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Experiment no. 11

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Basic Electrical Engineering

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Experiment no. 11

  1. 1. Maharashtra Institute of Technology, Aurangabad LABORATORY MANUAL Practical Experiment Instruction Sheet EXPERIMENT TITLE :Study of R-L-C series circuit. EXPERIMENT NO.11 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1 FY(All) DEPARTMENT: Electronics & Telecommunication Engineering LABORATORY : Basic Electrical Engineering Location Part I Page 50 Aim: Study of R-L-C series circuit. Apparatus: 1.Single phase variac 8Amp, (0-270V) 2.Rheostat 500Ω, 1.7A 3. Inductor (Variable) 5Amp, 250V. Rating 4. Capacitor 400V Rating at 50Hz 5. AC Ammeter (0-1A) 6. AC Voltmeter (0-150-300V) 7. Prongs One pairs Theory : The series RLC circuit above has a single loop with the instantaneous current flowing through the loop being the same for each circuit element. Since the inductive and capacitive reactance’s XL and XC are a function of the supply frequency, the sinusoidal response of a series RLC circuit will therefore vary with frequency, ƒ. Then the individual voltage drops across each circuit element of R, L and C element will be “out-of-phase” with each other as defined by: I=Imax∗sin(wt) Circuit Diagram Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable
  2. 2. Maharashtra Institute of Technology, Aurangabad LABORATORY MANUAL Practical Experiment Instruction Sheet EXPERIMENT TITLE :Study of R-L-C series circuit. EXPERIMENT NO.11 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1 FY(All) DEPARTMENT: Electronics & Telecommunication Engineering LABORATORY : Basic Electrical Engineering Location Part I Page 51 The instantaneous voltage across a pure resistor, VR is “in-phase” with the current. The instantaneous voltage across a pure inductor, VL “leads” the current by 90o The instantaneous voltage across a pure capacitor, VC “lags” the current by 90o Therefore, VL and VC are 180o “out-of-phase” and in opposition to each other. Relationship of voltage & current This means then that we can not simply add together VR, VL and VC to find the supply voltage, VS across all three components as all three voltage vectors point in different directions with regards to the current vector. Therefore we will have to find the supply voltage, VS as the Phasor Sum of the three component voltages combined together vectorially. Kirchoff’s voltage law ( KVL ) for both loop and nodal circuits states that around any closed loop the sum of voltage drops around the loop equals the sum of the EMF’s. Then applying this law to the these three voltages will give us the amplitude of the source voltage, VS. Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable
  3. 3. Maharashtra Institute of Technology, Aurangabad LABORATORY MANUAL Practical Experiment Instruction Sheet EXPERIMENT TITLE :Study of R-L-C series circuit. EXPERIMENT NO.11 : MIT(T)/ETC/Basic Electrical Engineering /Manual No.1 FY(All) DEPARTMENT: Electronics & Telecommunication Engineering LABORATORY : Basic Electrical Engineering Location Part I Page 52 As the three vector voltages are out-of-phase with each other, XL, XC and R must also be “out-of-phase” with each other with the relationship between R, XL and XC being the vector sum of these three components thereby giving us the circuits overall impedance Z=√R 2 +(XL−XC) 2 And X = XL – XC. If VL < VC i.e. XL < XC, X(Negative), Z decreasing, current decreasing, p.f. Leading If VL = VC i.e. XL = XC, (Series resonance condition), X = 0, Z = R, Current maximum at U.P.F. If VL > VC i.e. XL > XC, X will be positive, Z increasing, current decreasing, p.f. lagging. Observation Table: Sr No. I (Amp) VR (Volt) VL (Volt) VC (Volt) VR+L (Volt) VT (Volt) Calculations: Sr. No. XL = VL / I (Ω) L = XL / ω (H) ZT = VT / I (Ω) For simplicity only, the resistance of inductor coil has been ignored. Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable
  4. 4. Maharashtra Institute of Technology, Aurangabad LABORATORY MANUAL Practical Experiment Instruction Sheet EXPERIMENT TITLE :Study of R-L-C series circuit. EXPERIMENT NO.11: MIT(T)/ETC/Basic Electrical Engineering /Manual No.1 FY(All) DEPARTMENT: Electronics & Telecommunication Engineering LABORATORY : Basic Electrical Engineering Location Part I Page 53 Sample Calculations ( For second reading): 1) XL = VL / I = Ω 2) L = XL / I = H 3) Z = V / I = Ω 4) COSΦ = p.f. = R / Z 5) Plot phasor diagram. 6) Plot the graphs. Phasor diagram Conclusion: Various relations for V, I, Z and power factors are studied. Prepared By: Mr. S.S. Chate Approved By: Dr. G.S. Sable

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