I 1 - I 2 - I 3+ I 5- I 6 = 0

Transcription

1 S IR C.R.REDDY COLLEGE OF ENGINEERING ELURU (A.P) N etworks Lab (ECE7)

2 SIR C.R.REDDY COLLEGE OF ENGINEERING: : ELURU7 D EPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING E CE 7 NETWROKS L ABORATORY ( /4 EC E, I Semester ) erification of o hm s law and K irchhoff s laws erification of Superposition Theorem 3 erification of Thevenin s Theorem 4 erification of Maximum power Transfer Theorem 5 erification of Reciprocity Theorem 6 Series RLC resonance 7 Two port n etworks & Parallel re sonance 8 T ime response of RL & RC circuits 9 P arameters of an Iron core Inductor 0 C alibration of Energy meter Measurement of power in 3Φ circuit Series R LC vector diagram N etworks Lab (ECE7)

3 E xp. No : O HM S LAW &KIRCHHOFF'S LAWS Aim: To verify o hm s law and K irchhoff s voltage law and current law. Apparatus: S.No D escription R ating Q ty Φ Dimmerstat 30/ 070,8A I ncandescent lamp 5W 40W 60W 3 A mmeter ( 0 A)MI ( 03 A)MI 3 4 oltmeter ( 050/300) MI 4 5 C onnecting Board 6 Connect ing wires Theory: a ) Kirchhoffs oltage Law: According to this law, in any closed circuit or mesh, the algebraic sum of emfs a cting in that circuit or mesh is equal to the voltage drops of each element of the circuit. In mesh ABCD, =I(R+ R + R 3 ) b ) Kirchhoff s Current Law: According to this law, in any network of wires carrying currents, the algebraic sum of all the currents meeting at a node is zero or the sum of all the incoming currents is e qual to the sum of outgoing currents away from th at node. Let I, I, I3, I4, I5 I 6 be the currents at node O. I, I4, I5 are the currents entering the node O and I, I3, I6 are the currents leaving the node O. Then according to K irchhoff s l aw, I I I 3+ I 4+ I 5 I 6 = 0 i.e I+ I 4 + I 5 = I + I 3 + I 6 c) F ilament Lamp: N etworks Lab (ECE7) 3

4 Ohm s Law: At constant temperature the potential difference between two terminals of a conductor is p roportional to the current flowing though the conductor. is proportional to I =I.R Where R is the Resistance between those two terminals R = /I T he resistance of the filament lamp is determined by finding the current at d ifferent at voltages. The filament lamp does not follow the ohms law because the lamp works at d ifferent te mperatures. The resistance at a temperature t o c R t = R o [ + α 0 t ] Where Ro=Resistance at 0 o c. α o = temperature coefficient of resistance at 0 o c T he graph between resistance and current is not linear. The resistance of the filament lamp when the current flowing through the lamp is z ero is called as cold resistanc e. i.e the resistance at room temperature. Graph: C ircuit diagram for erification of KL: N etworks Lab (ECE7) 4

5 Circuit Diagram for verification of KCL: Circuit diagram for m easurement of resistance of a filament lamp Procedure: a ) Kirchhoff s oltage Law:. The connections are made as shown in the circuit diagram.. With the dimmer stat at zero output the supply switch is closed. 3, The output of the dimmers tat is adjusted to the voltage in steps as given in the t abular column and the r eadings of I,, 3 are noted for each step, 4. The dimmerstat is brought back to zero output and the supply switch is o pened. b) K irchhoff s s Current Law:. The connections are made as shown in the circuit diagram.. With the Dimmerstat a t ze ro output the supply switch is closed. 3. The output of t he dimmer stat is adjusted to the voltage in steps as given in the t abular column and all the ammeter readings are noted for each step. 4. The D immerstat is brought back to zero output and the supply s witch is opened N etworks Lab (ECE7) 5

6 c) m easurement of resistance of a filament lamp. T he connections are made as shown in the circuit diagram.. W ith the Dimmerstat at zero output the supply switch is closed. 3. T he Dimmerstat is varied in steps as given in the tabular column and the r espective Ammeter readings are noted. 4. T he Dimmerstat is brought back to zero output and the supply switch is opened T abular Column for erification of KL: A pplied voltage in volts in v olts S l.no in volts 3 in volts = I++3 T abular Column for erification of KCL: A pplied voltage in volts I i i n Amps I i n Amps I 3 i i n Amps I= I+ I I S l.no Tabular column for m easurement of resistance of a filament lamp: S l.no. i n olts I i n Amps R i n Ohms W i n Watts N etworks Lab (ECE7) 6

7 Specimen calculations: KL & KCL: = I++3 (for KL) I = I+ I + I 3 ( for KCL) Resistance of a filament la mp: R ; W I R I iva Questions:. W hy tungsten is used as filament in incandescent lamp?. Melting point of a Tungsten 3. W hat are the types of filaments that are used in filament lamps? 4. W hy gas is filled ins ide the filament lamp. 5. W hat is difference between AC and DC resistance 6. W hat is a linear circuit? 7. W hat is the heating effect of a electric current. 8. D efine ohm s law. 9. D efine Kirchhoff s oltage law. 0. D efine Kirchhoff s Current law.. F ilament of a lamp is made of. G ive the oltage Division Rule. 3. If one of the resistance in a parallel circuit is removed, what happence to the total r esistance. 4. The series circuit consists of five equal resistances and dissipates 0 watts of p ower. Then power dissipated i n each resistance? 5. T he power dissipation in each of three parallel branches is W. What is the total P ower 6. dissipation of the circuit? Precautions: ) Do not touch bare conductors when supply is ON ) Switch off all the measuring devices when NOT i n USE. 3 ) Ensure that dimmerstat is in minimum position before switching ON the s upply and before switching OFF the supply. 4 ) Ensure that there is no short circuit across the supply or any device, before s witching ON the supply. 5 ) Check for prager po larity of meters. Result: N etworks Lab (ECE7) 7

8 Exp. No : ERIFICATION OF SUPERPOSITION THEOREM A im : T o verify Superposition theorem. A pparatus : S l.no. D escription R ating Q ty.. D ual DC power supply 0 30, A. D igital DC Milli ammeter 0 00mA 3. Digital DC voltmeter Superposition theorem c ircuit board 5. C onnecting wires T heory: Any linear network containing multiple sources, the response in any element is e qual to the algebraic sum of responses due to individual sources. This theorem is applicable only in linear circuits, i.e., circuits consisting of resistance or impedance in which ohms law is valid. Superposition theorem can be applied to a circuit c ontaining current sources and even to circuits containing both current and voltage sources. The above theorem is applied when the current in any particular branch of n etwork containing number of voltage sources and current sources is to be determined. C ircuit diagram: a) F or the circuit with two sources b ) F or the circuit with 0 source N etworks Lab (ECE7) 8

9 c ) F or the circuit with 5 source P rocedure : a) b ) c ) F or the circuit with two sources. The connections are made as shown in the circuit diagram a.. W ith the voltage knobs of the Dual DC power supply at their minimum positions t he power supply is switched ON. 3. The voltage is adjusted to 0, the voltage is adjusted to 5 and the r eading of the Milliammeter is noted. 4. T he voltage knobs are brought back to their minimum positions and the power s upply is switched OFF. F or the circuit with 0 source. The connections are made as shown in the circuit diagram b.. With the voltage knobs of the Dual DC power supply at their minimum positions t he power supply is switched ON. 3. The voltage i s adjusted to 0 and the reading of the Milliammeter is noted. 4. The voltage knobs are brought back to their minimum positions and the power s upply is switched OFF. F or the circuit with 5 source. T he connections are made as shown in the circuit diagram c.. With the voltage knobs of the Dual DC power supply at their minimum positions t he power supply is switched ON. 3. The voltage i s adjusted to 5 and the reading of the Milliammeter is noted. 4. T he voltage knobs are brought back to their minimum positions and the power s upply is switched OFF. N etworks Lab (ECE7) 9

10 T abular Column : S l.no. C ondition of the circuit in olts i n olts T i n olts I in m A. W ith Two voltage sources. W ith 0 source only 3. W ith 5 source only Theoretical C alculations: A pplying mesh analysis for circuit diagram a, we get, Solving for I and I, we get, 47I00I = 0 00I+ 47I= 5 I = A ; I = A ; The current in the 00 b ranch is I I = 0.47 A A pplying mesh analysis for circuit diagram b, we get, 47I00I = 0 Solving for I and I, we get I 00I+ 47I= 0 = A ; I = 0.73 A; The current Ix in the 00 b ranch is I I = 0.08 A Applying mesh analysis for circuit diagram c, we get, 47I 00I Solving for I and I, we get, I = 0 00I+ 47I= 5 = 0.9 A ; I = A; The current Iy in the 00 branch is I + I = A Finally Ix+ I = 0.47 A = The current due to the two sources y. N etworks Lab (ECE7) 0

11 iva Questions:. S uper position theorem is valid for. When applying super position theorem to any circuit ideal voltage source is replaced by and ideal current source is replaced by 3. G ive the statement of superposition theorem. 4. G ive the limitations of super position theorem. 5. W hen the superposition theorem is applied to the circuits consisting of d ependent sources, how the dependent sources act 6. S uperposition theorem is essentially based on the concept of? P recautions:. D on t touch bare conductors when supply is ON. Wear shoes in labora tory to avoid shocks 3. S witch off the all the measuring devices when NOT in USE. 4. Ensure that there is no short circuit across the supply or any device, before s witching on the supply. 5. E nsure that the current knob of the dc power supply is in maximum position b efore switching on the supply. N etworks Lab (ECE7)

12 E xpt.3 A im: T o A pparatus T HEENIN S THEOREM v erify hevenin s : T T heorem. T heory : S l.no. D escription R ange Q ty.. D C power supply 030, A. D igital DC Milliammeter 000mA 3. D igital DC oltmeter The venin s theorem circuit board 5. P otentiometer C onnecting wires Consider a generator network consisting of generator & linear impedances as shown in figure. ZL i s the load impedance connected across terminals A & B. According to Thevenin s theorem this network can be replaced by an emf o c in series with an impedance ZAB as shown in figure. o c is the open circuit voltage i.e, the voltage measured at terminals A & B when ZL i s removed. Z AB is the impedance looking into terminals A & B with load ZC removed with all generators replaced by their internal impedances. The only restriction on this theorem is t hat network is not magnetically coupled to external circuits. C ircuit diagram : a) F or measurement of Load current N etworks Lab (ECE7)

13 b) F or measurement of Short circuit current c ) F or measurement of Open circuit voltage d ) For veri fication of Thevenin s Theorem N etworks Lab (ECE7) 3

14 P rocedure : a ) b) c) d) F or measurement of Load current. The connections are made as shown in the circuit diagram a.. With the voltage knobs of the DC power supply at their minimum positions the p ower supply is switched ON. 3. The voltage knobs are varied gradually such that the output voltage is adjusted to 5 olts and the ammeter reading is noted. 4. The voltage knobs are brought back to their minimum positions and the DC p ower supply is switched OFF. For measu rement of Short circuit current. The connections are made as shown in the circuit diagram. S tep No s to 4 of part a, are repeated. F or measurement of Open circuit voltage. The connections are made as shown in the circuit diagram c.. W ith the voltage knobs of the DC power supply at their minimum positions the p ower supply is switched ON. 3. The voltage knobs are varied gradually such that the output voltage is adjusted to 5 olts and the voltmeter reading is noted. 4. T he voltage knobs are brought back to their minimum positions and the DC p ower supply is switched OFF. F or verification of Thevenin s Theorem. The value of RT h which is calculated from the above readings is fixed using a p otentiometer and connected into the circuit as shown in the circuit diagram d.. The output of DC power supply is adjusted to the measured value of O C from the e arlier setup and the ammeter reading is noted. 3. The voltage knobs are brought back to their minimum positions and the DC p ower supply is switched OFF. b. T abul ar Column : S l.no. C ircuit diagram Q uantity to be measured M eter Reading. A L oad current I L = Amps. B S hort circuit current I SC = Amps 3. C O pen circuit voltage OC = olts 4. D L oad current I L = Amps N etworks Lab (ECE7) 4

15 Th eore tical Calculations : a ) F or circuit (a): A pplying KL for Circuit(a), I 56I 00I 56I 56I 00I 00I 3 00I 00I Solving I,I, I3 W e get, I = A; I A ; The current I t hrough 56 r esistor is, I I I = A; L b ) F or circuit (b): Equivalent resistance Re = (00 56) (00 00) = Therefore I = 0.746A Current through 56 resistance is I 56 = = 0.94A Current through 00 resistance is I 00 = A. Therefore I sc I 56 I00 = = A c ) F or Circuit (c) 5 A = B = C O.5 A B N etworks Lab (ECE7) 5

16 d ) F or circuit(d) R T H = I OC SC.5 = I = L TH R R TH L A iva Questions: ) While applying thevenin s theorem, thevenin s voltage is equal to ) Thevenin s impedance is 3) Norton s equivalent form in any complex impedance circuit consists of 4 ) What is the main application of thevenin s th eorem? P recautions:. D on t touch bare conductors when supply is ON. W ear shoes in laboratory to avoid shocks 3. S witch off the all the measuring devices when NOT in USE. 4. Ensure that there is no short circuit across the supply or any device, before s witching on the supply. 5. Ensure that the current knob of the dc power supply is in maximum position b efore switching on the supply. 6. C heck for proper polarity of meters. N etworks Lab (ECE7) 6

17 E xpt.4 M AXIMUM POWER TRANSFER THEOREM A im : T o verify Maximum power transfer theorem. A pparatus : S l.no. D escription R ange Q ty.. D immerstat 30/ 070, 8A. R heostat 600,.7A 4 3. A mmeter 0 A (MI) 4. M ultimeter 5. C onnecting wires T heory : M any circuits basically consist of sources, supplying voltage, current and power to the load; for example, a radio speaker system, or a microphone supplying the input signals to voltage pre amplifiers. Sometime it is necessary to transfer maximum voltage, c urrent or power from source to the load. The Maximum Power Transfer Theorem states that maximum power is delivered from a source to load when the load resistance is equal to the source resistance. This theorem can also be applied to complex impedance circuits. I f source impedance is complex then maximum power is transferred from source to load w hen load impedance is equal to complex conjugate of source impedance. C ircuit diagram : N etworks Lab (ECE7) 7

18 P rocedure :. T he connections are made as shown in the circuit diagram.. With the dimmerstat at zero output and the rheostat R L i n CUTOUT position the s upply switch is closed. 3. The output of the dimmerstat is adjusted such that s r eads The rheostat R L is gradually CUTIN in steps such that the current is decreased in steps of 0.05A and the voltmeter reading L i s noted. 5. T he dimmerstat is brou ght back to zero output and the supply switch is opened. T abular column : S l.no. S i n olts I L i n Amps L i n olts R L W i n Ohms i n Watts S pecimen Calculation : L R L I W I R L L L N ature of Graph : N etworks Lab (ECE7) 8

19 T heoretical Calculations: The equivalent resistance as seen from the load end of the circuit when the supply is short circuited is: RR R S R ; R S 00 ; R S = R R 300 The open circuit voltage ( i.e., RL is disconnected) 3 o c i s found by keeping the output open circuited AC OC S 3 ; R x R R 3 OC ; O C = The maximum power P OC 4R L ; P W iva Questions: Condition for Maximum power transferred to a load in a DC circuit. In a complex impedance circuit, the maximum power trans fer occurs when the load impedance is equal to 3. Maximum power transfer occurs at what % of its efficiency? 4. Applications of maximum power transfer theorem. 5. What is the valve of maximum power transferred to the load (RL).When E is generator EMF and Ri i s internal resistance. P recautions: D o not touch bare conductors when supply is ON S witch off the all the measuring devices when NOT in USE. 3 Ensure that dimmerstat is in minimum position before switching ON the supply a nd before switch ing OFF the supply. 4 Ensure that there is no short circuit across the supply or any device, before s witching ON the supply. 5 C heck for proper polarity of meters. N etworks Lab (ECE7) 9

20 E xpt.5 R ECIPROCITY THEOREM A im : T o verify reciprocity theorem. A pparatus : S l.no. Descri ption R ating Q ty.. D C power supply 030, A. 3. Digital DC M illiammeter Reciprocity theorem c ircuit board 000mA 4. C onnecting wires T heory: A ccording to this theorem if we apply input to a circuit, which consist of resistors, inductors, capacitors and transformers, including coupled circuits, the ratio of response in any element to the input is constant even when the position of input and output are i nterchanged. C ircuit a) diagram : W ith source across AB b) W ith source across CD N etworks Lab (ECE7) 0

21 P rocedure :. The connections are made as shown in the circuit diagram a.. With the voltage knobs of the DC power supply at minimum positions the power s upply is switched ON. 3. T he voltage knobs are varied, the output is adjusted to 5 and the Milliammeter r eading is noted. 4. The voltage knobs are brought back to their minimum positions and the power s upply is switched OFF. 5. Step No s to 4 are repeated for circuit diagram b also. T abular Column : S l.no. C ondition of the Circuit i n olts. S ource across AB S ource across CD I in m A R atio i n Ohms S pecimen Calculation : T heoretical Calculations : Ratio I T he mesh equations for Ci rcuit diagram a, are : I 56I 5 56I 56I I 56I 3 56I 0 Solving the above equations for the value of I3, 3 0 N etworks Lab (ECE7)

22 W e get, I 3 = A. T he mesh equations for Circuit diagram b, are : I 56I 0 56I 56I I 56I Solving the above equations for the value of I, W e get, = A. I 3 56I iva Questions: ) Reciprocity theorem is applicable to ) Condition for a reciprocal network in terms of ABCD parameters. 3 ) C ondition for a reciprocal network in terms of Z parameters. 4 ) Give the Statemen t of Reciprocity theorem. P recautions: D on t touch bare conductors when supply is ON W ear shoes in laboratory to avoid shocks 3 S witch off the all the measuring devices when NOT in USE. 4 E nsure that there is no short circuit across the supply or any device, before s witching on the supply. 5 Ensure that the current knob of the dc power supply is in maximum position b efore switching on the supply. 6 C heck for proper polarity of meters. N etworks Lab (ECE7)

23 E xpt.6 RLC SERIES RESONANCE & RL C P ARALLEL RESONANCE A im : T o plot a r esonance curve and calculate the resonant frequency. A pparatus : S l.no D escription R ange Q ty I nductor (DIB) C apacitor (DCB) 0. f R esistance (DRB) k A mmeter 0 50 ma (MI) M ultimeter Func tion generator C.R.O C onnecting wires T heory r ms : An a.c voltage of rms value when applied to an RL C circuit establishes an current I given by I = / Z where Z = R ( X C X L ). In this experiment X C X > L the effect of XC> X L is a leading power factor, since the current I leads by an angle, X C X L where =tan R. In an inductor copper loss takes place due to the resistance of i ts coil and core loss takes place in the magnetic core (in case of iron core inductor). In the capacitor losses takes place in di electric media used for making it. The losses taking place in the magnetic core of the inductor or di electric media of the capacitor are usually k nown. The copper losses are taken into account when the resistance of the coil is connected in series with inductance. The importance of R in the RL C series circuit is N etworks Lab (ECE7) 3

24 that, when XL= X C due to the variable inductor or variable capacitor or due to varying f requency the current is limited o nly by R. Circuit diagram for RLC series resonance : Circuit diagram for RL C parallel resonance : P rocedure :. T he connections are made as shown in the circuit diagram.. W ith the amplitude knob of the Function generator at minimum position, f requency at 00 Hz, the Function generator is switched ON. 3. The frequency is varied in steps as given in the tabular column and for each step by maintaining the output voltage constant at 0 peak to peak the voltmeter and M illiammeter readings a re noted for each step. 4. The frequency is brought back to 00 Hz the amplitude knob is brought back to i ts minimum position and the Function generator is switched OFF. N etworks Lab (ECE7) 4

25 Tabular Column f or series resonance : S l.no. F requency i n Hz (peak p eak) i n olts (rms) I n volts I i n ma Z i n Ohms T abular Column for parallel resonance: S l.no. F requency i n Hz (peak p eak) i n olts (rms) I n volts I i n ma Z i n Ohms S pecimen Calculation : For series resonance: W e have in an R L C circuit A t resonance as, X For parallel resonance: C urrent I= xy Admitance Y= G+J(BLB C ) At resonance BL= B C C urrent I= xg L = X I ; Z = R j L C C, e have, W Z = R, Then,, I I R N etworks Lab (ECE7) 5

26 N ature of graph : F or series resonance: For p arallel resonance: iva Questions :. G ive the dynamic impedance in parallel resonant RLC circuit. W hat is the condition for series r esonance? 3. G ive the formula for Resonant frequency of RLC series circuit. 4. At resonance RLC series circuit act as a 5. Below resonance frequency RLC series circuit act as a 6. Above resonance frequency RLC series circuit act as a 7. W hat is band width? 8. What is the power factor of the circuit at resonance 9. W hy current is maximum at resonance in RLC series circuit? 0. W hy impedance is minimum at resonance in RLC series circuit.. A t resonance voltage drop across inductor is equal to voltage drop across capacitor w hy?. What is current value at lower and upper cut off frequency in RLC series circuit t erms of maximum value? in 3. If XL> Xc, RLC series circuit act as a 4. If XL< Xc RLC circuit act as a 5. D efine Q f actor 6. W hat is the power factor of a parallel resonant circuit? 7. Series and parallel resonant circuits magnifies 8. W hat is the relation between apparent power(s), true power (P) & reactive power (Q). N etworks Lab (ECE7) 6

27 9. What is the phase angle between line voltage and phase voltage in a balanced star connected system 0. what is the power factor of RLC f requency series circuit at lower cut off and upper cut off. W hat are the units for susceptance. Insulation for all electrical equipment is designed for v alue. 3. The form factor for DC supply voltage is always 4. In a series resonant circuit the impedance above and below resonant frequency is & 5. G ive the expression for quality factor in series RLC circuit 6. W hat is meant by selectivity? 7. G ive the relation between bandwidth & quality factor 8. W hat is meant by ma gnification? 9. G ive the other name for parallel resonant circuit P recautions : ) D on t touch bare conductors when supply is ON ) W ear shoes in laboratory to avoid Electric shocks 3 ) S witch off the all the measuring devices when NOT in USE. 4 ) C heck for proper polari ty of meters. 5 ) Ensure that there is no short circuit across the supply or any device, before s witching on the supply. N etworks Lab (ECE7) 7

28 Expt. 7 T WO PORT NETWORK Aim: To find out Z p arameters, Y parameters, A B C D parameters and h parameters Apparatus : S l.no Descri ption R ating Q ty D C power supply 030, A D igital DC milli ammeter 000 ma 3 D igital DC voltmeter 00 4 T wo port N/W circuit board 5 C onnecting wires Theory: A part is normally referred to a pair of terminals of a network through which we can have access to network either for connecting a sources or for measuring, an O/P the network having only two pairs of terminals, through which it is accessible is c alled a two port network. The port at which the response is calculated in designated as O/P terminals of the another terminal pair at which excitation is calculated is designated as I/P terminals. The voltage of current at I/P terminals i.e port are & I. out of the 4 variables,, I, I o nly two are independent of the other two are expressed in terms of these independent variables in terms of network parameters. The various network p arameters are Z,Y,A,B,C,D,h. Procedure:. T he connections are made as shown in circuit diagram (a). W ith the voltage knobs of the DC power supply at their minimum p osition the power supply is switched ON. 3. The voltage knobs are varied such that the output of the power supply w ill be 0 and all the meter readings are noted. 4. T he voltage knob are brought back to their minimum positions and the p ower supply is switched OFF 5. Step no s to 4 are repeated for circuit diagram (b) and also for circuit d iagram (c) C ircuit diagram: N etworks Lab (ECE7) 8

29 Fig(a) port short circuited Fib(b) port short circuited Fig (c) when port open circuited Tabular column: Fig( d) when port open circuited S.No N ame i n olts I i n Amps i n volts I i n Amps Port shortcircuited Port shortcircuited 3 Port opencircuited 4 Port opencircuited N etworks Lab (ECE7) 9

30 S pecimen calculations; Z parameters: = Z I + Z I ; = Z I + Z I ; When port open circuited: Z I = 0; Z I When port open circuited: Z I = 0; Z I Yp arameters: I = Y + Y I = Y + Y = I = 0 I = I = 0 When port short circuited: I I Y = 0 Y = 0 When port short circuited: I I Y = 0 Y = 0 A B C D Parameters: = ABI I = CDI When port open circuited I A I = 0; C= I I= 0 When port short circuited: I B= 0 D= 0 I I A,D are dimension less quantities h Parameters: = h I + h = h I h I + N etworks Lab (ECE7) 30

31 When port short circuited: I h = 0 h = 0 I I When port open circuited: I h I = 0; h = I= 0 iva questions:. Give an example for lumped element & dist ributed element. G ive an example for bilateral element 3. D efine electric network 4. G ive the classification of Network elements 5. D efine active element 6. D efine passive element 7. W hat are unilateral elements? 8. W hat are bilateral elements 9. Give examples of active element s 0. G ive examples of passive elements. G ive examples of unilateral elements. G ive examples of bilateral elements 3. W hat are linear elements? 4. What are nonl inear elements 5. W hat are lumped elements? 6. W hat are distributed elements? 7. G ive examples for LUMPED parameters. 8. G ive examples for Distributed parameters. Precautions: ) D on t touch bare conductors when supply is ON ) W ear shoes in laboratory to avoid Electric shocks 3 ) S witch off the all the measuring devices when NOT in USE. 4 ) C heck for proper polarity of meters. 5 ) E nsure that there is no short circuit across the supply or any device, before s witching on the supply. Result: T he Z,Y, A B C D &h parameters are calculated. N etworks Lab (ECE7) 3

32 E xpt.8 T IME RESPONSE OF RL & RC CIRCUITS Aim: To find the time constant series RL & R A pparatus : C c ircuits S l.no D escription R ating Q ty R esistors KΩ 00Ω C apacitor 0. μf 3 I nductor 0mH 4 C RO 5 F unction generator 6 C onnecting wires Theory: In a network containing energy storage elements with change in e xcitation, the currents & voltages change from one stable to other is called transient state. The storage elements deliver their energy to the resistances, hence the response change with time gets saturated after some time, and is referred to as the transient r esponse. C onsider a circuit consisting of resistance and inductance as shown in fig. the inductor in the circuit is initially unchanged, and is in series with a resistor. When the switch is closed we find the complete solution for the current, the solution of the circuit is RT / i e. R C onsider a circuit consisting of resistance and capacitor as shown in fig. the capacitor in the circuit is initially unchanged, and is in series with a resistor. When the s witch is closed we find the complete solution for the current. The solution of the circuit t / RC is i e R Tabular column: R Ω) ( R ( Ω) C in f L in H Theoritical t ime constant Practical t ime constant Circuit diagram: N etworks Lab (ECE7) 3

33 S eries RC circuit S eries RL circuit Procedure:. Conne ct the circuit as shown in fig. A pply KHZ, peak to peak square wave signal as I/ P 3. c onnect th e I/P signal to channel and the O/P to channel of CRO value. Specimen calculations: t =L/R, L= t =RC, C= iva Questions: ) W hat is transient? ) W hy transients occur in electric circuits? 3 ) W hat is free and forced response? 4 ) D efine time constant of RL ci rcuit? 5 ) D efine time constant of RC circuit? 6 ) The time duration from the instant of switching till the attainment of steadystate is called? 7 ) The response of a circuit due to a lone is called natural response 8 ) In circuits excited by DC source at steady state behave as short circuit And b ehave as open circuit? 9 ) I n electrical circuits transient currents are associated with 0) In transient circuit analysis, complementary function gives r esponse. N etworks Lab (ECE7) 33

34 Precautions: ) Don t touc h bare conductors when supply is ON ) W ear shoes in laboratory to avoid Electric shocks 3 ) S witch off the all the measuring devices when NOT in USE. 4 ) C heck for proper polarity of meters. 5 ) E nsure that there is no short circuit across the supply or any device, before s witching on the supply. N etworks Lab (ECE7) 34

35 E xpt.9 P ARAMETERS OF AN IRON CORE INDUCTOR A im : To determine the resistance and inductance of an iron c ore inductor. A pparatus Theory: : S l.no. D escription R ating Q ty.. I ron core inductor 50 mh, A. D immerstat 30/ 070, 4A 3. D.C power supply 030, A 4. A mmeter 0 3 A (MC) 0 3 A (MI) 5. oltmeter 0 50 (MI) 6. W attmeter /A, 300, 60W, L PF 7. C onnecting wires T he property of a substance which opposes the flow of current through it is called resistance. The parameters of an iron core are resistance and inductance. In order to find the resistance, choke coil is connected to the DC supply. The choke coil consists o f resistance and inductance. Resistance can be calculated and it can be measured in this experiment resistance can only be calculated. The units of resistance is ohms. The impedance can be determined by connecting it to the AC supply inductance also can be calculated. B y knowing about resistance and impedance we can determine the value of inductive reactance. From its value we can calculate the value of impedance of given frequency. Resistance, impedance, reactance has same units ohms. Because these all have s ame characteristics i.e opposition of flow of current it. Reactance cannot be measured. In case of impedance as it is a combination of reactance and resistance it can apply only be c alculated, but not be measured. C ircuit diagram : a ) F or calculating DC resistance b) For calculating all the parameters of the Inducto r N etworks Lab (ECE7) 35

36 P rocedure a) b ) : F or calculating DC resistance. The connections are made as shown in the circuit diagram a.. With the voltage knobs of the D.C.Power supply at minimum positions the power s upply is switched ON. 3. T he voltage is varied in steps as given in the tabular column and the respective c urrents are noted. 4. The voltage knobs are brought back to their minimum positions and the power s upply is switched OFF. F or calculating all the parameters of the Inductor. T he connections are made as shown in the circuit diagram b.. W ith the Dimmerstat at zero output the supply switch is closed. 3. The Dimmerstat is varied in steps such that the output voltage is adjusted to the v alues given in the tabular column and for each step the readings of all the meters a re noted. 4. T he Dimmerstat is brought back to zero output and the supply switch is opened. T abular column (): I R S l.no. i n olts i n Amps in O hms N etworks Lab (ECE7) 36

37 T abular column (): S l.no. in olts I in A mps W i n W atts Z in O hms R in O hms X L in O hms L in H enry p.f S pecimen calculation : W Z ; R ; I I X L Z R ; X L L ; f R Cos ; Z iva Questions :. W hat is meant by true power?. W hat is apparent power? 3. W hat is power factor? 4. W hat is the power factor of pure resistive circuit? 5. P ower factor of 0 indicates what? 6 I n RC circuit power dissipati on is due to which component. 7 R.M.S value of sine wave indicates what? 8 De fine R.M.S value? 9 G ive the relation between R.M.S value and peak value of a sinusoidal waveform 0 D efine peak factor? G ive the peak factor of the sinusoidal wave form? D e fine form factor of sinusoidal wave form? 3 D efine impedance? 4 G ive phase relation in a pure inductor? 5 G ive phase relation in a pure capacitor? 6. W hat is the impedance of pure capacitor? 7. W hat is the average value of a sine wave over a full cycl e? 8. A sine wave voltage is applied across a capacitor, when the frequency of v is N etworks Lab (ECE7) 37

38 i ncreased? 9. A sine wave voltage is applied across a inductor, when the frequency of v is i ncreased? 0. For the same peak value, which wave will have highest R MS value?. The form factor of D.C voltage is?. The power consumed in a circuit element will be least when the phase difference b etween &I is? 3. Give the importance of impedance diagram? 4. What are compound circuits? 5. When the resistance of a n RC circuit is greater than X[c], Ф between applied 6. voltage and the total current is closer to? 7. W hen frequency of applied voltage in a series RC circuit is increases, what h appens to X[c]? 8. G ive the phasor diagram of series RL circuit? 9. G ive the phasor diagram of series RC circuit? 30. W hat is the phase angle between capacitor current and the applied voltage in a p arallel RC circuit P recautions : ) D on t touch bare conductors when supply is ON ) Wear shoes in laboratory to avoid Electri c shocks 3 ) S witch off the all the measuring devices when NOT in USE. 4 ) C heck for proper polarity of meters. 5 ) Ensure that there is no short circuit across the supply or any device, before s witching on the supply. N etworks Lab (ECE7) 38

39 E xpt.0 E NERGY METER CALIBRATION Aim: T o cal ibrate the given single phase energy meter Apparatus: S.no N ame R ange Q ty oltmeter 050M I A mmeter Ol OA 3 30,0A, S ingle phase energy meter 50HZ 4 W attmeter 300/0A 5 S topwatch Circuit Diagram: Procedure:. Connect the circuit as shown in the circuit diagram.. Apply the rated voltage of ary the load such that Y4 of it's rated current flows in the ammeter. 4. Notedown the readings of oltmeter, Ammeter and Wattmeter. 5. Notedown the time required for 5 revolu tions in the Energy meter. 6. ary the load to 'is, /3, full load current. 7. For every load noted own the oltmeter, Ammeter and Wattmeter readings; and n otedown time required for 5 revolutions. Tabular column: N etworks Lab (ECE7) 39

40 S.no L oad oltage C urrent P ower CosΦ=W/ I Time in sec f or 5 revolutions(t) Specimen calculations: M eter constant = 00 rev/kwh No.of units consumed for 5 rev.er= x 5 k w h 00 w time( t) No.of units consumed actually for 5 rev. Ea = x x60 E % error = r E x00 Ea iva Questions: ) W hat is the functioning of shading band in energy meter? ) I n energy meter driving torque is produced due to? 3 ) W hat is formula for braking torque in energy meter? 4 ) W hat is the condition for steady state speed of energy m eter disc? 5 ) W hat is ment by creeping? 6 ) H ow do you prevent the creeping? 7 ) W hat are the units for power? 8 ) W hat are the units for energy? P recautions:. Don't touch bare conductors when supply is ON. Don't Switch on the supply unless the circuit is approved by any Staffmember. 3. Wear s hoes in laboratory to avoid Electric shocks 4. Switch off the all the measuring devices when NOT in USE. 5. Check for proper polarity of meters. 6. Ensure that there is no short circuit across the supply or any device, before s witching on the supply. N etworks Lab (ECE7) 40

41 E xpt. POWER MEASUREMENT IN A 3 Φ BALANCED A.C CIRCUIT U SING TWO WATT METER METHOD A IM: c ircuit. To measure the 3 Φ power using two watt meter method in a balanced A.C A PPARATUS REQUIRED: S.NO A PPARATUS REQUIRED R ANGE Q UANTITY. A mmeter ( 0 0 ) A (M.I). olt meter ( 0 600) (M.I) 3. W att meter 600/0A (UPF) 4. 3Φ load 5. C onnecting wires T HEORY: a nd the The connections of the two current coils in series with the load in the two phases two r espectively. T he I f pressure coils are connected between two phases the current coil carrier IR and IB a nd the pressure coil are and YR third and In terms of instantaneous currents i R,i Y,i B and instantaneous voltages v R,v Y,v B. instantaneous total power is given by I n P = RI R + Y I Y + B I B case of y connected without neutral, we have I R I Y + I Y = ( I + I B = 0 R + I B ) phase Y B. S ubstitute equation i n equation P = RI R + Y (I R I B ) + BI B = R I R Y I R Y I B + B I B = I R ( P = R Y YRI R + YBI B ) + IB( B Y ) N OTE: T he watt meters read only the average power. W attmeter W number : i.e. Current coil carries I R N etworks Lab (ECE7) 4

42 W attmeter W Th erefore, P = W Pressure number : i.e. Current Pressure + W P = I YR R coil carries coil carries I B coil carries c osφ + B Y R Y B Y I B c osφ Thus, the total average power for a 3 Φ circuit is obtained by adding two reading of watt meter W nd W b etween T he a. In equation cos Φ and cosφ are the phase angles betwe en YB a nd IB. R I YR a nd I In terms of instantaneous currents I, Y, I B and instantaneous voltages, Y instantaneous total power is given by P ROCEDURE: 3. M ake the connections as per the circuit diagram.. C lose the supply (TPST) switch. 3. T h e load is applied in steps and for each step meter readings are noted. 4. R epeat step 3 until the rated current of load is reached. 5. L oad is removed in steps and switch is opened. 6. C alculate and verify the total power. T ABULAR COLUMN: 3 R R, B. and S.NO ( olts) W ( Wat ts) W ( Watts) W + W I L ( Amps) 3 LI L c osφ M ODEL CALCULATIONS: oltage across load (L) = Load current (IL) = A W att Total meter reading W W W + W = Watts = Watts = W atts power = 3 LI L c osφ Watts N etworks Lab (ECE7) 4

43 N etworks Lab (ECE7) 43

44 iva oce Questions: ) C an wattmeter measures the reactive power? ) W hat are the different methods for finding three phase power? 3 ) W hat type of load is used in this experime nt? 4 ) D efine Active power? 5 ) D efine reactive power? 6 ) D efine apparent power? 7 ) D efine Form factor? 8 ) D efine Peak factor? 9 ) W hat is the relation between voltage and current in a pure resistor? 0) W hat is the relation between voltage and current in a pure Inductor? ) W hat is the relation between voltage and current in a pure capacitor? ) D efine frequency? 3) W hat is electric power? 4) Why we are using ( 0 600) voltmeter in this experiment? 5) What type of wattmeter is use d in this experiment? P recautions:. Don't touch bare conductors when supply is ON. Don't Switch on the supply unless the circuit is approved by any Staffmember. 3. Wear s hoes in laboratory to avoid Electric shocks 4. Switch off the all the measuring d evices when NOT in USE. 5. Check for proper polarity of meters. 6. Ensure that there is no short circuit across the supply or any device, before s witching on the supply N etworks Lab (ECE7) 44

45 E xpt. S ERIES RLC ECTOR DIAGRAM Aim: T o draw the vector diagram of a series RLC c ircuit. Apparatus: S.no D escription R ange Q ty R heostat 00Ω,.7A I nductor 600mH, A 3 C apacitor 00μF, Φ dimmerstat 30/ 070, 8A 5 A mmeter 0 A (MI) 6 M ultimeter 7 C onnecting wires Theory: A n ac voltage of rms value e stablishes an rms current I given by when applied to an RLC series circuit I =/Z Where Z= ( ) X C X L R X C X L. t an R Where Φ is the angle between voltage and current i.e phase angle. When XL> X C t he circuit behaves as inductive and the current lags the voltage by an angle Φ. When > X L t he circuit behaves as capacitive the current leads the voltage by an angle Φ. X C Procedure:. T he connections are made as shown in the circuit diagram.. With the d immerstat at zero output the supply switch is closed. 3. T he dimmerstat is varied in steps such that the output voltage is adjusted to the values given in the tabular column and for each step the voltage across R, voltage across L and oltage across C as well as c urrent are noted. 4. T he dimmerstat is brought back to zero output and the supply switch is o pened. Circuit diagram: N etworks Lab (ECE7) 45

46 Tabular column: S.No in olts I in A mps in olts in olts 3 in olts 3 in olts Calculated in olts Φ in D egrees C osφ Specimen calculations: Φ ( =Tan Cos ) ( Sin 3) X L R Phase ector diagram: `Φ X L X angle Φ= Tan R R C = tan Sin ( Cos ) iva Questions:. The power consumed in a c ircuit element will be least when the phase difference b etween &I is?. When frequency of applied voltage in a series RC circuit is increases, what h appens to X[c]? 3. Give the phasor diagram of series RL circuit? 4. Give the phasor diagram of series R C circuit? 5. What is the phase angle between capacitor current and the applied voltage in a p arallel RC circuit P recautions:. Don't touch bare conductors when supply is ON. Don't Switch on the supply unless the circuit is approved by any Staffmember. 3. Wear s hoes in laboratory to avoid Electric shocks N etworks Lab (ECE7) 46

47 4. Switch off the all the measuring devices when NOT in USE. 5. Check for proper polarity of meters. 6. Ensure that there is no short circuit across the supply or any device, before switching on t he supply N etworks Lab (ECE7) 47