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Page 1: Power electronics phase control rectifier

Power Electronics

Phase Control Rectifier

Kumar goswami

M.TECH(Power electronics)

B.E.(electrical engg.)

Rcet bhilai

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Principle of Phase Control

Single phase Half wave Control with R

load

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Waveforms

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Performance Parameters

• Average O/P Voltage

The maximum value of output voltage occurs at α = 0° ,

Vom = (Vm/2ᴨ).2 = Vm/ᴨ

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• Average Load Current ,

• RMS value of load voltage (For electric heating and

incandescent lamps)

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• Power delivered to Resistive Load = (RMS load voltage x

RMS load current)

• Input Volt Amperes = (rms source voltage x total rms line

current) = Vs . Ior

• Input power factor = Power delivered to load/Input VA =

(Vor.Ior)/(Vs.Ior) = (Vor/Vs)

• Input displacement factor (DF) or fundamental power factor =

cos (angle between supply voltage and current)

• Input current distortion factor (CDF) – Ratio of rms value of

fundamental component Is1 of the input current to rms value

of input = Is1/Is

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• Rectification ratio : ratio of DC output power to AC

output power

Also known as rectification efficiency or figure of merit

. In case forward resistance Rd then

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• Form Factor (FF) – Ratio of rms value Vor of output voltage to

the dc value of Vo

FF is a measure of shape of output voltage.

Close to unity, better dc output voltage waveform

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• Voltage Ripple Factor (VRF) : Ratio of ripple voltage

to the average output voltage.

Effective or, Ripple value of the ac component of output

voltage is given by

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• Transformer Utilization Factor (TUF) :

Rms secondary voltage and current or, transformer VA

rating

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Single phase Half wave Control with

R-L load

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Single phase Half wave Control with

R-L load & Free Wheeling Diode

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• Freewheeling diode, by pass or commutating diode

• Two modes are :

Conduction mode

Free wheeling mode

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• Input pf is improved (power delivered to load in both

modes / Input KVA)

• Load current waveform is improved

• From above, load performance is better

• As energy stored in L transferred to R during the

freewheeling period, overall converter efficiency

increases.

• Supply current is unidirectional in both cases (dc

pulses) introduces dc component to supply line. This

is undesirable as as it leads to saturation of supply

transformer and harmonics etc

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Single phase Half wave Control with

R-L-E load

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• Firing angle lies :

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Full wave Controlled Converters

• SCR controlled converters (or rectifiers)

Classification:

According to No of supply phases to input

According to No of load current pulses during one cycle

of source voltage

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Single Phase Full wave Converters

• Single Phase Full wave mid point converter (M-2

connection)

• Single Phase Full wave Bridge converter (B-2

connection)

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Single Phase Full wave mid point converter

(M-2 connection)

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Waveforms

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Single Phase Full wave Bridge Converter

(B-2 connection)

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Waveforms