EE 415 – Electrical Engineering Senior Project - Final Report “Plasmatron” Plasma Exciter

Cover Page – 200kHz Plasma, generated by early, hand-made prototype unit at Advanced Energy, Voorhees, NJ... This has involved the creation of the necessary circuitry, rough bread-boardi

“Plasmatron” Plasma Exciter

Developed in Conjunction with

Advanced Energy Industries, Inc – Voorhees, NJ

Project by : Joseph Eugene Palaia, IV

May 13, 2002

Professor : Dr James K Beard Advisor : Mohammed Feknous New Jersey Institute of Technology - Mt Laurel, NJ

This report contains data proprietary to Advanced Energy Industries, Inc of Voorhees, NJ It's use is restricted to academic evaluation unless specifically approved in writing by a

designated representative of Advanced Energy Industries, Inc.

Cover Page – 200kHz Plasma, generated by early, hand-made prototype unit at

Advanced Energy, Voorhees, NJ 11/30/2000

A) Definition of Project

1 Introduction

a Description

The production of toxic and polluting chemicals due to the burning of fossil fuels

by internal combustion engines is a matter of extreme environmental impact With the continued growth of our society, the use of the internal combustion engine is becoming more and more prevalent as the number of vehicles in use continues to increase In the

US alone, 131,838,538 passenger cars were registered in 1998 Obviously, as the number

of cars increases, so does the volume of toxic and polluting emissions If we are to preserve our natural environment for our children and our children’s children, then we must find a way to curb this stream of pollutants

An early step has been taken in the state of California, which has recently

announced new state regulations which will greatly reduce the acceptable levels of vehicle pollution Under California’s new LEV II regulations to be phased in from 2004

to 2010, diesel passenger cars and light trucks will be included in the same category as gasoline-powered cars Also, in January of 2001, the US EPA announced the reduction ofemission standards for 2007 and subsequent model year heavy-duty diesel engines Theserepresent a 90% reduction of nitrogen oxide emissions, 72% reduction of non-methane hydrocarbon emissions, and 90% reduction of particulate matter emissions compared with the 2004 model standards As a result of these new regulations, most large diesel trucks will no longer be allowed to drive on California highways, and soon, on highways nationwide This could have an obviously devastating effect on the national economy,

and especially, on California’s due to the use there of about 525,000 heavy-duty diesel trucks and 680,000 diesel-fueled engines used in construction and agriculture.

To provide a solution to this problem, Massachusetts Institute of Technology in conjunction with Advanced Energy Industries, Inc has been in the process of developing

a plasma treatment device for use with these engines This device will break down

gasoline, diesel fuel, or other hydrocarbon fuels and create hydrogen-rich gas, a high quality fuel This is then used in the engine resulting in a drastic reduction of polluting chemicals, perhaps as much as a 100X reduction While an intern at Advanced Energy, the author has been responsible for providing prototype generators for the research being conducted at MIT This has entailed the design, construction, and troubleshooting of the amplifier circuit and necessary matching circuitry It is the intent to present the

development of this generator as the author’s senior project

b Background

A plasma, as defined by the American Heritage Dictionary is, “highly ionized gas composed of ions, electrons, or neutral particles It is a phase of matter distinct from solids, liquids, and normal gases.” By exposing complex molecules to this highly

energized state, the necessary energy is provided to increase reaction rates and break down these molecules This is the basic concept of the device currently in development

by MIT and AE, a device called the, ‘Plasmatron’ Hydrocarbon fuel is injected into a chamber, though a plasma which is generated inside The plasma provides the energy to break the bonds, releasing hydrogen In it’s nominal operation, one fourth of the

hydrocarbon fuel is routed through the Plasmatron and broken down The hydrogen-rich

fuel is combined with the remaining fuel and is provided to the engine The result is a modification of the combustion reactions leading to the reduced production of pollutants

In order to create this plasma, it is necessary to utilize the 12V or 24V DC system present in large diesel trucks and convert it to a much higher voltage In the Plasmatron, this voltage is delivered across a circular spark-gap There must be a sufficiently high voltage to breakdown the dielectric (air/fuel mixture) and provide an arc By injecting this mixture between the two circular electrodes off-center, the fuel follows a cylindrical motion around the inside of the chamber Ordinarily the arc would remain at the location

of the smallest distance between the electrodes This leads to erosion of the electrodes at these locations The cylindrical motion of the mixture forces the spark to also follow this cylindrical motion as it delivers it’s energy, hence a cylindrical plasma is formed

Generating the necessary voltage to break down this spark gap and matching the generator to the load is the project at hand This has involved the creation of the

necessary circuitry, rough bread-boarding of the circuit and initial testing, pc board design for integration into an early package, production of a fully operational prototype, and testing and improvement of said prototype Some of this work had been completed prior to EE413/EE415, and several prototype units with hand-soldered circuitry have been sent to MIT for testing What remained to be done at the beginning of EE415 was the design of a printed circuit board and it’s implementation in a more refined prototype package This will be presented as the conclusion of the author’s senior project

c Applications

The Plasmatron holds the potential for use in a number of commercial

applications Initial development is aimed towards use of the device in large trucks and equipment since these are often considered to be heavy polluters Eventually, as the device becomes more refined and compact, it will be introduced into the conventional automobile market

The device can also be used to provide a hydrogen source for fuel cells By running conventional fossil fuels through it, hydrogen, CO, and CO2 are produced Fuel cells are intolerant of CO but have no problem with CO2 This limitation can be

overcome by converting the CO to CO2 through use of a simple chemical reaction known

as the, “water-shift reaction.” The CO2, and hydrogen is then fed into the fuel cell along with oxygen from the atmosphere The result is CO2, water and electricity In the case of fuel cell vehicles this could provide a just-in-time hydrogen source, allowing for the storage of energy in the relatively stable hydrocarbon molecules rather than through hydrogen stored in large and potentially dangerous tanks

Finally, there is the possibility of using the Plasmatron in back-up power

generators Running the device initially off of a battery, hydrogen would be produced to begin the operation of the fuel cell The fuel cell would produce enough energy to

continue the operation of the Plasmatron, charge the battery and provide electrical power

to a load, all while producing virtually zero emissions and storing the energy in relatively stable, conventional fossil fuels

d Advantages and Disadvantages

There are many possible advantages to this plasma based system It’s

implementation on large trucks, industrial equipment, and eventually on conventional automobiles will result in a drastic reduction of toxic and polluting emissions

Implementation on fuel cell vehicles will remove the necessity and burden of carrying a dangerous and bulky hydrogen tank on board Implementation on backup generators will allow use of virtually any fossil fuel without the pollutants inherent in the use of internal combustion engines The Plasmatron’s small size and relative simplicity will make it suitable for use onboard vehicles without the requirement of reducing vehicle range and performance It will reduce the production of green house gases and conserve our

nonrenewable energy resources The result will be a cleaner environment for all mankind

In order to fulfill this promise, the Plasmatron will need to be cheap, small, and light in weight These are certainly prerequisites for application in the automobile

industry Initial development has been aimed for the large truck and heavy equipment industries since there, these restrictions are not as stringent Once in production, the device will undoubtedly undergo a period of size and cost reduction The fruit of this effort will be a device of suitable size, cost and weight for implementation under the hood

of every car in America

There remain a few disadvantages that will need to be overcome in order for the Plasmatron to become a viable pollution-reduction option Foremost on this list is the generation of radio frequency interference and noise The generation of a voltage of magnitude great enough to break down the spark gap within the device requires a

switching circuit utilizing a square wave signal Square wave signals retain high energy

even in harmonics of increasing frequency Sufficient shielding will have to be provided

so that this noise does not harm electronics in or around the vehicle

Another issue of some consequence would be the necessity to tailor the apparatus for each vehicle it would be installed in, since all vehicles are not built alike Mounting hardware, power connections and fuel flow hardware would have to be designed and modified for each different kind of vehicle on which the device was to be implemented This is simply a hurdle that will have to be dealt with at some point in time

Finally, this is a device which will compete directly with other pollution reductiondevices There are many groups around the world exploring concepts to reduce the emissions from vehicles to levels in agreement with the new EPA regulations It will be achallenge to maintain supremacy in this highly political and financial arena To do so it will be necessary for the device to be inexpensive, easy to install and maintain, as well as the most effective

2 Objective

The objective of this project was the construction of an LF (Low Frequency) Output, DC Input Generator / Amplifier The frequency is slightly variable in the range from approximately 50kHz to 200kHz The amplifier supplies as much as 1kW of

electrical power to a proprietary spark-gap apparatus through a suitable matching

network The apparatus is being provided by MIT for use in the testing of this prototype generator For experimentation and practicality purposes, the power delivered will be varied by manually controlling the level of DC input voltage

The generator and matching network were built and tested both at Advanced Energy Industries, Inc in Voorhees, NJ and at the NJIT, Mt Laurel Technology Center facility utilizing equipment in the laboratories of both facilities With the successful design, construction and testing of this prototype generator, all pertinent data has been included in this document and will be submitted for review by researchers at MIT, by the management of Advanced Energy, and by the faculty of NJIT A final presentation of the working prototype will be made on May 13, 2002 at NJIT – Mt Laurel This will

including a demonstration of the generator’s ability to create and maintain an atmosphericplasma (Generation of hydrocarbon plasmas had been left to MIT and others who are crazy enough to do it)

3 Design Specifications

LF Power Supply Specifications for Prototype Plasmatron Generator

4 DC/AC Conversion Efficiency: >60%, for car >80%

5 LF Output Impedance, Typical : 100  to 1000 

6 Output Voltage : 10kV to 20kV at specified frequency,

depending upon gap distance

Transformer Box (5” by 6” by 4” deep)

8 Operating Temperature: Room temperature (for car 0 to 175

degrees F)

9 DC Power Input Connections: Two wire connections (for car, one wire +,

chassis ground)

10 Output HV Connections: HV wire connection with ground return

terminal (for car, HV wire connection)

11 Cooling Conditions: Utilization of DC Fan(s) to cool generator

12 Logic Supply Connections: Separate, external terminals (for car, logic

driven off same supply as power)

13 Finished Cost of Prototype: <$300

4 Project Goals

a Size

The completed prototype unit needed to be of as compact a nature as possible This was realized through utilization of higher frequencies, which reduced the size of the magnetic components, as well as through the development of a printed circuit board More reduction in size will occur as the product is developed further Packaging of the prototype unit was geared towards ease of assembly and disassembly, since by the very nature of prototypes it will be modified and changed many times during the course of further development This approach will eventually lend itself towards ease in

manufacturing and final product assembly Since a large amount of power is running through this unit, it has also been necessary to be conscious of the fields produced by various components Elements of the circuitry were shielded as needed As a final

remark, as this will be a product intended for implementation in the automotive industry, excessive size would be prohibitive

b Cost of Further Development

In developing a project such as this, one must realize that the final product could pose a significant danger if proper precautions are not taken The product will involve theuse of lethal voltages and flowing fuel For this reason, the utmost care and attention must be taken to ensure that all necessary developmental and testing steps are taken While excessive costs of development are undesirable, there is a moral responsibility to take all necessary precautions prior to product distribution In the case of this particular prototype it has been desirable to minimize costs of materials and equipment while still

maintaining the ability to demonstrate the feasibility of the technology and provide for additional testing.

c Performance

It has been desirable to create a working prototype which meets or exceeds all of the outlined specifications Short of this, a working unit which met most or some of these conditions would also be valid for the current purpose This purpose is to demonstrate thefeasibility of the plasma technique in fossil fuel reforming To this end, the creation of the circuitry necessary to establish and maintain this plasma must be not of prohibitive size or cost In the case of the current prototype and senior project, the purpose is to create a unit capable of striking an atmospheric plasma and maintain a certain level of delivered power This shows the feasibility of the technique to strike a plasma and

demonstrates basic generator operation It is the author’s pleasure to report that the

project produced, meets or exceed all of these initially defined objectives

d Educational Value

This project has been of extreme educational value It has entailed exposure to nearly all of the parts of the engineering design process Initial circuit conceptualization, breadboard testing of the proposed circuit, printed circuit board design, packaging of the elements within a suitable enclosure, and modification of the circuit to meet desired design characteristics are the major areas which have been explored Familiarization withthis process, as well as with the process of documenting and presenting the project will undoubtedly have been of immeasurable value and will be experience put to good use in the future

B) Description of Author’s Contribution

Throughout the course of design and initial circuit prototyping, a number of individuals at Advanced Energy have lent assistance and their expertise The author underwent an early design review with many of the engineers of that facility Their

recommendations have influenced the path the design has followed since that time Also, the author’s mentor, Dr Anton Mavretic, has been instrumental in assisting with the design effort Although the initial circuit concept was his, through experimentation, prototyping, testing, and analysis the current circuit is almost entirely of the author’s design Having worked through the entire design process several times, the current circuitbears only a small resemblance to the original circuit proposed Some of this has been a result of trial and error, designing and simulating the proposed circuit design and then building that circuit on the bench to test it’s effectiveness Many changes have been necessary largely due to the unpredictability inherit in plasma generation Many factors such as plasma material, flow rates, and gap geometry, effect the resulting plasma

All prototypes have been constructed largely by hand directly by the author who has also been responsible for their continual improvement and modification He has added components and modified the circuit layout based upon the performance of the built prototype, many times trying things on his own and many other times referring to the judgment of the other engineers at Advanced Energy All testing has been performed

by the author and it has been the author’s responsibility to obtain materials either from in house at Advanced Energy or from local suppliers and distributors The current prototypebeing presented as the conclusion of the author’s senior project, utilizes all of the

experience and knowledge gained to this point by the author

In order to generate 20,000 V from 24Vdc we need to convert current to voltage through transformer action It is straightforward enough to use a torroidal transformer or cascaded toroidal transformers to step say 24Vac up to 20kVac So now the problem is togenerate an ac waveform from a 24V DC one This can be realized through a variety of switching scenarios

The author decided to implement a push-pull scheme to realize an AC waveform First using a 555 timer, a square wave signal is produced Next, using a J/K flip-flop, twoperfect 50% duty cycle signals are created, exactly 180 degrees out of phase with each other This is an important step because the push-pull configuration requires two power FETs, switching alternately The FETs create a path from the DC voltage, through the primary of a transformer to ground By connecting the secondaries of these two “push-pull” transformers out of phase, we create a signal which approximates a sinusoid This signal can then be applied to the center tap of an autotransformer which provides for the large voltage step-up In between the flip flop and the FETs, transistor buffers and gate

Figure 1 – Flow Diagram

driver ICs are inserted This adds isolation between the logic and power sections, adds a small amount of dead time between alternate switching signals, and meets the current requirements of the FET gate

Suitable matching is provided between the output transformer and the plasma loadthrough the addition of a series inductor The inductance of this component must be varied to provide for optimum matched conditions at different frequencies This can be accomplished by simply adding or removing turns from the coil

6 Schematic Circuit Diagrams

Figure 2 - Plasmatron 200kHz Logic Circuit Diagram

Figure 3 - Plasmatron 200kHz - Power Circuit Diagram

7 Necessary Equipment

a Design

o IBM compatible personal computer running Windows 98

o Manufacturer spec sheets for various components

o Ferronics Magnetic Component Design Tutorial

o Advanced Energy documentation on designing matching networks

o Autocad R14 and Gerber File Converter

b Construction

o Conductive straps and lab coat for use when handling ESD susceptible devices

o Soldering iron/station, solder, wire cutters, other misc tools

o PC Board Cutting Machine/Computer

c Testing

o Digital Multimeter

o Oscilloscope with HV Probe

o Portable, Low Power DC Supply (12V)

o Network Analyzer

o Spark-Gap Apparatus (Provided by MIT)

o High Power (1kW+) Variable DC Supply 12 – 24V

o Pump and Pressurized Tank for air flow

o Necessary Air-line connections and regulator

o Thermocouples and digital readout for temperature measurement

8 Design and Construction Effort

The circuitry presented in Figures 2 and 3 represent the current stage of evolution

in the project This was by no means the initial design, it has undergone several revisions since initial conceptualization Many of the changes and additions have been made to improve circuit operation based upon data obtained from previous rough prototypes

The main tasks which remained at the beginning of EE413 were to design and draw the PC board layouts for the Logic and Power sections, to cut and populate these boards, to construct and package the circuit, and to test and modify the generator as needed This was not an insignificant challenge Much effort was involved in the design

of the PC boards so as to insure equal trace lengths on both sides of the amplifier and adequate shielding of components from excessive noise

The amplifier design is fairly straightforward, with each successive stage

increasing the current of the gate signal The 555 timer provides the initial square wave signal at twice the output frequency This is necessary because the J/K flip-flop is

triggered only at the negative transition and the frequency of negative transitions is half the frequency of the signal The flip-flop creates a signal that has a perfect 50% duty cycle as well as another signal which is exactly 180 degrees out of phase with the first This is extremely important because for proper operation, only one side of the amplifier can be active at a time This section of the circuit was designed into what the author calls the “Low Level Logic Board”, which passes it’s signals on to the next board through a ribbon cable

The two signals from the flip-flop are run into individual NPN transistors This increases the drive capability of these signals from the low current level available at the

outputs of the flip-flop IC to a drive capability only limited by the transistors used and theavailable supply current This is sufficient to drive gate driver IC’s which provide currentthrough gate resistors to the gates of the power FETs The transistors and gate driver IC’s have been designed into what the author calls the “Buffer/Driver Board” which passes it’s signals on to the next board by a ribbon cable On both this board and the Low Level Logic Board, bypass capacitors have been inserted across the supply lines where necessary This has reduced supply ripple and resulted in much cleaner circuit operation.

The power FETs receive the gate signal through gate resistors which help

dissipate power stored in gate capacitance The FETs switch the High Power DC supply through the primarily of one transformer or the other and then to ground Diodes are inserted in the path between the transformer and the FETs They prevent potentially damaging voltage spikes from appearing on the drain of each of the FETs These

components are connected together and to the transformers by what the author calls the

“Power Board”

The secondaries of these two transformers are connected out of phase and as a result a sinusoidal signal is created This is the “push-pull” effect, with one side of the amplifier swinging the output above the reference, and the other below This AC signal isthen applied to the center tap of an autotransformer, which provides the necessary high voltage step-up Through the series inductor the amplifier is matched with the load

apparatus for maximum power transfer

Torroidal transformer specification and design has been conducted through use of various magnetic design tutorials available from Advanced Energy This has allowed the author to pick a suitable core for use with this frequency and power density Saturation

and other forms of core loss have been taken into account when calculating the necessary number of turns and turns ratios for each transformer as illustrated below.

a Transformer Analysis :