1. PHASE CONTROLLED CONVERTERS
UNIT II
PHASE CONTROLLED CONVERTERS

2. Phase-Control Converters
Single-Phase
Three-Phase
Semiconverter
Semiconverter
Full converter
Full converter
Dual converter
Dual converter
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3. ..is a one-quadrant converter and it has one polarity
Semiconverter
..is a one-quadrant converter and it has one polarity
Full converter
..is a two-quadrant converter and the polarity of its
output can be either positive or negative.
However
the output current of full converter has
one polarity only
Dual converter
..can operate in four quadrants ; both the output
voltage and current can be either positive or negative
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5. Average Output Voltage
Maximum
Output Voltage
Normalizing
Output Voltage
RMS Output Voltage
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6. (a) the rectification efficiency (b) the form factor FF
If the converter has a purely resistive load of R and the delay angle is , determine
(a) the rectification efficiency
(b) the form factor FF
(c) the ripple factor RF
and (d) the peak inverse voltage PIV of thyristor T1
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8. (a) the rectification efficiency (b) the form factor FF
If the converter has a purely resistive load of R and the delay angle is , determine
(a) the rectification efficiency
(b) the form factor FF
(c) the ripple factor RF
and (d) the peak inverse voltage PIV of thyristor T1
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9. (a) the rectification efficiency (b) the form factor FF
If the converter has a purely resistive load of R and the delay angle is , determine
(a) the rectification efficiency
(b) the form factor FF
(c) the ripple factor RF
and (d) the peak inverse voltage PIV of thyristor T1
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10. Semiconverter
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11. Single-Phase Semiconverter
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12. Single-Phase Semiconverter (RL-load)
Mode 1
Mode 2
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13. Single-Phase Semiconverter (RL-load)
RMS Current
for Thyristor
RMS Current
for Thyristor
RMS Output
Current
AVG Output
Current
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14. The single-phase semiconverter has an RL load of
L = 6.5mH, R = 2.5 Ohm, and E = 10 V. The input voltage is VS = 120 V(rms) at 60 Hz. Determine
(a) the load current IL0 at , and the load current IL1 at ,
(b) the average thyristor current IA
(c) the rms thyristor current IR
(d) the rms output current Irms
and (e) the average output current Idc
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15. Single-Phase Full Converter Rectification Mode Inversion Mode
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16. Single-Phase Full Converter
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17. Single-Phase Full Converter (RL-load)
Mode 1 = Mode 2
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18. Single-Phase Full Converter (RL-load)
RMS Current
for Thyristor
RMS Current
for Thyristor
RMS Output
Current
AVG Output
Current
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19. Dual
Converter
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20. Single-Phase Dual Converter
High-Power Variable-Speed Drives
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21. Three-Phase
Semiconverter
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22. 3 Phase Controlled Rectifiers
Operate from 3 phase ac supply voltage.
They provide higher dc output voltage.
Higher dc output power.
Higher output voltage ripple frequency.
Filtering requirements are simplified for smoothing out load voltage and load current.
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23. Extensively used in high power variable speed industrial dc drives.
Three single phase half-wave converters can be connected together to form a three phase half-wave converter.
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24. 3-Phase Half Wave Converter (3-Pulse Converter) with RL Load Continuous & Constant Load Current Operation
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26. Vector Diagram of 3 Phase Supply Voltages
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27. 3 Phase Supply Voltage Equations
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29. van
vbn
vcn
van
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30. Each thyristor conducts for 2/3 (1200)
Constant Load Current
io=Ia Ia Ia
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31. To Derive an Expression for the Average Output Voltage of a 3-Phase Half Wave Converter with RL Load for Continuous Load Current
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39. 3 Phase Half Wave Controlled Rectifier Output Voltage Waveforms For RL Load at Different Trigger Angles
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40. =300
=600
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41. =900
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42. 3 Phase Half Wave Controlled Rectifier With R Load and RL Load with FWD
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44. 3 Phase Half Wave Controlled Rectifier Output Voltage Waveforms For R Load or RL Load with FWD at Different Trigger Angles
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45. =00
=150
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46. =300
=600
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47. To Derive An Expression For The Average Or Dc Output Voltage Of A 3 Phase Half Wave Converter With Resistive Load Or RL Load With FWD
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52. Three Phase Semiconverters
3 Phase semiconverters are used in Industrial dc drive applications upto 120kW power output.
Single quadrant operation is possible.
Power factor decreases as the delay angle increases.
Power factor is better than that of 3 phase half wave converter.
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53. 3 Phase Half Controlled Bridge Converter (Semi Converter) with Highly Inductive Load & Continuous Ripple free Load Current
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55. Wave forms of 3 Phase Semiconverter for  > 600
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63. Wave forms of 3 Phase Semiconverter for   600
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67. To derive an Expression for the Average Output Voltage of 3 Phase Semiconverter for  >  / 3 and Discontinuous Output Voltage
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71. Six-pulse Diode Rectifier
Resistive Load
Supply Voltages:
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72. Six-pulse Diode Rectifier
Waveforms
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73. Six-pulse Diode Rectifier
Capacitive Load
Assumption:
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74. Six-pulse Diode Rectifier
Waveforms
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75. Six-pulse Diode Rectifier
Discontinuous Current Operation
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76. Six-pulse Diode Rectifier
Discontinuous Current Operation
Differential Equation:
Solution:
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77. Six-pulse Diode Rectifier
Discontinuous Current Operation
Peak dc current:
Average dc current:
Voltage – theta relation:
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78. Six-pulse Diode Rectifier
Continuous Current Operation
Note:
- With the increase of the load current, the rectifier will
enter into continuous current operation.
- During commutation interval, three diodes are on.
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79. Six-pulse Diode Rectifier
Definition of Total Harmonic Distortion (THD)
Phase voltage (pure sine):
Line current (distorted):
RMS line current:
Line current THD:
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80. Six-pulse Diode Rectifier
Definition of Power Factor (PF)
Per-phase average (real) power:
Per-phase apparent power:
Total power factor (PF):
Distortion factor (DF) :
Displacement power factor (DPF) :
PF = f (THD) :
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81. Six-pulse Diode Rectifier
Typical Waveforms / Harmonic Content
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82. Six-pulse Diode Rectifier
THD and PF
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83. Inductive load, quantitative analysis
Differential equation
The RMS value of output voltage, output current, and thyristor current can then be calculated.
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84. Used for applications up to 2 mega watt output power level.
Three Phase Dual Converters
For four quadrant operation in many industrial variable speed dc drives , 3 phase dual converters are used.
Used for applications up to 2 mega watt output power level.
Dual converter consists of two 3 phase full converters which are connected in parallel & in opposite directions across a common load.
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88. Outputs of Converters 1 & 2
During the interval (/6 + 1) to (/2 + 1), the line to line voltage vab appears across the output of converter 1 and vbc appears across the output of converter 2
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91. To obtain an Expression for the Circulating Current
If vO1 and vO2 are the output voltages of converters 1 and 2 respectively, the instantaneous voltage across the current limiting inductor during the interval (/6 + 1)  t  (/2 + 1) is given by
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94. Four Quadrant Operation
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95. There are two different modes of operation. Circulating current free
(non circulating) mode of operation
Circulating current mode of operation
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96. Non Circulating Current Mode Of Operation
In this mode of operation only one converter is switched on at a time
When the converter 1 is switched on,
For 1 < 900 the converter 1 operates in the Rectification mode
Vdc is positive, Idc is positive and hence the average load power Pdc is positive.
Power flows from ac source to the load
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97. When the converter 1 is on,
For 1 > 900 the converter 1 operates in the Inversion mode
Vdc is negative, Idc is positive and the average load power Pdc is negative.
Power flows from load circuit to ac source.
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98. When the converter 2 is switched on,
For 2 < 900 the converter 2 operates in the Rectification mode
Vdc is negative, Idc is negative and the average load power Pdc is positive.
The output load voltage & load current reverse when converter 2 is on.
Power flows from ac source to the load
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99. When the converter 2 is switched on,
For 2 > 900 the converter 2 operates in the Inversion mode
Vdc is positive, Idc is negative and the average load power Pdc is negative.
Power flows from load to the ac source.
Energy is supplied from the load circuit to the ac supply.
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100. Circulating Current Mode Of Operation
Both the converters are switched on at the same time.
One converter operates in the rectification mode while the other operates in the inversion mode.
Trigger angles 1 & 2 are adjusted such that (1 + 2) = 1800
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101. When 1 < 900, converter 1 operates as a controlled rectifier
When 1 < 900, converter 1 operates as a controlled rectifier. 2 is made greater than 900 and converter 2 operates as an Inverter.
Vdc is positive & Idc is positive and Pdc is positive.
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102. Vdc is negative & Idc is negative and Pdc is positive.
When 2 < 900, converter 2 operates as a controlled rectifier. 1 is made greater than 900 and converter 1 operates as an Inverter.
Vdc is negative & Idc is negative and Pdc is positive.
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