7. rectifier
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RectifiersRectifiers
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Single-phase, Half Wave Rectifier
Uncontrolled
Controlled Free wheeling diode
Single-phase, Full Wave Rectifier
Uncontrolled Controlled
Three-phase Rectifier
Uncontrolled Controlled
Overview
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Input can be single or multi-phase (e.g. 3-phase). Output can be made fixed or variable
Applications: DC welder, DC motor drive, Battery
charger, DC power supply, HVDC
DEFINITION:DEFINITION:Converting AC (from mains or other AC source) to DC powerby using power diodes or by controlling the firing angles of
thyristors/controllable switches.Basic block diagramBasic block diagram
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Uncontrolled Single Phase
Half Wave Rectifier
Uncontrolled Single Phase
Half Wave Rectifier
Uncontrolled Single Phase
Half Wave Rectifier
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Single-phase, Half-Wave, R - load
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Given the supply voltage v = 120 Vrms
, 60 Hz.Determines:
a) The average load voltage and currentb) The load voltage in r.m.s.
c) The average power absorbed by the load, RLd) The power factor of the circuit
AnswerAnswer
a) 54 V & 10.8 A,a) 54 V & 10.8 A, b) 84.9 V, c) 1440 W, d) 0.707b) 84.9 V, c) 1440 W, d) 0.707
ExampleExample
Single-phase, Half-Wave, R - load
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SolutionSolution
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Uncontrolled Single Phase
Full Wave Rectifier
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Full Wave Rectifier
Center-tapped (CT) rectifier requires center-taptransformer. Full Bridge (FB) does not. CT: 2 diodes FB: 4 diodes. Hence, CT experienced only onediode volt-drop per half-cycle Conduction losses for CT is half.
Diodes ratings for CT is twice the FB.
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Full Wave Rectifier
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Bridge Waveforms
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Center-tappedwaveforms
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Uncontrolled Three Phase
Half Wave Rectifier
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Three-phase half-wave rectifiers
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Uncontrolled Three PhaseFull Wave Rectifier
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In the top group (D1, D3), the cathodes (-) of the two diodes are at acommon potential. Therefore, the diode with its anode (+) at the highestpotential will conduct (carry) id. For example, when vs is ( +), D1 conducts id and D3 reverses (by taking loop
around vs, D1 and D3).When vs is (-), D3 conducts, D1 reverses.
In the bottom group, the anodes of the two diodes are at common potential.Therefore the diode with its cathode at the lowest potential conducts id. For example, when vs (+), D2 carry id. D4 reverses.When vs is (-), D4 carry id. D2 reverses.
Single-phase diode groups
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Three-phase full-wave rectifiers
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Three-phase full-wave rectifiers
vvoo==vvpp --vvnn
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Top group: diode with its anode at the highestpotential will conduct. The other two will be reversed.
Bottom group: diode with the its cathode at thelowest potential will conduct. The other two will bereversed.
For example, if D1 (of the top group) conducts, vp is
connected to van.. If D6 (of the bottom group)conducts, vn connects to vbn . All other diodes are off.
The resulting output waveform is given as:
vo = vp - vn For peak of the output voltage is equal to the peak ofthe line to line voltage vab .
Three-phase full-wave rectifiers
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Three-phase, average voltage
Considers only one of
the six segments.
Obtain its average
over 60 degrees or
/3 radians.
Considers only one of
the six segments.
Note that the output DC
voltage component of a
three - phase rectifier is
much higher than of asingle phase.
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Single Phase Half-WaveControlled Rectifier
Controlled Half Wave
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Controlled Half-Wave
Controlled Half Wave
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Controlled Half-Wave
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Single Phase Full Wave
Controlled Rectifier
Controlled Full
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Controlled FullWave, R load
Controlled Full
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Controlled FullWave, R load
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Three Phase Half Wave
Controlled Rectifier
Three Phase Half Wave Controlled Rectifier
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Three Phase Full Wave
Controlled Rectifier
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Three-phase full-wave
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pcontrolled rectifier
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