Re: High-Power Car Ignition Coils

At 10:29 PM 12/30/98 -0700, you wrote:

>Original Poster: Sam Barros <sambarros-at-yahoo-dot-com> 
>any real applications. In fact, the quotes I read were that ignition
>coils were designed to run at no more than 50 Watts and 20KV.

You keep talking about watts. You need to specify energy (joules) per pulse
and the number of pulses per second or power (energy/time).

>When this second cap is fully charged it will ionise the
>gas inside a neon lamp, the gas will conduct and trigger an SCR,
>dumping all the charge of C1 on the coil.

Am familiar with this typical light-dimmer circuit. You could probably hack
a $5 lamp dimmer from the hardware store:

Line  ------[Ballast lamp or inductor]------|-------||--------|
                                          __|______Capacitor  |
                                         |  Lamp   | (1-50uF) |
 (120VAC)                                |  Dimmer |          ] ignition
                                         |_________|          ] coil
                                            |                 ]
Power --------------------------------------|-----------------|

Oops, left off the line filter, to keep noise and flyback out of your power

>pulsing 300Watts trough 20uF of capacitance at 350V on them and

E=.5CV^2 so your getting 1.2 joules/pulse, and if you have a 50Hz line
frequency with an SCR circuit, your only driving them with 50 Watts. Your
electrolytic caps dissipation factor is probably less than 10% (5 watts).
Which means it should be a bit smaller than a beer can. 5 Watts in a
photoflash cap should make fast sport of it.

>and the SCR, which is rated for 5Amps, needs a medium sized heatsink.

I would use a snubber or free-wheel diode on that SCR. I've seen an circuit
for a kitchen stove's induction heater, which featured one. Basicaly a fast
turn on anti-parallel diode to the SCR.

> Things are getting really interesting now. I KNOW these coils will
>take at least 500WATTS before they start getting warm

Because 4/5 of that 500 watts is heating other parts, IMHO. Your car coil is
probably only excited by the switching transient, and the rest of the power
is just going to your lamp. Search the archives for recent discussions of
car coils, and how to remove the steel core, which saturates & limits power.

>I might even change C1 for a voltage Doubler
>and pump some 700V on the primary to see if it can take the power.
>Than I will get myself a bigger SCR and make a 4coil driver that would
>handle 1000Watts.

A circuit I simulated used a MOT to break down 2 to 4 series SCR's (no gate
trigger). Higher voltage means less dissapation. You might try using a MOT
as an inductive ballast instead of a resistor or halogen lamp. You might
also try putting a dimmer on the MOT to modulate its reactance?

>1- The halogen light gets EXTREMELY hot, and it is so bright it is
>giving me headaches.

Where do you think your power is going, the halogen lamp or the car coil?

>3- Has anyone tried ignition coil drivers before with good results?

SEARCH THE ARCHIVE! We need a good search engine/method for the Tesla
Archive. Then I, or some other SOB can use one of those cute standard
flame-forms on everyone ;-)

>I am REALLY interested in your experiments.

I am realy interested in yours, once you figure out how to most of your
power into the ignition coil. I want to know what the maximum power a coil
can handle is. My crude thermal estimate told me to keep the temperature
under 150 degrees C inside the core, my power dissipation would have to be
under 200 watts. But that is more of a guestimate (SWAG).

>this to run a Tesla coil, so, effectively it acts as a transformer and
>not a resonator.

You will get best performance if you used it as a resonant transformer.