Three Phase Controlled Rectifiers
description
Transcript of Three Phase Controlled Rectifiers
Power Electronics by Prof. M. Madhusudhan Rao 11
Three Phase Controlled Rectifiers
Power Electronics by Prof. M. Madhusudhan Rao 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.
Power Electronics by Prof. M. Madhusudhan Rao 33
• 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.
Power Electronics by Prof. M. Madhusudhan Rao 44
3-Phase Half Wave Converter(3-Pulse Converter)
with RL Load
Continuous & ConstantLoad Current Operation
Power Electronics by Prof. M. Madhusudhan Rao 55
Power Electronics by Prof. M. Madhusudhan Rao 66
Vector Diagram of 3 Phase Supply Voltages
V A N
V C N
V B N
1 2 00
1 2 00
1 2 00 RN AN
YN BN
BN CN
v vv vv v
Power Electronics by Prof. M. Madhusudhan Rao 77
3 Phase Supply Voltage Equations
We deifine three line to neutral voltages (3 phase voltages) as follows
Power Electronics by Prof. M. Madhusudhan Rao 88
0
0
0
sin ; Max. Phase Voltage
2sin3
sin 120
2sin3
sin 120
sin 240
RN an m
m
YN bn m
m
BN cn m
m
m
v v V tV
v v V t
V t
v v V t
V t
V t
Power Electronics by Prof. M. Madhusudhan Rao 99
van vbn vcn van
Power Electronics by Prof. M. Madhusudhan Rao 1010
io=Ia
Constant Load Current
Ia
Ia
Each thyristor conducts for 2/3 (1200)
Power Electronics by Prof. M. Madhusudhan Rao 1111
To Derive an Expression for the
Average Output Voltage of a 3-Phase Half Wave Converter
with RL Loadfor Continuous Load Current
Power Electronics by Prof. M. Madhusudhan Rao 1212
01
02
03
0
3065 1506
7 2706
2Each thytistor conducts for 120 or radians3
T is triggered at t
T is triggered at t
T is triggered at t
Power Electronics by Prof. M. Madhusudhan Rao 1313
56
6
If the reference phase voltage is sin , the average or dc output
voltage for continuous load current is calculated using the equation
3 sin .2
RN an m
dc m
v v V t
V V t d t
Power Electronics by Prof. M. Madhusudhan Rao 1414
56
6
56
6
3 sin .2
3 cos2
3 5cos cos2 6 6
mdc
mdc
mdc
VV t d t
VV t
VV
Power Electronics by Prof. M. Madhusudhan Rao 1515
0 0
0
Note from the trigonometric relationshipcos cos .cos sin .sin
5 5cos cos sin sin6 63
2co
cos 150 cos sin 150 sin32 cos 30
s .cos sin sin6 6
.cosm
dc
mdc
A
VV
B A B A B
VV
0sin 30 sin
Power Electronics by Prof. M. Madhusudhan Rao 1616
0 0
0 0 0 0
0 0
0 0
0
0
0
0
0 0
Note: cos 1
cos 180 30 cos sin 180 30 sin32 cos 30 .cos sin 30 sin
cos 30 cos sin 30 sin32 cos 30 .cos sin 30 s
80 30 cos 30
sin 180 30 sin 30
in
mdc
mdc
VV
VV
Power Electronics by Prof. M. Madhusudhan Rao 1717
03 2cos 30 cos23 32 cos2 2
3 3 33 cos cos2 23 cos2
Where 3 Max. line to line supply voltage
mdc
mdc
m mdc
Lmdc
Lm m
VV
VV
V VV
VV
V V
Power Electronics by Prof. M. Madhusudhan Rao 1818
max
The maximum average or dc output voltage is obtained at a delay angle 0 and is given by
3 3 2
Where is the peak phase voltage.And the normalized average output voltage is
mdmdc
m
ddcn n
VV V
V
VV V
cosc
dmV
Power Electronics by Prof. M. Madhusudhan Rao 1919
15 26
2 2
6
12
The rms value of output voltage is found by using the equation
3 sin .2
and we obtain
1 33 cos 26 8
mO RMS
mO RMS
V V t d t
V V
Power Electronics by Prof. M. Madhusudhan Rao 2020
3 Phase Half Wave Controlled Rectifier Output Voltage
Waveforms For RL Load at
Different Trigger Angles
Power Electronics by Prof. M. Madhusudhan Rao 2121
0
0
30 0
300
60 0
600
90 0
900
12 0 0
12 00
15 00
15 00
18 0 0
18 00
21 0 0
21 00
24 0 0
24 00
27 0 0
27 00
30 0 0
30 00
33 0 0
33 00
36 0 0
36 00
39 00
39 00
42 0 0
42 00
V an
V 0
V 0
V an
= 30 0
= 60 0
V bn
V bn
V cn
V cn
t
t
=300
=600
Power Electronics by Prof. M. Madhusudhan Rao 2222
03 0
06 0
09 0
01 2 0
01 50
01 8 0
02 10
024 0
027 0
030 0
0330
03 60
03 9 0
0420
0
V 0
V an
= 90 0
V bn V cn
t
=900
Power Electronics by Prof. M. Madhusudhan Rao 2323
3 Phase Half Wave Controlled Rectifier With
R Load and
RL Load with FWD
Power Electronics by Prof. M. Madhusudhan Rao 2424
a a
b b
c c
RV 0
L
R V 0
+
T 1
T 2
T 3
n n
T 1
T 2
T 3
Power Electronics by Prof. M. Madhusudhan Rao 2525
3 Phase Half Wave Controlled Rectifier Output Voltage
Waveforms For R Load or RL Load with FWD
atDifferent Trigger Angles
Power Electronics by Prof. M. Madhusudhan Rao 2626
0
0
30 0
30 0
6 0 0
6 0 0
9 0 0
9 0 0
1 20 0
1 20 0
1 50 0
1 50 0
1800
1800
2 10 0
2 10 0
2 40 0
2 40 0
270 0
270 0
30 0 0
30 0 0
33 0 0
33 0 0
3 60 0
3 60 0
3900
3900
4 20 0
4 20 0
V s
V 0
V a n
= 0
= 1 5 0
V b n V c n
t
V a n V b n V c n
t
=00
=150
Power Electronics by Prof. M. Madhusudhan Rao 2727
0
0
30 0
300
6 0 0
6 00
90 0
900
1 20 0
1 200
1 50 0
1 500
180 0
1800
210 0
2100
2400
2400
2700
2700
300 0
3000
33 0 0
33 00
360 0
3600
3 90 0
3 900
420 0
4200
V 0
= 3 0 0
V a n V b n V c n
t
V 0
= 6 0 0
V a n V b n V c n
t
=300
=600
Power Electronics by Prof. M. Madhusudhan Rao 2828
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
Power Electronics by Prof. M. Madhusudhan Rao 2929
01
0 01
02
0 02
0
306
30 180 ;
sin
5 1506
150 300 ;
sin 120
O an m
O bn m
T is triggered at t
T conducts from to
v v V t
T is triggered at t
T conducts from to
v v V t
Power Electronics by Prof. M. Madhusudhan Rao 3030
03
0 03
0
0
7 2706
270 420 ;
sin 240
sin 120
O cn m
m
T is triggered at t
T conducts from to
v v V t
V t
Power Electronics by Prof. M. Madhusudhan Rao 3131
0
0
0
0
0
0
180
30
0 0
180
30
180
30
3 .2
sin ; for 30 to 180
3 sin .2
3sin .
2
dc O
O an m
dc m
mdc
V v d t
v v V t t
V V t d t
VV t d t
Power Electronics by Prof. M. Madhusudhan Rao 3232
0
0
180
30
0 0
0
0
3 cos2
3 cos180 cos 302
cos180 1, we get3 1 cos 302
mdc
mdc
mdc
VV t
VV
VV
Power Electronics by Prof. M. Madhusudhan Rao 3333
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.
Power Electronics by Prof. M. Madhusudhan Rao 3434
3 Phase Half Controlled Bridge Converter
(Semi Converter)with Highly Inductive Load &
Continuous Ripple free Load Current
Power Electronics by Prof. M. Madhusudhan Rao 3535
Power Electronics by Prof. M. Madhusudhan Rao 3636
Wave forms of 3 Phase Semiconverter for
> 600
Power Electronics by Prof. M. Madhusudhan Rao 3737
Power Electronics by Prof. M. Madhusudhan Rao 3838
Power Electronics by Prof. M. Madhusudhan Rao 3939
0 0
1
3 phase semiconverter output ripple frequency of output voltage is 3
The delay angle can be varied from 0 to During the period
30 2107 , thyristor T is forward biased
6 6
Sf
t
t
Power Electronics by Prof. M. Madhusudhan Rao 4040
1
1 1
If thyristor is triggered at ,6
& conduct together and the line to line voltage appears across the load.
7At , becomes negative & FWD conducts.6
The load current contin
ac
ac m
T t
T Dv
t v D
1 1
ues to flow through FWD ; and are turned off.
mDT D
Power Electronics by Prof. M. Madhusudhan Rao 4141
1
2
1 2
If FWD is not used the would continue to
conduct until the thyristor is triggered at 5 , and Free wheeling action would 6
be accomplished through & .
If the delay angle , e3
mD T
T
t
T D
ach thyristor conducts
2for and the FWD does not conduct. 3 mD
Power Electronics by Prof. M. Madhusudhan Rao 4242
0
0
0
We deifine three line neutral voltages (3 phase voltages) as follows
sin ; Max. Phase Voltage
2sin sin 12032sin sin 1203
sin 240
RN an m m
YN bn m m
BN cn m m
m
v v V t V
v v V t V t
v v V t V t
V t
V
is the peak phase voltage of a wye-connected source.m
Power Electronics by Prof. M. Madhusudhan Rao 4343
3 sin653 sin6
3 sin2
3 sin6
RB ac an cn m
YR ba bn an m
BY cb cn bn m
RY ab an bn m
v v v v V t
v v v v V t
v v v v V t
v v v v V t
Power Electronics by Prof. M. Madhusudhan Rao 4444
Wave forms of 3 Phase Semiconverter for
600
Power Electronics by Prof. M. Madhusudhan Rao 4545
Power Electronics by Prof. M. Madhusudhan Rao 4646
Power Electronics by Prof. M. Madhusudhan Rao 4747
Power Electronics by Prof. M. Madhusudhan Rao 4848
To derive an Expression for the
Average Output Voltage of 3 Phase Semiconverter
for > / 3 and Discontinuous Output Voltage
Power Electronics by Prof. M. Madhusudhan Rao 4949
76
6
76
6
For and discontinuous output voltage:3
the Average output voltage is found from
3 .2
3 3 sin2 6
dc ac
dc m
V v d t
V V t d t
Power Electronics by Prof. M. Madhusudhan Rao 5050
max
3 3 1 cos2
3 1 cos2
3 Max. value of line-to-line supply voltageThe maximum average output voltage that occurs at a delay angle of 0 is
3 3
mdc
mLdc
mL m
mdmdc
VV
VV
V V
VV V
Power Electronics by Prof. M. Madhusudhan Rao 5151
17 26
2
6
The normalized average output voltage is
0.5 1 cos
The rms output voltage is found from
3 .2
dcn
dm
acO rms
VV
V
V v d t
Power Electronics by Prof. M. Madhusudhan Rao 5252
17 26
2 2
6
12
3 3 sin2 6
3 sin 234 2
mO rms
mO rms
V V t d t
V V
Power Electronics by Prof. M. Madhusudhan Rao 5353
Average or DC Output Voltage of a
3-Phase Semiconverter for / 3,
and Continuous Output Voltage
Power Electronics by Prof. M. Madhusudhan Rao 5454
562
6 2
For , and continuous output voltage3
3 . .2
3 3 1 cos2
dc ab ac
mdc
V v d t v d t
VV
Power Electronics by Prof. M. Madhusudhan Rao 5555
15 262
2 2
6 2
12
2
0.5 1 cos
RMS value of o/p voltage is calculated by usingthe equation
3 . .2
3 23 3 cos4 3
dcn
dm
ab acO rms
mO rms
VV
V
V v d t v d t
V V
Power Electronics by Prof. M. Madhusudhan Rao 5656
Three Phase Full Converter
• 3 Phase Fully Controlled Full Wave Bridge Converter.
• Known as a 6-pulse converter.• Used in industrial applications up to 120kW
output power.• Two quadrant operation is possible.
Power Electronics by Prof. M. Madhusudhan Rao 5757
Power Electronics by Prof. M. Madhusudhan Rao 5858
Power Electronics by Prof. M. Madhusudhan Rao 5959
Power Electronics by Prof. M. Madhusudhan Rao 6060
• The thyristors are triggered at an interval of / 3.
• The frequency of output ripple voltage is 6fS.
• T1 is triggered at t = (/6 + ), T6 is already conducting when T1 is turned ON.
• During the interval (/6 + ) to (/2 + ), T1 and T6 conduct together & the output load voltage is equal to vab = (van – vbn)
Power Electronics by Prof. M. Madhusudhan Rao 6161
• T2 is triggered at t = (/2 + ), T6 turns off naturally as it is reverse biased as soon as T2 is triggered.
• During the interval (/2 + ) to (5/6 + ), T1 and T2 conduct together & the output load voltage vO = vac = (van – vcn)
• Thyristors are numbered in the order in which they are triggered.
• The thyristor triggering sequence is 12, 23, 34, 45, 56, 61, 12, 23, 34, ………
Power Electronics by Prof. M. Madhusudhan Rao 6262
0
0
0
We deifine three line neutral voltages (3 phase voltages) as follows
sin ; Max. Phase Voltage
2sin sin 12032sin sin 1203
sin 240
RN an m m
YN bn m m
BN cn m m
m
v v V t V
v v V t V t
v v V t V t
V t
V
is the peak phase voltage of a wye-connected source.m
Power Electronics by Prof. M. Madhusudhan Rao 6363
The corresponding line-to-line supply voltages are
3 sin6
3 sin2
3 sin2
RY ab an bn m
YB bc bn cn m
BR ca cn an m
v v v v V t
v v v v V t
v v v v V t
Power Electronics by Prof. M. Madhusudhan Rao 6464
To Derive An Expression For The Average Output Voltage Of
3-phase Full Converter With Highly Inductive Load Assuming Continuous And
Constant Load Current
Power Electronics by Prof. M. Madhusudhan Rao 6565
2
6
6 . ; 2
3 sin6
dc OO dc
O ab m
V V v d t
v v V t
The output load voltage consists of 6 voltage pulses over a period of 2 radians, Hence the average output voltage is calculated as
Power Electronics by Prof. M. Madhusudhan Rao 6666
2
6
mL
max
3 3 sin .6
3 3 3cos cos
Where V 3 Max. line-to-line supply voThe maximum average dc output voltage is obtained for a delay angle
ltage
3 3
0,
3
dc m
m mLdc
m
m mdmdc
V V t d t
V VV
V
V VV V
L
Power Electronics by Prof. M. Madhusudhan Rao 6767
12
22
6
The normalized average dc output voltage is
cos
The rms value of the output voltage is found from
6 .2
dcdcn n
dm
OO rms
VV VV
V v d t
Power Electronics by Prof. M. Madhusudhan Rao 6868
12
22
6
12
22 2
6
12
6 .2
3 3 sin .2 6
1 3 33 cos 22 4
abO rms
mO rms
mO rms
V v d t
V V t d t
V V
Power Electronics by Prof. M. Madhusudhan Rao 6969
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.
Power Electronics by Prof. M. Madhusudhan Rao 7070
Power Electronics by Prof. M. Madhusudhan Rao 7171
Power Electronics by Prof. M. Madhusudhan Rao 7272
Power Electronics by Prof. M. Madhusudhan Rao 7373
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
Power Electronics by Prof. M. Madhusudhan Rao 7474
0
0
0
We deifine three line neutral voltages (3 phase voltages) as follows
sin ; Max. Phase Voltage
2sin sin 12032sin sin 1203
sin 240
RN an m
m
YN bn m m
BN cn m m
m
v v V tV
v v V t V t
v v V t V t
V t
Power Electronics by Prof. M. Madhusudhan Rao 7575
The corresponding line-to-line supply voltages are
3 sin6
3 sin2
3 sin2
RY ab an bn m
YB bc bn cn m
BR ca cn an m
v v v v V t
v v v v V t
v v v v V t
Power Electronics by Prof. M. Madhusudhan Rao 7676
• 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
To obtain an Expression for the Circulating Current
Power Electronics by Prof. M. Madhusudhan Rao 7777
1 2
3 sin sin6 2
3 cos6
The circulating current can be calculated byusing the equation
r O O ab bc
r m
r m
v v v v v
v V t t
v V t
Power Electronics by Prof. M. Madhusudhan Rao 7878
1
1
6
6
1
max
1 .
1 3 cos .6
3sin sin
63
t
r rr
t
r mr
mr
r
mr
r
i t v d tL
i t V t d tL
Vi t t
LViL
Power Electronics by Prof. M. Madhusudhan Rao 7979
Four Quadrant OperationConv. 2 Inverting2 > 900
Conv. 2 Rectifying2 < 900
Conv. 1 Rectifying1 < 900
Conv. 1 Inverting1 > 900
Power Electronics by Prof. M. Madhusudhan Rao 8080
• There are two different modes of operation. Circulating current free
(non circulating) mode of operation Circulating current mode of operation
Power Electronics by Prof. M. Madhusudhan Rao 8181
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 modeVdc is positive, Idc is positive and hence the average load power Pdc is positive.
• Power flows from ac source to the load
Power Electronics by Prof. M. Madhusudhan Rao 8282
• When the converter 1 is on,For 1 > 900 the converter 1 operates in the Inversion modeVdc is negative, Idc is positive and the average load power Pdc is negative.
• Power flows from load circuit to ac source.
Power Electronics by Prof. M. Madhusudhan Rao 8383
• When the converter 2 is switched on,For 2 < 900 the converter 2 operates in the Rectification modeVdc 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
Power Electronics by Prof. M. Madhusudhan Rao 8484
• When the converter 2 is switched on,For 2 > 900 the converter 2 operates in the Inversion modeVdc 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.
Power Electronics by Prof. M. Madhusudhan Rao 8585
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
Power Electronics by Prof. M. Madhusudhan Rao 8686
• 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.
Power Electronics by Prof. M. Madhusudhan Rao 8787
• 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.