Thyristor Voltage Controller Cwrk

8/11/2019 Thyristor Voltage Controller Cwrk

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Calculations

1.

Single phase half wave controller

a. Load Voltage waveform with diode b. Load Voltage waveform without diode

c. Anode to Cathode Voltage of SR1 d. Anode to Cathode Voltage of SR1

(With diode) (Without diode)

e. Gate voltage


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Sample Calculation

For Delay angle =

Output Voltage ( )

() Resistance() Er (V) Ec (V) VL(theoretical)

(V) (theoretical)

(degrees)

0 19 12 12.96 115.45

1 18.6 12 13.36 114.34

2 18.2 12 13.78 113.20

3 17.6 12.5 15.24 109.23

4 17 13 16.78 105.19

5 16 13.5 18.91 99.69

6 14.4 14 22.10 91.61

7 13.2 14.5 24.86 84.63

8 9.8 16 33.06 62.97

9 4.4 17.5 42.76 28.22

10 0 18 45.47 0


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Resistance () VL(practical)(V)

VL(theoretical)(V)

(theoretical)(degrees)

0 14 12.96 115.45

1 15 13.36 114.34

2 16 13.78 113.20

3 18 15.24 109.23

4 20 16.78 105.19

5 22 18.91 99.696 25 22.10 91.61

7 28 24.86 84.63

8 33 33.06 62.97

9 40 42.76 28.22

10 43 45.47 0


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0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80 100 120 140

OutputVoltage(V)

Delay angle (degrees)

Output voltages vs Delay angle

VL(practical) (V) VL(theoretical) (V)


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2. Single phase full wave controller

a. Load Voltage waveform

b. Anode to Cathode Voltage of SR1 c. Anode to Cathode Voltage of SR2

d. Gate voltage


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Sample Calculations

For Delay angle =

Output Voltage ( )

()

Resistance() Er (V) Ec (V) VL(theoretical)

(V)

(theoretical)

(degrees)

0 17.5 11.5 27.15 113.38

1 17 12 29.94 109.56

2 17 12.5 31.60 107.35

3 16.5 13 34.48 103.53

4 15.5 14 40.45 95.82

5 14.5 15 46.54 88.06

6 13.5 16.5 53.93 78.58

7 12 18 62.33 67.38

8 10 20 72.02 53.13

9 5 23 85.97 24.53

10 1.4 24 89.73 6.68


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VL(theoretical)(V)


0 12 27.15 113.38

1 13 29.94 109.56

2 15 31.60 107.35

3 17 34.48 103.53

4 19 40.45 95.82

5 22 46.54 88.06

6 33 53.93 78.58

7 43 62.33 67.38

8 57 72.02 53.13

9 78 85.97 24.53

10 86 89.73 6.68


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0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100 120

OutputVoltage(V)





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3. AC Voltage controller

a. Load Voltage waveform

b. Anode to Cathode Voltage of SR1 c. Anode to Cathode Voltage of SR2


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Sample Calculation

For Delay angle =

1.991 rad

Output Voltage

Resistance() Er (V) Ec (V) VL(theoretical)

(V)

(theoretical)

(degrees)0 18.5 12 50.78 114.06

1 18.5 12.5 52.81 111.91

2 18 12.5 54.19 110.44

3 17.5 13.5 59.49 104.70

4 17 14.5 64.51 99.08

5 16 16 72.12 90

6 14.5 17.5 80.16 79.28

7 13 19 86.88 68.76

8 11 21.5 94.04 54.19

9 4.5 24.5 101.49 20.82

10 1 25 101.99 4.58


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VL(theoretical)(V)


0 29 50.7776 114.0612

1 30 52.8137 111.90812 34 54.1887 110.4443

3 39 59.4892 104.7048

4 43 64.5104 99.0755

5 48 72.1249 90.0000

6 62 80.1620 79.2883

7 74 86.8784 68.7607

8 87 94.0378 54.1911

9 99 101.4933 20.8154

10 100 101.9945 4.5812


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0

20

40

60

80

100

120

0 20 40 60 80 100 120

OutputVoltage(V)





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Discussion

1.

Give a short discussion on the application of the thyristor voltage control in practice

The basic use of the thyristor voltage controller is to adjust the output voltage to a certain load. The two main

methods used are on-off control and phase angle control. There are many applications of the controller, some are

listed below:

Thyristor dimmer:

By changing the firing angle, the voltage across the lamp can be varied. Thus, the mean power output to the lamp

will change and so will the brightness of the lamp. This switching method is fast and consumes low power. The

basic diagram is shown below:

Six SCR in-line controllers

As the name implies, this makes use of six SCRs to control power output to the load. The load power can be varie

from 0-100% by changing the thyristor firing angles. This configuration is an ideal configuration for inductive loa

applications, unbalanced resistive loads and transformer coupled loads.

Single phase/Three phase rectifiers

These are used to convert AC supply to DC supply. By changing the firing angle, we can adjust the magnitude of

the voltage appearing across the load. The main uses for the rectifier are in AC-DC power supplies required for

electronic components and largely used in HVDC substations for long distance transmission of electricity. Other

applications maybe; charging of battery banks and setting the field voltage in synchronous generators. Below is a

basic 3 phase full-wave bridge rectifier:


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DC Motor control

Control of dc motors can be achieved by regulating the armature voltage, armature resistance or flux. In armature

voltage control, it is common to use a single phase full wave converter.

Converter 1 on the left and converter 2 on the right

The circuit above consists of dual single phase converters, this mode allows for both a positive armature voltage

and negative armature voltage across the motor and so four quadrant operation is possible. Converter 1 provides

operation in first and fourth quadrants, and converter 2 provides operation in second and third quadrants and so

provides four modes of operation: forward powering, forward braking (regeneration), reverse powering, and rever

breaking (regeneration).


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Thyristor Controlled Series Capacitor (TCSC)

TCSC is technology that can be used with new capacitor banks as well as exisiting cacpacitor banks. Some uses of

the capacitor banks are:

Increased dynamic stability of power transmission systems

Improved voltage regulation and reactive power balance

Improved load sharing between parallel lines

In a TCSC, the whole capacitor bank or alternatively, a section of it, is provided with a parallel thyristor controlle

inductor which circulates current pulses that add in phase with the line current so as to boost the capacitive voltage

beyond the level that would be obtained by the line current alone. By controlling the additional voltage to be

proportional to the line current, the TCSC will be seen by the transmission system as having a virtually increased

reactance beyond the physical reactance of the capacitor.

2. What is the reason for the directional diode?

The thyristor will conduct in its current direction as long as the current through it is greater than zero, once a gate

pulse has been given. The only way to stop it from conducting is to reverse the voltage or drive the current to zero

In the case of inductive loads, the load current lags from the output voltage, as a result when the supply goes into a

negative half cycle there is a part of the current that is still positive and so the thyristor is still conducting. This is

undesirable, therefore there is diode that opposes negative half cycle, such that it will stop conducting as soon as it

is reverse biased. As a result if we short the diode during the experiment, we can see that the thyristor conducts for

a small portion of the negative half cycle as well.


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EE 4092 Laboratory Practice IV

THYRISTOR VOLTAGE CONTROLLER

Name : S. B. Nawarathne

Index No : 090594D

Group : G17

Date of Sub : 15/07/2013

Instructed By : Dr. Anjula de silva

Thyristor Voltage Controller Cwrk

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