Power Electronics
Phase Control Rectifier
Kumar goswami
M.TECH(Power electronics)
B.E.(electrical engg.)
Rcet bhilai
Principle of Phase Control
Single phase Half wave Control with R
load
Waveforms
Performance Parameters
• Average O/P Voltage
The maximum value of output voltage occurs at α = 0° ,
Vom = (Vm/2ᴨ).2 = Vm/ᴨ
Continued….
• 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
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 :
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)
Single Phase Full wave mid point converter
(M-2 connection)
Waveforms
Single Phase Full wave Bridge Converter
(B-2 connection)
Waveforms
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