The argument goes round forever. A slayer exciter is continuous; no it is not, there are gaps; a fast interrupter is basically CW; no it is not. Both sides are arguing about the circuit, and it is not a property of the circuit.
What the question is really asking
Whether a coil is running CW or pulsed decides one practical thing: whether the topload earns its keep. In pulsed operation the topload is a charge reservoir. In CW there is nothing to accumulate, and its capacitance is a straight loss in voltage.
So the question is worth settling, and settling it by counting gaps does not work.
The criterion
Does the discharge reach its steady state within the time the coil is on? If it does, the physics is CW: a continuous balance of power, impedance and voltage. If it does not, the physics is pulsed: the energy of the bang, the accumulation of charge, and the topload as a reservoir.
That is the whole test, and it is about the time scale rather than about whether there are gaps. Run through the cases:
- DRSSTC, 300 µs at 200 bangs a second. The streamer is still growing when the bang ends. Pulsed. Needs a topload.
- QCW, a ramp of 5 to 20 ms. Steady state is deliberately never reached; that is what growing a sword means. Pulsed. Needs a topload.
- A slayer on half-wave mains, 10 ms. Reaches steady state with tens of times to spare. CW. Does not need a topload.
- True CW. Yes, obviously.
The slayer with one diode, worked through
Half of a 50 Hz cycle is 10 ms of conduction and 10 ms of pause. At 300 kHz that is about 3000 RF cycles inside one hump, and the corona settles in a fraction of a millisecond. Each hump is a self-contained CW session, and the presence of gaps does not make the regime pulsed.
What the half wave does change: the average power roughly halves, which is usually the point of doing it; the bus is a half sine rather than a shelf, so near the edges of the hump there is not enough voltage to break down at all and the corona really lives for 5 to 7 ms rather than 10; and you can hear 50 Hz hum instead of silence, because the corona is modulated at mains frequency. That last one is the simplest bench test that a coil is not running true CW.
What the evidence does not support
That the long videos are CW. Five minute videos of "continuous" operation are usually interrupted. Fast bangs look like CW to a camera and to an eye. Real CW needs switches that have been calculated and cooled, and its arcs are short and thick rather than long and branching.
davekni, on what real continuous costs: twenty seconds of continuous operation at 240 kHz with hard switching is not something the devices survive.
The numbers
- The threshold: whether steady state arrives inside the on time. Not a voltage, not a duty cycle.
- Corona settling time: a fraction of a millisecond.
- A 50 Hz half wave: 10 ms of conduction, of which 5 to 7 ms actually supports corona.
- RF cycles inside one hump at 300 kHz: about 3000.
- A DRSSTC bang: tens to hundreds of microseconds, which is why it is never CW whatever the bang rate.
What goes wrong
- A topload was fitted and the arc got shorter. The coil is running CW. There is nothing to accumulate, so the capacitance is pure loss. What a topload costs is the trade.
- A coil advertised as CW hums at mains frequency. It is a half wave, and the corona is modulated. Not a fault, but not CW either.
- The devices die after seconds of "continuous" running. They were not calculated for continuous. Very few are.
- A transformer feeding a half wave saturates. The single diode is pushing DC through the winding.
Where next
- What a topload costs, the decision this criterion exists to settle.
- The interrupter is the note, on ontime and bangs per second, which is what puts a coil on the pulsed side of the line and what turns it into an instrument.
The SSTC department is the one where this question comes up, because it is the topology that can genuinely be run either way. The other two are pulsed by construction.