Circuit Theory of Operation

Figure 3-2 shows that a high-voltage, current-limited transformer (Tl) is connected to a full bridge recti­fier (Dl-4) and charges an external storage capacitor (C) through a surge limit resistor (R18).The external storage capacitor is connected between the discharge ground and a spark electrode (Gl).The target load is now connected between the discharge ground and a spark switch electrode (G2). You will note that the load (R and L) takes on a complex value, usually highly inductive (not in all cases), with a small series resistance resulting from the inductor wire. Spark switch electrodes G1 and G2 are spaced to approxi­mately 1.2 to 1.5 times the breakdown distance of the current operating voltage used.

A third trigger electrode (TE1) discharges a fast, low-energy, high-voltage pulse into G2, creating a spike of voltage ionizing the gap between G1 and G2, now causing the stored energy in the external storage capacitor to discharge into the load impedance.

The charging voltage of the external storage capacitors is sampled by the resistor divider network (R17) that also provides the series dropping value for the meter (Ml).The charging voltage is programmed by control (R8) connected in series with R17.This control sets the trip level of comparator (II) biasing the relay driver transistor (Ql) where it turns off, deenergizing the primary winding of Tl through relay (RE1) contacts. Once R8 is set to a selected value, it automatically maintains this preset voltage level on the external storage capacitors. A safety pushbutton switch (S3) provides a manual hold for charging the external capacitor.

The light-emitting diode (LED) LAI indicates that the mam power is on. LED LA2 indicates the charge has reached its programmed value.

The spark trigger circuit is a conventional capaci­tor discharge (CD) system where the energy on the capacitor (C6) is dumped into the primary of the pulse transformer (T2).This train of positive, high – voltage pulses generated on the secondary winding of T2 is integrated onto capacitors C8 and C9 through isolation diodes D12 and D13. These high-voltage DC pulses cause ionization between the gaps by the discharging action of trigger electrode TEl. The input to this circuit is a voltage doubler consisting of capac­itors C4 and C5 and diodes D8 and D9. The "fire” switch (SI) energizes this circuit, causing immediate firing of the spark switch. A silicon control rectifier (SCR) switch dumps the charge on C6 and is gate – triggered by a DI AC triggering diode biased into breakdown by the setting of trimpot R14 and timing capacitor C7.

Circuit Theory of Operation

Figure 3-2 Pulser schematic

А 12-volt transformer (T3) powers the control cir­cuit, including the REl relay. Without these 12 volts, the system cannot be energized without manually actuating REl. Rectifier diodes DIO through 13 rec­tify the 12 volts-alternating curreni (VAC) that inte­grates onto the filler capacitor (Cl). Resistor R1 decouples the 12 volts for regulating via zener diodes (Z3, Z4), which are necessary for stable operation of the comparator circuit. The main power for the charging energy is from the 115 VAC lines, tused by FI and controlled by switch S4.

Special Note

Our lab at Information Unlimited has energy storage facilities consisting of 10 racks of 32 microfarad (MFD), 4500-volt oil-filled cans wired in parallel for a total capacity of 1,600 mfd or approximately 13,000 joules at 4,000 volts per rack. All racks connected in parallel produce 130,000 joules. It is paramount at these energy levels to properly wire and assemble the complete system with adequate spacing and conduc­tor or wire sizes in order to support the multi­megawatt pulses obtained. Explosion shields around the storage racks are used to protect operating per­sonal. us.

The charging time per rack is approximately 10 minutes. All 10 racks would be impractical with this charger, as it would take almost 2 hours. We use a 10,000-volt, 1-amp, current-controlled system that charges 130,000 joules in 1 minute. This 10 Kv, 1-amp high-powered charger is available on special request.

Construction Steps

In this section, it is assumed you are familiar with the use of basic shop tools and have had intermediate assembly experience.

The pulser is built on a metal chassis that is 10 X 17 X 1.5 inches of 22-gauge galvanized steel. It uses a
6,500-volt root means squared (RMS), 20-milliampere current-limited transformer. The layout shown should be followed as closely as possible. A higher-capacity transformer can be used with an obvious change in layout size. A suggestion is to connect in parallel up to four of the previous transformers, obtaining 80 milliamperes of charging current. A front panel is used for mounting a voltage meter and all controls. A key switch substituted for S4 is recommended when being used around unauthorized personnel.

The construction steps are as follows:

1. If you purchased a kit, lay out and identify all parts and pieces.

2. Cut a piece of.1-inch grid perforated circuit board 6.25 X 4.25 inches.

Dashed lines are wire runs on underside of board.

Solid black dots indicate holes used in board for то із mounting of components and connecting

tF frfiM ie VAC junctions

Figure 3-3 Pulser assembly board

Circuit Theory of Operation

3. Insert the components as shown in Figure 3-3 and solder using the leads of the components where necessary for the connection runs. The

dashed line shows the wiring routing and the connections underneath the board. Avoid bare wire bridges and potential shorts. Also avoid cold solder joints as these will surely be a problem. Solder joints should be shiny and smooth, but not globby.

4. Wire the following to the assembly board as shown in Figure 3-3:

To the chassis ground, 8 inches of #18 vinyl wire

ToTEl, 4 inches of 20 Kv high-voltage wire

To R18 resistor, 8 inches of #18 vinyl wire

To anodes of D3 and D4,12 inches of #18 vinyl wire (circuit ground)

To T3 12VAC (2), 8 inches of #22 vinyl wire To Ml meter (2), 8 inches of #22 vinyl wire

5. Verify all wiring; components; and the orienta­tion of all the diodes, semiconductors, and

electrolytic capacitors Cl, C2, C4, C5, and C7. Check the quality of soldering, potential shorts, and the cold solder joints. Solder joints should be shiny and smooth, but not globby. Double-check before powering up.

Note that a factory-assembled and tested con­trol board model #HEPBORDE is available on request.

6. The subassembly of the spark switch is as fol­lows (see Figure 3-4):

a. Fabricate BASE1 from a 4 3A – X 2-inch piece of 20-gauge galvanized steel. Bend a Ч2 – inch lip as shown.

b. Fabricate two BRKT1 brackets from a 2Ч2- X 1 4a – inch piece of 20-gauge galvanized steel. Bend a 3/4 -inch lip as shown.

c. Fabricate two BLK1 blocks at ’A X 1 X l’A inches from polyvinyl chloride (PVC) or similar material. They must have good insulating properties.

d. Fabricate a BLK2 block at 3/r X % X 3 inches from virgin Teflon material. It must support the high-voltage trigger pulse.

e. Carefully solder the COL1 collars 10 the BRK1 brackets. Rig up a fixture to guarantee coincidental alignment of the tungsten electrodes when completed. You will have to use a propane torch or a super-hoi iron for this step.

f. File off the sharp points on eight 8- X % – inch sheet metal screws. This is necessary to prevent the PVC material from breaking down due to corona produced by high voltage at sharp points.

g. Trial-position the parts, locating and drilling the necessary holes for assembling together. Follow the figure for proper locations.

trj

h. Attach large LUG1 block lugs to either the two sides or lip section of brackets

BRKTl. Noie the contact must be positive *

as current pulses are in the kiloamps.

i. Temporarily preset the main gap to V16 of an inch and the trigger gap to Чи of an

Circuit Theory of Operation

The trigger gap should be set to not less than 25" from its contact point on the bracket, if triggering is erradic it is suggested to experiment with this setting

Circuit Theory of Operation

The spark switch is the пеэгт of tne system and is where the stared energy in the capacitors over the charging period is quickly released into the target load as a very high powered pulse. It is important thet all connectiohe be able to support the high discharge currents and voltage potentials.

A hrgher-energy swlloh capebla of switching 20,000 joules is available on special request. Both switches use a high-vottage trigger pulse that depends on a relatively high Impedance feed line to the terget load for support of the trigger voltage pulse. This is usually not a problem with moderately inductive targets but can be if this value is low It can be solved by placing several ferrite cores or high u toroids in these lines. The cores produce a high reactance to the trigger pulse but saturate at the main discharge current

Construction of the sparK switch must take into consideration medium mechanical forces resulting from high-peak magnetic fields This is especially important In the higher-power approach and will require parallel wiring and terminating to reduce inductance and resistance. A sturdy base is always required being securely mounted. A protective shield must be placed over the assembly to protect the operator from potential shrapnel should a fault occur

NOTES For reliable triggering, the m depending on charge voltage used

Important Relationships Ipk = Ech*SQRT(C/L) Ipkt = pl/2*SQRT(L’C)

The design shown here Is for the НЄР90 and Is capable of switching up to 3000 joules (with a properly conditioned pulse) being usually sufficient to effectively experiment with MASS DRIVING. CAN CRUSHING EXPLODING WIRES MAGNETIZATION, AND OTHER RELATED PROJECTS

Circuit Theory of Operation

Figure 3-4 Spark gap switch and ignitor

High-Energy Pulser

High-Energy Pulser

Figure 3-1 High-energy pulser

This high-energy pulser is intended to supply the pulsed electrical energy in order to generate a power­ful magnetic pulse capable of accelerating objects, constricting cans, shaping metals, exploding and vaporizing materials, accelerating small projectiles to high velocities, powering small rail guns, and other funciions where conditioned magnetic energy is required (see Figure 3-1).

Construction and operation is intended for those wiih experience handling high-voltage, high-energy

systems. This is for the advanced builder and requires assembly skills. Expect to spend $200 to $500 mainly for the necessary storage capacitors with most parts being available through Information Unlimited (www. amazingl. com). A parts list can be found at the end ot the chapter in Table 3-1.

This device will be referenced for use with our mass accelerator, can crusher, wire exploder, and thermo plasma generator projects in subsequent chapters.

System Description

The described system is a valuable lab tool for the experimenter and researcher dealing with eiectroki­netic weapons, high-power magnets, electromagnetic pulses (EMPs), exploding wires/metal vaporizing, plasma pyrotechnics, high-pulse-powered lasers, elec­tromagnetic launchers, gravity propulsion, and other similar research.

The device provides constant current charging to an external capacitive energy bank up to 5,000 joules with the system. The voltage is adjustable from 500 to 5,000 volts and is preset by a front panel control.

Once set, the voltage will remain at this value until the firing period and then automatically recharges to the preset value as long as the safety charge button is activated. A meter monitors the voltage selected. A built-in, triggered spark switch using % – inch (9.5 mm), pure tungsten electrodes switches the stored bank energy into the target load within a period determined by the load inductance and resistance. A high peak-powered pulse approximately equal to dE/dt is now produced. (Power is the derivative of energy E.)

The system is intended for use as the energy – charging source and switch for many of our related projects. These projects include our mass accelerator driver as an example of a device capable of convert­ing magnetic energy into kinetic energy. Such proj­ects are shown in live action video at www. amazingl. com. Go to our High Voltage page and scroll down to the MASS 10. The other available support projects are listed and will be supplemented with more as we complete various research programs, obtain necessary releases, prepare the data on com­puter-aided design (CAD), and so on.

Electrical Pretest

To conduct a pretest, follow these steps:

1. Connect a 1000-voltmeter across +C5 and — of C6. If vou have a scope, you can check the wave shape on the collcctor of Ql and verify it, as in Figure 2-2.

Slide the PROJ1 projectile onto the mandrel and point the unit away from people or break­able objects. For maximum velocity, the pro­jectile must be evenly positioned onto the accelerator coil.

Connect 12 volts to the input and push switch SI. Note the voltmeter reading increases in value as long as the switch is held. A current meter on the 12-volt supply will indicate around an ampere of current and will vary through the charging cycle.

Allow the charging to reach 600 volts. Push switch S2 simultaneously while still holding SI

Electrical Pretest

Figure 2-6 Bracket and fly way fabrication

and note the projectile shooting off the mandrel.

The indicator lamp NE1 should light when the intended charge voltage level is reached. This is a maximum of 700 volts and should not be exceeded. The resistor divider, consisting of КУ and RIO, sets this point. You may have to vary these values to get the desired indication at the charge voltage level you want. Without this lamp, you must time the charging cycle and coordinate it with an external meter to obtain the charging time or always use the meter.

Note that the velocity will increase after the first several shots. This is due to the capacitors polarizing their electrolyte.

Obtaining More Velocity (Under No Condition Point or Shoot Tomard a Person)

Increase the mandrel diameter to I‘/« and wind 40 turns of #22 magnet wire in six to eight even wound layers on your.75-inch diameterX.312-wide nylon bobbin #BOBTHER. The measured inductance should he 120 to 150 microhenries. The objective here is to get the body of the projectile as close to all the copper windings as physically possible. This will reduce the reluctance and increase coupling. Further velocity increase can be obtained by removing sev­eral turns on the accelerator coil until the current reversing diodes start to blow. Our laboratory unit got down to 50 microhenries, obtaining a very dan­gerous velocity.

Electrical Pretest

Figure 2-7 Final assembly without cover

Electrical Pretest

Figure 2-8 Final assembly

BTHER

Fabrication

To create the fabrication, follow these steps:

1. Fabricate the chassis as shown in Figure 2-5. Be sure to make a trial fit and check the sizes of the panel components before actually mak­ing holes. Kits will usually contain a predrilled piece that will mate to the included parts.

Fabrication

Thin dashed lines are #20 bare bus wire and leads of components to make the underboard wire runs and connections

Thick aashed line is a piece of #18 bus wire to carry high discharge current

You may use insulated leads for two wire runs from Q1 toT1

You rnay use short pieces of bare wire to wire in pins of SCR1 or drill holes for actual pins.

Figure 2-3 Assembly board showing wiring under the board and part identification

Fabrication

Leads from L2 accelerator coil

for insulating from panel

Figure 2-4 Assembly board showing external wiring

Fabrication

Figure 2-5 Chassis fabrication

2. Fabricate a BKl brackct, a MAND1 mandrel, and a FLY1 flyway, as shown in Figure 2-6.

3. Add the cover as shown in Figure 2-7. Note to mate the clearance holes for screws with holes in the chassis section for the (SW4) #6 sheet metal screws.

4. Wind the LI accelerator coil, as shown in Fig­ure 2-6. Sleeve in a ‘A-inch section of MAND1 mandrel into the FLY1. Drill small holes for the start and finish of the winding into the side of the bobbin as shown. The measured coil inductance should read 90 to 100 micro­henries without the projectile, dropping down to 50 to 60 with the projectile in place. Con­nect in the coil leads as shown in Figure 2-4.

Note that the objective is to get the projectile body as close to the windings as physically pos­sible. This provides maximum magnetic cou­pling, and consequently optimum performance.

5. The final assembly is shown in Figure 2-8. Note the proper mounting of Ql using a mica washer, shown also in Figure 2-3.

Basic Theory

Your eiectrokinetic accelerator demonstrates two methods of eiectrokinetic acceleration.

First and Preferred Method

A flat, pancake-shaped accelerator coil is structured to match the dimensions of a circular aluminum ring that serves as the launch vehicle. This closed ring now becomes a shorted secondary winding of a pulse transformer that is as closely coupled to the primary windings as possible. A current pulse is produced in the secondary that is the aluminum ring induced by the current pulse in the primary. The result is oppos­ing magnetic fields that cause a mechanical repulsion pulse propelling the nonmagnetic aluminum ring. If the ring were magnetic, it would be attracted to the coil and completely counteract the repulsive force. It is the current flowing in the aluminum ring that causes the repulsive magnetic field (Lenz’s law).

The design of the accelerator coil must minimize the leakage inductance of the coil assembly and limit the impedance in the primary discharge circuit. A dis­advantage of this type of kinetic system is that the acceleration event occurs over a short distance inter­val. Therefore, the resulting peak forces must be very high to achieve a high velocity. The repulsive forces will vary as the inverse of the square of the separa­tion distance between the accelerator coil and the moving projectile.

Бессзпс) Method

The high-voltage/frequency output of the second­ary winding of Tl is rectified by the diode (DI) charging storage capacitors (C5,C6) through the low – impedance winding of the accelerator coil (12). Resistors (R7, R8) help to balance the voltage charge across the two individual capacitors. The charge across these capacitors is applied to L2 by the switch­ing function of the SCR switch. This energy exchange generates the magnetic pulse necessary to launch the projectile. The SCR switch is controlled by the trigger switch (S2) applying a voltage to the gate of the SCR when ready to fire the device.

This method uses a solenoid coil with a pitch equal to its diameter. This coil uses a magnetic pulse that attracts a small ball or rod-shaped projectile made from a magnetic material. The ball is accelerated into and along the coil axis, exiting with a velocity. The ini­tial positioning of the ball is critical to obtain the maximum exit velocity. The inner diameter of the coil should only be large enough to allow unobstructed movement of the projectile ball. Again, magnetic leakage and pulse width plays an important part in achieving optimum results.

Circuit Description

A single-ended inverter circuit is shown in Figure 2-2 consisting of a self-oscillating transistor (Ql) that res­onantly switches the primary of the voltage step-up transformer (Tl) and tuning capacitor (C3).The input power is 12 VDC at 1 amp and is controlled by the charging switch (SI).

The base drive to Ql is provided by the feedback winding (FB) of the Tl that must be properly phased. The bias for Ql is provided by the resistor (R2).The capacitor (C2) speeds up the switching by providing a low-impedance path for the feedback signal. The resistor (Rl) provides the starting bias for turning on Ql. The capacitor (Cl) bypasses the switching fre­quency to ground by providing a low-impedance path. A charging choke (Ll) is necessary to limit the switching current during the initial charging cycle of the storage capacitors.

Board Rssembly Steps

To assemble the board, follow these steps:

1. Lay out and identify all parts and pieces. Ver­ify them with the parts list, and separate the resistors as they have a color code to deter­mine their value. Colors are noted on the parts list.

2. Create a piece of, I-incli X. J-inch grid perfo­rated board at 5 % X 3 3/« inches. Locate and cut out sections for pins of Tl as shown in Fig­ure 2-3.

3. If you are building from a perforated board, insert components starting in the lower left – hand comer, as shown in Figure 2-3. Pay atten­tion to the polarity of capacitors with polarity signs and all semiconductors. Route the leads of the components as shown and solder as you go. cutting away unused wires. Attempt to use certain leads as the wire runs. Follow the dashed lines on the assembly drawing as these indicate connection runs on the underside of the assembly board. The heavy dashed lines indicate the use of thicker #18 bus wire, as this is a high-current discharge path.

Note that the Ql transistor must be mounted so that it mounts flush to its mounting surface at a right angle. This step is important for proper heat sinking and mechanical stability.

4. Secure large storage capacitors, C5 and C6, to the board using silicon rubber cement (room temperature vulcanizing [RTV]) or tape them in place, as shown in Figure 2-3.

Wave shape Q1 beginning of charging cycle

Wave shape Q1 end of charging cycle

Figure 2-2 Circuit schematic

Diode D3.4 are necessary when using the photoflash electrolytic capacitors to keep the voltage from reversing. Unfortunately these diodes also remove the repulsive energy of the negative reversing current from further accelerating the projectile Higher-quality pulse discharge capacitors could be used without the diodes but would be larger and more costly.

5. Wire in SCR1 using short pieces of bus wires for extensions through the holes of the board.

6. Attach the following leads, as shown in Figure 2-4:

Three З-inch leads of #20 (WR20) connected to SI and S2

Two 5-inch leads of #20 (WR20) for connected toNEl

One З-inch jump between D2 and + of C5

7. Double-check the accuracy of the wiring and the quality of the solder joints. Avoid wire bridges, shorts, and close proximity to other circuit components. If a wire bridge is neces­sary, sleeve some insulation onto the lead to avoid any potential shorts.