Power Lab Manual 7th Sem 2011_BGS

Department of Electronics & Communication

JSS ACADEMY OF TECHNICAL EDUCATION (AFFILIATED TO VTU) Uttarahalli-Kengeri Main Road, Mylasandra Bangalore 560060

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

POWER ELECTRONICS LAB MANUAL (06ECL78) (VII SEM) B. G. Shivaleelavathi, Assistant Professor, E&C Dept., JSSATE, Bangalore.

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INDEXSERIAL NO.1 2 3 4

CONTENTS Power Electronics lab syllabus Static characteristics of MOSFET and IGBT Static characteristics of SCR, TRAIC and DIAC Controlled HWR and FWR using RC triggering circuit SCR turn off using i) LC circuit ii) Auxiliary Commutation UJT firing circuit for HWR and FWR circuits Generation of firing signals for thyristors / TRIACs using digital circuits/microprocessor. AC voltage combination controller using

PAGE NO.3 4 to 9 10 to 17 18 to 25

5

26 to 33

6 7

34 to 43 44 to 47

8

TRIAC-DIAC 48 to 5051 to 73

9

Single phase Fully Controlled Bridge Converter with R and R-L loads

10

Voltage (Impulse) commutated chopper both 74 to 83 constant frequency and variable frequency operations Speed control of a separately exited DC 84 to 89 motor. Speed control of universal motor. Speed control of stepper motor. Parallel / Series inverter Model questions90 to 91 92 to 96 97 to 105

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12 13 14 15

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Department of Electronics & Communication 16 17

Viva questions Bibliography

Acknowledgements: I take this opportunity to thank my husband, parents, son, HOD of E&C Dept, E&C Department staff members and my colleagues

POWER ELECTRONICS LABSubject Code : 06ECL78 No. of Practical Hrs/Week: 03 Total no. of Practical Hrs. : 42 IA Marks : 25 Exam Hours : 03 Exam Marks : 50

1. Static characteristics of MOSFET and IGBT. 2. Static characteristics of SCR, TRIAC and DIAC. 3. Controlled HWR and FWR using RC triggering circuit 4. SCR turn off using i) LC circuit ii) Auxiliary Commutation 5. UJT firing circuit for HWR and FWR circuits. 6. Generation of firing signals for thyristors/ TRIACs using digital circuits/microprocessor. 7. AC voltage controller using TRIAC-DIAC combination. 8. Single phase Fully Controlled Bridge Converter with R and R-L loads 9. Voltage (Impulse) commutated chopper both constant frequency and variable frequency operations. 10. Speed control of a separately exited DC motor. 11. Speed control of universal motor. 12. Speed control of stepper motor.3 JSSATE , BANGLORE


13. Parallel / Series inverter.

1) STATIC CHARACTERISTICS OF MOSFET AND IGBT (i) STATIC CHARACTERISTICS OF MOSFET . AIM: To plot input and transfer characteristics of an MOSFET and to find ON state resistance and trans conductance. APPARATUS: 1. 0 50V DC Voltmeter 2. 0 100V AC Voltmeter 3. 0 100mA AC Ammeter 4. Regulated power supply 5. n-channel MOSFET(IRF-840) 6. Resistance (500/5W). DEVICE SPECIFICATIONS: IRF 840. 1. VDss-Drain to Source Breakdown voltage : 400 Volts. 2. Rds (on)-On state Resistance : 0.55 ohms. 3. ID-continuous drain current-25 C : 10 Amps. 4. ID-continuous drain current-100 C : 6.3 Amps. 5. RJC-Max thermal resistance : 1 C/Watt. 6. PD Max-power dissipation@ 25 C : 125 watts. CIRCUIT DIAGRAM:0 0m -5 0 A ID R1

VDS R2

0- 5 V 0

V 1

V 2 0 5 -1 V VS G

PROCEDURE: 4 JSSATE , BANGLORE

Department of Electronics & Communication i)Trans Conductance Characteristics: Make the connections as shown in the circuit diagram including meters. Initially keep V 1 and V2 minimum. Set V1=VDS1=say 10V. Slowly vary V2 (VGS) and note down ID and VGS readings for every 1 Volt and enter in the tabular column. The minimum gate voltage V GS that is required for conduction to start the MOSFET is called Threshold Voltage VGS(Th). The Drain current depends on magnitude of the Gate Voltage VGS which may vary from 2 to 5 Volts. Repeat the same for different VDS and draw the graph of VGS V/s ID. ii)Tabular Column: VDS1 (Volts) VGS (Volts) ID (mA) VDS2 (Volts) VGS (Volts) ID (mA)

iii)Drain Characteristics: Initially set V2 to VGS1=3.5 Volts. Slowly vary V1 and note down ID and VDS. For a particular value of VGS1 there is a pinch off voltage (Vp) between drain and source. If VDS is lower than Vp, the device works in the constant resistance region and ID is directly proportional to VDS. If VDS is more than Vp, constant Id flows from the device and this operating region is called constant current region. Repeat the above for different values of VGS and note down VDS Vs ID. Draw the graph of VDS Vs ID for different values of VGS. iv) Tabular Column: VGS1 (Volts) VGS2 (Volts)

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Department of Electronics & Communication VDS (Volts) ID (mA) VDS (Volts) ID (mA)

WAVEFORMS :ID mA Ohmic Active VGS4 >VGS3 > VGS2 >VGS1 VGS4 VGS3 VGS2 VGS1 VDS volts

0 Output Characteristics

ID

VG S (th) Transfer Characteristics

VD S

RESULT: VDS 1. RD = -------------ID = ------------------------------ .

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Department of Electronics & Communication ID 2. Gm = -------------VDS

= ------------------------------ mho.

CONCLUSION: We conclude that MOSFET is a voltage controlled device. VDS remains constant after it crosses the Vpeak value. (ii)) STATIC CHARACTERISTICS OF IGBT. AIM: To plot the characteristics of IGBT. APPARATUS: 1. 0 50V DC Voltmeter 2. 0 100V AC Voltmeter 3. 0 100mA AC Ammeter 4. Regulated power supply 5. Resistance (500/5W). 6. IGBT (IRGBC-20S) DEVICE SPECIFICATIONS: IRGBC 20S 1. Vce-Collector to emitter Voltage : 600 Volts. 2. Max Vce(on)-Collector to emitter Voltage : 3.0 Volts. 3. Ic-continuous collector current @ 25 C : 19 Amps. 4. ID-continuous collector current @ 100 C : 10 Amps. 5. Pd max-Maximum power dissipation : 60 Watts. CIRCUIT DIAGRAM:0-500mA IC R1

VCE R2

0 - 50V

V 1

V 2 0-15V VGE

PROCEDURE: i)Transfer Characteristics: Make the connections as shown in the circuit diagram with meters.

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Department of Electronics & Communication Initially keep V1 and V2 minimum. Set V1=VCE1=say 10V. Slowly vary V2 (VGE) and note down IC and VGE readings for every 1.0 Volt and enter in the tabular column. The minimum gate voltage VGE which is required for conduction to start the IGBT is called Threshold Voltage VGE(Th). If VGE is greater than VGE(Th) only very small leakage current flows from Collector to Emitter. If V GE is greater than VGE(Th), the Collector current depends on magnitude of the Gate Voltage. VGE varies from 4 to 8 Volts. Repeat the same for Vc and draw the graph of VGE V/S IC. ii)Tabular Column: VCE1 (Volts) VGE (Volts) IC (mA) VCE2 (Volts) VGE (Volts) IC (mA)

iii) Collector Characteristics: Initially set V2 to VGE1=5 Volts. Slowly vary V1 and note down IC and VGE. For a particular value of VGE1 there is a pinch off voltage (Vp) between Collector and Emitter. If VGE is lower than Vp, the device works in the constant resistance region and IC is directly proportional to VGE. If VGE is more than Vp constant IC flows from the device and this operating region is called constant current region. Repeat the above for different values of VGE and note down VCE V/S IC. Draw the graph of VCE V/S IC for different values of VGE. iv) Tabular Column: VGE1 (Volts) VCE (Volts) IC (mA) VGE2 (Volts) VCE (Volts) IC (mA)

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WAVEFORMS: COLLECTOR CHARACTERISTICS

VCE IC (mA)

IC

VGE3 VGE2 VGE1 OUTPUT = Resistance VCE IC =

VCE (volts)

TRANSFER CHARACTERISTICS

VCE IC (m ) A IC VGE T sfer ran R esistan ce = VGE = IC

VGE (volts)

RESULT: VCE 1. RON = -------------IC = ------------------------------ .

2. VGSTh = ------------------------------ Volts CONCLUSION:

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Department of Electronics & Communication We conclude that IGBT is a voltage controlled device. VCE remains constant after it crosses the Vpeak value. 2) STATIC CHARACTERISTIC OF SCR, TRIAC & DIAC (i) STATIC CHARACTERISTIC OF SCR

AIM: To plot the characteristics of an SCR and to find the forward resistance, holding current and latching current. APPARATUS: 1) 0 50V DC Voltmeter 2) 0 500mA DC Ammeter 3) 0 25mA DC Ammeter4)Resistor (1k/5w)

5)Regulated power supply 6)SCR (TYN616) 7)Rheostat DEVICE SPECIFICATIONS: TYN 616 1. Vrrm : 600V. 2. It(rms) : 16 A. 3. It(av) : 10 A. 4. It(sm) : 160 A. 5. It : 128 A/s. 6. di/dt : 100 A/s. 7. Igt : 25 mA. 8. Vgt : 1.5 V. 9. IH : 40 mA. 10. IL : 70 mA. 11. tq : 70s. 12. dv/dt : 500 V/s. CIRCUIT DIAGRAM:

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0-500mA IA

R1 V1

R2

0-25mA IG

VAK 0-50V

V2

PROCEDURE: i). V-I Characteristics: Make the connections as given in the circuit diagram. Now switch ON the mains supply to the unit and initially keep V1 & V2 at minimum. Set load potentiometer R1 in the minimum position. Adjust Ig-Ig1 say 10 mA by varying V2 or gate current potentiometer R2. Slowly vary V1 and note down VAK and IA readings for every 5 volts and enter the readings in the tabular column. Further vary V 1 till SCR conducts, this can be noticed by sudden drop of VAK and rise of IA readings. Note down this reading and tabulate. Vary V1 further and note down IA and VAK readings. Draw the graph of VAK V/S IA. Repeat the same for Ig=Ig2/Ig3 mA and draw the graph. Tabular Column: MODE 1, IG1= VAA (volts) V AK2 (volts) I AK (mA)

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V AA (volts) Department of Electronics & Communication

MODE 2, IG2= V AK (volts) I AK (mA)

To find latching current: Apply about 20V between anode and cathode by varying V1. Keep the load potentiometer R1 at minimum position. The device must be in the OFF state with gate open. Gradually increase Gate voltage- V2 till the device turns ON. This is the minimum gate current (Igmin) required to turn ON the device. Adjust the gate voltage to a slightly higher value. Set the load potentiometer at the maximum resistance position. The device should come to OFF state, otherwise decrease V1 till the device comes to OFF state. The gate voltage should be kept constant in this experiment. By varying R1, gradually increase anode current IA in steps. Open and close the Gate voltage V2 switch after each step. If the anode current is greater than the latching current of the device, the device stays ON even after the gate switch is opened. Otherwise the device goes into blocking mode as soon as the gate switch is opened. Note the latching current. Obtain more accurate value of the latching current by taking small steps of IA near the latching current value. Increase the anode current from the latching current level by load pot R1 or V1. Open the gate switch permanently. The thyristor must be fully ON. Now start reducing the anode current gradually by adjusting R1. If the thyristor does not turns OFF even after the R 1 at maximum position, then reduce V1. Observe when the device goes to blocking mode. The anode current through the device at this instant is the holding current of the device. Repeat the steps again to accurately get the IH. Normally IHVBBmax/Imax : R1>=VBDIAC/IDIAC R1>32/100ma R1>320 ohms Therefore , Let C=0.47 microfarads So, 0.00000047(320+R)=15mSec R=31900-320 =31580 ohms Choose a 100 kilo ohms potentiometer PROCEDURE: Make the connections as given in the circuit diagram. Switch ON the mains supply. Trigger the TRIAC using DIAC firing circuit. Vary the firing angle potentiometer and observe the AC voltmeter reading , waveform on the CRO & variation in lamp brightness and also note down the voltage variation across the lamp. For different positions ,we get different firing angle and for each setting note down the O/p voltage ac voltmeter reading in tabular column. Plot the graph of firing angle Vs ac load voltage. TABULAR COLUMN: Firing angle Practical -1 ()=sin (Vn/Vp) Vorms (Volts) Theoretical Vorms (Volts)

Vrms = Vm /2 Vorms = Vm [{( - )/(2 )} + {(sin 2 )/(2 )}]1/2 If =00; then Vorms = Vm /2 = Virms

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WAVEFORMS:

waveforms across Vsupply, capacitor (VFBO), TRIAC (VTRIAC), load(VL) with respect to source for = 90 degrees. RESULT: CONCLUSION : We conclude that power dissipation is less in case of DIAC firing circuit than UJT firing circuit. DIAC firing circuit has a better firing angle control than the UJT firing circuit.

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8) SINGLE PHASE CONTROLLED CONVERTER 1) SINGLE PHASE SEMI CONTROLLED CONVERTER AIM :-To conduct a suitable experiment on half controlled(semi controlled) converter with resistive and inductive load . APPARATUS :Dimmer-stat, isolator, rheostat, inductor (transformer/isolator)resistors ,single phase converter firing circuit, SCR converter module (power circuit module) . SINGLE PHASE CONVERTER FIRING CIRCUIT FRONT PANEL DIAGRAM:

SINGLE PHASE CONVERTER TRIGGERING UNIT - SCT90 120 ON / OFF 150 30 0 60

TRIGGER OUTPUTS + T1

180

FIRING ANGLE

TEST POINTS

T 1'

1 GND

2

3

T2

4

5

6

7

T 2'

POWER

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FRONT PANEL DETAILS: 1. Power 2. Firing angle 3. ON/OFF 4. Test points 5. Trigger outputs :- Main ON/OFF switch with built in LED Indicator. :- Potentiometer to vary the firing angle from 180 to 0 :- Switch for trigger output with soft start feature. :- To observe the signals at various points in the logic circuit for study purpose. :- T1 & T11 : For +ve Half Cycle. T2 &T21: For -ve Half Cycle.

This unit generates four line synchronized isolated triggering pulses to fire thyristors connected in single phase (1) Half wave (2) Full wave (3) Half controlled Bridge (4) Fully controlled Bridge and (5) AC phase control power circuit. The firing circuit is based on Ramp-comparator scheme. Isolation is provided by pulse transformer. FEATURES :1. 2. 3. 4. 5. 6. Work directly on 230V AC mains. Gate drive current of 200mA to trigger wide range of devices. Firing angle variation from 180 to 0 on a graduated scale. Test points to study the logic circuit Soft start and soft stop feature. Neatly designed front panel.

This unit along with our SCR converter modules, rectifier diode modules, single phase half controlled converter power circuit and single phase fully controlled converter power circuit can be used to conduct power electronics experiments on single phase. BACK PANEL DETAILS :Mains socket with built in fuse holder. Fuse -500mA. A spare fuse is also provided in the fuse holder. INSTALLATION: While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on the equipment. Use a properly earth grounded outlet socket to connect to the equipment. This is so because a floating earth ground will not provide a clean AC reference to the equipment. The power input plug is situated on the back panel of the unit. Use the power cord provided along with the equipment to the power outlet socket.

INPUT POWER SPECIFICATIONS:

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Voltage : 215V -245V AC at 45 to 55Hz. Current : 75mA (Max continuous) @ 230V AC. 500mA (Max surge). Fuse : 500mA (Slow Blow) capsule type 20x 5mm. Situated in the lower left corner of the equipment front panel is the power ON/OFF switch with built in LED indicator. The LED glows when the switch is in ON position. A fuse protects the equipment against over voltage and any short circuit. The fuse holder is an integral part of the power inlet plug situated on the back panel. A spare fuse is provided in the fuse holder. The power cord has to be removed from the plug, before you can access the fuse holder. While replacing the fuse, pull off the holder smoothly. Refer to figure shown below:

Power inlet plug

Pull here Fuse holder

Power inlet plug/fuse holder

Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, replace back the assembly in correct direction and press it until it flushes with the surface. Now connect power cord back into the plug. Switch on the mains supply to the equipment. Observe the signals at test points, trigger outputs and their phase sequence before connecting to the thyristor in the power circuit. The built in pulse transformer based isolation between the trigger circuits and the power

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Department of Electronics & Communication circuit provides isolation up to a tune of 1000V.

C IR C U IT D IA G R A M+ 12V 1K F IR IN G A N G L E P O T5V1

100K 1N 4007 100K

+ 12V

10 K +12V +12V 1 K T3 4 1 4 8 + 15V T1 T2 SV 1 0 .1 100 K 4K7 -12 V + 12V 4K 7 22K 1N 4007 4K 7 + 12V 4K 7 22K 1N 4007 1K 4K 7 4K 7 4K 7 41482N 2222

O F F /O N 1K 100F

1K

3 7 6 741 7 6 100K 1K 2 4 741 T5 4 T 3 4 1K

+12V

100K

4K 7

-1 2 V

47K

(7 5 m A ) 10K 1N 4007 0 + 15V

7V 5 1K 4148

3 3 Vu n + 12V

/5 W 33012V B C 107

1N 4007

GATE

1K 8 5V 1 T1

4K 7 4 1 4 8IN P4148

P /n 1 K 4K 7

7V S

2N 2222

T6

3 8 7 4 555 12K 6 5 1 2 0 .0 1 + 12V 414822P F

T S L - 1 0 0710K

1N 4007

CAT GATE

1K 8 5V 1 T1'

0 .0 1

CAT

1N 4148

P 7V 5

4K 7 3 8 7 4 555 12K 6 5 1 2 0 .0 1 4148 15V 0 .7 5 A 0 .0 1 15V 1N 4007 1N 4007

78121000F 25V 1000F 25V

+ 12V 1 0 0 0 F 0 .1 F 25V GND 1000F 0 .1 F 25V -1 2 V

7912

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TEST POINTS 1

2 3

Vc 4 5 6 7

8

TRIGGER OUTPUTS T1 & T1 T2 & T2

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Department of Electronics & Communication SERVICING DETAILS SINGLE PHASE CONVERTER FIRING CIRCUIT : a) Check the 3 pin Mains Cable used along with this unit b) Check the Fuse in the Mains socket c) Check the Mains Switch d) Check the transformer e) Check the firing angle potentiometer. f) Check the ON/OFF switch g) Check the zener diodes & IN4007 diodes at the output of the pulse transformer. h) Check +12V & -12v power supply (Check 7812 &7912 regulators) i) Check BC 107 & SL 100 transistors j) Check 2N2222 transistors k) Check 741/555ICs l) Check for any loose contacts. SINGLE PHASE SEMI CONTROLLED CONVERTER POWER CIRCUIT : SPECIICATIONS, 230V/5A The circuit arrangement of a single-phase full converter is shown in fig. During the positive half cycle, thyristor T1 and T11 are forward biased; and when these two thyristor are fired simultaneously at wt= , the load is connected to the input supply through T1 and T11 . In case of inductive loads, during the period wt ( + ), the input voltage is negative and the freewheeling diode Dm is forward biased. Dm conducts to provide the conductivity of current in the inductive load. The load current is transferred from T1 to Dm; and thyristor T1 IS turned off due to line or natural commutation. During the negative half cycle of the input voltage, thyristor T2 is forward biased. The firing of thyristor T2 at wt= + will reverse bias Dm. The diode Dm is turned off and the load is connected to the supply through T2 and T21. Figure shows the waveforms for input voltage, output voltage and Trigger Outputs. FRONT PANEL DIAGRAM:

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Department of Electronics & Communication This power circuit consists of four SCRs connected as semi- controlled bridge converter. A free wheeling diode is provided to observe the effect of free wheeling diode on inductive loads. Each device in the unit is mounted on an appropriate heat sink and is protected by snubber circuit. Short circuit protection is achieved using glass fuses. A circuit breaker is provided in series with the input supply for overload protection and to switch ON/OFF the supply to the power circuit. The front panel consists of input and output terminals. The gate and Cathode of each SCRs brought out on the front panel for firing pulse connection. Voltmeter and an Ammeter is mounted on the front panel indicates the output voltage and current. A separate full wave bridge rectifier is provided in the unit to get the DC supply for the field of DC Shunt Motors. The power circuit schematic is printed on the front panel.

SPECIFICATIONS: Input Voltage Load current Fuses Field supply MCB FRONT PANEL DETAILS: Input terminals Output terminals(+&-) Voltmeter(0 to 300V) Ammeter(0 to 5A) Circuit breaker T1 & T2 D1 & D2 DM Field(+ and -) (with indicator)

:15V to 230V AC. : 5 Amps maximum : 6 Amps fast blow glass fuses. : 220V 10%/2 Amps : Two pole 6 Amps/ 230V : To connect single phase input supply. : To connect load. : To indicate output voltage : To indicate output current. : 6 Amps AC power ON/OFF to the circuit and for protection . : SCR 16 TTS 12-16 A rms/1200Volts. : Diodes SPR 16PB-16A/1200V : Free wheeling diode SPR 16PB-16A/1200V : Field supply for DC motor for motor control experiments.

BACK PANEL DETAILS: Mains socket : For 230V AC mains supply to field supply bridge rectifier. Fuse holders : 2 fuses in series with input AC supply, a fuse at the output and a fuse for free wheeling diode.Fuse - 6 Amps SINGLE PHASE POWER CIRCUIT BLOCK DIAGRAM: : Dimmer Stat Isolation0-230V

Power Circuit Load

230 V ,50Hz

Transformer

Firing circuit 58 JSSATE , BANGLORE

Department of Electronics & Communication 1. Isolation Transformer: To suit single phase 230V/50Hz supply, ratio 1:1, KVA rating to suit the load rating with tapping at different voltages. Isolation of mains, phase and neutral with measurement circuit. Serves the purpose of di/dt protection of SCRs and safe measurement of waveforms by using oscilloscope. Isolation of Electric noise with mains. 2. Power circuit: Different power circuit configurations are possible using SCRs and diode modules. Half Wave Converter 1SCR Half Controlled Converter _ 2 SCRs & 2 Diodes AC phase Control 2 SCRs 3. Firing Circuit: Each SCR of the above Power Circuit to be triggered using independently isolated outputs using single phase converter firing unit. Trigger outputs phase sequence and variation to be checked before with the power circuit. Phase sequence to be compared with the power circuits phase sequence.

PROCEDURE :Switch on the mains to the circuit. Observe all the test points by varying the firing angle potentiometer and trigger o/ps ON/OFF switch. Then observe the trigger o/ps and their phase sequence .Make sure that all the trigger o/p sure proper before connecting to the power circuit.. Next connections in power circuit .Use a dimmer stat with a isolator and connect it to power circuit. Connect the R-load between load points .Connect firing pulses from the firing circuit to respective SCRs .Switch ON the MCB trigger o/ps and note down load voltage can be seen .Repeat this same for R-L load and with and note down waveform.

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TABULAR COLUMN: Firing angle Practical -1 ()=sin (Vn/Vp) Vodc (Volts)

Theoretical Vodc (Volts)

Vodc (th) = Vm (1+cos ) /

Free Wheeling Diode, Resistive Load, and Resistive and Inductive load

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WAVEFORMS:

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RESULT:CONCLUSION :The output voltage at various firing angles are noted with R load and RL load and the difference with and without free wheeling diode is observed. The relevant waveforms are traced.

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Department of Electronics & Communication (ii) SINGLE PHASE FULLY CONTROLEED CONVERTER AIM: To Study the Single Phase Fully Controlled Converter on Resistance, Resistance & Inductance Loads . APPARATUS: Single Phase Converter Firing Circuit, Single Phase Fully controlled Power circuit, Rheostat (150 Ohms/5A), Inductor(150 mH/5A), Power Scope, Connecting Wires etc., SINGLE PHASE CONVERTER FIRING CIRCUIT FRONT PANEL DIAGRAM:SINGLE PHASE CONVERTER TRIGGERING UNIT - SCT90 120 ON / OFF 150 30 0 60

TRIGGER OUTPUTS + T1

180

FIRING ANGLE

TEST POINTS

T 1'

1 GND

2

3

T2

4

5

6

7

T 2'

POWER

FRONT PANEL DETAILS: 1. Power :- Main ON/OFF switch with built in LED Indicator. 2. Firing angle :- Potentiometer to vary the firing angle from 180 to 0 3. ON/OFF :- Switch for trigger output with soft start feature. 4. Test points :- To observe the signals at various points in the logic circuit for study purpose. 5. Trigger outputs :- T1 & T11 : For +ve Half Cycle. T2 &T21: For -ve Half Cycle. This unit generates four line synchronized isolated triggering pulses to fire thyristors connected in single phase (1) Half wave (2) Full wave (3) Half controlled Bridge (4) Fully controlled Bridge and (5) AC phase control power circuit. The firing circuit is based on Ramp-comparator scheme. Isolation is provided by pulse transformer. FEATURES :-

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Department of Electronics & Communication 1. 2. 3. 4. 5. 6. Work directly on 230V AC mains. Gate drive current of 200mA to trigger wide range of devices. Firing angle variation from 180 to 0 on a graduated scale. Test points to study the logic circuit Soft start and soft stop feature. Neatly designed front panel.

This unit along with our SCR converter modules, rectifier diode modules, single phase half controlled converter power circuit and single phase fully controlled converter power circuit can be used to conduct power electronics experiments on single phase. BACK PANEL DETAILS :Mains socket with built in fuse holder. Fuse -500mA. A spare fuse is also provided in the fuse holder. INSTALLATION: While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on the equipment. Use a properly earth grounded outlet socket to connect to the equipment. This is so because a floating earth ground will not provide a clean AC reference to the equipment. The power input plug is situated on the back panel of the unit. Use the power cord provided along with the equipment to the power outlet socket. Input power specifications: Voltage : 215V -245V AC at 45 to 55Hz. Current : 75mA (Max continuous) @ 230V AC. 500mA (Max surge). Fuse : 500mA (Slow Blow) capsule type 20x 5mm. Situated in the lower left corner of the equipment front panel is the power ON/OFF switch with built in LED indicator. The LED glows when the switch is in ON position. A fuse protects the equipment against over voltage and any short circuit. The fuse holder is an integral part of the power inlet plug situated on the back panel. A spare fuse is provided in the fuse holder. The power cord has to be removed from the plug, before you can access the fuse holder. While replacing the fuse, pull off the holder smoothly. Refer to figure shown below: Power inlet plug

Pull here Fuse holder Power inlet plug/fuse holder

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Department of Electronics & Communication Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, replace back the assembly in correct direction and press it until it flushes with the surface. Now connect power cord back into the plug. Switch on the mains supply to the equipment. Observe the signals at test points, trigger outputs and their phase sequence before connecting to the thyristors in the power circuit. The built in pulse transformer based isolation between the trigger circuits and the power circuit provides isolation up to a tune of 1000V. Note that T1- T11 and T2- T21are from different secondary. Therefore T1 T11 will be in phase and T2-T21 in the opposite phase. The table below gives the usage of the trigger output against different experiments. SL.NO EXPERIMENT TRIGGER OUTPUTS T1 T1 T2 T2 1 I Phase half wave converter * 2 I Phase full wave converter * * 3 I Phase half controlled converter * * 4 I Phase full controlled converter * * * * 5 I Phase AC, phase control * *

C IR C U IT D IA G R A M+ 12V 1K F IR IN G A N G L E P O T5V1

10 0K 1N 4 007 1 00 K

+ 12V

10 K +12V +12V 1 K T3 4 1 4 8 + 15V T1 T2 10K SV 1 0 .1 100 K 4K7 -12V + 12V 4K 7 22K2 N 2222

O F F /O N 1K 10 0 F 3 741 2 4 7 6 1K T5 47K 4K 7 -1 2 V

+12V

10 0K

1K

7 10 0K 6 74 1 4 T 3 4 1K 1K

(7 5 m A ) 1 N 4 007 0 + 15V

7V 5

414 8

3 3 /5 W Vu n + 12V P 4K 7 3 8 7 6 1 2 1 2K 41 4822P F

1 N 4 0 07

GATE 1K 8 5V 1 T1

33 012V B C 107

4K 7 41 48IN 4 1 4 8

P /n 1 K

7V S

T S L -1 0 0 710K

T6

1 N 4 0 07

CA T GATE 1K 8 5V 1 T1'

4 555 5

1N 400 7 4K7 + 12V 4K 7 22K2N 2 2 2 2

4K 7 4K 7 414 8 P 7V 5

0 .0 1 + 12V

0 .0 1

CA T

1 N 41 48 1K

4K 7 3 8 7 6 1 2 1 2K 41 48 4 555 15V 0 .7 5 A 0 .0 1 15V 1N 4 007 1N 4 007

7 8121000F 25V 1000F 25V 1 00 0 F 25V 1 00 0 F 2 5V

+ 1 2V 0 .1 F GND 0 .1 F -1 2 V

1N 400 7 4K7

5

0 .0 1

7 912

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JSSATE , BANGLORE


TEST POINTS 1

2 3

Vc 4 5 6 7

8

TRIGGER OUTPUTS T1 & T1 T2 & T2

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JSSATE , BANGLORE

Department of Electronics & Communication SERVICING DETAILS SINGLE PHASE CONVERTER FIRING CIRCUIT : a) Check the 3 pin Mains Cable used along with this unit b) Check the Fuse in the Mains socket c) Check the Mains Switch d) Check the transformer e) Check the firing angle potentiometer. f) Check the ON/OFF switch g) Check the zener diodes & IN4007 diodes at the output of the pulse transformer. h) Check +12V & -12v power supply (Check 7812 &7912 regulators) i) Check BC 107 & SL 100 transistors j) Check 2N2222 transistors k) Check 741/555ICs l) Check for any loose contacts. SINGLE PHASE FULLY CONTROLLED CONVERTER POWER CIRCUIT : SFC230V/5A The circuit arrangement of a single-phase full converter is shown in fig. During the positive half cycle, thyristor T1 and T11 are forward biased; and when these two thyristor are fired simultaneously at wt= , the load is connected to the input supply through T1 and T11 . In case of inductive loads, during the period wt ( + ), the input voltage is negative and the freewheeling diode Dm is forward biased. Dm conducts to provide the conductivity of current in the inductive load. The load current is transferred from T1 and T11 to Dm; and thyristor T1 and T11 are turned off due to line or natural commutation. During the negative half cycle of the input voltage, thyristor T2 and T21are forward biased. The firing of thyristor T2 and T21 simultaneously at wt= + will reverse bias Dm. The diode Dm is turned off and the load is connected to the supply through T2 and T21. Figure shows the waveforms for input voltage, output voltage and Trigger Outputs. FRONT PANEL DIAGRAM:1 Ph. FULLY CONTROLLED CONVERTER POW ER CIRCUITL T1 N 1 Ph. IN ON M CB L N T2' LINE ~ ~ RECTIFIER + T1' DmA M ER M ET

AT2

+VO LT M TER E

V

SHC

FIELD

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JSSATE , BANGLORE

Department of Electronics & Communication This power circuit consists of four SCRs connected as fully controlled bridge converter. A free wheeling diode is provided to observe the effect of free wheeling diode on inductive loads. Each device in the unit is mounted on an appropriate heat sink and is protected by snubber circuit. Short circuit protection is achieved using glass fuses. A circuit breaker is provided in series with the input supply for overload protection and to switch ON/OFF the supply to the power circuit. The front panel consists of input and output terminals. The gate and Cathode of each SCRs brought out on the front panel for firing pulse connection. Voltmeter and an Ammeter is mounted on the front panel indicates the output voltage and current. A separate full wave bridge rectifier is provided in the unit to get the DC supply for the field of DC Shunt Motors. The power circuit schematic is printed on the front panel. SPECIFICATIONS: Input Voltage Load current Fuses Field supply MCB FRONT PANEL DETAILS: Input terminals Output terminals(+&-) Voltmeter(0 to 300V) Ammeter(0 to 5A) Circuit breaker T1,T11,T2 & T21 DM Field(+ and -) (with indicator)

:15V to 230V AC. : 5 Amps maximum : 6 Amps fast blow glass fuses. : 220V 10%/2 Amps : Two pole 6 Amps/ 230V : To connect single phase input supply. : To connect load. : To indicate output voltage : To indicate output current. : 6 Amps AC power ON/OFF to the circuit and for protection . : SCR 16 TTS 12-16 A rms/1200Volts. : Free wheeling diode SPR 16PB-16A/1200V : Field supply for DC motor for motor control experiments.

BACK PANEL DETAILS: Mains socket : For 230V AC mains supply to field supply bridge rectifier. Fuse holders : 2 fuses in series with input AC supply, a fuse at the output and a fuse for free wheeling diode. Fuse - 6 Amps SINGLE PHASE POWER CIRCUIT Single ph AC Input Single Phase Experiments Block Diagram 1.Isolation Transformer :68 Firing Circuit JSSATE , BANGLORE Isolation

Transformer

Power Load Circuit


To suit single phase 230V/50Hz supply, ratio 1:1, KVA rating to suit the load rating with tappings at different voltages. Isolation of mains, phase and neutral with measurement circuit. Serves the purpose of di/dt protection of SCRs and safe measurement of waveforms by using oscilloscope. Isolation of Electric noise with mains. 2.Power circuit :

Different power circuit configurations are possible using SCRs and diode modules. Half Wave Converter 1SCR Full Wave converter 2 SCRs Half Controlled Converter _ 2 SCRs & 2 Diodes Fully Controlled Converter 4 SCRs AC phase Control 2 SCRs 3. Firing Circuit :

Each SCR of the above Power Circuit to be triggered using independently isolated outputs using single phase converter firing unit. Trigger outputs phase sequence and variation to be checked before with the power circuit. Phase sequence to be compared with the power circuits phase sequence. 4. Load :

Load connection should include an ammeter and a current shunt for current waveform measurements. Use freewheeling diodes wherever necessary. Types of Loads: a) Resistance R b) Resistance and Inductive load R & L. c) Motor and Generator. Note: In case of DC motor control, field excitation is separate. Field supply should be ON before giving armature supply. It should be switched OFF only after switching off the armature supply. Lamp load: Due to di/dt limitation of SCRs and since the initial inrush current is 20 to 25 times more than load current in lamp loads and also since the cold resistance of the lamp is very less, lamp loads can be used with large safety factors. Precaution: Initially keep the input voltage low and firing angle at 1800.Slowly increase the voltage to the rated voltage and firing angle to 00.

CIRCUIT DIAGRAM:

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INSTRUCTIONS: 1. Check all the SCRs for performance before making the connections. 2. Check the firing circuit trigger outputs and its relative phase sequence. 3. Make fresh connections before you make a new experiment. 4. Preferably work at low voltages (20-30V) for every new connections. After careful verification it can be raised to the maximum ratings. (This is to reduce damages due to wrong connections and high starting current problems). 5. The thyristor has a very low thermal inertia as compared to machine and by any overload or short circuit the SCR will immediately get damaged. Therefore do not switch ON the supply until the instructor has checked the connections. 6. While observing the waveforms of two parameters on the oscilloscope, either differential input oscilloscope should be used or special differential modules should be used with normal oscilloscope. On normal oscilloscope, observation of wave forms can be done with respect to single common point only. Ground connections of other probe must be avoided. It will lead to short circuit if ground connections of both the probes are used since they are internally shorted. In no case should oscilloscope input ground point be disconnected. This is a dangerous practice. Use 10:1 oscilloscope probe to see the waveforms at high voltages. 7. Do not make Gate & Cathode measurements when the power circuit is ON. TABULAR COLUMN: Firing angle ()=sin-1 (Vn/Vp) Practical Vodc (Volts) Theoretical Vodc (Volts)

Vodc (th) = 2Vm (cos ) /

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JSSATE , BANGLORE


PARAMETERS AND OBSERVATIONS: 1. Input voltage waveform 2. Output Voltage waveform (across the load) 3. Output current waveform (through the shunt) 4. Voltage waveform across thyristors (make this measurement only if isolations is used) 5. Study of variation of voltage and current waveforms with the variation of firing angle. 6. Study of effect of freewheeling diode in case of inductive loads. WAVEFORMS:Vm 0 V V=VmSin wt + 2 Wt

Vo 2 + Wt

0

T1

Wt T2

Wt

VOLTAGE WAVE FORMS

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JSSATE , BANGLORE

Department of Electronics & Communication Free Wheeling Diode, Resistive Load, and Resistive and Inductive load

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RESULT: CONCLUSION: The output voltage at various firing angles are noted with R load and RL load and the difference with and without free wheeling diode is observed. The relevant waveforms are traced.

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SERVICING DETAILS: Single-phase fully- controlled converter: Power circuit: a) Check the devices SCRs and diodes. b) Check the fuse. c) Check the MCB. d) Check for any loose contacts. e) Check the field supply bridge rectifier.

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9) VOLTAGE COMMUTATED (IMPULSE COMMUTATED CHOPPER) BOTH CONSTANT FREQUENCY AND VARIABLE FREQUENCYAIM: To rig up DC Jones Chopper and to control O/P average DC Voltage both at constant frequency and variable frequency and at different duty cycles. APPARATUS: DC chopper power circuit ,DC chopper firing circuit, DC Regulated power supply (0-30V/2A), Rheostat (100hms/2A), CRO, connecting wires. DESCRIPTION : DC CHOPPER FIRING CIRCUIT: This firing unit provides triggering pulses for the Thyristors in auxiliary commuted chopper circuit configurations. It can be used for voltage commutation and current commutation chopper circuits consisting of one main load carrying Thyristor and one auxiliary Thyristor and associated commutation components. DC Chopper firing unit should be used together with our DC-Chopper power circuit to conduct DC-DC chopper experiments on resistance, resistance and Inductance and motor load. This firing circuit can also used for other chopper circuits also. SPECIFICATIONS: Power supply : 230V/50 Hz, single phase ac mains. Output : Two pulse Transformer isolated trigger pulses for main and auxiliary Thyristors. Gate Drive current : 200 mA Auxiliary Gate pulse width :100sec. Main Gate pulse width : Train of pulses Test points : 1 to 8 provides signals at various points of the logic circuit. Duty cycle : Variation from 10% to 90%. Frequency : Variation from 30 Hz to 300 Hz. Approximately. Control Voltage : Variation from 0 to 5V when the control switch is in INT position. External control voltage can be used by putting the switch to EXT position.

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JSSATE , BANGLORE

Department of Electronics & Communication FRONT PANEL DIAGRAM:

DC - CHOPPER TRIGGERING UNIT - DCT

10%

90%

Min.

Max.

DUTY CYCLE

FREQUENCY

TRIGGER OUTPUTS + T MAINGND

TEST POINTS1 2 3

T AUX

4

5

6

7

POWER

FRONT PANEL DETAILS: Power : ON/OFF switch with built-in indicator. Test points :1-7 test points for study of firing circuit. Duty cycle : Potentiometer to vary the duty cycle from 10% to 90% when the control switch is at INT position at the set frequency . Frequency : Potentiometer to vary the operating frequency of the chopper from 30Hz to 300Hz approximately. ON/OFF : Switch for main thyristor trigger pulse with soft start feature. Trigger Output TM : Main Thyristor Trigger pulse Train of pulses. Trigger Output TA. : Auxiliary Thyristor Trigger pulse of 100 sec. BACK PANEL DETAILS: Main socket with built in fuse holder. Fuse 500mA. 76 JSSATE , BANGLORE


NOTES: 1. The chopper cannot be tested without connecting the load. 2. The main thyristor T1 has to carry the resonant reversal current (along with load current) there by increasing current rating requirements. 3. The discharging and charging time of commutation capacitor are dependent on the load current and this limits the high frequency operation, especially at low load current. 4. The maximum value of the duty cycle is also limited to allow the commutation capacitor to discharge and recharge. 5. The thyristor T1 must be ON for a minimum time of tr = (LmC) to allow the charge reversal of the capacitor and tr is fixed for a particular circuit design. This imposes minimum duty cycle limit and hence minimum output voltage. 6. The firing circuit provides the trigger pulses in the following range: Duty cycle: 10% to 90% Frequency: 30Hz to 300Hz. When the frequency is varied, the duty cycle is maintained constant at the set value. For example if the duty cycle is 50% at 50 Hz and you have now selected the frequency to vary from 50 Hz to 100 Hz, the duty cycle still remains 50% at 100Hz. The range of chopping frequency/duty cycle provided is no guarantee that any chopper power circuit will work for the full range. The limits of operation of a given power circuit depend on various factors like (a) the turn off requirement of the main thyristor (which should be less than the available turn off time) (b) the peak load current (c) the input DC voltage (d) The source and load inductance (e) The commutation circuitry the value of C and Lm, etc., The function of firing circuit is only to provide properly sequenced and accurately timed trigger pulse in the said range. The trigger pulse for the main thyristor T1 is a continuous train of pulses for the whole of the ON time kT (where k is the duty cycle). This train of pulses will be followed by the firing pulse for commutation thyristor, also known as Auxiliary thyristor, T2. This auxiliary trigger pulse is a single pulse whose width is approximately 100 microseconds. INSTALLATION: While operating, keep the equipment in well-aerated cool place. Avoid direct sunlight on to the equipment. Use a properly earth grounded outlet socket to connect to the equipment. This is so because a floating earth ground will not provide a clean AC reference to the equipment. The power input plug is situated on the back panel of the unit. Use the power card provided along with the equipment to the power outlet socket. INPUT POWER SPECIFICATIONS: Voltage Current Fuse : 215 245 A/C at 45 to 55 Hz. : 75mA (Max. continuous)@ 230V A/C. 500mA (Max. surge.) : 500mA (Slow Blow) Capsule type 20 x 5mm.

Situated in the lower left corner of the equipment font panel is the power ON/OFF switch with built-in in LED indicator. The LED glows when the switch is in ON position.

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JSSATE , BANGLORE

Department of Electronics & Communication A fuse protects the equipment against over Voltages and any short circuit. The fuse holder is an integral part of the power inlet plug situated on the back panel. A spare fuse is provided in the fuse holder. The power card has to be removed from the plug, before you can access the fuse holder. While replacing the fuse, pull off the holder smoothly. Refer to the figure shown below. Power inlet plug

Pull here Fuse holder

Power inlet plug/fuse holder Remove and discard the blown off fuse and insert a new fuse in to the bay provided for it, Replace back it the assembly in correct direction and press it until it flushes with the surface. Now connect the power card back into the plug. Switch on the mains supply to the equipment. Observe the test points signals, Trigger outputs and their phase sequence before connecting to the thyristors in the power circuits. CIRCUIT DIAGRAM: D C C H O P P E R F IR IN G C IR C U IT

15V FREQ 100K 4 8 10K 2 1K 1K 3 741 6 U2 TP 2 100K TP 3 2 329C 10K -1 5 V 3 741 6 U3 5V 1K A 5V 3 1 01 11 6 2 9 74 LS 15 123 14 U4 7 5 1 8 6

TP 1

555 7 U 3 1 6 1 5 2

33K .0 1 .0 1 33K

5V

0 .0 1 0 .4 7 F

10K

5V 1

1 0K DU TY CYCLE 1 5 / 5 W

9V

GA TE

330

5V

B C 107 A TP 4 TP 5 8 4 3 555 7 U5 10K 6 1 5 2 9V 4K 7 1K 3019

1K81N 4007 GATE

5 V 1 (A U X ) CAT

1 5 / 5 W 330 BC 107 7V 5

1K8

5 V 1(M A IN ) CAT

220Pr

O N / O FF

1K

TP 7 2N 3019

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JSSATE , BANGLORE


DESIGN FOR JONES CHOPPER (VGE COMMUTATED CHOPPER) Ic = Cdv/dt; -(1); Ic = capacitor current v=Voltage across capacitor for constant load current ; equation can be Ic = CVs/tc or C = tcIo/Vs tc= commutating circuit time>tq(device turn-off time) i.e,tc>tq ; so now let tc = tq + t tq for TY612 is 70 Sec which is almost equal to100 Sec Let t= 20 Sec Therefore tc = 120Sec Let Vs= 30v; Ic =2 A. Therefore c = 120 Sec x 2/30 = 4 x 2 F = 8 F. Choose C = 10 F. Ic = {VsSin (Wot)}/Wo L ; Wo = 1/[LC] Icp = Vs/WoL= [ (30/2)]2 8 x 10-6 >=1.8mH Select L= 2mH or 8mH.

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JSSATE , BANGLORE


WAVEFORMS:DC - CHOPPER FIRING CIRCUIT - TEST POINTS

15 TP1 0 10V 5 TP2 5V 0 TP35V 0 TP4 5V 0 TP5 5V 0 TP6T7 P

TM TA

JONES CHOPPER POWER CIRCUIT: 30V/2A: This unit consists of two SCRs two diodes and L C commutation circuit to construct Jones chopper power circuit. Each device in the unit is mounted on an appropriate hear sink and is protected with an RC snubber circuit. All the components are independent and their connections are brought out to front panel. The cathode and gate of each SCR is brought out ob to separate terminals for firing pulse connection. A switch and a fuse are provided in series with the input DC Supply. The devices and components can also be used to build different chopper circuits. Integrated Thyristor Controller ITC 08 and DC chopper firing unit DCT provided triggering pulses for this power circuit. SPECIFICATION: 30V @ 2.0 Amps. FRONT PANEL DIAGRAM: 80 JSSATE , BANGLORE


SCR DC - CHOPPER POWER CIRCUIT - SDCP+ TM C com M C B TA DFW

+ OUTPUT L

230 VAC ~ ~ RECTIFIER + -

+ DC INPUT L' D1

FIELD

FRONT PANEL DETAILS: VDC IN : Terminal to connect DC input 10V to 30V DC. ON : ON/OFF switch for the input DC supply to the power circuit. Fuse : In series with the DC input for short circuit protection 2 Amps. T1 & T2 :SCRs TYN 616 D1 & D2 : diodes BYQ 28 200. C : Commutation Capacitor 10uF/100V. L1-0-L2 : Commutation Inductor 500-0-500 Micro henry/2 Amps. CIRCUIT DIAGRAM:

JONES CHOPPER T1 C VDC T2 D1DM

L1

LM

L2LOAD

CIRCUIT DIAGRAM

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JSSATE , BANGLORE

Department of Electronics & Communication CONNECTION DIAGRAM:

JO N E S - C H O P P E R P O W E R C IR C U IT 3 0 V /2A

T1 FUSE CDM LOAD

SWITCH

T2 L1 LM L2 D1

V dc In

PROCEDURE : To begin with switch ON the DC Chopper firing unit. Observe the test point Signals and Trigger output signals by carrying Duty cycle and Frequency Potentiometer by keeping the control switch into INT position. Be sure the trigger Outputs are proper before connecting to the power circuit. Now make the interconnections in the power circuit as given in the circuit diagram. Connect DC supply from a variable DC source. Initially set the input DC supply to 10 Volts. Connect a Resistive load. Connect respective trigger outputs from the firing circuit to the respective SCRs in the Power circuit. Initially keep[ the ON/OFF switch in the firing circuit in OFF position. Switch ON the DC supply. Apply Main SCR trigger pulses by pressing the ON/OFF Switch to ON position. Observe the voltage waveforms across load. We can observe the chopped DC waveform. If the commutation fails we can see only the DC voltage. In that case switch OFF the DC supply, Switch OFF pulses and check the connections and try again. Observe the voltage across load, across Capacitor, across Main SCR and auxiliary SCR by varying Duty cycle and frequency Potentiometer. Now vary the DC supply up to the rated voltage (30V DC). Draw the waveforms at different duty cycle and at different Frequency. Connect Voltmeter and Ammeter and note down values in the table.

TABULAR COLUMNS: 82 JSSATE , BANGLORE


SL.NO

V in

Ton

Toff

Duty cycle

Vo

Io

INSTRUCTIONS: 1. Check all the SCRs for performance before making the connections. 2. Check the firing circuit Trigger output and its relative phase sequence 3. Make fresh connection before you make a new experiment. 4. Preferably work at low voltages for every new connections. After careful verification it can be raised to the maximum ratings (This is to reduce damages due to wrong connections and high starting current problems) 5. The Thyristor has a very low thermal inertia as compared to machine and by any over load or short circuit the SCR will immediately get damaged. Therefore do not switch ON the supply until the instructor has checked the connections. 6. While observing the waveform of two parameters on the oscilloscope observation of waveforms can be done with respect to single common point only. Ground connection of other probe must be avoided. It will lead to short circuit if ground connections of both the probes are used. Since they are internally shorted. In no case should oscilloscope input ground point be disconnected. This is a dangerous practice. Use 10:1 oscilloscope probe to see the waveforms at high voltages. 7. Do not make Gate & cathode measurements when the power circuit is on

PARAMETERS AND OBSERVATIONS: 83 JSSATE , BANGLORE

Department of Electronics & Communication 1. Voltage wave form across capacitor. 2. Output voltage waveforms (across the load) 3. Output current waveforms (Through the shunt) 4. Voltage waveforms across Thyristor. 5. Study of variation of voltage and current waveforms with the variation of duty cycle and frequency. 6. Study of effect of free wheeling diode in case of inductive loads. PRECAUTIONS: 1.In case of DC motor control, field excitation is separate. Field supply must be ON before giving armature supply. It should be OFF only after switching off the armature supply. Without field supply load current is too high which is limited by armature resistance. 2.In case lamp load, due to di/dt limitation of SCRs and since the initial inrush current is 20 to 25 times more than load current, it can be done only with large safety factor. 3.Chopper cannot be tested without connecting load. RESULT: CONCLUSION : The chopper has been verified and tested .It is found that Vo(prac) = Vo(theor)

10) SPEED CONTROL OF SEPARATELY EXCITED DC MOTOR:

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JSSATE , BANGLORE


SPECIFICATIONS: Input Voltage Load current Fuses Field supply MCB FRONT PANEL DETAILS: Input terminals Output terminals(+&-) Voltmeter(0 to 300V) Ammeter(0 to 5A) Circuit breaker T1,T11,T2 & T21 DM Field(+ and -) (with indicator)

:15V to 230V AC. : 5 Amps maximum : 6 Amps fast blow glass fuses. : 220V 10%/2 Amps : Two pole 6 Amps/ 230V : To connect single phase input supply. : To connect load. : To indicate output voltage : To indicate output current. : 6 Amps AC power ON/OFF to the circuit and for protection . : SCR 16 TTS 12-16 A rms/1200Volts. : Free wheeling diode SPR 16PB-16A/1200V : Field supply for DC motor for motor control experiments.

BACK PANEL DETAILS: Mains socket : For 230V AC mains supply to field supply bridge rectifier. Fuse holders : 2 fuses in series with input AC supply, a fuse at the output and a fuse for free wheeling diode. Fuse - 6 Amps 1.Isolation Transformer :-

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JSSATE , BANGLORE


To suit single phase 230V/50Hz supply, ratio 1:1, KVA rating to suit the load rating with tappings at different voltages. Isolation of mains, phase and neutral with measurement circuit. Serves the purpose of di/dt protection of SCRs and safe measurement of waveforms by using oscilloscope. Isolation of Electric noise with mains. 2.Power circuit :

Different power circuit configurations are possible using SCRs and diode modules. Half Wave Converter 1SCR Full Wave converter 2 SCRs Half Controlled Converter _ 2 SCRs & 2 Diodes Fully Controlled Converter 4 SCRs AC phase Control 2 SCRs 3. Firing Circuit :

Each SCR of the above Power Circuit to be triggered using independently isolated outputs using single phase converter firing unit. Trigger outputs phase sequence and variation to be checked before with the power circuit. Phase sequence to be compared with the power circuits phase sequence. 4. Load :

Load connection should include an ammeter and a current shunt for current waveform measurements. Use freewheeling diodes wherever necessary. Types of Loads: a) Resistance R b) Resistance and Inductive load R & L. c) Motor and Generator. Note: In case of DC motor control, field excitation is separate. Field supply should be ON before giving armature supply. It should be switched OFF only after switching off the armature supply. Lamp load: Due to di/dt limitation of SCRs and since the initial inrush current is 20 to 25 times more than load current in lamp loads and also since the cold resistance of the lamp is very less, lamp loads can be used with large safety factors. Precaution: Initially keep the input voltage low and firing angle at 1800.Slowly increase the voltage to the rated voltage and firing angle to 00. INSTRUCTIONS: 1. Check all the SCRs for performance before making the connections. 2. Check the firing circuit trigger outputs and its relative phase sequence. 3. Make fresh connections before you make a new experiment.

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JSSATE , BANGLORE

Department of Electronics & Communication 4. Preferably work at low voltages (20-30V) for every new connections. After careful verification it can be raised to the maximum ratings. (This is to reduce damages due to wrong connections and high starting current problems). 5. The thyristor has a very low thermal inertia as compared to machine and by any overload or short circuit the SCR will immediately get damaged. Therefore do not switch ON the supply until the instructor has checked the connections. 6. While observing the waveforms of two parameters on the oscilloscope, either differential input oscilloscope should be used or special differential modules should be used with normal oscilloscope. On normal oscilloscope, observation of wave forms can be done with respect to single common point only. Ground connections of other probe must be avoided. It will lead to short circuit if ground connections of both the probes are used since they are internally shorted. In no case should oscilloscope input ground point be disconnected. This is a dangerous practice. Use 10:1 oscilloscope probe to see the waveforms at high voltages. 7. Do not make Gate & Cathode measurements when the power circuit is ON. 8. Vary the firing and note down Vodc, Iodc and speed N in RPM TABULAR COLUMN: Firing on the Firing angle Pottetiometer Deg ()=sin-1 (Vn/Vp) Practical Vodc (Volts) Theoretical Vodc (Volts) N Speed in RPM

Vodc (th) = 2Vm (cos ) / PARAMETERS AND OBSERVATIONS: 1. Input voltage waveform 2. Output Voltage waveform (across the load) 3. Output current waveform (through the shunt) 4. Voltage waveform across thyristors (make this measurement only if isolations is used) 5. Study of variation of voltage and current waveforms with the variation of firing angle. 6. Study of effect of freewheeling diode in case of inductive loads. 7. Fro various firing note the speed on the digital meter on the motor panel.

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JSSATE , BANGLORE


WAVEFORMS:Vm 0 V V=VmSin wt + 2 W t

Vo 2 + W t

0

T1

W t T2

W t

VOLTAGE W AVE FORM S

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JSSATE , BANGLORE

Department of Electronics & Communication Free Wheeling Diode, Resistive Load, and Resistive and Inductive load

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JSSATE , BANGLORE


RESULT: CONCLUSION: The output voltage at various firing angles are noted with DC Motor as load and the difference with and without free wheeling diode is observed. The relevant waveforms are traced.

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JSSATE , BANGLORE

Department of Electronics & Communication 11) SPEED CONTROL OF UNIVERSAL MOTOR Motor Specification: 0.5HP/220V AC/DC AIM: To Control the speed of the Universal through (i) AC-DC Power converter (FCR) and (ii)AC Voltage Controller Apparatus: Universal Motor, Isolation Transformer, dimmer-stat, Fully controlled bridge rectifier (FCR), ACVC, FCR Firing Circuit.

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JSSATE , BANGLORE

Department of Electronics & Communication Procedure: Make the inter connections in the power circuit as in the circuit for FCR and ACVC,. Switch on the the firing circuit and observe the trigger pulses. Make sure that the firing pulses are proper before connecting to the power circuit. Then connect the trigger output from the firing circuit to the corresponding SCRs/TRIAC. In the power circuit initially set AC input to 30V. Switch on the MCB. Switch on the trigger. First observe the output across R load by varying the potentiometer. If the output wave form is proper then you can connect the motor and increase the input voltage to the rated value i.e., 230V gradually. Vary the firing angle and note O/P voltage and speed of the motor Table (Fully Controlled Rectifier Firing on the Firing angle Practical Theoretical N Speed in RPM Potentiometer Deg ()=sin-1 Vodc (Volts) Vodc (Volts) (Vn/Vp)

Table (ACVC) Firing on the Firing angle Potentiometer Deg ()=sin-1 Vn/Vp)

Practical Vodc (Volts)

Theoretical Vodc (Volts)

N Speed in RPM

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JSSATE , BANGLORE


12) SPEED CONTROL OF STEPPER MOTOR: STEPPER MOTOR CONTROLLER This is Micro controller based controller circuit to accurately generates pulses to energizes the stepper motor winding in the desired sequence . Power transistor based driver circuit to driver circuit to drive the stepper motor. From this controller we can set the speed of the stepper motor in RPM, set the number of steps motor can move .We can set the direction of rotation forward and reverse direction. We can also set half step and full step mode. FRONT PANEL DETAILS: 1.Mains :Power ON/Off Switch to the unit with built-in indicator. 2.Display :Seven segment 5 digit display to display the parameter and values 3.Key board : a)Set :To set the Parameter. b)INC :To increment the set parameter values. c)DEC :To decrement the set parameter values. d)ENT :To enter the set values. e)RUN/STOP :To start and stop the stepper motor. .(Built in) 4.+v : 5v/2 amps DC supply for stepper motor.(Built in) 5.+5v :5 v for control circuit .(Built in) 6.GND :Supply ground point 7.FUSE :2 amp fast below glass fuse for short circuit protection. 8.A1,A2,B1 & B3: Outpoints to connect to the A1,A2,B1 &B3 leads of stepper motor. 9.LEDs :To indicate the status of output. BACK PANNEL DETAILS: Mains socket with built in fuse holder and a spare fuse. PROCEDURE:Connect A1, A2, B1 and B2 leads of stepper motor to the corresponding output terminal points. And two common terminal to +V supply. Switch ON the mains supply to the unit. Check the power supplies. The unit display S 00. Now press SET. Then the display shows rpm(revolutions per minute). If you press ENT now the speed mode is set and it displays 00. Then press INC Key to set the rpm. When the display shows rpm, if you press INC/DEC it goes to STEP mode or vice versa. After setting the Speed in rpm/ no of steps, press ENT Key. Then the parameter values is entered and it shows set direction of rotation. Press INC/DEC changes the direction of rotation. Then press ENT Key to set the direction of rotation. Then it displays Half step or Full step mode. Pressing INT/DEC will changes to HALF Step/ FULL Step mode or vice versa. Press ENT Key to set the Half step or Full step mode.

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Then it displays n-set rpm if speed is selected or S-set steps if steps is selected. This is the method for setting the parameter. After this if we press RUN/STOP key the Motor stops. If we select the STEP mode the motor moves the number of set steps and stops when we press RUN/STOP key. If we press again the motor moves again and stops. Set the step mode at 1 step and half step mode and check the output status by LED indication for each step of rotation and verify with the theoretical. Repeat the same foe Full step mode also. Repeat the above for the other direction. D.C.BRUSHLESS STEPPING MOTORS The stepping motor is an electromagnetic device which converts digital pulses into discrete mechanical rotational movements. In rotary stepper motor, the output shaft of motor rotates in equal increments, in response to a train of input pulses. CHARACTERISTICS:Construction:Stepping Motor is basically a Motor with two phases, eight salient poles, toothed iron rotor and a permanent magnet. This rotor is known as hybrid rotor. The rotor is suspended in the stator by means of sealed ball bearings. All parts of the motors are precision machined for better performance and accuracy of steps. Step Angle: 1.8*+ or - .1* non-cumulative. Holding Torque: 2.8 Kg cm. Dynamic Torque: Dynamic torque is mainly controlled by the electronic control circuits. Torque will drop down as the speed increases. Residual Torque or Detent Torque : Because of the presence of permanent magnet in the rotor. Working Temperature and insulation Class: Temperature of stepping motors may rise 50*C above ambient. It is observed that body temperature generally stabilizes at about 85*C to 90*C for continuous duty cycle. The insulation used is of class B type which can withstand hot spot temp of 130*C. For better heat dissipation motors duly fitted with heat sinks are recommended. This reduces the temp by about 10*C to 15*C. Working of stepping motor:The stepping action is caused by sequential switching of supply to the two phases of motor as shown in switching logic sequence table. The specified torque of any stepping motors is the torque at stand still (holding torque). This torque is directly proportional to the current to rated level within the time given for one step. This is mainly due to L/R time constant of winding. The drop in current level causes drop in torque as the speed increases. In order to improve torque at high speed it is necessary to maintain current at the rated level. Never exceed rated current of the motor. Stepping Motors differ form conventional DC Servo Motors in the following respects. 1.There is no control winding in stepping Motors. Both windings are identical. 2.The stepping rate (speed of rotation) is governed by frequency is governed by frequency of switching and not by supply voltage.

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Department of Electronics & Communication 3.A single pulse input will move the shaft of motor by one step. Thus number of steps can be precisely controlled by controlling number of pulses. 4.When there is no pulses input, the rotor will remain locked in the position in which the last step was taken since at any time two winding are always energized which lock the rotor electro magnetically. 5.Steping Motors can be programmed in there parameters namely : a) Direction. b) Speed. c) Number of steps. 6.Stepping Motor is brush less so no wear & tear. 7.Load & no load condition makes no difference in running currents of the motor. GENERAL INFORMATION:1.Resonance When a stepping motor is operated at its natural frequency an increase in noise and vibration occurs. This phenomenon is called as resonance. The frequencies at which this resonance occurs depends widely on the characteristic of load and it also varies from motor to motor. The change in inertial load will; change the resonance frequency. In half-step mode resonance may be reduced / avoided. 2.Ramp Acceleration (soft start) and declaration (soft stop are essential factors of controller . Acceleration is required to run the motor at high step rates and declaration is to stop motor accurately at specified position. 3.Half Step Mode Advantage Smother motion ,resolution factor increases by the factor2, reduces resonance problems. Disadvantages-Loss of torque(above 40%) In half step mode we do not offer guarantee for accuracy but error automatically gets corrected on next even half step. 4. Mounting-Flange Mounting. Motor must be mounted with reference to boss and not with reference to mounting holes. 5. Synchronization-N no. of SRI.SYN. Stepper motors can be operated simultaneously at time with single controller &N no. of drives. APPLICATION:Numerically controlled Machine Tools and Machining centers: Profile cutting, Grinding, Milling and Boring Machines, Lathes, park erosion Machines, sheet Metal presses, Industrial Robots ,etc. Plastic and packaging: Mark registration ,labeling, cut to length. Graphics: Photo printing and developing ,Photo type setting printing presses, Film projectors and cameral, etc Process control and Instrumentation: Textile web control, valve controls, Material Handling systems, Assembly lines, carburetor Adjusting, In process Gauging ,chart Recorders, servo Mechanism, Electronic gear box, profile, precise RPM control, RPM control, RPM meter calibration

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Department of Electronics & Communication Medical Instrumens:Infusion pumps, x-ray and Radioactive Machinery, Blood analyzers etc. Office Automation Equipments: Printers, plotters, Hard and Floppy Disc, Teleprinter and Typewriters, copying Machines and Accounting Machines

V=4*motor voltage Rs=3*Rm(Motor resistance/phase) Suitable for slow RPM SWICHING LOGIC SEQUENCE A1 Red 0 0 1 1 Q1 A2 Green 1 1 0 0 Q2 B1 Blue 0 1 1 0 Q3 B2 Black 1 0 0 1 Q4

Half step A1 A2 Red Green 0 1 0 0 1 0 1 0 1 0 0 0 0 1 0 1

B1 Blue 0 0 0 0 1 1 1 0

B2 Black 1 1 1 0 0 0 0 0

To change the direction red sequence from bottom to top Specification:Permanent magnet, Bifilar wound Steps per Revolution:200 Two phase. Step Angle:1 .8*+0r-0.1*non cumulative. 3kg.cm=0.1 N .m=13.90z-in No of leads-6

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13) SERIES / PARALLEL INVERTER (i)SERIES INVERTER AIM : To design the series Inverter circuit and test its working. APPRATUS REQUIRED : Series Inverter Module, Digital Millimeter , Power Supply, Patch chords . DESCRIPTION : This unit consists of power circuit and firing circuit sufficient to build and study the modified series inverter. Firing circuit: This part generates two pairs of pulse transformer isolated trigger two SCRs connected as series inverter ON/OFF switch is provided For the trigger pulses which can be used to switch ON the inverter. Frequency of the inverter can be varied from 100hz to 1Khz approximately. Power circuit : This part consists of two SCRs two diodes. A center tapped inductor with tapings and capacitors .Input supply terminals with ON/OFF Switch and a fuse is provided .All the devices in this unit mounted on a proper heat sink, snubbed circuit for dv/dt protection and a fuse in series with each device for short circuit protection. All the points are brought out to front panel for inter connection. They have to be interconnected as shown in the circuit diagram .Free wheeling diodes Can be connected across SCRs and its effect can be observed. Refer any standard text books for theoretical details. Front panel details: 1.Frequency: Potentiometer to vary the inverter frequency. 2. Trigger outputs: From 100HZ to 1KHZ approximately 3.ON/OFF: Switch for trigger outputs. 4.T1 and T2: Trigger outputs. 5.Power : Mains switch for firing circuit. 6.Vdc in: Terminals for dc input-30v/2amps Max. 7.ON/OFF: Switch for dc input 8.Fuse: Fuse for dc input 2amps Glass fuse. 9.T1 and T2: SCRs TYN612.12amps/60v 10.D1 and D2: Diodes BYW51-200 4amps/200v 11.L2 L1 Lm L1 L2: 10mH-5mH-0-5mH-10mH/2 amps 12.C1 and C1: 6.8 f/100v 13.C2 and C2: 10 f/100v.

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CIRCUIT DIAGRAM :

DESIGN OF SERIES INVERTER : (specimen calculation) wr ={(1/Lc)-(R2/4L2)} f r

Power Lab Manual 7th Sem 2011_BGS

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Transcript of Power Lab Manual 7th Sem 2011_BGS