Fundamentals of Management

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LONG REPORT

EXPERIMENT 5: DC MACHINES

ELECTRICAL MACHINES

EDB3023

LECTURER:        DR ZUHAIRI BIN BAHARUDIN                        

                        DR PERUMAL A/L NALLAGOWNDEN

NAME:                 FAZNOL FAZLY BIN ZAINOL NAHAR

MATRIC ID:        22284

SESSION:         TUESDAY / 10:00 AM – 12:00 PM

GROUP:                 A7

RUBRIC FOR LONG REPORT

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INTRODUCTION

Background

        In this lab experiment, there are three parts that are going to be considered. The three parts are measurement of the winding resistance, magnetic characteristics, and the no load test. For the measurement of winding resistance, a known DC winding voltage are going to be applied and the corresponding winding current will be measured. From the value obtained, the winding resistance can be calculated. The magnetic characteristics is where a known DC winding current are applied and the corresponding winding voltage and rpm are calculated. The last part which is the no load test is where we apply a DC voltage source until the machines rotate at the speed of 3000 rpm. The armature current and voltage are recorded and the power is calculated.

Objectives

1. Measurement of The Windings Resistance:

• Calculate the winding resistance of shunt DC machines with the Volt-Ampere method (Ohm's Law).

1. Magnetic Characteristics:

• Plot the magnetization characteristics of a DC machine.

1. No Load Test:

• The experiment is designed to measure the mechanical plus iron losses.

Scope

1. Measurement of The Windings Resistance:

• Considering the winding resistance of the DC machine by applying a known winding voltage and a measured winding current.

1. Magnetic Characteristics:

• Considering the magnetization of DC machine by applying a known winding current and a measured winding voltage and speed of the machine. The graph of winding voltage vs excitation current is plotted to see the magnetization characteristics of DC machine.

1. No Load Test:

• The experiment is designed to measure the mechanical plus iron losses. A voltage source is applied until the speed of the machine reach 3000 rpm and the armature voltage and current are measured. The power (no load) is then calculated.

THEORETICAL KNOWLEDGE

Measurement of The Windings Resistance

        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.

        Formulae involved:

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Magnetic Characteristics

        This experiment shows the electromotive force Eo against the excitation current Ie. 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.

Formulae involved:

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No Load Test

        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.

Formulae involved:

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PROCEDURE

MEASUREMENT OF THE WINDINGS RESISTANCE

1. Components:

DC Shunt Excitation Machine                 Model A4244

Slip Ring Three Phase Drive Motor                 Model A4223

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. Theoretical Diagram:

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1. Connection Diagram:

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Fig. 1 Connection Diagram

1. Conducting the Experiment:

1. The component was connected as shown in Fig. 1.
2. The D.C windings voltage PS3 was set to 0V.
3. The power supply was switched on. The PS3 voltage was increased gradually by adjusting the knob.
4. The voltage and current was measured and tabulated
5. Step 4 was repeated and their resistance was calculated and the values are tabulated.

MAGNETIC CHARACTERISTICS

1. Components:

DC Shunt Excitation Machine                 Model A4244

Slip Ring Three Phase Drive Motor                 Model A4223

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