single phase converter

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