single phase converter
TRANSCRIPT
SEMINAR ON SINGLE PHASE CONVERTER
By Vinod Srivastava M.E. Modular I & CRoll No.151522
INTRODUCTIONAC(~) DC(--)Diode rectifiers are uncontrolled rectifiersThe level of DC output voltage can not be controlled.e.g. single phase half wave and full wave rectifiers.
Single phase Full Wave Bridge Rectifier
.
A.C. in
D.C. out
CONTROLLED RECTIFIERRectifier designed with SCR’s are
controlled rectifier.AC is converted into regulated DC.The phase relationship between i/p
voltage & o/p current can be controlled.Level of the voltage can be regulated by
varying firing angle α.
Classification-• Single phase converterHalf wave converterFull wave converter
• Three phase converterHalf wave converterFull wave converter
Single Phase Half Wave Rectifier
Fig(a) Half wave rectifier for resistive load
Average value of output voltage
ttdvv iav sin221
On solving
)cos1(2
iav
vv
RESISTIVE – INDUCTIVE LOAD
Contd….Thyristor turns ON at ωt= α & voltage
appears across Load & current starts building up.
Inductor does not changes current instantaneously, so load current does not become zero at ωt = π.
Average value of output voltage
ttdvv iav sin221
)cos(cos2
,
iav
vvonsolving
SINGLE PHASE CONVERTER
Fig-single phase thyristor controlled rectifier with Ls=0
Input and output response
OperationIn the positive half cycle T1 and T2 are
forward biased.In the negative half T3 and T4 are
forward biased.T1 and T2 continue to conduct till T3 and
T4 are triggered.
Contd….T1T2 α to π + α T3T4 π + α to 2π + αα to π Vo +veα to π Io +veπ to π + α Vo -veπ to π + α Io +veα to π L stores the energy.π to π + α L releases the energy.
AVERAGE VALUE OF OUTPUT VOLTAGE
ttdvV mav
sin1
cos2 mav
vV
onsolving
Thus, Vav is +ve from o ˂α ˂ π/2 Vav is –ve from π/2 ˂ α ˂ π
Vo
Io
-Vo
Line Current
Contd….
Eq…(1)
Eq…(2)
Eq…..(3)
Eq…..(4)
Eq…..(5)
The current Is in fig a can be expressed in terms of its fourier components as-
Where only odd harmonics are present
Rms value of is1
Power, power factor and reactive volt amperes
(a)
(2), (4) & (6)
(2)
(6)
8
Eq…(6)Eq…(7)
Eq…(8)Eq…(9)
Eq…(10)
Eq…(11)
Effect of Ls
Fig (c)
Fig (e)
Fig (d)
Contd….The effect of inductance can not
be ignored in practical thyristor converters.
The current commutation takes a finite commutation interval u as in fig (d)
Fig(c) Eq…
(12)
Eq…(13)
(13)Eq…(14)
(14) (13) Eq…
(15)Eq…(16)
Eq…(17)
Contd….
Eq……(18)
THANK YOU