Fault Protection

The device used to provide protection against short circuit and ground faults. The devices
used for this protection are typically an instantaneous trip circuit breaker, an inverse time circuit
breaker, non-time delay fuses, or dual element (time-delay) fuses.

Disconnect

Another major component that is common to all AC motor starters is the disconnecting
device. In accordance with the National Electric Code, motors and controllers must be provided
with a means of safely disconnecting them from their source of supply so that maintenance of the
controller, motor, and its driven equipment can be accomplished with no hazard to personnel.
The devices to be used for disconnecting include circuit breakers, motor-circuit switches, and
molded case switches (non-automatic circuit interrupters).

Enclosure

A final component common to AC motor starters is the enclosure. An enclosure is a

surrounding case constructed to provide a degree of protection to personnel against incidental
contact with the enclosed equipment, and to provide a degree of protection to the enclosed
equipment against environmental conditions. Although other types of materials (e.g. polymeric)
are sometimes used, enclosures are typically sheet metal or cast metal construction. However, in
all cases, only material that will not support combustion in air is selected for enclosures.

Other Motor Control Circuit Components

Components used for control circuits include pushbuttons, selector switches, indicating
lights, control relays, control power transformers, auxiliary contacts, contactors, overload relays,
circuit breakers or MCPs, and electrical wiring.

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Pushbuttons

One component typically used in the control circuit of motor starters is the pushbutton.
The pushbutton is used to energize the control circuit. A simple pushbutton is composed of a set
of stationary contacts, a set of moving contacts, an operating plunger, a return spring, and a
housing to hold the assembly together. Pushbuttons are basically one of two types: one with
normally open contacts, and the other with normally closed contacts. For the normally open
pushbutton the operating plunger is held up by a return spring. This spring holds the moving
contacts away from the stationary contacts, and it, thereby, keeps the control circuit open and de-
energized. Depressing the plunger causes the moving contacts to engage the stationary contacts,
thus closing the circuit. Normally open pushbuttons are typically used to start a process.

In the normally closed pushbutton, the design of the contacts is opposite to that of the
normally open pushbutton. For this type, the contacts open, and the process stops when the
plunger is depressed. As a result of the internal tension caused by the return spring, the action of
both the normally open and normally closed pushbuttons is momentary. When the operator’s
finger is removed from the pushbutton, it returns to its original state.

Indicator Lights

Indicating lamps are another component used in motor starter control circuits. Their
function is a relatively simple but important one, which is to report the status of the control
circuit and, as a result, the status of the equipment controlled. Varieties of colors are used for the
lens of the indicating lights to report or warn of various circuit conditions. Colors typically
offered by manufacturers include red, green, blue, amber, white and clear. The most commonly
used types of indicating lights include the full-voltage, transformer and push-to-test types.

Control Relays

A control relay is a component that is used in a motor starter’s control circuit to interface
between a pilot device and the circuit that the pilot device controls. In effect, the control relay
allows the pilot device to control a current that is too large for the contacts of the pilot device.
Pilot devices used in motor controls typically monitor parameters such as time, pressure, liquid
level, and heat. Among its type are the following:

a. Electromechanical
One type of control relay is the electromechanical type. This relay uses an electromagnet to
move the output contacts from open to closed and closed to open. Relays of this type are
referred to as alternating current relays, if designed for actuation from an AC source, or
direct-current relays, if designed for DC operation.

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b. Time Control Relay

The timer control relay is available as either an electromechanical or solid-state type relay.
The relay can be purchased with normally open contacts, normally closed contacts, or a
combination of the two types. This type of relay functions as described above for either the
electromechanical or solid-state type, except that it has a built-in timing circuit that delays
the operation of the relay contacts.

II. TOOLS and MATERIALS NEEDED:

VOM and/or Continuity Lamp Tester

Drawing Materials
Set of Motor Control Components

III. PROCEDURE:

1. After the discussion, secure motor power and control circuit components for
familiarization and testing.

2. Using your test instruments, check the conditions of various motor control components
provided by the instructor.

3. Record the data and observations below and determine the condition of the components.

Summary of Findings
Note: NS - Normal State ES – Energized State

a. Magnetic Contactor

Main Contact/s

NO Terminal Markings / /
NO Resistance Reading/Condition NS / / ES / / /

Magnetic Contactor Coil

Coil Terminal Markings

Resistance Reading/Condition

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Auxiliary Contact/s

NO Terminal Markings
NO Resistance Reading/Condition NS ES

NC Terminal Markings
NC Resistance Reading/Condition NS ES

b. Overload Relay

Overload Heaters
Terminal Markings

Overload Contacts

NO Terminal Markings
NO Resistance Reading/Condition (NS)
Resistance Reading when tripped (ES)

NC Terminal Markings
NC Resistance Reading/Condition (NS)
Resistance Reading when tripped (ES)

Reset Button Condition

c. Pushbutton

Green Pushbutton
Resistance when Pressed (ES) Condition
Resistance when Released (NS)

Red Pushbutton
Resistance when Pressed (ES) Condition
Resistance when Released (NS)

Double Contact Red Pushbutton

Resistance when Pressed: Set 1 Set 2 Condition
Resistance when Released Set 1 Set 2

Double Contact Green Pushbutton

Resistance when Pressed: Set 1 Set 2 Condition
Resistance when Released Set 1 Set 2

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c. Indicating Light

Green Pilot Lamp

Resistance Reading Condition
CLT Testing

Red Pilot Lamp

Resistance Reading Condition
CLT Testing

Yellow/Orange Pilot Lamp

Resistance Reading Condition
CLT Testing

V. CONCLUSION:

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Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

ACROSS THE LINE MAGNETIC MOTOR STARTER (Non- Reversing)

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of an across the line voltage starter.

2. Connect properly the components in an across the line motor starter.
3. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

The across the line magnetic starter is the simplest method of controlling motor using
magnetic contactor. Energizing a holding coil closes the magnetic motor starter contacts. It is
relatively simple in construction, easy to maintain, and the least expensive of all AC motor
starters. This type of starter is used for control of motors where full-voltage starting is acceptable
and where the motor is to start up and run in one direction only.

Figure 1. Across the Line Motor Starter Circuit

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III. MATERIALS/DEVICES NEEDED:

IV. TOOLS AND EQUIMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

VI. PROCEDURE:

1. Draw the diagram of an across the line motor starter. Submit to the instructor for
checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit. Observe resistance reading and record the value in table 2.

5. Press the start button while the test probes are still at Line 1 and 2. Observe the
reading then record the data in table 2.

6. Trip the overload relay. Observe the reading then record the data in table 2.

7. Energize the circuit upon approval of the Instructor for checking.

Record your observation in evaluation.

8. De-energize the circuit after checking. Remove the connectors then clear the area.

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VII. OBSERVATIONS AND SUMMARY OF DATA:

Table 1: Motor Control Components’ Condition

Component Description Resistance Condition

Reading
Magnetic Contactor
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts NC
Overload Relay
Overload
heaters
Contacts
Pilot Lights
Red
Green
Yellow/Orange
Pushbuttons
Red
Green

Table 2 Circuit Continuity Test (De-energized)

Done while components are connected

Circuit Condition Test Observation Resistance Cause/s of Circuit

Reading Condition

Place Ohmmeter in L1
and 2
All components are in
inactive state

Place Ohmmeter in L1
and 2

Start button is in active

state (Pressed)

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Place Ohmmeter in L1
and 2

Overload relay is tripped

(Simulated)

VIII. CONCLUSION :( Discuss how an across the line motor starter function by referring to
your schematic diagram)

IX. EVALUATION:

1. Why is it important to place an indicator light in a motor control circuit?

2. Why is the reason of connecting in series a normally open contact of an overload relay and an
indicator lamp for fault condition?

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Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

TWO STATION MOTOR CONTROL (Non- Reversing)

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of a two station motor control.

2. Connect properly the components in a two station motor control.
3. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

The operation of a Two Station Motor Control is the same as the operation of the
across the line magnetic starter except that the two start and stop pushbuttons are connected in
parallel and series respectively.

This type of motor control connection is used to operate the motor from two
locations called, Station 1 and Station 2.

III. MATERIALS/DEVICES NEEDED:

IV. TOOLS AND EQUIPMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

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VI. PROCEDURE:

1. Draw the diagram of two-station motor control circuit. Submit to the instructor for
checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit. Observe resistance reading and record the value in table 2.

5. Press the start button for station 1 while the test probes are still at Line 1 and 2.
Observe the reading then record the data in table 2.

6. Do the same procedure for station 2 while the test probes are still at Line 1 and 2.
Observe the reading then record the data in table 2.

7. Trip the overload relay. Observe the reading then record the data in table 2.

8. Energize the circuit upon approval of the Instructor for checking.

Record your observation in the evaluation.

8. De-energize the circuit after checking. Remove the connectors then clear the area.

VII. OBSERVATIONS AND SUMMARY OF DATA:

Table 1: Motor Control Components’ Condition

Component Description Resistance Condition

Reading
Magnetic Contactor
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts NC
Overload Relay
Overload
heaters
Contacts

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Pilot Lights
Red
Green
Yellow/Orange
Pushbuttons
Red1/Red2
Green1/Green 2

Table 2 Circuit Continuity Test (De-energized)

Done while components are connected

Circuit Condition Test Observation Resistance Cause/s of Circuit

Reading Condition

Place Ohmmeter in L1
and 2
All components are in
inactive state

Place Ohmmeter in L1
and 2

Station 1 Start button is

in active state (Pressed)

Station 2 Start button is

in active state (Pressed)

Place Ohmmeter in L1
and 2

Overload relay is tripped

(Simulated)

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 35

VIII. CONCLUSION: (Discuss how two station motor control function by referring to your
schematic diagram)

IX. EVALUATION:

1. Cite applications of a two station motor control.

2. Why do we connect start pushbuttons in parallel in a two - station motor control?

2. Why do we connect stop pushbuttons in series in a two - station motor control?

GRADING CRITERIA:
Time (15) : Remarks:
Tools/materials (5) :
Job plan/ wiring diagram (20):
Accuracy of connection (50) :
Safety and Task Performance (10):

Time Started: Time Finished:

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 36

Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

FULL VOLTAGE NON-REVERSING MOTOR CONTROL WITH JOG

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of motor control system with jog.

2. Connect properly the components in motor control system with jog.
3. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

Jogging is defined as the brief closure of a motor circuit to energize a motor for a short
period of time and performs a small movement of driven machine. It is a condition when a
pushbutton is pressed and will stop when it is released. Jogging is used on machinery in which
the motor must run for short period of time to allow machine setup. Another term for jogging is
inching.

Some applications of jogging are the following: to align and space machine parts; to
position a tool accurately; to thread cloth, paper or sheet metal; and to provide small controlled
movements.

STOP JOG START

OL
M

Jog-Start-Stop Control Circuit

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 37

III. MATERIALS/DEVICES NEEDED:

IV. TOOLS AND EQUIPMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

VI. PROCEDURE:

1. Draw the diagram of a Start-Stop-Jog motor control circuit. Submit to the instructor
for checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit. Observe resistance reading and record the value in table 2.

5. Press the start button while the test probes are still at Line 1 and 2. Observe the
reading then record the data in table 2.

6. Press the dual contact pushbutton while the test probes are still at Line 1 and 2.
Observe the reading then record the data in table 2.

7. Trip the overload relay. Then press Dual Contact Pushbutton. Observe the reading
then record the data in table 2.

8. Energize the circuit upon approval of the Instructor for checking.

Record your observation in the conclusion.

9. De-energize the circuit after checking. Remove the connectors then clear the area.

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 38

VII. OBSERVATIONS AND SUMMARY OF DATA:

Table 1: Motor Control Components’ Condition

Component Description Resistance Condition

Reading
Magnetic Contactor
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts NC
Overload Relay
Overload
heaters
Contacts
Pilot Lights
Red
Green
Yellow/Orange
Pushbuttons
Red
Green

Table 2 Circuit Continuity Test (De-energized)

Done while components are connected

Circuit Condition Test Observation Resistance Cause/s of Circuit

Reading Condition

Place Ohmmeter in L1
and 2
All components are in
inactive state

Place Ohmmeter in L1
and 2

Start button is in active

state (Pressed)

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 39

Circuit Condition Test Observation Resistance Cause/s of Circuit

Reading Condition

Place Ohmmeter in L1
and 2

Dual Start Button is in

active state (Pressed)

Place Ohmmeter in L1
and 2

Overload relay is tripped

(Simulated) and Dual
Pushbutton is pressed

VIII. CONCLUSION :( Discuss how a Start-Stop-Jog Motor Starter function by referring to

your schematic diagram)

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 40

IX. EVALUATION:

1. What is the function of the double contact pushbutton in a Start-Stop-Jog motor control
circuit?

2. Give motor control situations wherein jogging or inching is applicable

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 41

Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

FORWARD – REVERSE MOTOR CONTROL
(No Immediate Reversal)

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of a Forward – Reverse Motor Control with no

immediate reversal.
2. Connect properly the components in a Forward – Reverse Motor Control with no
immediate reversal.
3. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

To reverse the direction of a three-phase motor, it is possible to simply interchange any

two-phase conductors at the motor or the motor starter. But if the reversing of the motor is a
required operation of the machine, then reversing motor starters are available.

The Forward-Reverse motor control is used in a system where forward and backward or
upward and downward movement in the operation is needed.

Stop Before Reversing (Medium Motors)

The stop before reversing logic is generally used for medium size motors. Stopping the
motor first, before reversing its direction, eliminates the overcurrent surge and potentially
damaging mechanical stress that can result with the attempt to rapidly reverse a large rotating
inertia (load). Operation of the circuit in Figure 36 begins by closing the forward pushbutton to
energize the forward contactor coil (F). This action closes the main forward contacts to the motor
terminals starting the motor in the forward direction. In sequence with this action, auxiliary
contact Fa closes to seal in the forward coil (F) circuit, and auxiliary contact Fb opens to block
the reverse coil (R) circuit. To reverse the motor when it is running in the forward direction, it is
necessary to first push the stop pushbutton. Pushing the stop pushbutton deenergizes the forward
contactor, which in turn opens the main forward contacts and allows Fa to open and Fb to close.
At this point, the reverse pushbutton can be pushed to energize the reverse contactor coil circuit.
In sequence then, the main contacts of the reverse contactor close (reversing motor lines L1 and
L3), Ra closes to seal in the reverse coil circuit, and Rb opens to block the forward coil circuit.
The circuit logic for the stop before reversing starter requires only that the stop button be pushed
before an attempt is made to reverse the direction of the motor. Whether the motor is allowed to

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 42

come to a complete stop before actually reversing is an option of the operator based on the
motor’s size and inertia.

Forward – Reverse Motor Control

(No Immediate Reversal)

Mechanical and Electrical Interlocks

All reversing starters have two magnetic contactors mounted in one enclosure. The
contactors provide for connection of the power leads to the motor terminals. One contactor
(forward contactor) is connected to the three phases of the motor so that the motor starts and runs
in the forward direction. The other contactor (reverse contactor) is connected so that when it
closes, two of the lines to the motor are interchanged, thus reversing the direction of rotation of
the motor. With regard to the operation of the two contactors, it is necessary that they be
interlocked to prevent both of them from closing at the same time. If both contactors were to
close at the same time, the result would be a dead short circuit across two of the phases.
Interlocking is used to prevent this condition from happening. Both mechanical and electrical
interlocks are used. Mechanical interlocks typically use an insulated linkage fastened between
the moving assemblies of the two contactors to prevent their simultaneous closing. Electrical
interlocking circuits vary in purpose and complexity, but the basic technique consists of using
normally open and normally closed contacts in both the forward and reverse coil circuits to
maintain each coil circuit open while the other is closed.

III. MATERIALS/DEVICES NEEDED:

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 43

IV. TOOLS AND EQUIPMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

VI. PROCEDURE:

1. Draw the diagram of a Forward – Reverse Motor Control with no immediate reversal.
Submit to the instructor for checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit. Observe resistance reading and record the value in table 2.

5. Press the forward start button while the test probes are still at Line 1 and 2. Observe
the reading then record the data in table 2.

6. Press the reverse start button while the test probes are still at Line 1 and 2. Observe
the reading then record the data in table 2.

7. Trip the overload relay. Then press forward start pushbutton. Observe the reading
then record the data in table 2.

8. Energize the circuit upon approval of the Instructor for checking.

Record your observation in the conclusion.

9. De-energize the circuit after checking. Remove the connectors then clear the area.

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 44

VII. OBSERVATIONS AND SUMMARY OF DATA:

Table 1: Motor Control Components’ Condition

Component Description Resistance Condition

Reading
Magnetic Contactor 1
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts NC
Magnetic Contactor 2
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts
Overload Relay
Overload
heaters
Contacts
Pilot Lights (F/R)
Red
Green
Yellow/Orange
Pushbuttons (F/R)
Red
Green

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 45

Table 2 Circuit Continuity Test (De-energized)

Done while components are connected

Circuit Condition Test Observation Resistance

Reading Cause/s of Circuit
Condition

Place Ohmmeter in L1
and 2
All components are in
inactive state

Place Ohmmeter in L1
and 2

Forward Start button is

in active state (Pressed)

Place Ohmmeter in L1
and 2

Reverse Start button is

in active state (Pressed)

Resistance Cause/s of Circuit

Circuit Condition Test Observation Reading Condition

Place Ohmmeter in L1
and 2

Stop Button is in active

state (Pressed)

Place Ohmmeter in L1
and 2

Overload relay is tripped

(Simulated) and Forward
Start button is pressed

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 46

VIII. CONCLUSION:(Discuss how a Forward-Reverse with no immediate reversal function

by referring to your schematic diagram)

IX. EVALUATION:

1. Why is there a need to stop medium motors before reversing its direction in a control circuit?

GRADING CRITERIA:
Time (15) : Remarks:
Tools/materials (5) :
Job plan/ wiring diagram (20):
Accuracy of connection (50) :
Safety and Task Performance (10):

Time Started: Time Finished:

CCA
 47

Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

FORWARD – REVERSE MOTOR CONTROL
(Immediate Reversal)

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of a Forward – Reverse Motor Control with

immediate reversal.
2. Connect properly the components in a Forward – Reverse Motor Control with
immediate reversal.
3. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

To reverse the direction of a three-phase motor, it is possible to simply interchange any

two-phase conductors at the motor or the motor starter. But if the reversing of the motor is a
required operation of the machine, then reversing motor starters are available.

The Forward-Reverse motor control is used in a system where forward and backward or
upward and downward movement in the operation is needed.

Full-Speed Reversing (Small Motors)

One type of control logic used in full-voltage reversing starters is the full-speed reversing
logic. The circuit arrangement for this type logic allows the direction of a motor to be reversed
without pushing the stop button. This mode of operation has the advantage of reversing the
direction of the motor in the shortest possible time. However, use of this type of logic is
acceptable only for small motors with relatively low mass and thus low inertia. The arrangement
of this circuit is basically the same as for all full-voltage reversing starters, except that the
forward pushbutton and the reverse pushbutton have an additional normally closed contact block.
The starter has two contactors, one connected to apply the three phases to the motor so that the
motor starts and runs in the forward direction. The other contactor is connected so that when it
closes, two of the lines to the motor are interchanged, thus reversing the direction of rotation of
the motor.

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 48

Forward – Reverse Motor Control

(Immediate Reversal)

Starting the motor and operating it in the forward direction is initiated by closing the
forward pushbutton. This action energizes the forward contactor (F), which in turn closes the
main contacts to the motor terminals, thus starting the motor in the forward direction. The same
action that closes the normally open contact of the pushbutton also opens its normally closed
contact. This temporary open circuit prevents an unwanted start in the reverse direction. As the
forward contactor operates, it causes its auxiliary contacts to operate also. The normally open
auxiliary forward contact (Fa) closes to seal in the forward coil circuit, and the normally closed
auxiliary forward contact (Fb) opens to block the reverse contactor coil circuit. To reverse the
direction of the motor (without first pushing the stop pushbutton), simply push the reverse
pushbutton. The opening of the normally closed contact of the reverse pushbutton causes the coil
circuit for the forward contactor (F) to momentarily open. The circuit for the reverse contactor
coil (R) circuit momentarily closes. When the forward contactor opens, it operates its auxiliary
contacts (Fa , Fb). Fa opens to keep the forward (F) coil circuit open, while Fb closes to allow the
reverse coil (R) circuit to energize. When the reverse contactor picks up, it closes it main
contacts to the motor terminals, which in this case causes lines L1 and L3 to be interchanged,
reversing the direction of the motor. Auxiliary contacts Ra and Rb operate in unison with the
reverse contactor. The normally open Ra contact closes to seal in the reverse coil circuit, while
the normally closed Rb contact opens to block the energizing of the forward coil circuit.

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 49

III. MATERIALS/DEVICES NEEDED:

IV. TOOLS AND EQUIPMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

VI. PROCEDURE:

1. Draw the diagram of a Forward – Reverse Motor Control with immediate reversal.
Submit to the instructor for checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit. Observe resistance reading and record the value in table 2.

5. Press the forward start button while the test probes are still at Line 1 and 2. Observe
the reading then record the data in table 2.

6. Press the reverse start button while the test probes are still at Line 1 and 2. Observe
the reading then record the data in table 2.

7. Trip the overload relay. Then press forward start pushbutton. Observe the reading
then record the data in table 2.

8. Energize the circuit upon approval of the Instructor for checking.

Record your observation in the conclusion.

9. De-energize the circuit after checking. Remove the connectors then clear the area.

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 50

VII. OBSERVATIONS AND SUMMARY OF DATA:

Table 1: Motor Control Components’ Condition

Component Description Resistance Condition

Reading
Magnetic Contactor 1
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts NC
Magnetic Contactor 2
NO
Main Contacts
NO
NO
Auxiliary NO
Contacts
Overload Relay
Overload
heaters
Contacts
Pilot Lights (F/R)
Red
Green
Yellow/Orange
Pushbuttons(F/R)
Red
Green

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 51

Table 2 Circuit Continuity Test (De-energized)

Done while components are connected

Circuit Condition Test Observation Resistance

Reading Cause/s of Circuit
Condition

Place Ohmmeter in L1 and

2
All components are in
inactive state

Place Ohmmeter in L1 and

2
Forward Start button is in
active state (Pressed)

Place Ohmmeter in L1 and

2
Reverse Start button is in
active state (Pressed)

Resistance Cause/s of Circuit

Circuit Condition Test Observation Reading Condition

Place Ohmmeter in L1 and

2

Stop Button is in active

state (Pressed)

Place Ohmmeter in L1 and

2

Overload relay is tripped

(Simulated) and Forward
Start button is pressed

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 52

VIII. CONCLUSION :( Discuss how a Forward-Reverse with immediate reversal function by

referring to your schematic diagram)

IX. EVALUATION:

1. Why is “immediate reversal” motor circuit applicable only for controlling small motors?

GRADING CRITERIA:
Time (15) : Remarks:
Tools/materials (5) :
Job plan/ wiring diagram (20):
Accuracy of connection (50) :
Safety and Task Performance (10):

Time Started: Time Finished:

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 53

Name: Course: Subject:

Group No. Time: Days: Rm. Date:
Professor/Instructor: Rating:

Laboratory Activity No.

SEQUENTIAL MOTOR CONTROL
(Manual: Using Pushbutton)

I. OBJECTIVES:

At the end of the laboratory activity, the students should be able to:

1. Describe the principle of operation of a manual Sequential Motor Control using

pushbutton.
2. Connect properly the components in a Sequential Motor Control using
pushbutton.
2. Observe safety while connecting the motor control circuit.

II. TECHNICAL INFORMATION:

There are cases where machines should be started in a specific manner or one after
another; this type of control applied to these industrial machines is called sequential motor
control. One example of this is shown in Figure 1.

Motor 1 needs to operate first for motor 2 to function.

M1- magnetic contactor coil 1

M2- magnetic contactor coil 2

Manual Sequential Motor Control Circuit

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 54

III.MATERIALS/DEVICES NEEDED:

IV. TOOLS AND EQUIPMENT NEEDED:

V. CIRCUIT DIAGRAM: (See attached paper for motor circuit connection diagram)

VI. PROCEDURE:

1. Draw the diagram of a manual Sequential Motor Control circuit. Submit to the
instructor for checking (prepare the diagram on a separate bond paper).

2. Prepare tools, materials and devices needed for the activity. Check their condition
using an ohmmeter. Record resistance reading on table 1.

3. Connect the circuit as shown in the diagram.

4. Place the test probes of the ohmmeter to Line 1 and Line 2 to test the continuity of the
circuit.

5. Energize the circuit upon approval of the Instructor for checking.

Record your observation in the conclusion.

6. De-energize the circuit after checking. Remove the connectors then clear the area.

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 55

VIII. CONCLUSION: (Discuss how does a manual sequential motor control function by
referring to your schematic diagram)

IX. EVALUATION:

1. Cite examples/situations in which sequential motor control is applicable?

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 56

Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

SEQUENTIAL MOTOR CONTROL
(Automatic using Timer)

I. Objectives:
At the end of the activity, students should be able to:

1. Discuss the operation of a sequential motor control circuit.

2. Draw accurately a manual and automatic sequential motor control circuit.
3. Appreciate the importance of gaining skills in drawing and interpreting a sequential
motor control.

II. Technical Information:

There are cases where machines should be started in a specific manner or one
after another, this type of control applied to these industrial machines is called sequential motor
control. A good example would be a conveyor system composed of four sections. The sections
must start in correct sequence. If for some reason, one motor will not start, the next motor in line
will not start as well. Figure 1 shows an example of a manual sequential motor control.

Start
STOP
Motor 1 OL’s
M1
M1
Start
Motor 2
M2

M2

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 57

S12 S13 S14

S5 S6 S7

1 10 1 11 1 12
14 15 16
S8 S10 S9
S1 S3 S2 THERMAL_OL
THERMAL_OL THERMAL_OL THERMAL_OL 1A
THERMAL_OL THERMAL_OL 1A 1A 1A
1A 1A

8
2

7 9
1 3

S11
S4

M
3PH_MOTOR
M

3PH_MOTOR M2
M1

Power Circuit of a Manual Sequential Motor Control

Motor 1 needs to be energized before operating motor 2. Closing Start Motor 1

pushbutton will energize coil of magnetic contactor 1 (M1) and closing contact M1 to maintain
motor 1 operation.
Pressing Start Motor 2 pushbutton will energize coil 2 of magnetic contactor 2 operating
motor 2. Normally open contact M2 will provide the seal in for the circuit of motor 2
Sequential Motor Control Using Time Delay Relay

In a circuit, it is an advantage to have a timing contact as well as instantaneous contact

from the same energized relay coil. The timing contact can be arranged to delay after energizing
or de-energizing the coil.

TR

Timer Relay Coil

Normally Open Instantaneous Contact

Normally Close Instantaneous Contact

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 58

J1 J1 J1
J1
T T T
T

10.000m 10.000m
10msec 10msec 10msec 10msec
a b c d
a. Normally Closed – Time Delay After Deenergizing (NCTC)
a. Normally Closed – Time Delay After Energizing (NCTO)
a. Normally Open– Time Delay After Energizing (NOTC)
a. Normally Open – Time Delay After Deenergizing (NOTO)

Symbols for Timing Contact

Typical Schematic Diagram

Timer Relay

III. Application (Draw diagram on separate bond paper)

1. Draw the ladder diagram of three motors that will start one after the other using
three start pushbuttons. Include indicator lamps that will show which motor is
running and showing idle and fault condition for each motor.

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 59

2. Draw the ladder diagram of two motors that will functions as follows: Pressing
Start pushbutton, motor 1 will energize. After a preset time of three seconds,
motor 2 will function but de-energizing motor 1 at the same time. The process
should be repeated until pressing the Stop pushbutton turning off both motors.
Draw indicator lamps.
3. Draw the ladder diagram of three motors (M1, M2, M3) that will energize one
after another using timer relay with an interval of 10 seconds. Ten seconds after
energizing motor three, all motor will be de-energize and the sequence will be
repeated until Stop button is pressed turning off the whole circuit interrupting the
sequence. Show the idle and fault conditions using pilot light indicators.
4. Draw the ladder diagram of a forward – reverse motor control circuit that will
change direction automatically after 5 seconds using a limit switch.

IV. Evaluation:

1. Differentiate an OFF delay from an ON delay timer relay?

V. Conclusion

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 60

Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

REDUCED VOLTAGE STARTER CIRCUITS

I. Objectives:
At the end of the laboratory activity, students should be able to:

1. Discuss the operation of some types of reduce voltage starters motor starters.
2. State the importance of reduced voltage /current starters.
3. Draw accurately some examples of reduce voltage starters motor starter circuits.
4. Appreciate the importance of gaining skills in drawing and interpreting a reduce
voltage starters.

II. Technical Information:

Reduced voltage starting minimizes the shock on the driven machine by reducing the
starting torque of the motor. A high torque, applied suddenly with full voltage starting, may
cause belts to slip and wear or may damage gears, chains, or couplings. The material being
processed, or conveyed, may be damaged by the suddenly applied jerk of high torque. By
reducing the starting voltage, or current at the motor terminals, the starting torque is decreased.

The category of reduced voltage methods generally includes all starting methods which
deviate from standards, line voltage starting. The reduced voltage starters achieve either to
reduce line current or reduce starting torque.

It is important to note that when the voltage is reduced to start a motor, the current is also
reduced, and so is the torque that the machine can deliver. Regardless of the desired result,
remember that the other will always follow.

It is also necessary for an electrician/electrical practitioner to understand the behavior of

a motor during startup and acceleration periods. Such understanding enables one to select the
proper starting method to conform to local power company regulations.

There are several types of reduced voltage starting methods, which includes primary
resistance starting: a resistance unit connected in series with the stator reduces the starting
current; autotransformer or compensator starting: manual or automatic switching between the
taps of the autotransformer gives reduced voltage starting; impedance starting: reactors are used
in series with the motor; part winding starting: stator winding of the motor are made up of two
or more circuits; the individual circuits are connected to the line in series for starting and in
parallel for normal operation; and the solid-state electronic control: control of current or
acceleration time is achieved by gating silicon controlled rectifiers with the AC half cycle.

CCA
 61

M
M
1 2
1

2
Primary Resistance Starting Autotransformer Starting 1

1
M
1 M

2
Solid State Electronic Control
Part winding Starting

III. Application (Draw diagram on separate bond paper)

1. Draw the ladder diagram of PRIMARY RESISTANCE, AUTOTRANSFORMER, and

PART WINDING MOTOR STARTERS using magnetic contactors and time delay relay.
Indicate pilot light indicators to show Idle, Run and Fault conditions.

IV. Evaluation:

1. What are the functions of reduced voltage starters?

2. Discuss the importance of reduced voltage starters?

IV. Conclusion (Explain how a reduced voltage starter functions. Select a circuit to be
discussed)

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 62

Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

REDUCED VOLTAGE STARTER
(Wye-Delta Starter)

I. Objectives:
At the end of the laboratory activity, students should be able to:

1. Discuss the operation of a Wye-Delta Starter motor control circuit.

2. Draw accurately a Wye-Delta Starter motor control circuit.
3. Appreciate the importance of gaining skills in drawing and interpreting a Wye-Delta
Starter.

II. Technical Information:

Wye/Delta starters are probably the most common reduced voltage starters in the 60Hz
world. They are used in an attempt to reduce the start current applied to the motor during start as
a means of reducing the disturbances and interference on the electrical supply.

Traditionally in many supply regions, there has been a requirement to fit a reduced
voltage starter on all motors greater than 5HP (4KW). This regulation was introduced in order to
reduce the start current. Wye-Delta starter is one of the lowest cost electromechanical reduced
voltage starters that can be applied and this is why it has been so popular.

The Wye/Delta starter is manufactured from three contactors, a timer and a thermal overload.
The contactors are smaller than the single contactor used in a Direct On Line starter as they are
controlling winding currents only. The currents through the winding are 1/root 3 (58%) of the
current in the line.

There are two contactors that are close during run, often referred to as the main contactor and
the delta contactor. These are AC3 rated at 58% of the current rating of the motor. The third
contactor is the wye contactor and that only carries wye current while the motor is connected in
wye. The current in wye is one third of the current in delta, so this contactor can be AC3 rated at
one third of the motor rating.

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 63

Wye – Delta Motor Starter Circuit

1 2 3

4 5 6

Winding Connection For Wye And Delta

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 64

VI. Application (Draw diagram on separate bond paper)

1. Draw the ladder diagram of WYE - DEL.TA motor starter using magnetic contactors and
time delay relay. Indicate pilot light indicators to indicate Idle, Wye – Run (Wye-Delta)
and Fault conditions.

VII. Evaluation:

1. What are the functions of a wye-delta starter?

IV. Conclusion (Explain how a wye-delta motor control operates by referring to your circuit
diagram)

GRADING CRITERIA:
Time (15) : Remarks:
Tools/materials (5) :
Job plan/ wiring diagram (20):
Accuracy of connection (50) :
Safety and Task Performance (10):

Time Started: Time Finished:

CCA
 65

Name: Course, Yr. & Sec. Subject:

Group No. Time: Days: Rm: Date:
Professor/Instructor: Rating:

Laboratory Activity No.

APPLICATION OF FORWARD-REVERSE MOTOR CONTROL

I. Objectives:
At the end of the activity, students should be able to:

1. Discuss circuits involving the application of Forward-Reverse Motor Control.

2. Draw accurately Forward-Reverse motor control circuit
3. Appreciate the importance of gaining skills in using Forward-Reverse Circuit in
actual situations.

II. Technical Information:

The Forward-Reverse motor control is used in a system where lateral or vertical

movements are required in an operation such as in elevators, conveyors or cranes.

Forward –Reverse control can be done manually or automatically with the use of limit
switches and timer relay (TR).

Limit Switches in Forward –Reverse Motor Control Application

Switches are commonly employed as input devices to indicate the presence or absence of
a particular condition in a system or process that is being monitored and/or controlled. In
motorized electromechanical systems, limit switches provide the function of making and
breaking electrical contacts and consequently electrical circuits. A limit switch is configured to
detect when a system's element has moved to a certain position. A system operation is triggered
when a limit switch is tripped. Limit switches are widely used in various industrial applications,
and they can detect a limit of movement of an article and passage of an article by displacement
of an actuating part such as a pivotally supported arm or a linear plunger. The limit switches are
designed to control the movement of a mechanical part. Limit switches are typically utilized in
industrial control applications to automatically monitor and indicate whether the travel limits of a
particular device have been exceeded.

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Typical Limit Switches

V. Application (Draw diagram on separate bond paper)

1. Draw the ladder diagram of a motor control circuit that limits the Forward and Reverse
motion of an overhead crane driven by a motor using two single pole limit switches X
and Y. Limit switches automatically stops the motor once the crane reaches the other end.
Pressing the Reverse pushbutton allows the motor to run in counter direction, moving the
crane to the opposite side.

2. Draw the ladder diagram of a motor control circuit that limits the Forward and Reverse
motion of an elevator driven by a motor using two limit switches X and Y both with NC
and NO contacts. The circuit should allow automatic reversal of the elevator once the lift
reaches the topmost part and vice versa.

Note: Show the Idle for both circuits.

IV. Conclusion: (Explain the function of the limit switch in a Forward-Reverse Motor
Circuit)

GRADING CRITERIA: Circuit A

Time (15) : Remarks:
Wiring diagram presentation (40) :
Accuracy of circuit diagram connection (45) :

GRADING CRITERIA: Circuit B

Time (15) : Remarks:
Wiring diagram presentation (40) :
Accuracy of circuit diagram connection (45) :

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

ACROSS THE LINE MAGNETIC MOTOR STARTER

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

ACROSS THE LINE MAGNETIC MOTOR STARTER

RUN AND FAULT STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

TWO STATION MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

TWO STATION MOTOR CONTROL

RUN AND FAULT STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FULL VOLTAGE NON-REVERSING MOTOR CONTROL WITH JOG

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FULL VOLTAGE NON-REVERSING MOTOR COTROL WITH JOG

RUN AND FAULT STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FORWARD-REVERSE MOTOR CONTROL (NO IMMEDIATE REVERSAL)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FORWARD-REVERSE MOTOR CONTROL (NO IMMEDIATE REVERSAL)

FORWARD AND REVERSE RUN STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FORWARD-REVERSE MOTOR CONTROL (WITH IMMEDIATE REVERSAL)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

FORWARD-REVERSE MOTOR CONTROL (WITH IMMEDIATE REVERSAL)

FORWARD AND REVERSE RUN STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

MANUAL SEQUENTIAL MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

MANUAL SEQUENTIAL MOTOR CONTROL

RUN AND FAULT STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 1. SEQUENTIAL MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 2: SEQUENTIAL MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 3: SEQUENTIAL MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 4: SEQUENTIAL MOTOR CONTROL

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

REDUCED VOLTAGE STARTER (WYE-DELTA)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

REDUCED VOLTAGE STARTER (WYE-DELTA)

RUN WYE/RUN DELTA

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

REDUCED VOLTAGE STARTER (PRIMARY RESISTANCE)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

REDUCED VOLTAGE STARTER (AUTOTRANSFORMER)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

REDUCED VOLTAGE STARTER (PRIMARY WINDING)

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 1: MANUAL FORWARD-REVERSE W/LIMIT SWITCH

IDLE STATUS

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NAME: DATE;
COURSE, YEAR AND SECTION: ACTIVITY NO:

Problem 1: AUTOMATIC FORWARD-REVERSE W/LIMIT SWITCH

IDLE STATUS

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