Re: Energy storage in primary?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Jolyon,

On 28 Jan 2003, at 8:01, Tesla list wrote:

 > Original poster: "Jolyon Vater Cox by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 >
 > Is it possible to build a TC where energy is stored initially as high
 > current in an inductor (the primary) rather than high voltage in a 
capacitor?
 > I am thinking of a setup where current ramps up slowly through the inductor
 > before being abruptly switched off (by semiconductor switch or similar)
 > after a predetermined current or period of time has been exceeded; the
 > current in the primary rising and falling as "saw-tooth" waveform.

Exactly how a car ignition coil works.

 > As primary input power for this would be largely determined be current
 > rather than the voltage of the PSU
 > how high would the current have to be/ how low could the voltage be for
 > decent spark output say, a minimum of 6 inches or more?
 >
 > For the control logic would this likely need an exotic switch-mode power
 > supply IC with PWM and dead-time control or could a simple astable like a
 > 555 do the job?
 >
 > For the high-current, high-speed switch would bipolar transistors (e.g.. TV
 > line-output power devices) or MOSFETS be suitable or would IGBTs be 
necessary?
 >
 > Would it not be necessary to connect a capacitor across the switch to
 > absorb/slow down the high-voltage transient produced when the switch opens/
 > would necessary voltage rating of switch and capacitor be comparable to
 > that of the primary capacitor in a conventional spark-gap TC?

Again, exactly what is done in a "conventional" car ignition system.

Regards,
Malcolm