Pulsed Solid State Tesla Coil (ISSTC I) or AKA "The BBC Coil"

DRSSTC I in action in Bill Shepard's sunroom.  Arcs are approximately 55-60".

Introduction

In early 2004, Steve Ward demonstrated remarkable success with his first ISSTC which was introduced to him by

the infamous Jimmy H.  Both Steve Ward and Jimmy H. have broken the 4 foot barrier with their impressive coils with both

52" and 74" respectively.  Anyways, why let them have all the fun, right?  So now its my turn to start blowing up some MOSFETs

and IGBTs!  And I look forward to it.  And since everyone has their own special name for their coil and topology this coil is

known as "The BBC", or Big Bad-Ass Coil which is a DRSSTC or Double Resonant Solid State Tesla Coil.

            DRSSTC Photo Gallery I - Big Arcs   

            DRSSTC Photo Gallery II - Big Arcs  

    DRSSTC Photo Gallery III - Big Arcs 

Schematics for Express PCB Board Artwork

Please note these schematics are for the Express PCB Board Artwork only!

These schematics are identical to Steve Ward's original schematics and do not represent

the final configuration of my DRSSTC.

Click here to view page 1 of the ExpressPCB schematic (Full-Bridge Half Section)

Click here to view page 2 of the ExpressPCB schematic (Self-Resonant SSTC Driver)

Click here to view page 3 of the ExpressPCB schematic (Low Voltage Power Supply)

ExpressPCB Artwork

I decided to use Express PCB to manufacturer the boards for this particular design because I wanted to make

everything open source.  Express PCB is a free downloadable program and can be obtained at www.expresspcb.com.

This single artwork file contains an entire full of boards including the following:

(3) Full-Bridge Power Boards (half-sections)

(2) Self-Resonant Driver Boards with onboard low voltage power supplies

(1) Self-Resonant Driver Board (small version with low voltage power supplies)

(2) Pulse Modulator (interruptor) boards for external control

Click here to download the Express PCB artwork file.

Self-Resonant Controller

Self-Resonant Controller Board

Full-Bridge Power Section

Full-Bridge Power Section

Power Assembly

Full-Bridge Power Assembly mounted on heatsink with fan.

High Current Bus Bar Design

For connection between the full-bridge assembly and the DC bus, I opted for a bus bar design

because of the high currents.

Initial copper bus bar is first cut from a 26mil thick copper sheet.

The bus bar is then bent into the correct shape and covered with Kapton tape which has

a very high dielectric strength.  The application of the Kapton tape didn't come out as nice looking

as I thought it would, but it will serve its purpose well.

Finished Full-Bridge assembly with bus bar connections.

Primary Design

Primary Coil with Strike Rail

Primary Specifications:

12" Diameter Solenoid Winding

10 Turns of 0.25" Copper Tubing

0.25" Conductor Spacing

Upper Strike Rail (to protect against secondary strikes)

Secondary Design

(Dimensions in inches)

Secondary Specifications:

6.5" Diameter Foam Core PVC Coilform

25" Winding Length

26 AWG Magnet Wire

Approx. 1350 Turns

Ls = 74.40mH (measured)

Rs = 95.84 ohms (measured)

Fres = 160kHz (measured)

DC Bus

The DC Bus provides the instantaneous energy (current) required by the DRSSTC during each pulse.  During the ON time, the high

current is supplied to the primary coil directly from the DC storage capacitor.  During the OFF time, the DC storage capacitor is

charged up again by the input AC power which is fed through a large bridge rectifier.

DC Storage Capacitor Specifications:

Vishay-Sprague Powerlytic 36DX

3500uF rated at 450VDC

Primary Capacitor Design

The primary capacitor will be a MMC capacitor type and comprised of an array of  0.33uF polypropylene capacitors rated at

2000V each.  The capacitors are GE part number 42L3332.  For my initial design, the capacitance value of my primary

capacitor was chosen according to the following relationship:

Primary Fres = Secondary Fres

The Primary Fres was calculated by assuming only 8 turns (23.7uH) of the primary coil were used.  This allows me to have

plenty of headroom on the primary coil to tune in either direction from 1 turn (1uH) to 10 turns (33.7uH).  The total primary capacitance

of this MMC capacitor is 0.11uF rated at 12kV.

Primary Capacitor Specifications:

Two parallel strings of 6 capacitors

0.11uF rated at 12000V

GE Part Number 42L3332 (0.33uF @ 2000V)

Total 12 Capacitors

Gate Transformer Design

The gate transformer was designed using both PSPICE and verified by bench testing.

Gate Transformer Specifications:

Core:  Fair Rite Toroid 5978006401 (Type 78 Material)

Primary Turns:  10T

Primary Rs:  0.003 ohm

Iprimary:  300uH

Secondary Turns: 20T

Isecondary1:  1.22mH

Secondary 1 Rs:  0.160 ohm

Isecondary2:  1.22mH

Secondary 2 Rs:  0.160 ohm

Coupling factor (k) = 0.9993 

Note:  All values were measured in the lab.

Base Current Feedback Transformer Design

This transformer is used to sample the secondary base current of the DRSSTC and use it to drive the full-bridge

power section of the system.

Base Current Feedback Transformer Specifications:

Core:  Fair Rite Toroid 5978006401 (Type 78 Material)

Primary Turns:  2T

Primary Rs:  TBD

Iprimary:  TBD

Secondary Turns: 70T

Isecondary:  10.15mH

Secondary  Rs:  TBD

Coupling factor (k) = TBD

Internal Modulator Specifications

The internal modulator is an onboard 555 timer based circuit which is used to pulse the DRSSTC.  It is primarily used for

troubleshooting purposes only as an external modulator is used during actual operation of the system.

Internal Modulator Specifications:

Min. pulsewidth:  41us

Max. pulsewidth:  200us

Min. PRF:  69Hz

Max. PRF:  4.3kHz

(using 0.022uF timing capacitor on 555 timer)

Resonator Frequency Testing

After the secondary coil was built, I decided to measure the actual resonant frequency of each secondary / topload combination that I would

be using in this DRSSTC.  Resonant frequency was measured by injecting a signal source (HP 200 oscillator) into the base of the secondary

and then monitoring the output current.  At resonant, output current would be maximized.

Photo of Test Unit	Description	Resonant Frequency
	Secondary Coil 6.5" x 25" AWG 26     Toroid None	Fres = 160 kHz (measured)
	Secondary Coil 6.5" x 25" AWG 26     Topload 20" x 5" Toroid	Fres = 111 kHz (measured)
	Secondary Coil 6.5" x 25" AWG 26     Topload 18.5" x 2.5" Toroid	Fres = 121 kHz (measured)
	Secondary Coil 6.5" x 25" AWG 26     Topload 32" x 7" Toroid	Fres = 89.5 kHz (measured)

   Design and PSPICE Simulations

DRSSTC System Simulation

Gate Drive Transformer Design

DRSSTC Links

JimmyH's DRSSTC Website

Jimmy H. is the first person (to my knowledge) to come up with and build a DRSSTC.  His monster IGBT DRSSTC is capable

of creating greater than 6 foot arcs.  Very impressive!

Steve Ward's DRSSTC Webpage

Steve Ward has built a plethora of amazing SSTCs.  His current ISSTC putting out over 4 foot arcs is breathtaking!

Logo, photos and original text are Copyright © 2004  by Eastern Voltage Research Corp.

All Rights Reserved. © 2004  Christopher Hill  Web Master.

Last modified  August 16, 2005 08:05:23 PM