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7/28/2019 1.Generation of High DC Voltages _NEW
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GENERATIONOF HIGH DC
VOLTAGESPresented By
AKHIL ASHOK
E8A8701
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CONTENTS
Introduction
Generation of High DC Voltages
Half and Full Wave Rectifier
Rectifier Valve Construction
Ripple Voltages with HW and FW Rectifier
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INTRODUCTION
What is HV?
Types of HV:
High DC Voltage (e-Microscope, X-Ray, etc.)
High AC Voltages of Power/High Frequency (about
1 million volt or more to test power apparatus rated
for EHT voltages)
High Transient or Impulse Voltages (to simulateover-voltages due to lightning or switching surges)
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GENERATIONOF HIGH DC VOLTAGES
Mainly used in
- Research work in Physics
- Insulation test on Cables and Capacitors
- Impulse Generator
How to Generate HDC?
For DC Voltages up to 100KV, Electronic Valve
Rectifiers are used.AC Supply to Rectifier tubes maybe Power Freq
or AF (AF low ripple avoid costly filters)
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HALFAND FULL WAVE RECTIFIER
Rectifier Circuits for producing HDC Voltages
from AC maybe:
Half Wave
Full Wave Voltage Doubler
Rectifier maybe e-tube (PIV =250KV) or solid
state device (PIV up to 20KV lab use silicon
diodes ).
For Higher Voltages units are used in series.
(special care should be taken in order to make
uniform distribution of transient voltage)
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The value of RC = 10 x Period of AC Supply
PIV at least 2Vm
To limit charging current an R in series with
transformer
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RECTIFIERVALVE CONSTRUCTION
Special construction
Protective Shield or Grid around the filament and
cathode.
Anode usually circular plate
Heater and Cathode experience large electrostatic
force during non-conduction period.
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To Protect various elements:
Anode firmly attached fixed to valve cover
A steel mesh structure or protective grid kept
at Cathode potential surrounds cathode and
filament (hence mechanical forces between A
& K reflected on grid only)
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RIPPLE VOLTAGESWITH HW AND FW
RECTIFIER
Fluctuation in output DC, V is called Ripple
Ripple depends on:
Supply Frequency
Time Constant
Reactance of Supply Transformer
In HW, Ripple Freq = Supply Freq
In FW, Ripple Freq = 2 x Supply FreqRipple Voltage can be kept low by proper choice
of C and Transformer Reactance for given load.
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TRANSFORMERRECTIFIERSETSFOR
ELECTROSTATIC PRECIPITATORS
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HIGHVOLTAGEBOARDRECTIFIERASSEMBLY
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REFERENCES
High Voltage Engineering
M M Naidu, V Kamaraju
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THANK YOU
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