Ee 472l Expt 2.Docx

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EE 472 Laboratory

Experiment No._2_

Separately Excited DC Generator

Performed by : Duldulao, Caryl Xyra L.
Date Performed : November 27, 2012
Date Submitted : December 4, 2012

Engr. Timoteo V. Limsiaco
Laboratory Instructor

I. MATERIALS:

* Digital Wattmeter (DWM)
* Digital Multi-meter (DMM)
* Variac
* Plastic Coupling
* 10 Alligator Clips (Big Wire)
* 10 Banana Plug (Big Wire)
* 1 Banana Plug with Flat Plug Combination

II. WIRING DIAGRAM:

Circuit Diagram of the Connections

Actual Wiring of the Shunt Generator with Connected Loads

III. DATA AND RESULTS:

VS| Loads| VFL| IA| IF| IL| Eg| VnL| %VREG|
30 V| 1| 40.2| 1.3| 0.13| 1.17| 1.69| 40| 0.74%|
40 V| 2| 48.2| 3.1| 0.18| 2.92| 4.03| 40| 20.398%| 50 V| 3| 55.5| 4.6| 0.22| 4.38| 5.98| 40| 27.9%|
60 V| 4| 59.7| 6.31| 0.27| 6.04| 8.203| 40| 32.998%| 70 V| 5| 60.6| 8.22| 0.31| 7.91| 10.686| 40| 33.99%|

PDEV| PDEL| | RA| 1.3 Ω|
52.39 W| 1.977 W| | Rf| 212 Ω|
149.42 W| 11.767 W| | RSE| 0.6 Ω|
255.3 W| 26.192W| | | |
367.707 W| 49.456W| | | |
448.132 W| 84.526 W| | | |

CALCULATIONS:

Eg=IaRa

Ea1=1.31.3=1.69V

Ea2=3.11.3=4.03V

Ea3=4.61.3=5.98V

Ea4=6.311.3=8.203V

Ea5=8.221.3=10.686V
PDEV=EaIa

PDEV1=1.69V1.3=2.197W

PDEV2=4.03V3.1=12.493W

PDEV3=7.36V4.6=33.856W

PDEV4=8.203V6.31=51.76W

PDEV5=10.686V8.22=87.84W

PDEL=EaIL

PDEL1=1.69V1.17=1.97W

PDEL2=4.03V2.92=11.767W

PDEL3=5.98V4.38=32.24W

PDEL4=8.203V6.04=49.55W

PDEL5=10.686V7.91=84.53W

%VREG=VnL-VFLVFLx 100%

%VREG1=40-40.340.3x 100%=0.74%

%VREG1=40-48.248.2x 100%=17.01%

%VREG1=40-55.555.5x 100%=27.9.%

%VREG4=86.1-59.759.7x 100%=32.998%

%VREG5=86.1-60.660.6x 100%=33.99%

IV. OBSERVATIONS:

* We created the circuit according to the circuit diagram instructed to us to do.

* Before we start, measuring the armature resistance and the field winding resistance is necessary if it is working properly.

* We then started to make the shunt generator for a test run without the load to measure the RPM using the tachometer.

* We consulted the nameplate to determine if the values we have are proper.

* We then connected the load and started making the generator perform its function.

* The DMM is used to determine the values for each region that need to be measured and wrote it down to our table of data and results.

V. CONCLUSIONS:

A kind of excitation of generators where the magnetic field of the main poles is excited by a current supplied to the windings of the main poles from the armature (rotor) winding. A self-excited generator is thus distinguished from a separately excited generator, in which the windings of the main poles receive current from an external source. Self-excitation is made use of most often in DC generators. When a self-excited generator is started, the initial current in the field winding is produced by the electromotive force (emf) induced in the armature winding by the residual magnetic field of the main poles. To sustain self-excitation, the initial current must reinforce this field. The additional magnetic flux increases the emf in the armature and, consequently, the current in the windings of the main poles.

VI. QUESTIONS:

1. What would happen if there is no load in the experiment?

* The generator would run at a constant speed with the two-pole switch kept open.

2. What is a separately excited DC generator?

* A separately excited DC generator is a generator where its field current may be obtained from an external source, such as a battery or a rectifier, or variac.

3. In the experiment ,did the terminal voltage increase or decrease when additional load was placed on the generator?

* Using the calculated values as the basis for our answer, we...
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