DRSSTC
Dual resonant solid state Tesla coil
Dual resonant solid state Tesla coil
A DRSSTC tunes the primary as well as the secondary and drives it in bursts, so the current in the tank is measured in hundreds of amps while the average power stays modest. That trade is what makes the timing questions sharp: a switch that opens in the wrong part of the cycle turns the whole design into a heater.
tap any part
duty 3.60 %
Every part of the diagram answers for itself. Pick one.
Rectifier
DC bus
- start heresupplyin QCW
The bus bank: sizing the reservoir
A sagging bus eats the top of the ramp and looks exactly like a tuning problem. It is not one, and the reason to fit a doubler is not the voltage. It is the energy.
- start heresafety
What will actually kill you
Not the arc. The things on this page are at DC or mains frequency, they are inside the cabinet, and they do not announce themselves.
The bridge
- start herepower stage
IGBT or MOSFET, and why SiC is not an upgrade here
One choice that sets both the frequency you can run and how long the bridge lives. And SiC is not the automatic upgrade it looks like.
- start herehow it worksin SSTC
What the bridge does
Four transistors arranged so they can connect the primary across the supply one way round and then the other. Everything else exists to serve it.
- power stage
The bridge: half or full, layout, and what kills it
Peak temperature is not the mechanism. The size of the swing tears bond wires over thousands of cycles, a long way below anything on the datasheet.
- tuning
Dead time as a fraction of the period
A setting that is sensible at 150 kHz eats a quarter of the period at 365. The same nanoseconds are a completely different setting.
- power stage
Paralleling bridges: transformers or a split tank
You cannot wire the outputs together. Something has to force them to share, and the two mechanisms that do are not equally safe.
- timing
ZCS against ZVS: why switching at zero fails
Turning off exactly at the current zero reads like the ideal and is the opposite. The residual current is what commutates the node, and late kills while early only heats.
- power stage
Snubber capacitance, and the bet it makes on ZVS
Win it and the energy returns to the tank for nothing. Lose it and half CV squared goes into the die every transition, which doubles the penalty for missing.
Gate drive transformer
Driver
- start herehow it works
What the driver does
Four jobs on one board. Without it the power section is a box of parts, and the frequency it has to find is not a number you can set once.
- driver design
Phase lead: the delay chain and the ZVS floor
A driver that fires on the current zero is already late. The lead is how you pay that back, and it is made of two things that are nothing like each other.
- driver
The UD boards: which revision you are holding
The logic core did not change from 2.1 to 2.7, so modifications transfer between revisions. The part designators do not, and that is what wrecks a repair.
- timing
Choosing a phase lead inductor
A thin paper trail, three worries attached to it that turn out to be unfounded, and one failure that keeps happening. It is mechanical.
Interrupter and modulator
- start herecontrol
The interrupter: bangs per second, ontime and duty
Bangs per second is the frequency of the note in hertz. There is no best rate, only a note, and two settings on this box kill transistors.
- safety
The fibre link, and the fail-safe rule
A broken fibre must turn the coil off. The receiver does not guarantee that by itself: with no light its output is undefined.
Current transformers
- start herehow it works
What a current transformer is
A ferrite ring on one of the thick conductors. It is how the driver finds out what the tank is doing, and it is the only sense the machine has.
- protection
Overcurrent protection: OCD, pulse skip and why it fails
Nothing limits the primary current in a doubly-resonant coil. Test the actual threshold rather than the position of the knob, and start it low.
- tuning
Tuning by the shape of the current envelope
The shape of the primary current across one bang tells you whether the coil is tuned. One capture, one answer, and almost nobody uses it.
- instruments
Scoping a coil without killing anything
More equipment dies at the bench than in the arc. Never float the scope: it stays earthed and the isolation goes on the circuit under test.
Tank capacitor
- start heretank
Sizing a tank capacitor by RMS current
Voltage and pulse rating usually pass with room to spare. What kills a bank is RMS current, and smaller capacitors carry more of it per nanofarad.
- tank
Choosing tank impedance: current is expensive
Everything that grows with current grows as its square. What high voltage on the tank costs is a rating you fix with series links for pennies.
Primary
- start herehow it works
What the primary is for
A few turns of heavy copper that are not connected to the secondary anywhere, and are not trying to be.
- tank design
Coupling: what it buys, and why it is not length
Wind the primary tighter and the arc gets longer. It is the first thing anybody tries, and the record holders run the loosest coupling on the list.
- tank
Primary design: impedance, turns and detuning
Nobody sets the primary current. It comes out of a division, and the number you actually choose is the impedance of the tank.
- tuning
The two poles, and which one the driver lands on
Couple a primary to a secondary and the resonance splits in two. The frequency you carefully measured is a mode that no longer exists.
Secondary
- start herewindingin SSTC
Winding and measuring a secondary
Not a transformer winding that happens to be long. Almost everything that goes wrong with one goes wrong because it was wound as though turns were the point.
- failure
What a ground strike does
One event, five consequences, and the mild strike is the one that moves the machine to the wrong mode.
Topload
Breakout point
- start herehow it works
What a breakout point is for
It looks like an afterthought and it is one of the few parts you can actually aim the discharge with. Short beats long, and it is a consumable.
- first run
No sparks, or short ones: what to check and in what order
The order to look in, and the order matters: the cheap checks are also the ones that are usually wrong, and none of the three classic causes is a tuning problem.