Study of Series R-L-C Circuit

 Aim:- Study of Series R-L-C Circuit to;

1.     Calculate the values of unknown parameters of R-L-C circuit.

2.     Determine the power factor of the circuit.

3.     To draw a phasor diagram of the circuit based on practical data and find out the applied voltage and power factor from the phasor diagram.

Apparatus Required:-

S. No.

Name of Equipment

Type

Range

Quantity

 

1.

Ammeter

MC

0-5A

1

 

3.

Voltmeter

MC

0-300V

3

 

4.

Inductive Coil

Variable

5A, 250V

1

 

5.

Rheostat

Single tube

500ohms, 5A

1

 

6.

Capacitor

-

-

1

 

7.

Single Phase variac

-

230V, 10A

1

 

 

 

Theory:- In the present circuit, resistance R, inductor L and copulation C are connected in series across a voltage Source V. Thus the current in all the elements is same, whereas voltage across each element would be different. The resultant applied voltage V is the phasor sum of all the voltages across these elements. In such a series circuit, following basic relations can be derived:

                               Voltage across the resistance, VR = IR

                              Voltage across the inductance, VL = IXL

                              Voltage across the capacitance, VC = IXc

                              Power drawn by the circuit, P =VI

                              Power factor of the circuit, = P/VI

Where,

                             XL = Inductive reactance  =   =  2  

                             XC Capacitive reactance =  =

The power factor of such a circuit is lagging the power Factor of this dreat will be leading Hence, by measuring the voltage across various elements, applied voltage: current flowing in the circuit and the power consumed by the circuit, all the parameters of the circuit can bị calkulated.

 

Circuit Diagram:-       

Diagram


PROCEDURE:

1.     Connect the circuit as per the circuit diagram shown in fig.

2.     Adjust the setting of variac, so that applied voltage to the R-L-C series circuit is zero.

3.     Switch-ON the main supply.

4.     Apply a low voltage to R-L-C series circuit and record the readings of ammeter, wattmeter and voltage across resistor, inductor, capacitor and across the terminals C and E of the variac. Voltages should be measured by a single voltmeter to increase the accuracy of measurement.

5.     Repeat step 4 for increased voltage applied to the circuit. It is sufficient to record 3 or 4 set of readings.

6.     Switch-off the main supply.

7.     Draw the phasor diagram, corresponding to one set of reading, preferable at higher voltage, and verify the calculated value of power factor.

 

 

Observation Table:-

S. No.

V (V)

I(mA)

VR(V)

VL(V)

VC(V)

1.

230.5

0.4

51.7

103.3

320.2

 

Calculation:-

S. No.

R=

XL=

XC =

Z =

P.F. =

1.

129.25

258.25

800.5

576.25

0.231

 

Precaucation:-

1.     Make the connections properly.

2.     Note the readings of voltmeters and ammeters properly.

3.     Remove insulations from the connecting wire so as the current will flow properly

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