SEGI COLLEGE, SUBANG JAYA

in collaboration with University of Sunderland

COURSEWORK Laboratory Report (20%)

ELX 214Electrical Power System

& Machines

SUBMISSION DATE:

NAME: ______________________________________________

ID: ___________________________________________________

GROUP MEMBERS:

_______________________________________________________

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LABORATORY ETHICS

1. Sign in the attendance sheet.

2. A student coming in 20 minutes after laboratory session has started will be considered ABSENT.

3. Switch off the hand-phone during laboratory sessions.

4. No eating and drinking inside the laboratory

5. Forbid make noisy or interfere other student.

6. Students must obtain PERMISSION from the instructor prior to leaving a laboratory session.

7. Students must do PRE-LAB assignments and understand the relevant worksheets, PRIOR to attending the relevant laboratory session.

8. Data acquired must approved by instructor (stamped and signed).

9. Data acquired by other students are not allowed and will be penalized heavily.

10. After complete the experiment, students must tidy the table, chair and equipments before leave the laboratory.

ELX214 ELECTRICAL POWER SYSTEMS & MACHINES LABORATORY - REPORT EVALUATION

No Criteria Excellent4

Good3

Poor2

Very Poor1

Weightage

Score

1. Report format & Organization General

format and structure

Cover page, title, objective

presentation and tidiness

Complete report and fully complied with criteria. Nice presentation.

Complete report and fully complied with criteria.

Some criteria are missing. Poor presentation.

Major criteria are missing, untidy, bad presentation

2

3. Results Results in the

form of data, graphs etc.

Complete and accurate results, neatly presented

Complete and neatly presented, minor mistakes

Incomplete result, major mistakes

Major data are missing

4

4. Discussion Ability to

present, inteprete, and analyse result

Compare with theoretical values @ ideal conditions

Answer questions or explain observations posed on lab sheet

All points of discussion on the results obtained covered and elaborated.

Some points of discussion on results obtained covered and elaborated.

Some points of discussion on results obtained covered but not properly elaborated.

Very few points of discussion, not properly elaborated

4

5. Conclusion Provide

answers to objectives stated earlier

Ability to learn something from the experiment

The closing paragraph summarizes and draws a well developed conclusion

The closing paragraph summarizes and draws a sufficient conclusion

The closing paragraph attempts to summarize but draws a weak conclusion

Concluding paragraph is not apparent

2

6 Attitudes Punctualit

y to the lab

Cooperation with group

Excellent Good Fair Poor 2

No Criteria Excellent4

Good3

Poor2

Very Poor1

Weightage

Score

members.

Total Score(max 56 ) = SUM{Score x Weightage}

Total Marks (max 20)= Total Score/2.8

*any part of the report suspected of plagiarism will be given zero mark.

Lecturer : ______________________________________________

Signature : _______________________________

Date: ________________

EXPERIMENT 1:DC MACHINES LABORATORY

1.1 MEASUREMENT OF THE WINDINGS RESISTANCE This experiment can be performed on various DC Machine.

1.1.1 OBJECTIVES Calculate the winding resistance of various DC machines with the Volt-Ampere method (Ohms Law).

1.1.2 THEORETICAL REVIEW The windings resistance cause internal voltage drops that reduce the machine’s efficiency. Therefore it must be as low as possible. It is calculated by applying known DC voltages and measuring the resulting current flows.

1.1.3 FORMULAE

PARAMETER SYMBOL UNIT Winding Voltage V Volts Winding Current I Amperes Winding Resistance R Ohms

R=V/ I

1.1.4 COMPONENTS DC Compound Excitation Machine Model A4240 DC Series Excitation Machine Model A4242 DC Shunt Excitation Machine Model A4244 Power Supply Model A0240 Cables Model A4890 Cables Support Model A4891 Voltmeter With adequate range for this test Ammeter With adequate range for this test

1.1.6 EXECUTION

The components must be connected as shown in the circuit diagrams

and must be grounded.

MANUAL DATA COLLECTION AND ANALYSIS

- Set the D.C. windings voltage PS3 = 0 V.

- Switch on the power supply.

Increase PS3 gradually by operating on the front knob. It must be

increased in 2% steps up to 10% max.

Do not exceed 10 % of nominal winding voltage to avoid excessive

winding temperature

- Measure the voltage and current for any step and enter them in the

worksheet tables.

- Repeat the above steps for all windings and calculate their resistance

with the formula given above.

1.2 MAGNETIC CHARACTERISTICS

This experiment can be performed on shunt excitation DC generators.

1.2.1 OBJECTIVES

Plot the magnetization characteristics of a DC machine.

1.2.2 THEORETICAL REVIEW

This experiment shows the electromotive force Eo against the

excitation current le.

The resulting graph shows that for the same value of excitation current

there are two different values of electromotive force, one for the

ascending and one for the descending curves. Usually the medium

value of Eo is considered.

The area enclosed in the magnetization loop represents the power

losses for magnetic hysteresis (residual magnetism) in the armature

iron.

1.2.3 MEASUREMENTS

PARAMETER SYMBOL UNIT

Armature Voltage V Volts

Excitation Current le Amperes

Speed n rpm

1.2.4 COMPONENTS

DC Shunt Excitation Machine Model A4244

Squirrel Cage Three Phase Drive Motor Model A4220

Power Supply Model A0240

Cables Model A4890

Cables Support Model A4891

Coupling Base Model A4840

Ammeter With adequate range for this test

Voltmeter With adequate range for this test

RPM Meter

1.2.6 EXECUTION

The components must be connected as shown in the circuit diagrams

and must be grounded. The DC machine is mechanically coupled to the

driving motor.

MANUAL DATA COLLECTION AND ANALYSIS

- Set the excitation voltage PS4 and drive motor supply voltage PS1 =

0

- Switch on the power supply and adjust PS1 to nominal motor voltage.

- When the motor is up to speed gradually increase the excitation

current from 0% to 100% in 10% steps by adjusting PS4.

- At each step enter in the worksheet table the values of voltage and

excitation current

- Repeat the above steps while decreasing the excitation current from

100% to 10%

- Plot the graph

1.3 NO LOAD TEST

This experiment is performed on shunt and compound excitation DC

Machines.

4.3.1 OBJECTIVES

The experiment is designed to measure the mechanical plus iron

losses.

4.3.2 THEORETICAL REVIEW

The mechanical losses are caused by friction on bearings, brushes and

ventilation. They are not affected by the load and depend only on

rotation speed. Copper losses may be

disregarded due to the low current absorbed in these conditions.

When in rotation, the rotor is subject to the alternating flux generated

by the excitation

winding on the stator and this causes the iron losses due to hysteresis

and Eddy currents.

1.3.3 FORMULAE

PARAMETER SYMBOL

UNIT

Armature Voltage Va Volts

Armature Current Ia Amperes

Input Power (no-load) P Watts

Mechanical Losses Pm Watts

Magnetic Losses Pfe Watts

P=Va * Ia = Pm + PFe

1.3.4 COMPONENTS

DC Compound Excitation Machine Model A4240

DC Shunt Excitation Machine Model A4244

Power Supply Model A0240

Cables Model A4890

Cables Support Model A4891

Coupling Base Model A4840

Ammeter With adequate range for this test

Voltmeter With adequate range for this test

RPM Meter

1.3.6 EXECUTION

The components must be connected as shown in the circuit diagrams

and must be grounded.

MANUAL DATA COLLECTION AND ANALYSIS

- Set the excitation voltage PS4 and armature voltage PS3 = 0

- Switch on the power supply and adjust PS4 to nominal voltage.

Start the motor by gradually increasing the armature voltage PS3

- When the motor is at nominal speed measure the current and voltage

and enter the values in the worksheet table

- Decrease step by step the armature voltage and adjust the excitation

voltage to keep the motor at nominal speed

- Choose a suitable stepping value and repeat the above procedure at

each step

- The experiment is completed when the armature voltage is so low

that the motor begins to slow down

- Plot the graph

1.4 DETERMINATION OF WORKING CHARACTERISTICS

This experiment can be performed on various DC motors

1.4.1 OBJECTIVES

Find the motor’s working characteristics by loading it with a brake

dynamo.

Measure its torque and mechanical power at various load conditions

Calculate the motor efficiency

Plot the load characteristics for analysis

1.4.2 THEORETICAL REVIEW

The motor drives a loaded brake dynamo whose stator is mounted on

bearings and capable of rotating. Since the torque between its stator

and rotor is proportional to the generated electrical power, a

dynamometer installed on its stator to counteract its rotation gives a

reading of the motor’s torque.

The torque’s value can be read in two ways:

- by a load cell connected to a torque meter

- by an arm and weights system

The torque can be varied by varying the dynamo’s electrical load.

The measured torque includes the losses on bearings, ventilation and

on collector brushes. However, they are small and do not affect

significantly the experiments results.

1.4.3 FORMULAE

PARAMETER SYMBOL UNIT

Armature Voltage Va Volts

Armature Current Ia Amperes

Excitation Current le Amperes

Arm Length a m

Weight G N

Torque T Nm

Speed n mm-i

Excitation Current le A

Input Power Pi Watts

Output Power P0 Watts

Efficiency

T= G*a

Po = 2 π n T/60

Pi= Va*(Ia + Ie)

= Po/Pi

1.4.4 COMPONENTS

DC Compound Excitation Machine Model A4240

DC Series Excitation Machine Model A4242

DC Shunt Excitation Machine Model A4244

Braking DC Generator Model A4430

Coupling Base Model A4840

Power Supply Model A0240

Resistive Load Model A4510

Starting Rheostat Model A4610

Excitation Rheostat Model A4630

Cables Model A4890

Cables Support Model A4891

Ammeter (Al, A2) With adequate range

for this test

Voltmeter (V) With adequate range

for this test

RPM Meter

1.4.6 EXECUTION

The components must be connected as shown in the circuit diagrams

and must be grounded. The motor must be coupled to the brake

dynamo.

MANUAL DATA COLLECTION AND ANALYSIS

- Set the armature voltage PS3 and excitation voltage PS4 = 0 and

the starting and excitation rheostats to maximum resistance.

- Level the dynamo by putting weights and counterweights on the

graduated arm. Lock the counterweight.

- Switch the power supply on. Start the motor and ensure that the

rotation is opposite to that caused by the weight. If necessary,

exchange weights. Reduce the starting rheostat gradually.

- Adjust the speed to nominal value by varying the excitation

rheostat.

- Move the weight to the maximum value indicated in the attached

worksheet table.

- Load the dynamo by varying the resistive load and level it by

adjusting the excitation voltage PS4.

- Check and if necessary adjust nominal voltage PS3

- Enter the read values in the worksheet table

- Move the weight to the other measurement values and repeat

the above procedure

- Plot the graphs of the load characteristics

- NOTE: measurements should be made as quick as possible to

avoid overheating.

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CONCLUSION:

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