LIST OF THE EXPERIMENTS

1. Magnetic Amplifier 2

2. Torque Speed characteristics of AC Servomotor 5

3. Study of DC Servomotor 8

4. DC position control system 10

5. Study of Digital control system 13

6. Synchro Transmitter and Receiver pair 17

7. Study of Lead and Lag compensators 20

8. Study of PID controller 24

9. Study of Second order system 27

10. Temperature control using PID 31

11. Study of First order system 35

1

1. MAGNETIC AMPLIFIER

AIM: To study the characteristics of series connected Magnetic Amplifier and parallel connected Magnetic Amplifier.

APPARATUS: Magnetic Amplifier study unit, Rheostat- 250Ω/1A, patch cards.

PROCEDURE:a) Series Connected Magnetic Amplifier.

1. Connections are made as per circuit diagram shown in fig1 with the help of patch cards. Take care of the polarity of the winding.

2. Connect control voltage supply VC with DC current meter (IC) in series with control winding.

3. Connect the load rheostat and load current meter (IL) as shown in circuit diagram.4. Vary control winding current IC in steps and record the corresponding load current

in table-15. Plot the graph between IC and IL.

b) Parallel Connected Magnetic Amplifier

1. Connections are made as per circuit diagram shown in fig2 with the help of patch cards. Take care of the polarity of the winding.

2. Connect control voltage supply VC with DC current meter (IC) in series with control winding.

3. Connect the load rheostat and load current meter (IL) as shown in circuit diagram.4. Vary control winding current IC in steps and record the corresponding load

current in table-25. Plot the graph between IC and IL.

PRECAUTIONS:

1. Use the AC voltage available on the panel (a step down transformer to furnish the desired AC voltage).

2. Do not exceed control winding current above 100mA.

Result: The characteristics of series connected Magnetic Amplifier and parallel connected Magnetic Amplifier are studied and drawn.

2

Fig 1

S. No Control winding current (IC, mA)

Load winding current (IL, mA)

Table-1

3

Fig 2

S. No Control winding current (IC, mA)

Load winding current (IL, mA)

Table-2

4

2. TORQUE SPEED CHARACTERISTICS OF A.C. SERVO MOTOR

AIM: To study the Speed- torque characteristics of A.C. Servo motor.

APPARATUS: Voltmeter, AC servomotor kit

PROCEDURE:

(1) Study all the controls carefully on the front panel shown in fig1.(2) Initially keep load control switch at OFF position, indicating that the armature

circuit of dc machine is not connected to auxiliary dc supply 12V dc. Keep servomotor switch also at OFF position.

(3) Ensure load potentiometer and control voltage transformer at minimum position.(4) Now switch ON mains supply to the unit and also AC servomotor supply switch. (5) Vary the control voltage transformer and observe that ac servomotor starts rotating

and speed will be indicated by the tachometer on the front panel.(6) With load switch OFF position, vary the speed of the ac servomotor by moving the

control voltage and note down the back emf generated by dc machine (now working as dc generator or tacho). Enter results in the table-1.

(7) Now with load switch at OFF position, switch on ac servomotor and keep the speed in minimum position.

(8) Now set the control winding voltage at a particular value. You can observe that the ac servomotor stars moving with speed indicated by tachometer and set the speed for maximum speed.

(9) Now switch ON the load switch and start loading ac servomotor by varying load potentiometer slowly. Note down the corresponding values of current from ammeter and speed provided in the unit and enter these results in table-2. And also enter the back emf for different speed.

(10) Repeat the steps from 7 to 9 for different control voltage 200,180 etc..(11) Plot the sped - torque characteristic for various values of control winding

voltages.

Result: The characteristics of A.C servo motor for various control voltages are drawn.

5

Fig 1

S.No Speed(rpm) Eb ( volts)123..

Table-1

6

J.FTm Servo

Amplifier

A CT SU IA GT NI AN LG

Vc

CONTRO WINDING

SPEED

TORQUE

Control voltage, Vc = Volts

S.No.

Ia (mA)N

(rpm)Eb (Volts) P = EbIa

T= torque (gm.cm)P*1.019*104*60

= --------------------------2N

123..

Table-2

7

3. STUDY OF D.C SERVO MOTOR

AIM: To obtain the transfer function of D.C. servomotor.APPARATUS: 1. spring balance kit 2. D.C. Servo motor.

SPECIFICATIONS: Operating voltage: 12V; No-load speed at rated voltage: 1500rpm; Starting torque: 13.3 N-mt; Moment of inertia, J: 0.4 Kg.cm2; Armature resistance: 7.3ohm; Armature inductance: 21.4H.

PROCEDURE:Speed –torque/ torque – current characteristics:

1. Make the connections as shown in circuit diagram. Connect the motor to control unit using a pin-connected card.

2. Make power ON to the unit, keep RPM meter switch at output speed position.3. Adjust the voltage using potentiometers of DC power supply to 8V. Keep knob

‘k’ of spring balance loading system for no-load position.4. Note the speed of motor N, armature current Ia and T1, T2 of spring balance .

Increase the load on dc servomotor by adjusting Knob ‘k’ of the spring balance loading system in proper steps and note the readings N, Ia, T1, T2 . Tabulate the results.

Back- Emf Characteristics:

1. Keep minimum load on motor by adjusting Knob ‘k’ of spring balance loading system.

2. Use same circuit connections as above.3. Vary dc voltage from minimum to maximum in proper steps by adjusting the pot

and note armature voltage, Ia, N and tabulate the results.Transfer function:

Transfer function of the d.c servomotor is given by

G( s )=Km

S ( STm+1) Km: Motor gain constant Tm: Motor time constantKm = KT /(Raf+ Kb KT ) = 1/ Kb if ‘f ‘is neglected.

Tm = RaJ/ Kb KT

GRAPH: (i) Plot the graph between Eb and . Where w is speed in red/sec. Calculate the motor back-emf constant: Kb = Eb/ v /rad/sec. (ii) Plot the graph between torque and armature current. Calculate torque constant : KT = T/Ia Result : The transfer function of the DC servomotor is obtained.

8

A

V

A

AAAA

T2

T1

+ -

+

-

-

+

DC Servo Motor

Spring Balance

Source

Circuit Diagram:

Observations:Torque – Current characteristics

V= 8v

T1 T2 Teq

T = 2* Teq

N-Cm SpeedArmatureCurrent, Ia

Back emf characteristics

T1 = T2 =Armaturevoltage

Ia Speed W=2N/60 Eb= V-IaRa

Graphi) Torque- current characteristics ii) Back E.M.F characteristics

T T

Ia W

kT = T/ Ia kb= Eb /W

9

0-500mA MC

0-20V MC

4. DC POSITION CONTROL SYSTEM

AIM: To study the performance characteristics of a D.C. Motor angular position control system.

APPARATUS: DC Position control system unit.

PROCEDURE:

a) Tacho out ( -ve feedback)1. Keep Tacho-out position in SW1 and switch on SW3 and SW4 in fig1.

2. Set amplifier gain at say 20 and feedback gain at 20. 3. Then vary input potentiometer in clockwise direction and observe output potentiometer. 4. Note down the remarks in table1 i.e whether critically damped or under damped or overdamped or undamped. ( Oscillations w.r.t time) 5. Repeat above procedure for different values of amplifier gain and feedback gains and note down the remarks.

b) Tacho In ( -ve feedback)1. Keep Tacho-in position in SW1 and switch on SW3 & SW4 and

feedback in degenerative mode in fig1.2. Set amplifier gain at say 20 and feedback gain at 20.3. Then vary input potentiometer in clockwise direction and observe

output potentiometer.4. Note down the remarks in table2 i.e whether critically damped or

under damped or overdamped or undamped. ( Oscillations w.r.t time)5. Repeat above procedure for different values of amplifier gain and

feedback gains and note down the remarks.

Observations:

1. In Tacho-out, for low gains observed the critical and overdamped; for medium range of gains observed underdamped; for high gains observed continuous oscillations- undamped.

2. In Tacho-in, for low gains observed critical damping and for high gains observed the overdamped.

Result: The dc positional control system is studied and plots are drawn.

10

Fig 1

Tabular Columns

Tacho out ( -ve feedback)Amplifier Gain Feedback Gain Input Output Remarks

Table-1

Tacho In ( -ve feedback)Amplifier Gain Feedback Gain Input Output Remarks

Table-2

11

MODEL GRAPH

12

5. STUDY OF DIGITAL CONTROL SYSTEM

AIM: To study the digital control of a simulated system using an 8-bit microprocessor and to obtain the parameters peak time and peak overshoot for different values of gain and delay setting.

APPARATUS: Lab trainer consisting of digital control system with microprocessor based digital controller.

PROCEDURE:

Process Identification:

The first step before any control is attempted is to be experimentally determine the process parameters, the gain k and the location of double poles ‘a’ may be determined easily from the step response. Actually, a square wave input is used. So that a continuous display of the response is available on the CRO for measurements. For proper time measurements, the time base should be synchronized with the square wave input from fig(1).The process parameters are now calculated as

K= P≃P value of the response at steady stateP≃P value of the squre wave input

a = (1.678)/ time to reach ½ of steady state value, t1/2

An explicit expression for G(s) is written as

G( s )= Ka2

( s+a)2

a) Fixed forward gain – variable sampling rate:

The steps to be followed for an experimental verification as under:1. Connect the circuit as shown in fig(2)2. Execute the program DELETE available at the adress5000H. Give a value

of gain and delay setting of ‘0’ when asked by the program.3. Observe the circuit out pulse on the CRO and measure the time between

any two pulses. This is the actual sampling period.4. Observe on the CRO response of the system and obtain the peak overshoot

by noting the peak and steady state values.5. Repeat steps 2 to 4 for different delay setting (1, 2, 3…) and tabulate the

results.

13

b) Fixed sampling rate – variable forward gain:

This experiment may be conducted in a manner very similar to that of the last section. Connections are same as before. The delay is kept at the lowest level, i.e., 0 and the response is situated for various values of p- gain 1, 2, 3… similar results are observed.

OBSERVATIONS:

Gain setting = Delay setting

Sampling period tin ms

Peak time,tp in ms

Cpeak (Volts)

Css

(Volts)%Mp ξ n x 103 n x 103

Delay setting = Gain setting

Sampling period ms

Peak time,tp in ms

Cpeak (Volts)

Css (Volts)

%Mp ξ n x 103 n x 103

Result: The response of a system with and without digital controller are studied and plots are drawn.

14

Digital Controller Process

Output

R(s)+

C(s)+ Digital

Controller Process

R(s)

Determination of process parameters:

Fig (1)

Fig (2)

Program: GO 5000H FILL PC 4 FILL DEL (0…….1) FILL EXECUTE

15

Model Graphs:

(i) Without digital controller:

(i) Without digital controller:

(ii) With digital controller:

16

6. SYNCHRO TRANSMITTER AND RECEIVER PAIR

AIM: To study the properties of synchro pair and study of synchro pair as an error detector.

APPARATUS: Synchro pair unit, Voltmeter.

PART “A”: STUDY OF SYNCHRO TRANSMITTER:

In this part of the experiment because of the transformer action the angular position of rotor is transformed into a unique set of stator voltages.

Procedure:

1. Connect the system to main supply.2. Switch ON the main switch.3. Do not connect any wires between the stator winding of TX and TR.4. Starting from zero position, note down the voltage between stator terminals i.e.,

Vs1s2, Vs2s3 and Vs3s1 in a sequential fashion. Enter the readings in table-1and plot graph of angular position versus voltage for all the three phases.

PART “B”: STUDY OF SYNCHRO TRASMITTER & RECEIVER:

In this part of the experiment we can study the phenomenon of transmitting motion to distance by electrical means.

Procedure:

1. Connect the system to main supply.2. With the help of patch cords establish connections between corresponding terminals

of TX and TR stators i.e., connect s1, s2 to s2 & s3 to s3 of TX & TR respectively.3. Switch ON the two switches.4. Move the pointer (rotor position of TX in steps of 300 ) and observe the new rotor

position of TR.5. Enter the input angular position and output angular position in the table-2 and plot

the graph.

Result: The properties of synchro pair are studied and their characteristics are drawn

17

V/2

VStator winding of transmitter

N

S2

S1S3

S21

S11S31

V

V/2V/2

600600

R1

R2

R11

R21

Stator winding of receiver

A.C. Line

Rotor winding of transmitter

Rotor winding of receiver

0

3/2VTransmitter Stator N

S2

S1S3

S21

S11S31

3/2V

3/2V0

600600

R1

R2

R11

R21

Receiver Stator

A.C. Line

Rotor transmitter

Rotor Receiver

300 300

Circuit Diagram:

18

Observations:

S.NoRotor

Position (Degrees)

Stator Terminal Voltage (R.M.S)

Vs1s2 Vs2s3 Vs3s1

123...

. Table-1

S.No.

Synchro Tx Shaft Position

Synchro Tr shaft position.

12..

. Table-2

Model Graphs

19

7. STUDY OF LEAD -LAG COMPENSATORS

AIM: To study the frequency response of lead and lag networks.

APPARATUS: Lead and lag networks study unit, patch cards.

LEAD COMPENSATOR:

Procedure:

a) Make the connections as shown in fig.1

b) Connect the sine wave output to the network input.

c) Note down the peak voltage input using digital voltmeter provided on the unit by varying the amplitude of sine wave to some value say 3V.

d) Now vary the frequency from 20Hz to 2000Hz and note down the corresponding output voltage and phase angle difference and enter the readings in table1.

e) Compare the measured values with theoretical values.

f) Plot the graph between gain and frequency (magnitude plot) and between phase and frequency (phase plot).

Observations: Vin = 3volts

S. No Frequency, Hz

Phase Angle,Degrees

Output voltageVo,volts

Gain20log (Vo/ Vin )

20

LAG COMPENSATOR:

Procedure:

a) Make the connections as shown in fig.2

b) Connect the sine wave output to the network input.

c) Note down the peak voltage input using digital voltmeter provided on the unit by varying the amplitude of sine wave to some value say 3V.

d) Now vary the frequency from 20Hz to 2000Hz and note down the corresponding output voltage and phase angle difference and enter the readings in table2.

e) Compare the measured values with theoretical values.

f) Plot the graph between gain and frequency (magnitude plot) and between phase and frequency (phase plot).

Observations: Vin = 3volts

S. No Frequency, Hz

Phase Angle,Degrees

Output voltageVo,volts

Gain20log(Vo/ Vin )

Results: Lag and lead networks are studied and bode plots are drawn.

21

Fig 1

Fig 2

22

MODEL GRAPH

23

8. P.I.D CONTROLLER

AIM: To study the effect of PID controller on a second order system.

APPARATUS: PID control unit assembly, CRO.

Procedure: P-controller

(i) Assemble the circuit shown in fig (a)(ii) Apply a step input (i.e., square wave signal of amplitude of 1.0V).(iii) Vary the value of Kp and observe the output C(s) on CRO.(iv) See the effect of Kp on output waveform.(v) Note down the time domain specifications for each of Kp value.

PI-controller (i) Add the circuit of Integrator block as shown in fig.(a) Note the effect of this block

on the output performance by varying the value of KI as done in the case of P controller.

(ii) Note open loop response also. PD-controller

(i) Replace Integrator block by Derivative block and repeat the same experiment as done in PI controller.

PID controller(i) Assemble the circuit as shown in fig.(a)(ii) Adjust the potentiometer KI & KP such that almost exact square wave is obtained at

the output. Thus response is almost similar to input.(iii) Study open loop response for PID controller

Observations:With P controller

kp tr ts tp ess Mp ς ωn

With PI controller

kp KI tr ts tp ess Mp ς ωn

Result: The effect of different controllers on second order system is studied and plots are drawn

24

Fig (a)

With PD controller

Kp KD tr ts tp ess Mp ς ωn

With PID controller

Kp KI KD tr ts tp ess Mp ς ωn

25

MODEL GRAPHS:

26

9. STUDY OF SECOND ORDER SYSTEM

AIM: To study the response of a second order system by using RLC and op-amp and make the measurement of time domain specifications.

APPARATUS: Second order system study unit

PROCEDURE:a) By using RLC

6. Connections are made as per fig1.7. Measure resistance value by using multimeter by setting potentiometer R on the unit

with main switch in OFF position.8. Now switch ON the mains supply, observe the signal source output by selecting

square wave input and set input voltage say 5V by using amplitude potentiometer. 9. Then observe the output on CRO.10. Plot response and measure the all time domain specifications and record in table1.

b) By using OP-AMP(i) For square wave input

6. Switch ON the mains supply, observe the signal source output by selecting square wave input as in fig2 and set input voltage say 5V by using amplitude potentiometer.

7. Keep the damping factor at say 0.3 and time constant at 3msec.8. Then observe the output on CRO and plot the response.9. Measure time domain specifications and record in table2.10. Repeat the above procedure for different values of damping factors say at 0.7 &1.

(ii) For step input1. Select step input as in fig3; adjust the amplitude potentiometer to get 5V.2. Select 5sec time constant and damping factor at say 0.3 and switch off the signal.3. Now switch on the signal and monitor the output on multimeter.4. Note down the output voltage with respect to time.

OBSERVATIONS:

The parameters are R = Ω; L = 2H; C = 0.32μF

Undamped natural frequency, ωn =

1

√LC and f =

12π √LC

Damping factor, ξ =

R2 √CL

Percentage peak overshoot, %Mp = e

−Πξ

√1−ξ2

* 100

27

Rise time, tr =

Π−θωd ; θ = Tan

−1(

√1−ξ2

ξ )

Peak time, tp =

Πωd ; ωd=ωn√1−ξ2

Damped natural frequency

Settling time, ts =

4ξωn for 2% tolerance

Transfer function =

ωn2

s2+2 ξωn s+ωn2

Tabular Form:Time response specifications Theoretical Practical

Table-1

S. No ζ td tr tp Mp ts ess

0.3

0.7

Table-2

PRECAUTIONS:

3. Make sure that the signal source is correct before connecting the input of second order system.

4. Readings are taken without parallax error.

Result: The response of second order system is studied and time domain specifications are compared between theoretical and practical values.

28

Fig 1

Fig 2

29

Fig 3

30

10. TEMPERATURE CONTROL USING PID

AIM: To study and observe the different analog controllers on temperature control process.

APPARATUS: Temperature controller unit

PROCEDURE:

a) Proportional controller

(12) Study all the controls carefully on the unit.(13) Establish the connection between conditioning unit and the model process with

help of cables provided as in fig1.(14) Connect red 3 and black 1 with help of patch card shown in fig1 and give

connection to only RTD from PID controller then switch on the kit.(15) Set the temperature in ohm by using SET potentiometer such that deviation is

zero which corresponds to room temperature. And set the proportional band control to 10%.

(16) Fix the maximum deviation (+5) by varying set temperature in ohms and also fix minimum deviation (-5)

(17) Adjust the set temperature pot at higher than room temperature then switch off the kit.

(18) Then connect heater socket and switch on the kit also turn on fan regulator.(19) Now vary the load and observe the deviation indicator and record the deviation

readings at intervals of 10-15seconds in table1 until the deviation indicator stabilizes at some point.

(20) Draw the graph between time and deviation.

b) Proportional+ Integral controller

(1) Connect red3 to black 2 and red 1 to black 1 with the help of patch cards in fig1. Keep proportional band in same position as in proportional controllers.

(2) Keep coarse control for integral action at 10% band and fine control at midway.(3) Repeat same procedure as in proportional controller from step7 to step9.

c) Proportional+ Derivative controller

(1) Connect red 3 to black 3 and red2 to black1 with the help of patch cards in fig1.(2) Keep coarse control for derivative action at 10% band and fine control at midway.(3) Repeat same procedure as in proportional controller from step7 to step9.

31

d) Proportional+ Integral + Derivative controller

(1) Connect red3 to black3, red2 to black2, red1 to black1 with the help of patch cards in fig1.

(2) Keep coarse control for integral at 10% band and fine control at midway and coarse control for derivative at 10% band and fine control at midway.

(3) Repeat same procedure as in proportional controller from step7 to step9.

S.No Time(sec)Deviation

( Degree C) 123..

Table-1

Result: The different analog controllers on temperature control process are studied and observed.

32

Circuit Diagarm

Model Graphs:

Fig 2: Proportion Action

33

Fig 3: Proportion+ Integral Action

Fig 4: Proportion + Derivative Action

34

11. STUDY OF FIRST ORDER SYSTEM

AIM: To study the response of First Order linear system for a given input signals.

APPARATUS: The linear system simulator study set-up, connecting wires, CRO

SPECIFICATIONS:

Square wave: frequency 40 Hz – 100 Hz, p-p amplitude 0-5v. It acts as a step input signal.

PROCEDURE:

1. Give step input to the first order system shown in circuit diagram.2. Observe the waveform for output on CRO without feedback.3. Point out 63.2% of final value in the response.4. Then measure the time taken for initial point to the above mentioned final value.

This time is called “time constant” of the system.5. Find the gain of the system by using output/input. 6. The transfer function is obtained.7. Now with feedback observe the output on CRO and repeat the procedure from

step3 to step6.

Observations:

(1) Without feedback: Input = ; output = ; Gain = output/input = k Transfer function = k/ (1+sτ) where τ: Time constant Response c (t) = k (1-e-t/τ)(2) With feedback: Input = ; output = ; Gain = output/input = k Transfer function = k/ (1+k+sτ) where τ: Time constant Response c (t) = k (1-e-t (k+1)/τ)/k+1

Result: The response of first order system with and without feedback was studied and plots are drawn.

35

1sT

k

SK

Circuit Diagram

Linear system simulator

MODEL GRAPHS:

36

37

38

39

40

41