Experiment No.: 4
Use of Voltmeter, Ammeter, Wattmeter to Determine Active, Reactive and Apparent Power
Consumed in Given R-L-C Series Circuit and Draw Phasor Diagram.
- To use voltmeter, ammeter, wattmeter to determine active, reactive and apparent power
consumed in given R-L-C series circuit.
- To draw the phasor diagram of that circuit.
Let V volts (rms) be applied to an R-L-C series circuit and the current flowing through the circuit be I amps. The impedance Z=V/I. If voltage across resistor is VR then R=VR/I
If voltage across inductor is V r,L, the impedance of the inductor coil is given by
Again the voltage across the resistance R and coil VR, L, then
From the above two equation the value of R and XL can be found out. If the voltage across the capacitor is VC then the reactance of the capacitor is given by XC=VC/I. hence the value of capacitance C=1/ωVC where ω=2πf is the angular frequency. the power factor is given by (R+r)/Z. If VC>VL, The pf is leading otherwise lagging.
The power consumed P=I2(R+r) or VI cos Ø
- The circuit is connected as shown in the circuit diagram with resistor, the inductor coil and capacitor in series.
- The variac is adjusted to zero output position and the circuit is switched on.
- A suitable voltage is applied from the variac so that a reasonable current flows through the circuit. The output voltage of the variac and voltage across the resistor, inductor and the capacitor are noted along with the current.
- Different readings are taken by varying voltage from the variac.
- Readings are noted from the data sheet.
|Sl no||Voltage (V)||Current (mA)||Frequency (kHz)||R (Ω)||L (mH)||C (nF)||VR (V)||VR (V)||VC (V)||PF = cos Ø||Active power|
XL = 2πfL = 2π×13.05×103×7.75×10-3= 635.46 Ω
XC = 1/2πfC = 1/(2π×13.05×103×22.08×10-9)= 552.34 Ω
cos Ø = R/Z = R/√(R2+(XL – XC)2) = 546/√(5462+(635.46 – 552.34)2) = 546/552.29 = 0.98 lag
Active power = VIcosØ = 5.02×9.09×10-3×0.98 = 44.71 mW
Rective power = VIsinØ = 5.02×9.09×10-3×0.198 = 9.034 mVAR
Apparent power = VI = 5.02×9.09×10-3 = 45.62 mVA
|Sl. No.||Name of the apparatus||Quantity||Specification||Makes name|
|1.||Single phase variac||1||230/0-270 V ac|
|2.||LCR Trainer Kit||1||Sushama Electronics|
|3.||Digital Multimeter||3||0-750 V, 10 A||Akademika|
- The phasor diagram of different voltage and current for at least two observation are drawn in the graph paper.
- The value of power factor and magnitude of the supplied voltage are found from phasor diagram.