Pe Manual1

DEPT OF E & CE, R.V.C.E. POWER ELECTRONICS LAB MANUAL 1

POWER ELECTRONICS LABORATORY

USER MANUAL

DEPARTMENT OF ELECTRONICS AND

COMMUNICATION ENGINEERING

R V COLLEGE OF ENGINEERING

PRACTICAL HANDOUTS

REVISED: AUGUST 2009


SAFETY WARNING:

Before using this laboratory, read, understand and follow the Safety

Precautions mentioned inside this manual

This is an educational laboratory where high-voltage terminals and large

current-carrying components and circuits are exposed for ease of measurements.

Therefore, regardless of the voltage and current levels, these should be treated as high

voltages and high currents, and the safety precautions mentioned in the manual must

be followed.

Contents

Expt # Title Page #

Safety Precautions 03

General instructions 05

01 Static Characteristics of SCR and DIAC 06

02 Static characteristics of MOSFET and IGBT 13

03 Half and Full controlled bridge rectifier with R and RL load 21

04 HWR and FWR control using RC triggering circuits 25

05 AC Voltage Regulator using TRIAC-DIAC combination

06 UJT firing circuits for HWR and FWR

07 Speed control of separately exited DC motor

08 Speed control of Universal motor (AC Motor)

09

10

11

12

Few important questions


SAFETY PRECAUTIONS

1. Why is safety important?

Attention and adherence to safety considerations is even more important in a power

electronics laboratory than it’s required in any other undergraduate electrical engineering

laboratories. Power electronic circuits can involve voltages of several hundred volts and currents

of several tens of amperes. By comparison the voltages in all other teaching laboratories rarely

exceed 20V and the currents hardly ever exceed a few hundred milliamps.

In order to minimize the potential hazards, we will use dc power supplies that never

exceed voltages above 40-50V and will have maximum current ratings of 20A or less. Most of

the time we will use dc supplies of 20V or less and 1 A or less output current capability.

However in spite of this precaution, power electronics circuits on which the student will work

may involve substantially larger voltages (up to hundreds of volts) due to the presence of large

inductances in the circuits and the rapid switching on and off of amperes of current in the

inductances. For example AC voltage converter has an output voltage that can theoretically go

to high values. Moreover the currents in portions of some converter circuits may be many times

larger than the currents supplied by the supplies powering the circuits.

2. Potential problems presented by Power Electronic circuits

• Electrical shock may take a life.

• Exploding components (especially electrolytic capacitors) and arcing circuits can cause

blindness and severe burns.

• Burning components and arcing can lead to fire.

3. Safety precautions to minimize these hazards

3.1 General Precautions

• Be calm and relaxed, while working in Lab. When working with voltages over 40V or

with currents over 10A, there must be at least two people in the lab at all times.

• Keep the work area neat and clean.

• No paper lying on table or nearby circuits.

• Always wear safety glasses when working with the circuit at high power or high voltage.

• Use rubber floor mats (if available) to insulate yourself from ground, when working in

the Lab.

• Be sure about the locations of fire extinguishers and first aid kits in lab.

• A switch should be included in each supply circuit so that when opened, these switches

will de-energize the entire setup. Place these switches so that you can reach them quickly

in case of emergency, and without reaching across hot or high voltage components.


3.2 Precautions to be taken when preparing a circuit

• Use only isolated power sources (either isolated power supplies or AC power through

isolation power transformers). This helps using a grounded oscilloscope and reduces the

possibility of risk of completing a circuit through your body or destroying the test

equipment.

3.3 Precautions to be taken before powering the circuit

• Check for all the connections of the circuit and scope connections before powering the

circuit, to avoid shorting or any ground looping that may lead to electrical shocks or

damage of equipment.

• Check any connections for shorting two different voltage levels.

• Check if you have connected load at the output.

• Double check your wiring and circuit connections. It is a good idea to use a point-to-

point wiring diagram to review when making these checks.

3.4 Precautions while switching ON the circuit

• Apply low voltages or low power to check proper functionality of circuits.

• Once functionality is proven, increase voltages or power, stopping at frequent levels to

check for proper functioning of circuit or for any components is hot or for any electrical

noise that can a affect the circuit’s operation.

3.5 Precautions while switching on or shutting down the circuit

• Reduce the voltage or power slowly till it comes to zero.

• Switch of all the power supplies and remove the power supply connections.

• Let the load be connected at the output for some time, so that it helps to discharge

capacitor or inductor if any, completely.

3.6 Precautions while modifying the circuit

• Switch on the circuit as per the steps in section 3.5.

• Modify the connections as per your requirement.

• Again check the circuit as per steps in section 3.3, and switch ON as per steps in section

3.4.

3.7 Other Precautions

• No loose wires or metal pieces should be lying on table or near the circuit, to cause

shorts and sparking.


• Avoid using long wires, that may get in your way while making adjustments or changing

leads.

• Keep high voltage parts and connections out of the way from accidental touching and

from any contacts to test equipment or any parts, connected to other voltage levels.

• When working with inductive circuits, reduce voltages or currents to near zero before

switching open the circuits.

• Be aware of bracelets, rings, metal watch bands, and loose necklace (if you are wearing

any of them), they conduct electricity and can cause burns. Do not wear them near an

energized circuit.

• When working with energized circuits (while operating switches, adjusting controls,

adjusting test equipment), use only one hand while keeping the rest of your body away

from conducting surfaces.

GENERAL INSTRUCTIONS:

Students are hereby strictly informed to

• Wearing shoes is compulsory in the laboratory.

• Write the datasheets of the experiment to be conducted before coming to lab.

• Write the theory of the experiment in the record and to get it signed by the in charge in

advance before doing the experiment

• Marks are allotted for the writing and in time submission of datasheets and record,

Conduction of the experiment, writing theory of the experiment in advance and for the

results.

• Power on the circuits only after showing the rigged circuit to the faculty incharge.


EXPERIMENT 1 - STATIC VI CHARACTERISTICS OF SCR AND DIAC

THEORY TO BE WRITTEN TO THIS EXPERIMENT:

List and define all the Power semiconductor devices

Explain constructional details and characteristics of SCR and DIAC

Applications of Power Semiconductor Devices

Briefly explain the types of Power Electronic Converter Circuits

a) Static characteristics of SCR:

OBJECTIVE:

To understand and to study:

a) the properties and characteristics of SCR

b) Gate triggering of SCR

c) Effects of Gate current on Forward Blocking Voltage

d) Turn-on and turn-off switching characteristics

AIM: To plot the VI characteristics of SCR and hence determine

1. Forward break over voltage (VFBO)

2. Holding current (IH)

3. Latching current (IL)

4. SCR On-state voltage (VAK)

REQUIREMENT: SCR (TYN612)

APPARATUS REQUIRED: Ammeters: 0-100 m amps, 0-1 amps

Resistors: Regulated (tubular) 10W, 1K

Rheostat 1.5K, 1W

Regulated Power Supply: 0-30W, 0-300W

Voltmeter: DMM / Voltmeter


DEFINITIONS:

HOLDING CURRENT: Holding current is the minimum anode current that flows through the

SCR to maintain it in forward conducting state (ON state) in the absence of Gate supply.

LATCHING CURRENT: Latching current is the minimum forward anode current that flows

through the SCR when it enters forward conduction mode (ON state) from forward blocking state

(the time of triggering). If forward current is less than latching current, SCR does not turn-on.

FORWARD BREAKOVER VOLTAGE (VFBO): Forward break over voltage is the voltage at

which the SCR starts conducting.

CIRCUIT DIAGRAM:

PROCEDURE:

1. Rig up the circuit as shown in figure above.

2. Set the Gate current, say Ig = 2.5 mA, vary the anode voltage supply V2 (0-300)V

3. If the gate current is not sufficient, SCR will be in forward blocking state.


4. Increase the gate current (say Ig = 4 mA). By increasing the VAK, current conduction increases

through the device. The voltage at which the current conduction takes place is called forward

break over voltage (VFBO1), note down the values of VAK and IA.

5. Once the device is turned on, the voltage across the device is very low, i.e., VT 1V, where

VT is the on state drop.

6. To measure IL: Set the anode voltage to some value (say 100V). Now vary the gate supply

monotonically till the device changes from forward blocking to forward conduction state and

note down the current through the device.

7. Repeat the above step for different values of Anode voltage say, 100V, 110V, 120V and note

down the Latching current, the latching current remains same for a given device.

8. To measure IH: Once the device is turned on, switch off the gate supply. Now reduce the

anode voltage, the anode current IA reduces. At one point, the current IA goes to zero. The

anode current present in the SCR just before the SCR changes its state from forward

conducting state to forward break over state is called “Holding current, IH”. Note down the

value of IH

9. Repeat the procedure for different values of Gate current, say Ig1 = 4 mA, Ig2 = 4.3 mA > Ig1,

the device will turn on at a lower forward break over voltage, VFBO2.

10. Vary the input voltage (V2) so that we get varying values anode current IA (use DMM to

measure) and note down the VFBO

11. Plot the VI characteristics and indicate the device parameters: IH, IL, VFBO, VT and Ron.

Measurements and waveforms

TABULAR COLUMN:

Ig1 = __ A Ig2 = __ A

VAK (V) IA (mA) VAK (V) IA (mA)

VFBO1 =

IL1=

VFBO2 =

IL2 =


VI Characteristics of SCR:

LAB REPORT:

The lab report should have a brief abstract detailing what has been done in the experiment. The

remaining part of the report should consist of the information asked below along with any

discussion you feel is necessary.

1. Attach a graph output voltage anode voltage versus anode current using data mentioned above.

Plot the theoretical and practically calculated results on the same graph. Compare the two plots

and comment about the differences between ideal values and practical values of SCR.

2. Attach a copy of the waveforms and tabular columns for different anode voltage and gate

current.

3. Comment on the changes in the output for the change in the inputs.

CONCLUSION /INFERENCE:


b) STATIC VI CHARACTERISTICS OF DIAC

AIM: To plot the VI characteristics of DIAC and hence determine

(i) Forward and reverse VI characteristics of DIAC

(ii) Breakdown voltage in both the directions.

OBJECTIVE:

To understand and study the

a) Operation (forward and reverse characteristics) and Characteristics of DIAC

REQUIREMENT: DIAC (DIATB3)

APPARATUS REQUIRED:

Ammeters: 0-100 m amps

Resistors: Regulated (tubular) 10W, 1K

Regulated Power Supply: (0 - 300) W, (0 - 30)W

Voltmeter: DMM / Voltmeter

CIRCUIT DIAGRAM


NOTE:

DIAC is a bidirectional diode

Breakdown voltage is the minimum voltage required for the DIAC to start conduction

PROCEDURE:

1. Rig up the circuit as shown in the circuit diagram

2. Vary the supply gradually and note down the corresponding voltage and current

3. Note down the breakdown voltage

4. Reverse the DIAC terminals and note down the corresponding breakdown voltage by varying

the supply gradually

5. Tabulate the current v/s voltage readings for both the directions

6. Plot the forward and reverse VI characteristics of DIAC

MEASUREMENT AND WAVEFORM:

FORWARD CHARACTERISTICS REVERSE CHARACTERISTICS

VT1T2 (V) I (mA) VT1T2 (V) I (mA)

VBO Forward break down voltage =

VBR Reverse break down voltage =


VI Characteristics of DIAC

LAB REPORT:

The lab report should have a brief abstract detailing what has been done in the experiment. The

remaining part of the report should consist of the information asked below along with any

discussion you feel is necessary.

1. Attach a graph of anode voltage versus anode current as the data mentioned above. Plot the

ideal and practically calculated results on the same graph. Compare the two plots and comment

about the differences between ideal values and practical values of DIAC.

2. Attach a copy of the waveforms and tabular columns for forward and reverse characteristics.

3. Comment on the changes in the output for the input values in both the directions of operation

of DIAC.



EXPERIMENT 2- STATIC CHARECTERISTICS OF IGBT AND MOSFET


Characteristics of Ideal switches

Switching characteristics and switching Limitations of Power transistors

Compare and differentiate the properties of MOSFET and IGBT

Comment on

ON state and OFF state voltage

input and output impedance

Switching and conduction losses and

Turn-off time

a) Static Characteristics of POWER MOSFET

Conduct a suitable experiment to obtain Drain and Transfer Characteristics for a given

Power MOSFET and hence determine its Drain Resistance and Transconductance.

AIM:

i. To plot the VI characteristics of power MOSFET

ii. To obtain the device parameters

OBJECTIVE:

a) To learn about Power MOSFET

b) To understand the characteristics, gate control requirements and models of MOSFET

APPARATUS REQUIRED:

1. MOSFET IRF 840, IGBT (IRG4BC205)

2. Regulated Power Supply: (0 - 30)V - 2 No’s

3. Rheostat 30 Ohms

4. Resistors 30 20W, 10K 1/2W (2 No’s), DMM

5. Ammeter (0 - 2)A

6. Digital Volt Meter


NOTE:

The minimum Gate Voltage (VGS) required to turn on the MOSFET is called “THRESHOLD

VOLTAGE”, (VTH).

CIRCUIT DIAGRAM:

PROCEDURE:

Drain Characteristics:

1. Rig up the circuit as shown in circuit diagram

2. Set the value of VGS slightly greater than Threshold voltage (VTH) to a constant value

(not too high)

3. If VTH = 3.5 Volts, set VGS = 3.6Volts, Vary the VDS and note down the VDS and

corresponding changes in the ID.

4. Repeat the above step for different values of VGS.

5. Plot VDS V/S ID characteristics on the graph sheet and hence compute RDS


Transfer Characteristics:


2. Set the value of VDS to a constant value, say 8 Volts, vary the gate supply and note down

the value of VGS for which the device is turned on, once the device is turned on, Voltage

(VT) remains constant, ID increases

3. Repeat the above step for different values of VDS

4. Plot the VGS V/S ID characteristics and obtain the device parameters and compute GM

MEASUREMENT AND WAVEFORMS:

Drain Characteristics: VDS V/S ID |VGS = Constant

(VGS > VT)

VGS1 = ___(V) VGS2 = ___(V)

VDS (V) ID(mA) VDS (V) ID (mA)

Transfer characteristics: VGS V/S ID | VDS = constant

VDS1 = ___ V VDS2 = ___ (V)

VGS (V) ID (mA) VGS (V) ID (mA)


Characteristics of MOSFET:

LAB REPORT:

GM = (IDS / VGS) = ________ mho

RDS = (VDS / IDS) = ________ ohm

For the given MOSFET (IRF840),

Transconductance (GM) = __________ Mho

Drain resistance, RD = __________ Ohm

VT, Threshold voltage VT = __________ Volts


The lab report should have a brief abstract detailing what has been done in the

experiment. The remaining part of the report should consist of the information asked below

along with any discussion you feel is necessary.

Attach a graph of VDS v/s ID and VGS v/s ID for the values as mentioned above. Plot the

practical and theoretically calculated results on the same graph. Compare the two plots

and comment about the differences between ideal and practical characteristics of

MOSFET.

Attach a copy of the waveforms and tabular columns for

Drain characteristics and

Transfer characteristics.

Comment on the characteristics and working of MOSFET

CONCLUSION / INFEERENCE:


b) STATIC CHARACTERISTICS OF IGBT

AIM:

a) Conduct a suitable experiment to plot the VI Characteristics for a given IGBT and

b) Determine Forward Resistance, Transconductance and Threshold Voltage.

OBJECTIVE

To study and learn the

a) Structure of IGBT

b) Characteristics and Operation of IGBT

APPARATUS REQUIRED:

1. IGBT (IRG4BC205)

2. 0 – 30V Power Supplies (2 No’s)

3. Resistors: 30 20W, 10K 1/2W (2 No’s), DMM

4. Ammeter – (0 – 2)A

5. Digital Volt Meter

6. Regulated Power Supply: (0 - 30)V (2 No’s)

CIRCUIT DIAGRAM


PROCEDURE:

1. Transfer Characteristics:

1. Rig up the circuit as shown in the circuit diagram.

2. Set VCE, say about 8Volts, vary the gate voltage VGE and note down the changes in IC.

3. Repeat the above step for different values of VCE

4. Plot the characteristics on a graph sheet.

2. Output Characteristics:

1. Set VGE slightly greater than VT say about 4.3Volts, vary VCE and note down the values

of IC.

2. Repeat the above step for different values of VCE

3. Plot the characteristics on a graph sheet

MEASUREMENT AND WAVEFORMS:

Output or collector characteristics: IC V/S VCE |VGE = Constant

VGE = ______ (V) VGE = ______ (V)

VCE (V) IC (mA) VCE (V) IC (mA)

Transfer characteristics or gate characteristics: IC V/S VGE |VCE = Constant

VCE = ____(V) VCE = ____(V)

VGE (V) IC (mA) VGE (V) IC (mA)


CHARACTERISTICS OF IGBT

LAB REPORT: 1. Threshold Voltage, VT = _______Volts

.2. Transconductance, GM = _______Mho

.3. Forward Resistance, Rf = _______Ohm

The lab report should have a brief abstract specifying what has been done in the



Attach a graph of VCE v/s IC and VGE v/s IC for the values as mentioned above. Plot the

practical and theoretically calculated results on the same graph. Compare the two plots

and comment about the differences between ideal and practical characteristics of

MOSFET.


Output characteristics and

Transfer characteristics.

Comment on the characteristics and working of IGBT

CONCLUSION / INFERENCE:


EXPT 3 - HALF AND FULL CONTROLLED BRIDGE RECTIFIER


Briefly explain all the types of commutation

Define and explain different types of controlled rectifiers

Explain the effect of inductor and freewheeling diode in the rectifier circuit

AIM:

a) To study the working principle of FWR with R and RL loads

b) To observe the waveforms VL, VSCR and to plot the response curve VDC V/S ,

Objective: To realize a half and full controlled bridge rectifier circuit using SCRs and suitable

gate controlled circuitry and to study its response for:

1. R load

2. R-L load

APPARATUS REQUIRED:

Isolation Transformer

Control bridge rectifier module

Single phase firing module

Load module with freewheeling diodes

CIRCUIT DIAGRAM (HCB)

CIRCUIT DIAGRAM (FCB)


PROCEDURE:

1. Check the secondary of the transformer (12-0-12) using CRO or DMM in AC mode

2. Rig up the circuit as shown using specific kits.

3. Adjust the gate circuit for minimum pulses (maximum triggering angle) before switching on

the supply to the rig.

4. Observe the output waveforms VS, VSCR1, VSCR2, VL and IL on CRO.

5. Vary the POT, (1KW) to vary the firing angle and measure the value of , and

correspondingly record the VDC using DMM in DC mode.

6. Connect the inductor load and observe the waveform across it ( negative spikes are obtained )

7. Connect freewheeling diodes and note difference in waveform.

8. For continuous current, α should be less. This comes into picture only in inductive load.

9. Tabulate the values of VDC, and , and plot the response curve VDC V/S , and the

necessary waveforms for both R and RL load.

OBSERVATION

R Load R-L Load

Without freewheeling diode With freewheeling diode

α VL α VL α VL


LAB REPORT:

The lab report should have a brief abstract specifying what has been done in the



Attach a graph of v/s VL values both for half wave and full wave rectifiers separately

. Plot the practical and theoretically calculated results on the same graph. Compare the

two plots and comment about the differences between ideal and practical characteristics.



R and RL load for Half Wave Controlled Rectifier with and without

freewheeling diodes and

R and RL load for Full Wave Controlled Bridge Rectifier with and without

freewheeling diodes.

Comment on the output for R and RL load with and

The effect of freewheeling diode on the output

CONCLUSION / INFERENCE:


EXPT 4 – HALF WAVE AND FULL WAVE RECTIFIERS USING RC

TRIGGERING CIRCUITS

THEORY TO BE WRITTEN TO THIS EXPERIMENT

List the important features of firing circuits

Mention the different ways to turn on an SCR

Briefly explain the R, RC and UJT triggering circuit

OBJECTIVE

Understand the RC triggering circuit and

To implement the Half wave and Full wave rectifiers using RC triggering.

AIM:

a) To study the working of Half wave and Full wave controlled rectification using RC

triggering

b) To plot the response curve, VDC v/s ,

c) To draw the waveforms at different points

APPARATUS REQUIRED:

SCR (TYN612)

DIODES IN401 or BY127 (5 No’s)

RESISTORS 470 (10W), 470 (1/2 W), 100K POT

DCB

Transformer (12-0-12)

CRO

BNC

DMM

CIRCUIT DIAGRAM:

RC HALF WAVE TRIGGERING CIRCUIT:


RC FULL WAVE TRIGGERING CIRCUIT:

PROCEDURE:


2. Check the transformer secondary voltage using CRO/DMM in AC mode

3. Observe the output voltage (VL) variation across the load RL using DMM in DC mode by

varying the 100K POT

4. .Observe the load voltage waveform on CRO by varying the 100K POT.

5. Observe the waveform at various points(SCR, capacitor) and note the voltage levels.

6. Use the triggering pulses obtained to fire the SCR’s in either HWR or FWR configuration.

7. Plot the delay angle V/s output voltage levels in HWR & FWR for identical delay angles.

8. Compare the output voltage levels in HWR & FWR for identical delay angles.

OBSERVATION:

HWR FWR

(deg) VL (V) (deg) VL (V)





LAB REPORT: The lab report should have a brief explanation specifying what has been done in

the experiment. The remaining part of the report should consist of the information asked

below along with any discussion you feel is necessary.

Attach a graph of v/s VL values of the expected and practically obtained graph both for

half wave and full wave rectification separately

Plot the practical and theoretically calculated results on the same graph. Compare the two

plots and comment about the differences between ideal and practical characteristics

Comment on the variation of and with the change in the 100K POT value

EXPERIMENT No 5: UJT FIRING CIRCUIT FOR HWR AND FWR


(1) Explain the working of UJT as relaxation oscillator.

(2) List the applications of UJT.

(3) What are intrinsic standoff ratio, peak points and valley points, explain?

(4) Explain why a thyristor has to be protected from di/dt and dv/dt and how?

AIM: To conduct a UJT Triggering Circuit For HWR and FWR and to display triggering

Pulses, load voltage waveforms also plot:

(1) Load voltage v/s delay angle

(2) Load voltage v/s conduction angle

OBJECTIVE:

a) To study the working principle of UJT firing circuit.

b) To study the principle of line synchronized UJT firing circuit.

REQUIREMENTS:

Diode (IN4001 or By127) – (2)

UJT (2N 2646)

Resistors: 500 – 10W, 220 – (2), 1K – (3), 100, 100K POT – (2),

470 - 20W – (2), 470 – 5W,

Capacitor 0.1 µF – (2)

Zener Diode (12V)

SCR (TYN 612)

Pulse transformer 1:1:1

Step-Down Transformer 230V/ (15-0-15)

Voltmeter

CRO

BNC

PIN CONFIGURATION OF UJT

CIRCUIT DIAGRAM:

HALF WAVE RECTIFIER

FULL WAVE RECTIFIER

IDEAL WAVEFORMS

PROCEDURE:

1.

2.

3.

4.

5.

PROCEDURE:

1. Check the transformer secondary voltage using DMM

2. First, rig up the UJT firing circuit and check the voltages at different points as

shown in the waveforms on CRO.

3. Observe the variation of pulse frequency,

(R 100K POT). Verify the pulse train fo

4. Develop the HWR circuit using SCR and load

5. Observe the waveforms

POT.

Check the transformer secondary voltage using DMM

First, rig up the UJT firing circuit and check the voltages at different points as


Observe the variation of pulse frequency,


Develop the HWR circuit using SCR and load

Observe the waveforms




Observe the variation of pulse frequency,



Observe the waveforms VSCR and V




Observe the variation of pulse frequency, f = 1/T

(R 100K POT). Verify the pulse train for one half


and VL. Verify the changes with respect to 100K

Check the transformer secondary voltage using DMM (AC mode) or CRO.


f = 1/T by varying the charging resistor

r one half cycle.

Develop the HWR circuit using SCR and load resistor.

. Verify the changes with respect to 100K

(AC mode) or CRO.


by varying the charging resistor


(AC mode) or CRO.







6. Measure the load voltages with respect to ‘’ using DMM (DC Mode) and

measure – the delay angle using the CRO.

7. The load voltage can be verified using the formula, form value as

VDC = (Vm (1+cos) ) volts. Where, Vm = 21/2

Vrms of sec voltage.

8. Plot the input waveform, variation of load voltage with respect to , Zener

voltage, Voltage across the capacitor, Voltage across SCR and the voltage across

load.

DESIGN STEPS:

i. Time period of output pulse

T = RC ln 1

/(1-) secs.

Where

R = Charging resistor

C = Capacitor

n = intrinsic standoff ratio – 0.63 for (2N 2626)

OR

T = RC ln(VBB – VV)/( VBB – VP) Secs

Where,

VBB = Supply voltage

VP = Peak voltage

VV = Valley voltage

ii. Rmax = (VBB – VP)/IP

iii. Rmin = (VBB-VV)/IV

Where,

IP = Peak current

IV = Valley current

iv. Base resistance, Rb2 = 104/VBB (an empherical formula)

OBSERVATIONS:

HWR FWR

VL (v) VL (v)

LAB REPORT:


experiment. The remaining part of the report should consist of the information asked


1. Attach a graph of input waveform, variation of load voltage with respect to , Zener

voltage, Voltage across the capacitor, Voltage across SCR and the voltage across load.

Plot the theoretical and practically calculated results on the same graph. Compare the two

plots and comment about the differences between ideal and practical values.

2. Attach a copy of the waveforms and tabular columns for load voltage versus .

3. Comment on the plotted waveforms.


EXPERIMENT 6 : AC VOLTAGE CONTROLLER USING TRIAC –DIAC

COMBINATION


(1) Explain the Master Circuit Breaker.

(2) Clearly classify the AC Voltage Controllers stating the principle of operation.

(3) List the advantages and disadvantages of on-off control and phase angle control

circuits.

(4) Mention the Merits, demerits and applications of AC Voltage Controllers

AIM: To study the performance of an Ac Regulator using Triac- Diac combination and

Incandescent lamp as load. To plot variation between load voltage and delay

angle.

OBJECTIVE:

a. To understand the operation and characteristics of AC Voltage Controllers.

b. To understand the performance parameters of AC Voltage Controllers.

REQUIREMENTS:

Resistors 1K (2), 10K , 1M , 500 5W

Diac (DIATB3)

Triac (BT136)

Capacitors 0.1µF/30V, 0.1 µF/300V

Auto-Transformer

Voltmeter

Lamp

MCB

CRO

PIN DESCRIPTION:

CIRCUIT DIAGRAM:

PROCEDURE:

1. Rig up the circuit as shown in the above circuit diagram.

2. Set Auto-Transformer to 80V.

3. Out-put can be controlled by potentiometer.

4. Vary 1M ohm pot to obtain various values of AC.

5. The variation of AC is indicated by intensity of lamp.

6. Tabulate the variation between delay angle and load voltage and plot the graph.

OBSERVATIONS:

(delay angle ) VL (volts)

540

720

.

.

LAB REPORT:




1. Attach a graph of input waveform, variation of load voltage with respect to , Voltage

across triac and voltage across diac. Plot the theoretical and practically calculated results

on the same graph. Compare the two plots and comment on the differences between ideal

and practical values.

2. Attach a copy of tabular column for load voltage versus .

3. Comment on the plotted waveforms.

4. Explain the effect of source and load inductances on AC Voltage Controllers.

CONCLUSION/INFERENCE:

EXPERIMENT 7: SPEED CONTROL OF SEPERATELY EXITED DC MOTOR


(1) Explain the following terms Rotor, Stator and Winding in DC Motor.

(2) Explain the effect of load inductance on load current.

(3) Define the performance parameters of a controlled rectifier.

(4) Explain the working of converters with

a) Pure inductive load

b) RL load with finite inductance and

c) Resistive load.

AIM:

To control speed of a separately exited DC Motor through control technique using

a static controller realized using SCR.

OBJECTIVE:

a. To study the working of half controlled bridge rectifier.

b. To study the principle of speed control of separately excited DC MOTOR USING

HCB

REQUIREMENTS:

Transformer 230V/40V (PP)

Line commutation firing module

Power Module

DC Motor

Tachometer

DMM

CRO

CIRCUIT DIAGRAM:

PROCEDURE:

1. First check the firing pulse from line synchronized firing module using a power

supply 12V, and input from transformer 12-0-12V.

2. Check the variation of pulse width on CRO by varying POT.

3. Make the power circuit as shown in circuit diagram.

4. Ensure the gate pulses G1K1 and G2K2

5. Set the angle knob in the module to maximum and switch it on.

6. Observe the speed change in the motor by varying ‘’ in the firing module.

7. Connect a DMM across motor, record the voltages for different firing angle ‘’.

8. Verify the values using the formula VDC = (Vm/)(1+cos) volts.

9. Measure the ‘’ using CRO by taking load voltage or VSCR.

10. Observe the waveform and plot v/s speed (RPM).

11. Now gradually reduce the speed by reducing the resistance in POT and switch off

the power supply, finally switch off the firing module.

OBSERVATIONS:

(delay angle ) Speed (rpm)

LAB REPORT:




1. Attach a graph of input waveform and output waveform. Plot the practically calculated

results on a graph sheet. Observe the plot and comment on the readings.

2. Attach a copy of tabular column for delay angle () versus speed of motor (RPM).

3. Comment on the plotted waveform.


EXPERIMENT 8 : SPEED CONTROL OF UNIVERSAL MOTOR (AC Motor)


(1) Explain field and armature winding

(2) Explain types of induction motors

(3) Explain the working principle of 1- phase controlled type AC Voltage

Controller connected to i) R Load

ii) RL Load and

iii) L Load

(4) Explain the problem caused by short single pulse triggering of thyristors in an

ACVC when the load is inductive and how it can be solved.

AIM: To control the speed of AC motor using static controller.

OBJECTIVE:

(1) To study the working principle of 1-. AC controller using SCR’s.

(2) To study the working principle of phase control of TRIAC (Light dimmer)

APPARATUS REQUIRED:

Power module (1- AC controller)

Line commutated firing module

AC motor/Universal motor

(230V/45V) Transformer

AC Regulator

Tachometer

AC Motor

DMM

Motor

CIRCUIT DIAGRAM:

PROCEDURE:

1. Test the firing module for pulses G1K1 and G2K2 and the variation.

2. Rig up the circuit as shown in the diagram.

3. Set the firing module to minimum position and switch on the firing module.

4. Observe the speed of the motor by varying the firing angle .

5. Measure the value of using power scope for different settings of POT.

6. Record the voltage across motor using DMM (ac mode) and speed using

tachometer for different settings of POT on firing module.

7. Again gradually reduce speed and switch off the power module and firing

module

8. Plot the response curve voltage versus speed (rpm).

OBSERVATIONS:

Speed(rpm)

LAB REPORT:




1. Attach a graph of input voltage, load voltage and voltage across thyristor waveform.

Plot the practically calculated results on a graph sheet. Observe the plot and comment on

the readings.

2. Attach a copy of tabular column for delay angle () versus speed of Universal motor

(RPM).

3. Comment on the obtained result.


EXPT - 9 PARALLEL INVERTER

AIM:

To study the operation and working of a single phase parallel inverter, To display the output waveforms across load and commutation elements and To plot the efficiency curve

APPARATUS REQUIRED:

Inverter modules, Ammeter, DMM, Power supply, rectifier module and firing module.

CIRCUIT DIAGRAM PARALLEL INVERTER:

L and C are not connected internally in the module Use a external ”Commutation components” module for l and C connection

OBSERVATION:

RL

(ohms)

VDC

(volts)

IDC

(amps)

PDC

(watts)

VAC

(volts)

IAC

(amps)

PAC

(watts)

η=(PAC / PDC) x100

PROCEDURE:

1. Rig up the circuit using inverter circuit modules as shown in the circuit diagram. 2. Note that the commutating elements L and C are not present in the kit. They are shown as

dotted line in the module. 3. Measure VDC across A and B and IDC across A to A interconnection of two modules. 4. Now fix a load resistance. The load resistance actually consists of four 180Ω/40W

resistances in parallel. If a resistor is switched on (through switch), it is connected else it is not been taken into consideration.

5. IAC can be measured using AC ammeter 6. Vary RL and note down VAC and IAC. 7. Plot ή c/s load.

WAVEFORMS;

PARALLEL INVERTER:

LAB REPORT:


EXPERIMENT -10 Digital Firing Circuit

AIM:

a. To design and develop a digital firing circuit using proper IC’s b. To study the working of digital firing scheme

REQUIREMENTS: IC’s CD 4047(3 No’s), 7408 (1 No.), SL100 (2 No’s) Pulse Transformer (1 No.), Diodes IN4001 (5 No’s), DC source 0-30V of 1 No.

Circuit Design:

Procedure:

• Rig up the circuit as shown in the circuit diagram and check the output at each ICs • Check the output pulse variation at MSMV by varying 220K POT • Check the pulses at G1K1 and G2K2 • Convert the G1K1 and G2K2 to FWRs and observe the output across load by varying

22K POT of MSMV • Also record the values and plot the graph of VC v/s α

Ideal Waveforms:

Lab Report:

Conclusion/ Interference

EXPT – 11: SCR TURN OFF USING LC COMMUTATION CIRCUITS

AIM: To rig up a chopper circuit and thereby to determine the output voltages for various duty cycles and hence compare the output voltage with theoretical values.

APPARATUS REQUIRED:

Chopper module, Input Transformer, commutation module, firing module, DMM

CIRCUIT DIAGRAM:

OBSERVATIONS

VIN = 34.9V, TON = 1.9mS

Vi (dc) TON TOFF

δ (Duty cycle)

TON/(TON+TOFF)

Vo (practical) VO(Theoritical) =delta X Vi

TON (theoretical) = 2*π*(LC)1/2

Where L = 20.55 mH,

C = 16.67 µF

TON (theoretical) = 2π√ ms = 3.67mS.

VO (Theoritical) = δVi

δ =

PROCEDURE:

1. Rig up the circuit using various chopper modules as shown in the circuit diagram. 2. Verify the DC voltage across the output of DC chopper. 3. Vary the knob of triggering module and hence obtain variable values of duty cycle. 4. Note TON is always constant and TOFF is varied. 5. Tabulate the values of TON, TOFF and Vo for various triggering points on the gate trigger

circuit. 6. Observe the waveforms at load and commutation elements. 7. Plot a graph between VO and duty cycle.

WAVEFORMS:

LAB REPORT:


EXPERIMENT -12 SPEED CONTROL OF STEPPER MOTOR

AIM: To interface the stepper motor to microprocessor and to rotate it clockwise or anticlockwise directions for a given degree

APPARATUS: Microprocessor (8085) kit, Power supply and Stepper motor

Four step Sequence

Four step input sequence gives 1.80/step. For four step it gives 7.20.

Example: If given angle = 1800 then count value = .

= 25,

In Hex it is 19H

Use 19 as counter and store 07, 09B, 0D & 0E in four memory locations.

Instruction Opcode Instruction Length in (byte):

Program: MVI A, 80H 3E, 80 2 Mem C000

OUT DB D3, DB 2 C002

MVI C, 19H 0E, 19 2 C004

LOOP2: MVI B, 04 06, 04 2 C006

LXI H, C300 21, 00, C3 3 C008

LOOP1: MOV A, M 7E 1 C00B

OUT PC D3, DA 2 C00C

LXI D, FF07 11, 07. FF 3 C00E

CALL DELAY CD, BE, 04 3 C011

INX H 23 1 C014

DCR B 05 1 C015

JNZ LOOP1 C2, 0B, C0 3 C016

DEC C 0D 1 C019

JNZ LOOP2 C2, 06, C0 3 C01A

HLT 76 1 C01D

Phase1 Phase2 Hex Value 10 11 07 10 11 0B 11 01 0D 11 10 0E

Note: See the opcode sheet and enter the opcodes of the above instructions.

Circuit connection

• Connect the circuit with VDD = +12V VCC = +05V and Ground connections

OBSERVATIONS:

LAB REPORT:


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