10ECL78-Power Electronics Lab

Transcription

1 Circuit Diagram-1: Circuit Diagram-2: To find the Latching Current: Dept. of ECE, CIT, Gubbi Page No. 1

2 Experiment No. 1 a) Static Characteristics of SCR Static Characteristics of SCR and DIAC Date: / / Aim: To obtain static V-I characteristics of SCR for different gate currents and also measure holding current IH, latching current IL and on state resistance of SCR. Apparatus Required: Sl. No. Particulars Range Quantity 1. SCR TYN Resistors As per design 1 each 3. Ammeter 0-20/200mA 2 4. Multimeter Diode BY Transformer DRB CRO Probes - 1 set Procedure: To Plot the V-I Characteristics of SCR: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Both RPS-1 and RPS-2 should be in zero position and the supply switch is ON 4. To find Gate current required to trigger the SCR: Fix the anode voltage VAK around 20V (by using the RPS-2). Increase the gate current gradually by using RPS-1 until the SCR turns on (VAK meter becomes approximately 0.7V). 5. Bring the RPS-2 to zero position. Now adjust the gate current to the required value by using RPS Increase the RPS-2 gradually and the corresponding readings of V AK and I A are noted down. 7. When RPS-2 reaches a particular value, SCR turns on for the second time. Note down that RPS-2 value i.e the break over voltage. 8. Repeat the steps 6 and 7 for some other gate current value. 9. Graph between V AK and I A is plotted. To find the Holding Current (I H ): 1. Connections are made as shown in the circuit diagram Keep the anode voltage around 20V by using RPS-2 and turn on the SCR by applying the required gate current by using RPS Bring back RPS-1 to zero position and switch off. 4. Gradually reduce the anode voltage by using RPS-2. Anode current also decreases slowly, at certain value, the anode current will jumps to zero suddenly. Note down this current value. (This is Holding Current). Dept. of ECE, CIT, Gubbi Page No. 2

3 Design: V AK = V AA I A R A R A = (V AA V AK ) / I A Assume V AAmax = 30 V, V AKon = 0.7 V, and I A = 100 ma Then R A = 293 choose R A = 300 and P RA = ( V AAmax V AKon ) 2 / R A = 2.86 W Therefore R A = 300 / 10 W Tabular Column: IG 1 = ma, V BO1 = V IG 2 = ma, V BO2 = V V AK in Volts I A in ma V AK in Volts I A in ma Ideal Graph: I A in ma Ron = V AK / I A I A IG 2 > IG 1 Latching Current I L V AK Holding Current I H V BR IG 2 IG 1 0 V BO2 V BO1 V AK in V Dept. of ECE, CIT, Gubbi Page No. 3

4 To find the Latching Current (I L ): 1. Connections are made as shown in the circuit diagram Keep DRB in maximum resistance position 3. Apply the VAA around 20V by using RPS 4. Observe the square waveform across the anode and cathode of SCR (now SCR is operating in Gate dependent mode) 5. Now reduce the DRB (from higher range to lower) gradually till the square wave disappears (now SCR is operating in Gate independent mode) 6. Note down the anode current at which the square wave disappear (This is Latching Current) Calculation: On state resistance R on = V AK / I A = Result: The on state resistance of SCR R on = The holding current I H = ma The latching current I L = ma At gate current I G1 = ma the break over voltage V BO1 = V I G2 = ma the break over voltage V BO2 = V Dept. of ECE, CIT, Gubbi Page No. 4

5 Circuit Diagram-3: 2kΩ /1W Structure of DIAC Circuit Symbol of DIAC Design: - P DIAC = V DIAC x I DMAX I DMAX = P V DIAC DIAC 0.5w 28V 17.8mA R a(min) = V aa I V D(max) DIAC mA 1.79k 2 (max) P (max) = I D R a(min) = (17.8 ma) 2 x 1.79k Choose R a = 2 k /1W = 0.56 W Ideal Graph: Dept. of ECE, CIT, Gubbi Page No. 5

6 b) Static Characteristics of DIAC Aim: To Design & study the V-I characteristics of DIAC and determine the Break over voltage. Apparatus Required: Procedure: Sl. No. Particulars Range Quantity 1. DIAC-DB Power Supplies 0-60V 1 3. Wattage Resistors 2kΩ/1W 1 4. Ammeter 0-20/200mA 1 5. Multimeter Connections are made as shown in the circuit diagram-3. 2 Consider as T1 is positive w.r.t. T2 and by varying the supply voltage gradually in step-by step, note down the corresponding values of V & I. 3 Note down V & I at the instant of firing of DIAC and after firing (by reducing the voltmeter ranges and increasing the ammeter ranges) then increase the supply voltage V. Note down corresponding values of V & I. 4 The point at which DIAC fires, gives the value of break over voltage VBO1. 5 Plot a graph of V V/S I. 6 Now consider T2 is positive w.r.t T1 and repeat steps no. 2, 3 & 4. Tabular Column: Forward Characteristics: Reverse Characteristics: V in Volts I F in ma -V in Volts -I F in ma Result: Dept. of ECE, CIT, Gubbi Page No. 6

7 Circuit Diagram-4: 300 / 30W Ideal Graph: Transfer Characteristics: Ic(mA) Output Characteristics Ic(mA) Constant current region V CE2 VCE Ic V GE2 V CE2 > V CE1 V CE1 V GE1 Ic VG E2 > V GE1 V GE Constant resistance region V GE (V) V CE (V) Dept. of ECE, CIT, Gubbi Page No. 7

8 Experiment No.2 Date: / / Static Characteristics of MOSFET and IGBT a) Static Characteristics of IGBT Aim: To conduct an experiment to plot the transfer characteristics and output characteristics of an IGBT and to find the transconductance and output resistance. Apparatus Required: Sl. No. Particulars Range Quantity 1. IGBT-G4BC20S Ammeter 0-20/200mA 1 3. Multimeter - 1 Procedure: Transfer Characteristics: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Initially both RPS-1 and RPS-2 are kept at zero output position. 4. By varying the RPS-2, set V CE around 1V. 5. Now increase V GE by varying the RPS-1 gradually and note down the corresponding collector current. 6. Repeat the steps 4 and 5 for some other V CE value (Say 2V). 7. Draw the graph between V GE and I c. Output Characteristics: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Both RPS-1 and RPS-2 should be in zero output position and supply switch is ON 4. By varying RPS-1, set V GE to some value (slightly greater than the Threshold voltage determined from the transfer characteristics). 5. Now increase the V CE by varying the RPS-2 gradually and note down the corresponding collector current. 6. Repeat the steps 4 and 5 for some other V GE value. 7. Graph between V CE Vs I c is plotted. Dept. of ECE, CIT, Gubbi Page No. 8

9 Tabular Column: Transfer Characteristics V CE1 = V V GE in Volt I C in ma V CE2 = V V GE in Volt I C in ma Output Characteristics V GE1 = V V GE2 = V V CE (V) I C (ma) V CE (V) I C (ma) Dept. of ECE, CIT, Gubbi Page No. 9

10 Calculations: Trans conductance Output Resistance g m = Ic / V GE = mho R o = V CE / Ic = Results: The transconductance g m = mho The output resistance R o = Dept. of ECE, CIT, Gubbi Page No. 10

11 Circuit diagram-5: 300Ω/30W Ideal Graph: Transfer Characteristics: Drain Characteristics ID(mA) ID(mA) Constant current region V DS2 VDS ID V GS2 V DS1 V GS1 V DS2 > V DS1 ID V GS2 > V GS1 V GS Constant resistance region V T V GS (V) V DS (V) Dept. of ECE, CIT, Gubbi Page No. 11

12 b) Static Characteristics of MOSFET Aim : To conduct an experiment for plotting the transfer characteristics and drain characteristics of an MOSFET and to find the transconductance and drain resistance. Apparatus Required: Sl. No. Particulars Range Quantity 1. MOSFET (IRF 540) Milliammeter 0-20/200mA 1 3. Multimeter - 1 Procedure: Transfer Characteristics: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Initially both RPS-1 and RPS-2 are kept at zero output position. 4. By varying the RPS-2, set V DS around 3V. 5. Now increase V GS by varying the RPS-1 gradually and note down the corresponding drain current. 6. Repeat the steps 4 and 5 for some other V DS value. 7. Draw the graph between V GS and I D. Output Characteristics: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Both RPS-1 and RPS-2 should be in zero output position and supply switch is ON. 4. By varying RPS-1, set V GS to some value (slightly greater than the Threshold voltage determined from the transfer characteristics). 5. Now increase the V DS by varying the RPS-2 gradually and note down the corresponding drain current. 6. Repeat the steps 4 and 5 for some other V GS value. 7. Graph between V DS Vs I D is plotted. Dept. of ECE, CIT, Gubbi Page No. 12

13 Tabular Column: Transfer Characteristics V DS1 = V V DS2 = V DS2 = V V V GS (V) I D (ma) V GS (V) I D in ma Output/Drain Characteristics: V GS1 = V V GS2 = V V DS (V) I D (ma) V DS (V) I D (ma) Dept. of ECE, CIT, Gubbi Page No. 13

14 Calculations: Trans conductance Drain Resistance g m = I D / V GS = mho R D = V DS / I D = Results: The transconductance g m = mho The drain resistance R D = Dept. of ECE, CIT, Gubbi Page No. 14

15 Circuit diagram-6: Half Wave Rectifier using RC Triggering T Y N R Design: RC 1.3T 2 The SCR will turn ON only when Capacitor voltage : V C = V g(min) +V D1 Transformer Secondary : V S I R V g(min) c V S Ig(min) R Vc I g(min) R V g(min) V D1 R V s V I g(min) g(min) V D1 From the data sheet of TYN612, V g(min) = 1.3V, V D1 = 0.7V, I g(min) = 2mA, I g(max) = 25mA R (min) = I gt(max) mA 1.277k R (max) = mA 16k Choose R 1 =100 Then R 2 = 1kΩ Dept. of ECE, CIT, Gubbi Page No. 15

16 Experiment No.3 Date: / / Controlled HWR and FWR using RC triggering circuit Aim: To study the performance & waveforms of HWR & FWR by using RC triggering Circuit. Apparatus Required: Procedure: Sl. No. Particulars Range Quantity 1. SCR TYN Transformer 230/ V 1 3. CRO Probe - 1 set 4. Diode- BY Resistor DRB,DCB 1 1. Connections are made as shown in circuit diagram-6,7. 2. Keep the value of DRB at 1K and DCB at 0.1uf. Switch ON the supply. 3. Now vary the firing angle by increase the value of resistance in DRB in steps, observe the waveforms and note down the corresponding values of V n and V m from CRO and V odc from the DC voltmeter. The readings are tabulated in the tabular column. 4. If the firing angle ranges from 0 to 90º, then the firing angle α is calculated by using formula α = sin -1 (V n /V m ) in degrees. 5. The conduction angle β is calculated using the formula, β = 180-α. 6. The current and power is calculated by I odc = V odc /R ampere and P odc = V 2 odc/r Watts respectively. 7. A graph of V o v/s α, V o v/s β, I o v/s α, I o v/s β, P odc v/s α and P odc v/s β are to be plotted. 8. Compare the practical output voltage with the theoretical output voltage, ( ) ( ) V. Where V m = 2*V rms. Dept. of ECE, CIT, Gubbi Page No. 16

17 Waveforms: Graph: Dept. of ECE, CIT, Gubbi Page No. 17

18 Full Wave Rectifier using RC Triggering Circuit diagram-7: Design: RC 50/2f R max Vs Vgt Igt(min) = mA = 16.32k R min Vs Vgt Igt(max) = mA = 1.3k Waveforms: Dept. of ECE, CIT, Gubbi Page No. 18

19 Tabular Columns: Half Wave Rectifier: V m = V Sl. No. V n α<90º α>90º ( ) ( ) V odc V oth Full Wave Rectifier: V m = V Sl. No. V n α<90º α>90º ( ) ( ) V odc V oth Dept. of ECE, CIT, Gubbi Page No. 19

20 Simulation: HWR: FWR: Result: Dept. of ECE, CIT, Gubbi Page No. 20

21 Circuit Diagram-8: Half Wave Rectifier Full Wave Rectifier Dept. of ECE, CIT, Gubbi Page No. 21

22 Experiment No.4 Date: / / U. J. T. firing circuit for HWR & FWR circuits Aim: To design a UJT firing circuit for both Half and Full wave rectifier and to study the performance of it. Apparatus Required: Sl. No. Particulars Range Quantity 1. SCR TYN Transformer 230/ V 1 3. Multimeter Diode- BY Resistor As per design 5 6. Capacitor As per design 1 7. DRB 1 8. Zener Diode 12V 1 9. UJT- 2N Pulse Transformer 1:1: CRO Probes Procedure: 1. Check the components/equipments of their correctness. 2. Connections are made as shown in circuit diagrams Set the DRB at 10K. 4. Now switch ON the supply. 5. By keeping the CRO probes across the load, waveforms are observed. 6. Now vary the firing angle by increase the value of resistance in DRB in steps, observe the waveforms and note down the necessary values. 7. A graph of V o v/s α and V o v/s β are to be plotted. 8. The practical output voltage (V omax ) is compared with V oth. For HWR, ( ) V For FWR, ( ) V Dept. of ECE, CIT, Gubbi Page No. 22

23 Design: Given η=0.7, R BB =5KΩ, V BB =20V, =2V,, ; ChooseC f =0.1µf ( ) ; Choose R b =220Ω ( ) and ( ) Choose Ideal Waveforms: Dept. of ECE, CIT, Gubbi Page No. 23

24 Tabular Columns: Half Wave Rectifier: V m = V Sl. No. V n α<90º α>90º ( ) ( ) V odc V oth Full Wave Rectifier: V m = V Sl. No. V n α<90º α>90º ( ) ( ) V odc V oth Dept. of ECE, CIT, Gubbi Page No. 24

25 Ideal Graph: V DC (V) Calculations: in deg Dept. of ECE, CIT, Gubbi Page No. 25

26 Simulation Circuit: Note: Similarly Construct for FWR Result: Dept. of ECE, CIT, Gubbi Page No. 26

27 Circuit Diagram-9: Dept. of ECE, CIT, Gubbi Page No. 27

28 Experiment No. 5 Date: / / Aim: Digital firing circuit for Single phase fully controlled Rectifier To draw the output waveforms of fully controlled rectifier using digital triggering circuit Apparatus Required: Sl. No. Particulars Range Quantity 1. 1-Phase fully controlled rectifier unit Digital triggering circuit unit CRO with probes 1 Procedure: 1. Digital firing circuit kit T1, T2, T3 and T4 terminals are connected with the corresponding SCR terminals in the rectifier unit. 2. Ensure the thumb wheel switch (F.A/D.cy) in the DFC kit should show 000 and the toggle switch in 180 o position. 3. Now switch ON rectifier unit then DFC kit. 4. Observe the output waveforms across the Load. 5. Vary the firing angle by varying the thumb wheel switch (F.A/D.cy) in the DFC kit in steps and observe the waveform. Circuit given is for fully controlled bridge rectifier. Students can try for Half Wave and Semicontrolled Converter. Note:For the detailed operation of DFC refer Appendix. Dept. of ECE, CIT, Gubbi Page No. 28

29 Waveforms: Dept. of ECE, CIT, Gubbi Page No. 29

30 Tabular Column: Sl. No. α in degrees V DC in Volts Ideal Graph: V DC(V) Resistive Load Inductive Load (deg) Result: Dept. of ECE, CIT, Gubbi Page No. 30

31 Circuit Diagram-10: Dept. of ECE, CIT, Gubbi Page No. 31

32 Experiment No.6 Aim: Date: / / Single phase Fully Controlled Bridge Converter with R and R-L loads To conduct an experiment on single phase fully controlled rectifier with R, R-L loads and vary the DC output voltage. Apparatus Required: Sl. No. Particulars Range Quantity FullyControlledBridge converter Module Fully Controlled Bridge Firing Module Resistor 300 / 30 W 1 4. Diode BY Transformer CRO with Probes Multimeter Resistive-Inductive Load - 1 Procedure: 1. Firing module triggering pulses are connected with the corresponding SCR terminals in the rectifier unit. 2. Ensure the firing angle variation POT is in zero position. 3. Now switch ON rectifier unit and then firing module. 4. By keeping the CRO probes across the Load (R, R-L) the waveforms are observed. 5. Now vary the firing angle by turning the POT in steps, observe the waveforms and note down the necessary values. 6. The graph between Vs VDC is plotted (for both R & R-L load). Dept. of ECE, CIT, Gubbi Page No. 32

33 Waveforms: Tabular Column: Vm = V : T = ms Sl. No. t (msec) (deg) (deg) V DC (V) (R - Load ) V DC (V) (R-L Load ) Note: = T t * 180 : = Ideal Graph: V DC(V) Resistive Load Inductive Load Calculations: (deg) Dept. of ECE, CIT, Gubbi Page No. 33

34 Result: Dept. of ECE, CIT, Gubbi Page No. 34

35 Circuit Diagram-11: Waveforms: Dept. of ECE, CIT, Gubbi Page No. 35

36 Experiment No. 7 Date: / / AC Voltage Control by using TRIAC-DIAC Combination Aim: To conduct an experiment to control the AC voltage using TRIAC-DIAC combination. Apparatus Required: Sl. No. Particulars Range Quantity 1. TRIAC BT DIAC SD Resistor & Capacitor As per design 1 each 4. Dimmerstat (1-ph Auto-Trans.) Transformer DRB CRO with Probes Incandescent Lamp 60W 1 9. Multimeter AC Milliammeter (0-200)mA (MI) 1 Procedure: 1. Check the components/equipments for their correctness. 2. Connection are made as shown in circuit diagram Set the DRB in minimum resistance position. 4. Keep the 1-Phase Auto-transformer in zero output position and the supply switch is ON. 5. Set the Auto-transformer output voltage around 150V (use Multimeter to measure). 6. Increase the DRB value in steps and observe Irms and Vrms (measure across transformer secondary) values and tabulate it. 7. Bring back the Auto-transformer output to Zero position and the supply switch is OFF. 8. The graph between Vs Vrms and Vs Irms are plotted. Note: Since 150V AC input is applied do not touch any components when supply is Switched ON. Dept. of ECE, CIT, Gubbi Page No. 36

37 Tabular Column: V m = V, T = ms R ( ) t (msec) (deg) (deg) V rms (V) I rms (A) Note: = T t * 180 : = Ideal Graph: V RMS (V) I RMS (A) (deg) (deg) Dept. of ECE, CIT, Gubbi Page No. 37

38 Result: Dept. of ECE, CIT, Gubbi Page No. 38

39 Impulse Commutated Chopper: Circuit Diagram-12 Wave forms: Dept. of ECE, CIT, Gubbi Page No. 39

40 Experiment No.8 Date: / / Voltage (Impulse) Commutated Chopper both constant frequency and variable frequency operations a) Constant frequency operation: Aim: To study the performance of voltage commutated chopper for constant frequency operations. Apparatus Required: Sl. No. Particulars Range Quantity 1. SCR-TYN Resistors 30Ω/30W 1 3. DIB Diode-BY DCB Power supply 1 9. Firing module 1 Procedure: 1. Connections are made as shown in the circuit diagram Input DC voltage is set to convenient value (4v to 11v). 3. By varying duty cycle knob of triggering circuit module step by step gradually note down corresponding T on and T from the CRO and VO from DC voltmeter and tabulate. 4. Duty cycle D is calculated by using 5. A graph of V O v/s D is plotted. D= T ON /T 6. Observe load and device voltage waveforms. Dept. of ECE, CIT, Gubbi Page No. 40

41 Graph: Tabular Column: Sl. No. Duty Cycle T ON CRO T CRO D= V o volts Dept. of ECE, CIT, Gubbi Page No. 41

42 Aim: b) Variable frequency operation: To study the performance of voltage commutated chopper for variable frequency operations. Apparatus: Sl. No. Particulars Range Quantity 1. SCR-TYN Resistors 30Ω/30W 1 3. DIB Diode-BY DCB Power supply 1 7. Firing module 1 Procedure: 1. Connections are made as shown in the circuit diagram-12 for constant frequency operation. 2. Input DC voltage is set to convenient value (10V to 25V). 3. Vary the output voltage by changing the duty ratio, D= by keeping Ton or T off constant and note down V o from DC voltmeter and tabulate. 4. Observe load and device voltage waveforms also tabulate the values accordingly. 5. A graph of V O v/s f is plotted. Tabular Column: Sl. No. Duty Cycle T ON CRO T CRO D= V o volts Result: Dept. of ECE, CIT, Gubbi Page No. 42

43 Circuit Diagram-13: Dept. of ECE, CIT, Gubbi Page No. 43

44 Experiment No.9 Date: / / Speed Control of a Separately Excited DC Motor Aim: To study speed control of DC motor and record armature voltage and speed for different values of α. Apparatus Required: Sl. No. Particulars Range Quantity 1. DC Motor speed control unit Sep. excited DC Motor 1 2. Tachometer Contact Type 1 3. Connecting probes - - Procedure: 1. Check the components/equipments of their correctness 2. Keep the voltage selector switch in OFF position and supply switch is ON. 3. The LCD display shows POWER MOSFET/IGBT CHOPPER 0FF DCY 0: FRQ - 50 Digital volt meter and ammeter shows Measure the Field voltage using digital voltmeter. It should be 220V ± 10% approximately and the neon lamp glows. 5. Now keep the voltage select switch at position 1 and measure the voltage at VDC terminals. It should be 24 volts. The output voltage should be 48 volts when VOLT- SELECT switch at position 2, 110 volts when the VOLT-SELECT switch at position 3, 220 volts when the VOLT-SELECT switch position at 4 approximately. 6. Make sure that the DC supply is correct. Now observe the driver output using CRO by varying duty cycle and frequency. 7. Make sure that the driver output is proper before connecting to the gate/emitter or gate/source of IGBT or MOSFET. 8. Now all the outputs are proper. Make the connections as given in the circuit diagram Vary the duty cycle in steps and keep the frequency as constant and observe the speed of the motor and note down the values of V, I and RPM. 10. Now change the frequency in steps and keep the duty cycle as constant and tabulate the necessary values. 11. Draw the graph between duty cycle Vs speed and Frequency Vs speed. NOTE: Connect field supply to the field terminals of the Motor before connecting to the armature supply. And the field supply should be removed only after switching OFF the armature supply. Dept. of ECE, CIT, Gubbi Page No. 44

45 Tabular Columns: Vin= V : Frequency= Hz Duty cycle (%) Vout (V) Io (A) Speed (rpm) Vin= V : Duty cycle = % Frequency (Hz) Vout (V) Io (A) Speed (rpm) Dept. of ECE, CIT, Gubbi Page No. 45

46 Chopper Simulation Circuit: Result: Dept. of ECE, CIT, Gubbi Page No. 46

47 Universal Motor (DC): Circuit Diagram-14: Universal Motor (AC) Graph: Circuit Diagram-15: Tabular column DC motorac Motor Vm= V T= ms V DC Speed (rpm) t (msec) (deg) (deg) Vrms (V) Speed (RPM) Dept. of ECE, CIT, Gubbi Page No. 47

48 Experiment No. 10 Speed Control of Universal Motor Date: / / Aim: To study speed control of Universal motor and plot speed v/s α. Apparatus Required: Procedure: Sl. No. Particulars Range Quantity 1. Universal Motor 1 2. Tachometer Contact Type 1 3. Connecting probes Diode-IN4001 DC Motor: a. Connections are made as shown in circuit diagram-14. b. Vary the Firing angle by varying resistor pot, note down the value of V n, V m, V DC and speed. c. Calculate firing angle. d. Plot the graph of speed verses firing angle. Note : For AC operation resistor value is varied using DRB and for DC operation use resistor pot. AC Motor: a. Connections are made as shown in circuit diagram-15. b. Above procedure is repeated for AC Motor. Note: = T t * 180 : = Result: Dept. of ECE, CIT, Gubbi Page No. 48

49 Circuit Diagram-16: Dept. of ECE, CIT, Gubbi Page No. 49

50 Experiment No. 11 Date: / / Single phase full bridge Inverter/Parallel Inverter a) Bridge Inverter Aim: To conduct an experiment on 1-phase full bridge PWM Inverter (IGBT based) Apparatus Required: Sl. No. Particulars Range Quantity 1. 1-phase full bridge Inverter Module Rheostat (0-100) /5A 1 3. Connecting probes - - Procedure:.. 1. Now make the connections as given in the circuit diagram Connect DC supply from (0-30) V regulated power supply unit. 3. Connect resistive load ohms 5 Amps Rheostat at load terminals (keep the sliding switch in middle position). 4. Connect driver output signals to the Gate and Emitter of corresponding IGBTs. 5. Switch ON the DC supply. 6. SwitchON the mains supply. The LCD display shows 1-ph PWM inverter with modulation type and M- (modulation index) 00 and F-100 Hz and in OFF position. Now M-00 Blinks. Press INC key to set the M.I. from %. 7. Set the Modulation Index value in steps (keep the frequency as constant) and press the Run/STOP button then measure the output voltage and tabulate it. 8. Set the frequency value in steps (keep the M.I value as constant) and press the Run/STOP button then measure the output voltage and tabulate it. NOTE: The SET key works only when it is in OFF position. This is to avoid change of modulation type when the power circuit is ON. Dept. of ECE, CIT, Gubbi Page No. 50

51 Tabular column: Modulation Type: Frequency: Modulation Index (%) Output voltage (V) Modulation Type: Frequency: Modulation Index (%) Output voltage (V) Modulation Type: Modulation Index: Frequency (Hz) Output voltage (V) Dept. of ECE, CIT, Gubbi Page No. 51

52 Modulation Type: Modulation Index: Frequency (Hz) Output voltage (V) Simulation Circuit: Result: Dept. of ECE, CIT, Gubbi Page No. 52

53 Circuit Diagram-17: Firing Module: + 15V G1 GND K1, K2-15 V G2 Design: Circuit designed for operating frequency of f=1khz,assume C=0.1µF Calculate L: ( ) L= 3.94H Dept. of ECE, CIT, Gubbi Page No. 53

54 b) Parallel Inverter Aim: To convert DC to AC using Parallel Inverter Apparatus Required: Sl. No. Particulars Range Quantity 1. Thyristor s TYN DCB DIB Transformer 12V-0-12V 9V-0-9V 1 Procedure: 1. Make the connections as given in the circuit diagram. 2. Connect DC supply from (0-5) V regulated power supply unit. 3. Check the triggering pulses from firing module. 4. Switch ON the DC supply. 5. Adjust DCB and DIB to convert DC to AC. 6. Note down the frequency of AC Signal. Result: Dept. of ECE, CIT, Gubbi Page No. 54

55 Circuit Diagram-18: Commutation Circuit Pulse Transformer Design: Given η=0.7, R BB =5KΩ, V BB =20V, =2V,, ; Assume C f =0.1µf ( ) ; Choose R b =220Ω ( ) and ( ) Choose Waveform: Dept. of ECE, CIT, Gubbi Page No. 55

56 Experiment No. 12 Date: / / LC Commutation Circuit (Class B Commutation Circuit) Aim: To conduct an experiment to study the LC commutation circuit. Apparatus Required: Sl. No. Particulars Range Quantity 1. SCR TYN UJT 2N Diode BY Pulse Transformer CRO Probes - 1 set 6. Multimeter DCB DRB and DIB - 1 each 9. Resistor 30 / 30W 100, each Procedure: 1. Check the components / Equipment for their working condition. 2. Connections are made as shown in the circuit diagram Set the value of C f around 0.1 f and observe the triggering pulses in the pulse transformer. 4. Set the value of L around 1 to 5 mh and C around 1 to 10 Farads apply the input signal (Vi/p). 5. Observe the output waveform across the load. 6. By varying the value of C f or L or C vary T ON, and T OFF. 7. Note down T ON and T OFF and plot a graph of Duty cycle Vs V DC Dept. of ECE, CIT, Gubbi Page No. 56

57 Tabular Column: Sl. No. T ON in ms T OFF in ms Duty cycle V DC th In volt V DC th in volt V DC th = Duty cycle X V i /p T ON = LC Ideal Graph: V DC in V Duty Cycle Dept. of ECE, CIT, Gubbi Page No. 57

58 Calculations: Result: Dept. of ECE, CIT, Gubbi Page No. 58

59 Circuit diagram: Dept. of ECE, CIT, Gubbi Page No. 59

60 Experiment No. 13 Date: / / Study on Stepper Motor speed control Aim: To study the speed control techniques of the stepper Motor. Theory: Stepping motor is an electric motor which converts digital electric input in to a mechanical motion. Compared with other motor that can perform the same or similar functions, a control system using stepping motor has several significant advantages as follows: 1. No feed back is normally required for either position control or speed control. 2. Positional error is non-cumulative. 3. Stepping motor is compatible with modern digital equipment. In stepping motor the stator core has 6 salient poles or teeth, while the rotor has 4 poles. Three sets of windings are arranged as shown in figure1. Each set has 2 coils connected in series. A set of winding is called a phase, consequently this machine is three phase motor. Current is supplied from a DC power source to the winding via switches 1, 2 & 3. In state (1), the winding of phase 1 is supplied with current through switch 1 or phase 1 is excited. The magnetic flux is built up at the stator poles of phase II in the manner shown in state (2) and,a counter clockwise torque is created owing to tension in the inclined magnetic field lines. The rotor will then, eventually, reach state (3). Thus the rotor rotates through a fixed angle, which is termed the step angle, 15 o in this case, as one switching operation is carried out. If switch I is now opened to de- energize phase I, the rotor will travel another 15 o to reach state (4). The angular position of the rotor can thus be controlled in units of the step angle by a switching process. If the switching is carried out in sequence, the rotor will rotate with a stepped motion; the average speed can also be controlled by the switching process. The most important feature of the stepping motor is that it revolves through a fixed angle for each pulse applied to the logic sequencer. The rated value of this value of this angle (degrees) is referred to as the step angle. Upon receiving a step command pulse, the logic sequencer determines the phase to be excited (or energized) and the phase to be de-energized and sends signals to the motor driver which is the stage which controls current supplied to the motor. The logic sequencer is usually assembled with TTL or CMOS integrated circuit chips. When potential of an output cannel from the logic sequencer is on level H (high) the power driver works to excite corresponding phase of the winding similarly if the output is at level L(low), the phase of the same number is not excited or it is turned off. Modes of excitation: 1. Single phase excitation. 2. Two phase excitation. 3. Half-step mode excitation. Dept. of ECE, CIT, Gubbi Page No. 60

61 Dept. of ECE, CIT, Gubbi Page No. 61

62 Single phase excitation: Table1 shows the sequences of a single phase excitation mode for 3 & 4 phase motor. The shaded parts in the table represent the excited state, & the white blanks show the phases to which current is not supplied & so are not excited. The operation by single phase excitation is also known as 1 phase on drive. Two phase excitation: The operation of a motor in which 2 phases are always excited is called 2 phases on operation. The sequence for 3 & 4 phases motor are shown in table 2. Half step mode excitation: The excitation scheme that is a combination of single phase & 2 phase excitation is so called half step operation. The excitation sequence for three phase motor is given in table 3. Dept. of ECE, CIT, Gubbi Page No. 62

63 Circuit diagram: Waveform: Dept. of ECE, CIT, Gubbi Page No. 63

64 Experiment No. 14 Date: / / Study on Cyclo Converters Aim: To study the working of a single phase centre tap transformer type cyclo-converter. ApparatusRequired: Procedure: Sl. No. Particulars Range Quantity 1. Cyclo converter kit Resistor 100Ω/30watt Digital Multimeter Patch chords - As required 1. Switch ON the mains supply to the firing circuit. 2. Observe the trigger outputs by changing frequency division and by varying the firing angle. 3. Make sure that the firing pulses are proper before connecting to the power circuit. 4. Next make the power circuit connections as given in the circuit. 5. Connect the firing pulses from the firing circuit to the respective SCR s in the power circuit. 6. Connect R-load (50 ohms/ 25Watts) or 24V lamp at the output. 7. Connect V input AC supply from the centre tap transformer. 8. Switch ON the AC supply to the power circuit. 9. Keep the firing angle at and frequency division at 2. Switch ON the trigger outputs. 10. Vary the firing angle and note down the AC voltage across load using multimeter and tabulate the readings. 11. Draw the voltage wave forms for different firing angle. Repeat the same for different frequency division. 12. The circuit works as single phase AC voltage controller when the frequency division is at 1. It works as cyclo converter from 2-10 division. Dept. of ECE, CIT, Gubbi Page No. 64

65 Tabular column: SL. No. N (per cycle) Vo Dept. of ECE, CIT, Gubbi Page No. 65

66 Result: Dept. of ECE, CIT, Gubbi Page No. 66

67 VIVA QUESTIONS-1 Static Characteristics of SCR, TRIAC 1. Explain the construction details of a thyristor. 2. What are the applications of SCR. 3. Define Latching current and Holding current. 4. Define forward break over voltage. 5. Explain the working of SCR with the help of two transistor analogy. 6. Explain different thyristor turn on methods. 7. Explain dv/dt and di/dt protection circuits of a thyristor. 8. Explain different types of thyristors. 9. Explain the importance of series and parallel operation of thyristors. 10. Define the turn off time of SCR. 11. Explain the V-I characteristics of SCR. 12. Explain the V-I characteristics of TRIAC. 13. Explain the different modes of operation of an TRIAC. 14. What are the applications of SCR. 15. What are the applications of TRIAC. 16. Explain how do we find latching current. Static Characteristics of MOSFET, IGBT 1. Explain the constructional details of MOSFET. 2. Explain the construction details of IGBT. 3. Explain different types of MOSFETs. 4. Compare enhancement and depletion MOSFETs. 5. Define Pinch off voltage, threshold voltage of MOSFETs. 6. Explain the characteristics of MOSFET. 7. Explain the characteristics of IGBT. 8. Explain the advantages and disadvantages of MOSFET. 9. Explain the advantages and disadvantages of IGBT. 10. Explain the control characteristics of MOSFET and IGBT. 11. Compare IGBT with BJT. 12. Compare MOSFET with BJT. 13. What are the applications of MOSFET and IGBT. Controlled HWR, FWR using RC triggering, UJT triggering Circuit 1. What is a firing circuit. Why is it needed. 2. What are the requirements of a firing circuit. Dept. of ECE, CIT, Gubbi Page No. 67

68 3. Explain R triggering circuit. 4. What are the advantages of pulse triggering circuits. 5. Compare R triggering and RC triggering circuits. 6. Explain the working of RC triggering circuit. 7. Explain the construction of UJT. 8. Explain the V-I characteristics of UJT. 9. Explain the working of UJT triggering circuit. 10. Explain the principle of digital firing circuits. 11. What is the roll of pulse transformer. AC Voltage Controller using TRIAC-DIAC Combination 1. How TRIAC can be used in AC voltage controller. 2. Explain the working of the circuit given for AC voltage controller. 3. Explain the characteristics of DIAC. 4. What are the applications of AC voltage controllers. 5. What type of triggering is suitable for ac voltage controller with inductive load. Single phase half and full controlled converter 1. What is a controlled converter. 2. What are the performance parameters of a converter. 3. Compare half controlled converter and full controlled converter. 4. What is the effect of inductive load on converters. 5. Explain the roll of free wheeling diode. 6. explain the working of a controlled converter. 7. What is a dual converter. 8. Compare single phase and three phase converters. 9. What are the applications of controlled converters. LC and Auxiliary commutation circuits. 1. What is a commutation circuit. 2. Why do we need commutation circuits. 3. Compare natural or line commutation and forced commutation. 4. What are different types of commutation circuits. With the help of neat circuit diagram explain the working of each circuit. 5. Explain the working of LC commutation circuit. 6. Explain the working of Auxiliary commutation circuit. 7. What is a chopper. 8. What are the types of chopper. Dept. of ECE, CIT, Gubbi Page No. 68

69 9. Explain the principle of step down and step up choppers. 10. Explain the working of voltage commutated chopper. 11. What are the application of choppers. 12. What is pulse width modulation control of a chopper. 13. What is the frequency modulation control of a chopper. 14. What are the applications of choppers. 15. Explain the classifications of choppers. Speed control of Induction motor and DC motor 1. Explain the working of the circuit used for speed control of Induction motor. 2. Explain the working of the circuit used for DC motor. 3. What type of triggering pulses are used in speed control of motor circuits. Dept. of ECE, CIT, Gubbi Page No. 69

70 Viva Questions-2 1. What is power Electronics? 2. Mention the different methods of varying the power? 3. What are the advantages of silicon over germanium? 4. What is power device? 5. Mention the different types of power devices? 6. What is an SCR? 7. What are the features of SCR? 8. What are the applications of SCR? 9. What is a Diac? 10. What are the features of Diac? 11. What are the applications of Diac? 12. What is a Triac? 13. What are the features of Triac? 14. What are the applications of Triac? 15. What is power MOSFET? 16. What is power IGBT? 17. What are the applications of MOSFET & IGBT? 18. Compare SCR, DIAC & TRIAC? 19. Compare MOSFET, BJT & IGBT? 20. What is turn on time? 21. What is turn off time? 22. What is static Characteristics? 23. What is dynamic Characteristics? 24. What is the difference between the Static & Dynamic Characteristics? 25. Explain the Turn on Characteristics & Turn off Characteristics of SCR? 26. Explain the gate characteristics of SCR? 27. What is a current controlled device? 28. What is a Voltage controlled device? 29. Explain O/p & Transfer characteristics of MOSFET & IGBT? 30. Explain the intension of using power device in power control circuit? 31. What is a power control? 32. Why SCR is called as Unidirectional Controlled device? 33. Why Diac is called as Bidirectional controlled device? 34. Why Triac is called as Bidirectional controlled device? 35. What is rectifier? 36. What is an Inverter? 37. What is step down chopper? What is its o/p voltage equation? Dept. of ECE, CIT, Gubbi Page No. 70

71 38. What is step up chopper? What is its o/p voltage equation? 39. What is buck boost regulator? What is its o/p Voltage equation? 40. What is cuck regulator? What is its o/p Voltage equation? 41. Explain the working operation of single phase controlled Half wave rectifier with a) R Load (b) RL Load (c) RL load with free wheeling diode 42. What is an intention of using free wheeling across inductive load in rectifier circuit? 43. What is pulse width? 44. Why turn off time of the circuit should be greater than turn off time of the device? 45. Explain the working operation of single phase full wave controlled rectifier with a) R Load (b) RL Load (c) RL load with free wheeling diode 46. Explain the working operation of single phase half wave controlled rectifier with a) R Load (b) RL Load (c) RL load with free wheeling diode 47. Explain the working operation of single phase full controlled bridge rectifier with a) R Load (b) RL Load (c) RL load with free wheeling diode 48. Define average output voltage, RMS Voltage, peak or maximum voltage? 49. Derive an expression of average output voltage, RMS output voltage of any wave form concerned to rectifier, ac voltage controller, chopper? 50. What are cyclo converters? 51. What is cyclo inverter? 52. Why forced commutation circuit is employed in case of cyclo inverter? 53. What are the advantages of three phase circuit over single phase circuit? 54. What is firing angle or delay angle? 55. What is conduction period? 56. What is meaning of triggering? 57. What are the different types of triggering methods (can be used to trigger SCR)? 58. What are the different types of triggering methods, temperature triggering, light triggering and gate triggering? 59. Why gate triggering is preferred than other types? 60. Mention the different types of gate triggering circuit? 61. Explain the working operation of RC triggering circuit? 62. Why firing angle in case of R triggering circuit if limited to 90 degrees? 63. Explain the working operation of RC Triggering circuit? 64. Explain how firing angle will be extended to more than 90 0 by using Rc triggering Circuit? 65. What is Unijunction Transistor (UJT)? 66. Write equivalent circuit of UJT? 67. Show that V peak=vp =nv BB + V diode where n = intrinsic stand off ration, VBB= applied or base voltage? Dept. of ECE, CIT, Gubbi Page No. 71

72 68. Why UJT triggering circuit is superior than R & RC triggering circuit? 69. What is UJT Relaxation oscillation? 70. What is line synchronized UJT triggering circuit? 71. Explain the working operation of UJT relaxation oscillator? 72. Explain the working operation of line synchronized UJT triggering circuit with wave forms at different points? 73. Design of UJT triggering circuit? 74. When UJT will conduct? 75. How UJT exhibits negative resistance property? 76. Why SCR, DIAC, TRIAC are called negative resistance devices? 77. Derive an expression of frequency of UJT triggering pulse? 78. What is the function of pulse transformer? 79. What are the different types of voltage ratings, current ratings and power ratings? Explain each them? 80. Why do we require protection circuits for power devices? 81. What is di/dt rating? How do you protect SCR against high di/dt rating? explain 82. What is dv/dt rating? How do you protect SCR against high dv/dt rating? explain 83. What is over current? How do you protect SCR against over current? explain 84. What is over voltage? How do you protect SCR against over voltage? Explain 85. How device will be protected against heavy power dissipation? 86. Why triac has 4 modes of operations? 87. Why 1 st & 2 nd mode of operations are operating in 1 st Quadrant and 3 rd & 4 th mode of operations are operating 3 rd quadrant? 88. Why mod (1) is mot sensitive among all modes? 89. What is Commutation? 90. What is commutation circuit? 91. What is forced commutation circuit and natural commutation circuit? 92. Mention the different types of forced commutation circuits? 93. Explain the working operation of each forced commutation circuit with wave forms & derivation of designed equations ( Class A, Class B, Class C, Class D, Class E and Class F commutation circuit) 94. What is latching current? What is its significance? 95. What is holding current? What is its significance? 96. What is dv/dt rating? What is its significance? 97. What is dual converter? 98. Why full wave bridge controller bridge rectifier with RL Load (not with free wheeling diode) is preferred in dual converter than half wave bridge controlled rectifier with RL load (not free wheeling diode)? Dept. of ECE, CIT, Gubbi Page No. 72

73 99. Why dual converter is called as four quadrant operator? 100. What is semi converter? 101. What is full converter? 102. Why gate is preferred at base of NPN transistor & not at the base of PNP transistor in SCR? 103. Derive an expression of anode current (SCR Current)? 104. Explain the working operation of SCR with two transistor analogy? 105. Explain the working operation of each practical power Electronics experiments with circuit diagram, wave forms & designed equation? 106. Why output voltage is more at lesser value of firing angle? 107. What are the differences between uncontrolled output & controlled output? 108. How do you design zener voltage regulator? 109. How do you select (design) the value of gate resistor and load resistor concerned to SCR experiments? 110. Why do you check SCR, Triac, Diac, Diode, Zener Diode, wires by using ohm meter? 111. How do you check an ammeter, voltmeter & power supply? 112. Why load resistor has higher wattage? 113. What is series Inverter? Mention the advantages, disadvantages and application of series inverter? Explain its working operation? 114. What is parallel inverter? Explain its working operation? 115. What is continuous mode & discontinuous mode of operations concerned to rectifier with a) RL Load b) RL load with free wheeling diode? 116. Input voltage = device voltage + output voltage. Prove above words? 117. What are the blocking & reverse blocking? 118. What is blocking state or region? 119. What is forward blocking and reverse blocking? 120. What is reverse recovery time? 121. What is gate pulse? 122. Why gate pulses are preferred than continuous gate voltage? 123. S.T Turn on time =td + tr + ts 124. S.T Turn off time =trr +tgr 125. How do you design gate pulse width? 126. What is snubber circuit? How do you design snubber? 127. What is heat sink its purpose is what? 128. What is circuit breaker and fuse? Why these are used in power circuit? 129. What is ac voltage controller? Mention the different types? What are its applications? Dept. of ECE, CIT, Gubbi Page No. 73

74 130. Explain the working operation of a) on and off AC Voltage controller b) Unidirectional or Half wave controller C) Bidirectional or full wave AC Voltage controller with R load and RL Load with wave forms with equations? 131. Why continuous gate pulses are applied to full wave ac voltage controller with RL Load circuit? 132. Explain the working operation of static on load tap changer? 133. Why negative gate voltage should not be applied to gate of SCR? 134. Write symbols, static characteristics of all power devices concerned to syllabus? 135. Name different current controlled power devices? 136. Name different Voltage controlled power devices? 137. What is I 2 t rating? Dept. of ECE, CIT, Gubbi Page No. 74

75 Question Bank 1. Conduct a suitable experiment to obtain the V-I characteristics of the SCR and determine holding current, latching current and on state resistance. 2. Conduct a suitable experiment to determine the V-I characteristics of unidirectional four layer switch for two different gate currents. Determine breakdown voltage for two cases. 3. Conduct a suitable experiment to obtain the V-I characteristics of the DIAC. Experimentally determine the breakdown voltage in quadrant-i and Quadrant- III. 4. Conduct a experiment to obtain transfer characteristics and output characteristics of an IGBT. Determine the value of trans-conductance and output resistance. 5. Design and simulate an experiment toobtain transfer characteristics and drain characteristics of an MOSFET. Determine the value of trans-conductance and drain resistance. 6. Design and simulate an experiment using SCR in an half wave rectifier circuit to vary the DC voltage fed to load using R-C triggering circuit. Plot a graph of output DC voltage v/s firing angle ( ). 7. Design and simulate an experiment using SCR in an full wave rectifier circuit to vary the DC voltage fed to load using R-C triggering circuit. Plot a graph of output DC voltage v/s firing angle ( ). 8. Conduct an experiment to control the illumination of an incandescent lamp using TRIAC-DIAC combination. Plot a graph of Vrms v/s firing angle ( ) and Irms v/s firing angle. 9. Conduct a suitable experiment on half / full controlled converterbridge with R and RL load. Plot a graph of output DC voltage v/s firing angle ( ). Dept. of ECE, CIT, Gubbi Page No. 75

76 10.Conduct an experiment to turn off SCR by using LC commutation circuit. Plot graph of duty cycle v/s output DC voltage. 11.Conduct an experiment to turn off SCR by using Auxiliary commutation circuit. Plot graph of duty cycle v/s output DC voltage. 12.Conduct an experiment to obtain AC output voltage using bridge inverter circuit. 13.Conduct a suitable experiment to control the speed of a stepper motor. 14.Conduct a suitable experiment to control the speed of a DC motor. Plot a graph of speed v/s firing angle ( ). 15.Conduct a suitable experiment to control the speed of a universal motor. Plot a graph of speed v/s firing angle ( ). 16.Conduct an experiment to generate the firing signals for thyristors/ triacs using digital circuits/ microprocessor. 17.Design and simulate an experiment toobtain synchronized triggering pulses using UJT to turn on an SCR in a full wave rectifier/half wave rectifier with resistive load. Plot a graph of output DC voltage v/s firing angle ( ). 18.Conduct an experiment to convert fixed DC voltage to variable DC voltage by using voltage commutated chopper. Plot a graph of duty cycle v/s output DC voltage. * * * * * * Dept. of ECE, CIT, Gubbi Page No. 76

77 REFERENCES 1. SCR Manual, 5 th Edition, N.Y., General Electric Company, B.K.Bose, Power Electronics and AC Drives, Prentice-Hall, Englewood Cliffs, New Jersey 07632, P.C.Sen, Thyristorised DC Drive, New York: Wiley Interscience, B.K.Bose, Evaluation of Modern Power Semiconductor Devices and Future Trends of Converters, IEEE Trans. Industry Applications, vol. 28, No. 2, pp , March/April, NED MOHAN, Power Electronics, John Wiley and Sons, M.H.Rashid, Power Electronics, Prentice-Hall of India, New Delhi, G.K.Dubey and C.R.Kasarabada, Power Electronics and Drives, IETE Book Series, Vol. 1, TM HILL P.C.Ltd., New Delhi B.K.Bose, Energy, environment and advances in Power Electronics, IEEE Trans. On P.E. Vol 15, No.4, July O.P. Arora, Power Electronics Laboratory, Theory Practice and Organization,2010, NAROSA publishing house private limited. Dept. of ECE, CIT, Gubbi Page No. 77