DeltatronGohar Arslan (2K11 – EE – 022)

Kumail Hassan (2K11 – EE – 034)

Usman Masood (2K11 – EE – 052)

Abdul Rahman (2K11 – EE – 064)

Saad Khurram (2K11 – EE – 136)

Introduction

Voltage multiplier

circuits

Cock-Croft Walton

Multiplier Circuit

Insulated Core Transformer

Allibone Dynamitron Deltatron

Insulated core transformer (ICT)

• Series connection of full wave rectifiers

• Each rectifier produces Vo voltages andn rectifiers will produce nVo volts.

• All the rectifiers are insulated from

transformer core and from each other

Allibone Voltage Multiplier

• Each stage has a HV transformer andtwo half wave rectifiers

• Storage capacitors are connected in series

• The main problem in this circuit is theinsulation

Dynamitron

• Parallel fed cascade circuit

• High frequency input of MHz

• Load-ability of this circuit is several times

of mA and voltage of MV range

• A Dynamitron type high voltage power supply

utilized in a neutron generator in operation for 14MeV neutron

therapy at the Eppendorf Hospital in Hamburg.

Deltatron

• It is also called Engetron

• First time it was described by international conference Electronic Materials and Nanotechnology for Green Environment (Enge) in US patent

• Combination of Cockcroft-Walton & Cascaded Transformer DC rectifier

• It has no iron core

• High stability

• Small ripple factor

• Fast regulation

• Combined R-C voltage divider is for fast regulation

• This might be limited up to 1 MV and some mA

• Termination circuit is used to stop the process

Why not Cockcroft-Walton?

• If the generator supplies any load current I, theoutput voltage will never reach the value 2nVmax

• There will also be a ripple on the voltage

• Therefore we have to deal with two quantities:

1) Voltage drop ΔV0

2) Peak-to-Peak ripple 2δV

• Fig. shows the shape of the output voltage

Equations

• For a given load, however, V0 may rise initially with the number ofstages n, but reaches an optimum value and even decreases if n is toolarge

• For a generator with Vmax= 100 kV

f = 500 Hz

C = 7µF and

I = 500 mA

nopt= 10

It is, however, not desirable to use the optimum number of stages, asthen V0max is reduced to 2/3 of its maximum value 2nVmax. Also thevoltage variations for varying loads will increase too much.

Voltage Multiplier With Cascaded Transformers• Disadvantage can be reduced of Walton circuit if single- or full-wave

rectifier systems, each having its own AC power source, are connected inseries at the DC output only.

• In this circuit, every transformer per stage consists of a low voltage primary, a high voltage secondary and a low voltage tertiary coil.

• As none of the HV secondary windings is on ground potential, a DCvoltage insulation within each transformer is necessary, which can besubdivided within the transformers.

Disadvantage

• Limitations as far as the number of stages is concerned, as the lower

transformers have to supply the energy for the upper ones, this

circuit, excited with power frequency, provides an economical DC

power supply for HV testing purposes with moderate ripple factors

and high power capabilities.

Engetron

• Primarily consists of series connected transformers(without iron-core)

• Transformers are coupled by series capacitors Cs

• Capacitors compensate stray inductance

• A capacitors Cp is connected in parallel to provide overcompensation of magnetizing currents

• The chain of transformers is loaded by terminating resistor

Deltatron / Engetron

• Network acts like a terminated transmission line

• E.g. having ac voltages constant and a phase shiftbetween high frequency supply and termination

• Walton cascaded are directly series connected providing HVDC output voltage for whole unit

• Frequency oscillator ranges from 50 to 100kHz

Deltatron / Engetron

• 25 stages can be used in modular structure

• Modules are very small so can be stacked in cylindrical unit

• Insulated by SF6

• Regulation due to load variations is very small (response time typically about 1ms)

• For continuous and stable DC output high product of fC is necessary

Applications

• Electrostatic printing.

• As a power source of high voltage particle accelerators.

• As a source for electrostatic quadrupole lenses.

Limitations

• Decreased stray capacitances due to increased input frequency.

Xc=1/2πfc

• Corona effect.

• Losses due to leakage in diodes, capacitors and insulation are significant considerations in applications using very low capacitor values and in applications, which operate at high temperatures(>125°C).

• Input and output voltages.

Environmental Limitations

• Non linear corona effect and contamination due to depositinginsulating film arises due to high altitudes.

• Dielectric oils or gases to surround the custom multiplier assembly toprovide excellent isolation, reduced corona effects, minimalmechanical stresses, and usually good cooling, they can also damageor degrade some encapsulants and remove assemblylabeling.(chemical exposure).

• Humidity severely limits the voltage isolation capabilities of air-insulated applications.

Environmental Limitations

• High temperatures can induce significant mechanical stresses, due to mismatches in material thermal expansion coefficient. Similarly, very low temperature extremes can induce mechanical stresses due to material thermal expansion mismatches. Low temperatures can also cause radical changes in the physical characteristics of the encapsulant, making it brittle, or causing the encapsulant to exhibit non-linear shrinkage effects.

Thank You…!!!