Principles of Electrical Engineering (GEL 104)

About: 

Course Code: GEL 104

 

This lab is held as part of B. Tech curriculum in First Year and both semester of all branches of the B. Tech program.

The following experiments are conducted in the lab:-

S NO

TITLE AND DESCRIPTION OF EXPERIMENTS

PHOTOGRAPH

1.

Study of Cathode Ray Oscilloscope

1.  Understanding and operating oscilloscope front panel including triggering, sweep & time base adjustments.

2.  Comparing phase/frequency difference of two signals and making Lissagous patterns by applying two separate signals from function generators

2.

Step response of RLC circuits

1.   Connect the circuit as per circuit diagram and apply square wave to series R-C and R-L-C circuits respectively and obtain waveforms wherever possible.

2.  Adjust the values of the components (R-L-C) to obtain responses corresponding to under damped, critically damped and over damped cases.

                               I.            RC- circuit: frequency =200-500Hz

C=0.22µF

R=470Ω

                            II.            RLC – Circuit: Frequency= 20Hz

C=0.22µF

R=470Ω

3.

Steady state response of RLC circuits

Connect R-L-C series circuit and excite it using sinusoidal voltage. Measure voltage difference in phase and amplitude and obtain the phasor diagram of the circuit.

4.

Verifying Network Theorems

Verify KCL & KVL Theorems

1.      Connect the circuit as per circuit diagram.

2.      Measure the current I1, I2 and I3.

a)      Verify KCL.

b)      Input impedance equals V1/I.

3.      Also measure the current I2, I4 and I5. Again verify KCL.

4.      Measure the voltages between nodes (i) S and A (ii) A and B, (iii) B and G. verify KVL.

5.      Verify KVL for loops SAGS, ABGA and SABGS.

Verify Superposition Theorem

1.      Open the circuit BC. Connect a voltage (about 5V) between B and C ( in series with 50 ohm resistor ) (C negative w.r.t. B)

2.      Measure current I2. You have also measured I2 in first part of the experiment. That was V1 alone.

3.      Also measure I2 with source V1 replaced by a short.

4.      Verify superposition theorem.

 

Verifying Thevenin Theorem

1.      Connect the networks as per circuit diagram each R=120 Ohm.

2.      Apply a voltage between A and B (about 5V).

3.      Measure the current in branch AA.

4.      Calculate the input resistance, Does it agree with the theoretically determined value?

5.      Measure the voltage between (i) B and C, (ii) B and D (iii) C and D. Comment on the results.

6.      Replace branch CD by a short circuit. Measure the current in branch AA comment.

7.      Replace branch CD by an open. Measure the current in branch AA comment.

 

5.

Applications of diodes

1)     Half wave rectifier:

(a.)   Connect the series circuit comprising of the generator, diode and resistor (10kΩ). Set the Oscillator frequency to about 500Hz and convenient amplitude (about 5V).

(b.)  Observe the Oscillator waveform across the resistor on the scope. (Sketch the waveforms)

(c.)   Measure the peak and dc value of both waveforms.

(d.)  Connect a large electrolytic capacitor across the resister. Repeat your observations.

 

2)     Diode Clipping Circuit :

(a.)    Connect the series circuit of the function generator, diode & dc source set about 2V and resister (10kΩ). Set the oscillator frequency to about 500Hz and convenient amplitude (about 5V)

(b.)  Observe the oscillator waveform and the waveform across the diode on the scope (Sketch them).

(c.)   Measure the peak and dc value of both waveforms.

(d.)  Reverse the diode polarity and repeat the observations.

(e.)   Reverse the source polarity and repeat the observations.

3)     Diode Clamping Circuit :

(a.)    Connect the series circuit comparing of the function generator, diode & dc source set to about 2 V and capacitor (0.01µF). Set oscillator frequency to about 500Hz and a convenient amplitude (about 5V).

(b.)  Observe the oscillator waveform and the waveform across the diode dc source branch on the scope (sketch them.)

(c.)   Measure the peak and dc value of both waveforms.

(d.)  Reverse the diode polarity and repeat the observations.

(e.)   Reverse the dc source polarity and repeat the observations.

6.

Applications of Operational Amplifiers

1.      Voltage Follower:

Setup the voltage follower circuit (voltage gain 1) as per circuit diagram and carry out the following:

1.       Measure the output of signal generator directly on the CRO and adjust it to be 2V peak to peak.

2.       Measure the output of signal generator across 100 ohm resistor with the same amplitude setting as in (i).

3.       Disconnect the 100 Ω resistor and connect the signal generator output to the input of circuit as per circuit diagram and measure the output.

 

2.      Inverting Amplifier :

Set up the circuit as per circuit diagram. Choose resistances R1 and RF to achieve gain 1 and 5 respectively. Verify the operation at different frequency say 1 KHZ and 40 KHZ (by plotting input vs. Output Curve). Does the gain depend upon the frequency of operation?

3. Non – Inverting Amplifier:

Set up the circuit as per circuit diagram chooses resistances R1 and Rf to achieve gains 2 to 5. Verify the operation for different frequency and by plotting the output vs. input curve.

 

 

 

 

 

7.

Power measurement in AC circuits

Single phase

1.    Make the connections as per circuit diagram. If the current coil of wattmeter can't carry the load current use a current transformer in conjunction with it.

2.    For a particular set up of R-L load, note the meter readings.

3.    Calculate the power factor

P.F. = Power (Watt)/Apparent power (VA) where

Apparent Power = Voltmeter reading * Ammeter reading

Power = Wattmeter reading * Multiplying factor of wattmeter

Three phase

1.    Make the connections as per circuit diagram.

2.    First measure the power with resistive load and in this case two-wattmeter reading will be the same.

3.    Connect the choke coil of same inductances in each phase.

4.    Increase or decrease the inductances by equal amounts and record the meter readings.

5.    Calculate the power factor,

P.F. = W√3/(Line voltage * Line current)

 

8.

Single-phase transformer B-H loop

1.    Connect as per circuit diagram.

2.    An isolating transformer is to be provided because one plate each of the X and Y set of plates of CRO is grounded, otherwise the neutral of the single phase supply will interfere with either X and Y plate connections.

3.    R of the integrating circuit should be sufficiently large to restrict the current and to provide a large time constant.

4.    B-H curve is now seen on the CRO.

5.    B-H for various no load input voltages (thus various flux densities) can be shown by changing the taps on rheostat.

 

9.

Single-phase transformer OC and SC tests

Open Circuit Test:

1.    Make the connections as per circuit diagram.

2.    The secondary of transformer under test is kept open and the full voltage is applied to the primary. Low current range ammeter and high voltage voltmeter are used.

3.    Read the no load current, power and applied voltage.

4.    Take the readings by varying the applied voltage.

5.    Plot the no load current and power vs. input voltage and calculate Rc and Xm.

 

Short Circuit Test:

1.    Now use the high current rating of ammeter and low voltage rating of voltmeter.

2.    Short the secondary and apply the reduced voltage to the primary so that the full load current passes through the windings.

3.    Take the voltage, current and power readings.

4.    Take readings at 50% and 25% of rated current.

5.    Plot total short circuit power vs. input current and calculate circuit parameters.

 

 

Faculty Instructor: 
All
Lab Instructor: 
Mr Meharban Singh
Mr Dilbag Singh