ELECTRIC POWER ENGINEERING EXPERIMENT MODULE · 2018. 10. 4. · 2.1.1 DC Generator DC Generator is a DC machine that converts mechanical energy into electrical energy with the principle

University of Indonesia

2018

ELECTRIC POWER ENGINEERING EXPERIMENT MODULE Electrical Conversion Energy Laboratory, Electrical Engineering, University of Indonesia

Electrical Conversion Energy Laboratory ELECTRICAL ENGINEERING UNIVERSITY OF INDONESIA

Electrical Power Engineering Experiment

ASSITANT PROFILE



MODULE II

DC MOTOR

Objectives :

1. Understand construction of DC Motor.

2. Understand principle of DC Motor.

3. Know to analyze equivalent circuit of DC Motor.

1.1 INTRODUCTION

1.1.1 DC Motor

DC Motor is a DC machine converts electrical energy into mechanical energy

with principle of electromagnetic induction. In the construction of DC Motor,

there are two main components, stator and rotor. Stator is the stationary part and

the function is to produce main magnetic field and rotor is the rotating part. Image

1.1 is the simple construction of DC Motor.

Figure 1.1 Construction of DC Motor.

To run a DC Motor, rotor is flowed by current through the brush and the

commutator. The currents in the rotor pass through the magnetic field in stator and

cause Lorentz Forces. This forces rotate the DC Motor. Lorentz force can be

represented by the following equation:



The DC Motor can be analyzed by equivalent circuit. The equivalent circuit

of a separately excited DC Motor is shown in Image 1.2:

Figure 1.2 Separately Excited DC Motor.

In separately excited DC Motor, some equations apply:

Vf = excitation voltage (Volt)

Ip = excitation current (Ampere)

Ia = armature current (Ampere)

n = rotor speed (rpm)

T = torque (Nm)

Pin = input power (Watt)

Pout = output power (Watt)



1.1.2 Types of DC Machine

Based on the system of excitation, DC machine is divided into two:

1. Separately excited DC machine

2. Self excited DC machine

a) Series DC Machine

b) Shunt DC Machine

c) Compound DC Machine



1.1.3 Power Flow of DC Motor

Figure 1.3 Power Flow of DC Motor

1.2 EXPERIMENT EQUIPMENTS & TOOLS

1 DC Motor

1 DC Generator

1 Power Supply Module

DC Motor/Generator Module 1,5 KW, 1500 rpm, 220 V, 0,8 A

Field Rheostat Module 600 Ω, 225 W

2 DC Voltmeter/Amperemeter Modules

1 DC Breaker Module 220 Vdc, 30 A



1.3 EXPERIMENT CIRCUIT

Figure 1.4 Circuit of DC Motor

1.4 STEPS OF RUNNING AND LOADING DC MOTOR

1.4.1 Starting Motor

Look for the rating of motor (input voltage, armature current, field current,

and field voltage)

Look for the rating of generator which is the motor load (voltage, armature

current, field current, and coupling)

Turn on the switch on power supply module

Set the field rheostat until maximum A1 is obtained

Turn the voltage regulator on power supply module slowly to a certain

voltage where V1 (V) is below 220 V

Decrease the value of A1 to a certain value below 0.47 A

Motor rotates in no load state

1.4.2 Adjusting Motor Rotation

Look for rotation of motor



By adjusting V1 from the power supply module and A1 can be determined

by motor speed

1.4.3 Loading Motor

Motor load is DC Generator

Rb resistance at maximum position

Set the field rheostat of generator until Vout generator is 220 V

Pull DC breaker to position 1

By setting Rb to the maximum position, the motor is loaded from no load

state to nominal load

1.4.4 Turning Off Motor


Set the field rheostat until the value of A1 is maximum

Set voltage regulator on power supply module until the value of V1 is 0V

1.5 DC MOTOR EXPERIMENTS

1.5.1 No Load Characteristic

Experiment steps:

a. Determine n = n (Ip), V = C, T = 0

Start the motor according to 1.4.1

Set voltage regulator on power supply module until certain value of V1

Set field rheostat and note the value of A1 and n for every change of A1

b. Determine n = n(V), Ip = C, T = 0

Set field rheostat for certain A1

Set voltage regulator on power supply module and note the value of V1

and n for every change of V1

1.5.2 Characteristic of Rotation Control

Experiment steps:

a. Determine n = n(ip), V = C, T = C

Start the motor according to 1.4.1



Load motor with certain coupling according with (III.2 and III.3)

Set voltage regulator on power supply module until certain value of V1

For certain value of coupling, set field rheostat, note the value of A1 and n

for every change of A1

b. Determine n = n(V), Ip = C, T = C

Set field rheostat until certain value of A1

For certain value of coupling, set voltage regulator, note the value of V1

and n for every change of V1

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.



MODULE III

DC GENERATOR

Objectives:

1. Understand different of construction of DC Motor and Generator DC.

2. Understand principle of DC Generator.

3. Know to analyze equivalent circuit of DC Generator.

4. Understand how to calculate the efficiency of DC Generator.

2.1 INTRODUCTION

2.1.1 DC Generator

DC Generator is a DC machine that converts mechanical energy into

electrical energy with the principle of electromagnetic induction. The construction

of DC Generator is same as the DC Motor.

On the principle, DC Generator uses Faraday Law to produce electrical

energy. Faraday law can be represented by the equation:

sin

Basically, there is no difference between DC machine and AC machine but

DC machine have commutators that function as rectifier. Image 2.1 is equivalent

circuit of DC Generator.

Figure 2.1 Equivalent circuit of DC Generator.

The input power of DC Generator is not entirely converted into electrical

energy. There are some losses described in power flow diagram:



Figure 2.2 Power flow of DC Generator.


1 DC Motor

1 DC Generator

1 Power Supply Module

DC Motor/Generator Module 1,5 KW, 1500 rpm, 220 V, 0,8 A

Field Rheostat Module 600 Ω, 225 W

2 DC Voltmeter/Amperemeter Modules

1 DC Breaker Module 220 Vdc, 30 A

2.3 EXPERIMENT CIRCUIT

Figure 2.3 Circuit of DC Generator



2.4 STEPS OF RUNNING DC GENERATOR

2.4.1 Starting Generator

DC breaker on position 0 and armature coils are not connected with load

Set field rheostat of generator (A4) until the value of Vout generator is 220

V

By setting A4 (field current/Ip) from minimum value until maximum, the

generator is no load state

2.4.2 Loading Generator

Rb on maximum position

Pull DC breaker on position 1

By setting Rb, the generator is load state

2.4.3 Turning Off Generator


Set field rheostat until the value of A1 is maximum

Set voltage regulator on power supply module until V1 is 0V

2.5 DC GENERATOR EXPERIMENTS

2.5.1 No Load Experiment

Experiment Steps:

a. Determine V = V(Ip), n = C, Ia = 0

Set the circuit according to Figure 2.3

Start motor according to 1.4.1

Hold the rotation of motor and note the value

Change the value of A4 by setting Rp on field coil of DC Generator until

certain value and note the value of A4 and V2

b. Determine V = V(n), Ip = C, Ia = 0



Hold A4 and note the value



Change the value of n by setting V1 until certain value and note the value

of n and V2

2.5.2 Load Experiment

Experiment Steps:



Hold the rotation of motor and note the value

Hold A4 and note the value

Rb on maximum position


Set Rb and note the value of A3 and V2 for every change of Rb



MODULE 4

SYNCHRONOUS GENERATOR

Objective:

1. Understand construction of synchronous generator

2. Understand synchronous generator working principle

3. Understand the characteristic of phasor diagram in difference load types

4.1 INTRODUCTION

4.1.1 Syncrhonous Generator

The electrical machine can be defined as a device that converts electrical

energy into mechanical energy or mechanical energy into electrical energy. An

electrical generator can be defined as an electrical machine that converts

mechanical energy into electrical energy. It typically consists of two parts: stator

and rotor. The rotating and stationary parts of an electrical machine can be called

as rotor and stator respectively. The rotor of synchronous generator acts as a

power-producing component and is called as a field windings. The

electromagnets or permanent magnets mounted on the rotor are used to provide

magnetic field of an electrical machine. The stator of synchronous generator

called as an armature windings because the main voltage is induced in stator

windings. The magnetic poles on the rotor can be of either salient or non-salient

(cylindrical) construction.

Figure 4.1 A non-salient and salient two pole rotor of synchronous generator



Stator Construction:

The stationary part of the machine is called Stator. It includes various parts like

stator frame, stator core, stator windings and cooling arrangement. They are

explained below in detail.

a. Stator Frame: It is the outer body of the machine made of cast iron, and it

protects the inner parts of the machine.

b. Stator Core: The stator core is made of silicon steel material. It is made

from a number of stamps which are insulated from each other. Its function

is to provide an easy path for the magnetic lines of force and accommodate

the stator winding.

c. Stator Winding: Slots are cut on the inner periphery of the stator core in

which 3 phase or 1 phase winding is placed. Enameled copper is used as

winding material. The winding is star connected. The winding of each

phase is distributed over several slots. When the current flows in a

distributed winding it produces an essentially sinusoidal space distribution

of EMF.

Rotor Construction:

The rotating part of the machine is called Rotor. It includes various parts like rotor

core, rotor windings, Slip rings, Brushes, Bearing, and Shaft. They are explained

below in detail:

a. Rotor Core: The rotor core is made of silicon steel stampings. It is placed

on the shaft. At the outer periphery, slots are cut in which exciting coils

are placed.

b. Rotor Winding: It is placed on the rotor slots, and current is passed

through the winding in such a way that the poles are formed according to

the requirement.

c. Slip Rings: Slip rings provide DC supply to the rotor windings.

d. Brushes: Brushes are made of carbon, and they slip over the slip rings. A

DC supply is given to the brushes. Current flows from the brushes to the

slip rings and then to the exciting windings.

e. Bearing: Bearings are provided between the shaft and the outer stationary

body to reduce the friction. They are made of high carbon steel.



f. Shaft: The shaft is made of mild steel. Mechanical power is taken or given

to the machine through the shaft.

There are two types of rotor construction, namely the salient pole type and the

cylindrical rotor type.

Figure 4.2 Rotor

4.1.2 Excitation System

A DC Current must be supplied to the field circuit on the rotor. Since the rotor

is rotating, a special arrangement is required to get the DC Power to its field

windings. There are three methods of excitation:

Figure 4.3 A brushless Excitation circuit



a) Slip rings link the rotor’s field winding to an external dc source

b) Brushless Exciter -- An ac generator with fixed field winding and a rotor

with a three phase circuit diode/SCR rectification supplies dc current to the

field windings

c) Pilot Exciter -- To make the excitation of a generator completely

independent of any external power sources.

Many synchronous generator that include brushless exciters also have slip

rings and brushes, so that an auxiliary source of dc field current is available in

emergencies.

4.1.3 Equivalent Circuit

Figure 4.4 The Equivalent Circuit of a synchronous Generator

Vf : Field Voltage (DC)

Rf : Field Variable Resistance

If : Field Current

Lf : Field Self-inductance

Ea : Induced Voltage

Ra : Armature Resistance

Ia : Armature current

Xs : Synchronous Reactance

Vɸ : Terminal Voltage



4.1.4 Power Losses

A Synchronous generator is a synchronous machine used as a generator. It

cinverts mechanical power to three-phase electrical power. The source of

mechanical power, the prime movers, may be a diesel engine, a steam turbine, a

water turbine, or any similar prime movers. In real life, not all the mechanical

power going into synchronous generator becomes electric power out of the

machine. The difference between input power and output power represents the

losses of the machine.

Figure 4.5 The power-flow diagram of synchronous generator




1. 1 power supply

2. 1 DC voltmeter/ammeter

3. 1 AC voltmeter

4. 1 AC ammeter

5. 4 field rheostat

6. 1 synchronous motor/generator

7. 1 DC motor/generator

8. 1 synchronous machine

9. 1 DC machine

10. 1 synchronizing module

11. 3 Variable Resistance

12. 3 Variable Inductance

13. 1 frequency meter

Figure 4.6 No-Load Experiment circuit



4.3 EXPERIMENT STEPS:

4.3.1 No-Load Experiment

1. Arrange circuit based on Figure 4.6

2. Make sure the Rheostat is in full-load condition

3. Make sure the synchronizing module is off.

4. Turn on the main power supply.

5. Increase the AC voltage value gradually and very slowly so that there is no

large current surge in the stator. Pay attention to the DC ammeter!

Maximum current is 3 A. If the current has reached 3 A, the voltage should

not be increased again

6. Set the AC voltage so that it reaches the desired current value (A2). Record

V2 and A3 values

7. repeat step number 6 with a different current value (A2).

8. Turn off the supply source after all data has been taken.

4.3.2 With-Load Experiment

1. Arrange no-load experiment circuit and modifying it with:

a. Remove the cable at [1,2,3] Sync Module.

b. Reconnect the cable at [2,3] Sync Module to [1,2] Freq. Meter

c. Connect [1,2,3] Sync Module to [4,5,6] PF Meter (1->4; 2->5; 3->6)

d. Connect [1,2,3] PF Meter to different (-) Variable Inductance

e. Connect (+) Variable Inductance to (-) Variabel Resistance.

f. Connect different (+) Variable Resistance to make one node

g. Turn on the Synchronizing Module

h. Turn on the main power supply.

i. Record the value of A3,V2,PF Meter and Frequency Meter

j. repeat step (i) with a different laod value (R ohm +L Henry).

k. Turn off the supply source after all data has been taken.



MODULE V

PARALLEL OPERATION OF SYNCHRONOUS GENERATOR

Objectives:

1. Know and understand how to paralleling the synchronous generator

5.1 INTRODUCTION

Parallel operation of generators is by far the most common form of operation.

Generators may be operated in parallel on a small scale, e.g. two or three

generators operating in parallel to provide power to a remote community, or large

scale, e.g. the north american power grid

Benefits of parallel operation include:

Redundancy: failure of one unit does not affect the integrity of the power

supply, generators may be taken out of service for preventative maintenance

Scaling: many units can combine to provide a power demand, rather than

requiring fewer very large generators

Resource management: generators can be located and operated to best meet

the generating conditions, instead of having to be located and operated to meet

the requirements of a local load. An example of this may be a nuclear power

plant, which may take many weeks to bring up to full operating conditions.

Using a nuclear generating station at full power to meet a "base load" with

smaller more rapid response generators is one way to supply fluctuating load

requirements.

Efficiency: Generators operating at full load are more efficient than those

operating at low loads. It is more efficient to meet a changing load by adding

or removing smaller generators than having a single large generator operating

inefficiently.

The condition required for paralleling:

The rms voltage of the two generator must be equal

The two generators must have the same phase sequence

The phase angles of two a phases must be equal



The frequency of the new generator (oncoming generator) must be slightly

higher than the frequency of the running system

Voltage and Frequency Relationship

When considering synchronous generators operating alone it becomes

clear that the terminal voltage of the machine is dependent on the reactive power

being supplied to the load. When supplying more reactive power, the termial

voltage falls. In general, the effect of changes to terminal voltage with reactive

load can be plotted as shown. Increasing the inductive load on the generator

reduces the terminal voltage, adding capacitance increases the terminal voltage.

Reductions to the terminal voltage can be compensated by increasing the no load

voltage E

Figure 5.1 Generator Voltage Variation With Reactive Power

Infinite Bus:

The infinite bus is a useful concept that summarizes how most people

already view the power grid. It can be applied when the power grid is sufficiently

large that the action of any one user or generator will not affect the operation of

the power grid.

In an infinite bus:

System frequency is constant, independent of power flow

System voltage is constant, independent of reactive power consumed or

supplied



An infinite bus assumed in many small electrical applications. As an example,

we take for granted that the voltage supply to a residential outlet will be 120V

and 60Hz

Figure 5.2 f-P and V-Q plots for an infinite bus

5.2 EXPERIMENT STEPS

1. Arrange with-load experiment circuit and modifying it with:

a. Remove the Ampere meter (A3).

b. Connect [1,2,3] Sync Motor to [4,5,6] Sync Module.

c. Connect [4,5,6] Sync Module to [2,1,3] Power Supply AC (220/380 V

– 10 A is infinite bus PLN)

d. Connect [4,6] Sync Module to [1,2] Frequency Meter

e. Connect [1,3] Sync Module to [3,4] Frequency Meter

f. Connect [1,3] Sync Module to Voltmeter (V3)

g. Connect [6,4] Sync Module to Voltmeter (V2)

h. Equalize the synchronous generator voltage value to be worth 380 V

(equal to PLN electricity Vphase).Mengukur nilai frekuensi listrik PLN.

i. adjust the synchronous generator's electrical frequency value so that it

is slightly higher than PLN's electricity frequency

j. Turn on Sync Module when all three conditions (Phase sequence,

Voltage value and Frequency) are done. (paralleling done)



MODULE 7

INDUCTION MOTOR STARTING

OBJECTIVES :

1. Understand the characteristics of rotor current starting.

2. Understand the methods of induction motor starting

6.1 INTRODUCION

To get the large starting torque in induction motor in squirrel cage rotor or

wound rotor, it needs large starting current 5 to 10 times from steady-state current

approximately.

If the motor supply comes from the main feeder there will usually be no

problem with the start of the electric motor. However, it will be a problem if a

large capacity electric motor is placed in an area far from the main feeder.

However, there are some cases where the motor capacity is too large compared to

supply capacity, especially if large capacity electric motors combine with small

capacity auxiliary motors in a production process that is likely to run

simultaneously. Calculation of the amount of the starting motor electric current

neeed to determine the effect on the production process and the system that is

being run.

Figure 6.1 Graph of rotor current to speed of rotor

The start current have reactive characteristics, whose values are usually

assumed. Therefore the power factor at start is usually lagging by 15 to 30 percent

of the nominal power factor. To keep the motor working and the contactor does

not operate, the voltage must not fall more than 70% of the nominal voltage.

However, if the safety and continuity factors are very important, the voltage drop



is limited to less than 10% of the nominal voltage. To reduce the starting current

which very large, statcom (static compensator) can be used.

During the starting time period, the motor in the system will be considered

a small impedance connected to a bus. The motor will take a large current from

the system, about six times its rating current, and can cause voltage drop on the

system and cause interference with other load operations. So it needs starting

method to reduce the voltage drop

a. Direct On Line Starter

Direct On Line starter is a direct starting. This method used for ac motors that

have a small power capacity. The meaning of direct connection is when the motor

that will be run directly switched on to the voltage source mesh according to the

nominal motor voltage. It means that there is no need to adjust or reduce the

voltage at starting.

The starting current is from 4 to 7 from the full load current. It needs to

calculate the current at the start of the motor, as well as the range of overload. One

of the advantages of the DOL method is the low capital cost. Capital costs the

one-time purchasing equipment when it bought.

b. Star Delta Starter

This starter reduces the surge of current and torque at start. Consist of 3

contactors, namely Main Contactor, Star Contactor and Delta Contactor, Timer for

transfer from Star to Delta and an overload relay. At start, the starter is connected

in Star. The stator coil only receives a voltage of about 0.578 (one per root three)

from the line voltage. So the current and torque produced will be smaller than

DOL Starter. After approaching the normal speed, the starter will move to become

Delta connected. This starter will work well if the start of the motor doesn’t have

any load.



Figure 6.2 Star Delta Starter Diagram

c. Autotransformer

The method is autotransformer inserted into the motor line voltage reduces

the voltage to the motor terminal depending on the selected tap. After starting the

motor, the transformer is released. Starting this way is by connecting the motor to

the lowest autotransformer secondary voltage tap. After a while the motor is

accelerated, the autotransformer is disconnected from the circuit and the motor is

connected directly at full voltage.

In the starter autotransformer, the current flowing is

where :

Vm = Secondary voltage from AutoTransformer

V1 = Supply voltage

IDOL = Direct on line current

The starting characteristics of the autotransformer are as follows:

The motor terminal voltage is less than the line voltage (by the transformer

ratio).

The current of the motor exceeds the current starting (with the opposite of

the transformer ratio).

Initial torque is reduced by the square of the terminal voltage.



d. Soft Starter

Soft Starter is used to adjust or smooth the start of the electric motor. The

principle of work is to regulate the voltage that enters the motor. First, the motor

is only given a low voltage so that the current and torque are also low. At this

level the motor is moves slowly and does not cause surges. Then the voltage will

be increased gradually to the nominal voltage and the motor will rotate with a

nominal RPM condition.

The softstarter main component is the thyristor and the circuit that regulates

the thyristor trigger. The thyristor output can be set via its pin gate. The circuit

will control the voltage level that will be released by the thyristor.

Figure 6.3 Thyristor Firing Angle Configuration

In addition, Softstarter also have a soft stop feature. When the motor stop, the

voltage is also reduced slowly or not just released like the starter using the

contactor.



Figure 6.4 Soft Starter Diagram

e. Frequency Drive

Frequency Drive is often called VSD (Variable Speed Drive), VFD (Variable

frequency Drive) or Inverter. VSD consists of two main parts, namely the AC

voltage rectifier (50 or 60 HZ) to DC and the reverse from DC to AC voltage with

the desired frequency. VSD utilizes motor properties are as follows :

120

Where :

RPM = speed of motor rotation

F = frequency

P = number of poles

Thus if the frequency of motor is increased it will increased the motor

speed and also the opposite.



7.2 EXPERIMENT EQUIPMENT & TOOLS

1 NE7010 MACHINE TEST SET

1 DC machine

1 Three-phase quirrel cage induction motor



7.3. EXPERIMENT

Asynchronous motor start with Y-∆ switch

7.3.1 EXPERIMENT CIRCUIT

Figure 6.5 Asynchronous Motor Circuit.

Figure 6.6 DC Generator Circuit



7.4 EXPERIMENT STEPS :

a. Ensure that all equipment is ready to used

b. Make sure that the rotor resistance is installed in the circuit by rotating

counterclockwise

c. Select "supplies selector" to "fixed (DOL)" position

d. Turn on the power supply by raising the power supply circuit breaker

(MCB) to the "ON" position

e. Select "star delta switch" to the delta position

f. Press the "Supply Reset" button

g. Press the "Start Button" button to start run the motor

h. Observe and record the magnitude of the stator peak current (A1), the

steady state stator current (A1), the motor rotational speed (n), and the

time it takes for the current to reach a stable condition.

i. Turn off the machine by pressing the "Stop Button" for the next the data.

j. Select "star delta switch" to star position

k. Repeat steps f, g, and h

l. When the observation is complete, turn off the motor by pressing the "Stop

Button" button and turn off the power supply by lowering the power

supply circuit (MCB) to the "OFF" position



MODULE VIII

ONE PHASE TRANSFORMER

Objectives:

1. Understand construction of Transformer and parts of it

2. Obtain magnetization circuit of Transformer

3. Obtain equivalent impedance of Transformer

4. Know the effect of loading on Transformer

8.1 PRELIMINARY

8.1.1 General Understandings

A transformer is an electromagnetic device that converts the AC voltage to a

level to AC voltage at another voltage level which works the principle of

electromagnetic induction without changing the frequency.

In the field of electric power the use of transformers is grouped into:

1. Power Transformer

2. Measurement Transformer

3. Testing Transformer

The work of a transformer based on electromagnetic induction, requires the

presence of magnetic couplings between the primary and secondary circuits. This

magnetic coupling is an iron core where the joint flux is carried out.

The basic construction of transformer consists of a primary coil and a

secondary coil wrapped around an iron core which is electromagnetically

connected to each other. There are two types of iron core forms, namely the core

and shell types.

The working principle of a transformer is that when the primary coil is

given an AC voltage, a magnetic flux will emerge which flows on the iron core,

then it will induce a voltage in the secondary coil.



Figure 8.1 Core type Transformer (left) and Shell type Transformer (right)

8.1.2 Ideal Transformer

In the ideal transformer, there is no energy that converted into other forms

of energy so that the electrical power in the secondary coil is equal to the

electrical power in the primary coil. In ideal transformer, the ratio between

voltages is proportional to the ratio of the number of turns. Thus it can be written

with the following equation:

Pp = Primary Power (Watt)

Ps = Secondary Power (Watt)

Vp = Primary Voltage (Volt)

Vs = Secondary Voltage (Volt)

Ip = Primary Current (Ampere)

Is = Secondary Current (Ampere)

Np = Numbers of Primary Coil

Ns = Numbers of Secondary Coil

However, in reality there is no ideal transformer. This occur because there

are always losses which include the following:

1. Copper losses; losses caused by heating arising due to the current flowing on

the conductor wire resistance found in the primary and secondary coils of the



transformer. Copper losses are proportional to the square of the current

flowing in the coil.

2. Eddy current losses; losses caused by heating due to the emergence of eddy

currents contained in the transformer iron core. These losses occur because

the iron core is too thick so that there is a voltage difference between its sides

so the current flows in circles on that side.

3. Hysteresis losses; losses associated with the rearrangement of magnetic fields

in the iron core every half cycle, so that fluxes occur back and forth on the

iron core. These losses are not linear and complex

4. Flux Leakage; Flux leakage occurs because there are several fluxes that do

not penetrate the iron core and only pass through one of the transformer coils.

This flux will produce self inductance on the primary and secondary windings

so that it will affect the power value supplied from the primary side to the

secondary side of the transformer.

8.1.3 Equivalent Circuit

Not all fluxes (Ф) produced by magnetic currents IM are joint fluxes (ФM),

some of them only include primary coils (Φ1) or secondary coils (Φ2). In the

circuit model (equivalent circuit) used to analyze the workings of a transformer,

the presence of leaky fluxes Ф1 and Ф2 is shown as reactances X1 and X2. While

the loss of resistance is shown by R1 and R2. Thus the 'model' series can be

written as follows:

Figure 8.2 Equivalent Circuit

if the secondary circuit parameters are expressed in the primary price, the

price needs to be multiplied by a2 factor.



Now the circuit model becomes as seen in the following figure:

Figure 8.3 Equivalent Circuit seen from Primary Side of Transformer

8.1.4 Voltage Regulation and Efficiency

Through existing calculations, it can be described the phasor diagram for the

three load conditions as follows:

Figure 8.4 The phasor diagram of transformer with (a) resistive load (b) inductive

(c) capacitive:

Vp / a > Vs, so VR in transformers must be greater than 0. (Unity)

Vp / a > Vs for lagging load, so VR in transformers must be larger than 0.

Vs > Vp / a, so VR in transformers must be less than 0. (Leading)



The reactive load power will predominantly influence the transformer

secondary voltage. Inductive loads will cause a voltage drop quite significant on

the secondary side of the transformer (V2). The capacitive load will causes

secondary voltage (V2) to be greater than the primary voltage (V1).


1 Transformer module

1 voltage source module

2 AC ammeter module (3/5 Aac)

2 AC voltmeter module (0-250 Vac)

1 resistance variable module

1 inductance variable module

1 capacitance variable module

1 Wattmeter

1 cos φ meter

Cable jumper

8.3 EXPERIMENTS

8.3.1 No Load Experiment

Steps:

1. Arrange a series of experiments starting from the primary side then secondary

2. Turn on the power supply. Then set the input voltage to zero value gradually.

3. Write: Io (A1), V2, Po for each increase in V1.

4. After the experiment is complete, lower the power supply.

8.3.2 Short Circuit Experiment



Steps:

1. Arrange a series of experiments starting from the primary side then secondary

2. Double check the circuit and make sure there are no errors in the circuit. Turn

on the power supply.

3. Write V1, I2, and Phs for each I1 increase by adjusting the power supply.

4. After the experiment is complete, turn off the power supply

8.3.3 Loaded Experiment

Steps:

1. Arrange a series of experiments.

2. Turn on the power supply until the nominal (seen in V1) and make sure it is

constant.

3. Turn on the load gradually then write the measurement results based on what

is needed.

4. After the experiment is complete, turn off the power supply and gather tools

and things that used before.



MODULE IX

THREE PHASE TRANSFORMER

Objectives:

1. Know some windings configurations in Transformer.

2. Know the ration between primary and secondary voltage in some

configurations.

9.1 PRELIMINARY

Almost all electricity generated and distributed by a three-phase AC system.

Therefore, we have to know how to use the transformer in a three-phase AC

system. There are two types of three-phase transformers, which use 3 single-phase

core type transformers. Another type uses a shell type transformer and consists of

3 pairs of primary-secondary coils on each side.

Figure 9.1 Shell type (left) & Core type (right)

These three-phase transformer can be connected in such this ways:

1. Wye-Wye configuration

In this configuration, phase-to-phase voltage ratio (L-L) on primary and

secondary side is equal to the ratio of each transformer. Thus, there is a phase

shift of 30° between phase-to-neutral voltage (L-N) and phase-to-phase

voltage (L-L) on the primary and secondary sides. This configuration will be

very good only if the load inside is balance, because, in a balanced load

condition, the neutral current (IN) will be equal to zero. And if there is an

unbalanced condition, there will be a neutral current which can cause losses.



√3

The primary phase voltage is proportional to the secondary phase voltage and

the ratio of the transformer windings, the comparison between the primary

voltage and the secondary voltage for this configuration is:

√3

√3

2. Wye-Delta Configuration

This configuration is used on transmission lines as voltage risers. The ratio

between the secondary and phase-to-phase primary voltage is √

times the

ratio of each transformer. There is a 30° angle between phases voltage

between primary and secondary which means that the Y-Δ transformer cannot

be paralleled with the Y-Y transformer or Δ-Δ transformer. In this

configuration, the voltage of the primary wire-to-wire is proportional to the

primary phase voltage (VLp = √3VPp), and the voltage of the secondary

wire-to-wire is equal to the phase voltage (VLs = VPs), so that the voltage

ratio in the Y-Δ relationship is:

√3

√3



3. Delta-Wye Configuration

This configuration is used to reduce the voltage from the transmission level to

the low voltage level. In Δ-Y, the voltage of the coil to the primary coil is the

same as the primary phase voltage (VLp = VPp), and the secondary voltage

(VLs = √3VPs), the voltage ratio in this configuration is:

√3 √3

4. Delta-Delta Configuration

In this configuration, the coil voltage to the coil and the phase voltage are the

same for the primary and secondary transformers (VRS = VST = VTR = VLL),

the voltage ratio is:

9.2 THE USED EQUIPMENT & TOOLS

3 Transformer module

1 voltage source module



3 AC ammeter module (3/5 Aac)

3 AC voltmeter module (0-250 Vac)

3 Variable Resistance module

Cable jumper

9.3 EXPERIMENTS

9.3.1 Wye-Delta Experiments

Steps:

1. Arrange the circuit according to the circuit plan above

2. Turn on the power supply

3. Take a note the voltage number in the primary coil measured in the voltmeter

4. Take a note the voltage number in the secondary coil measured in the

voltmeter

5. Turn off the power supply

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