PELICAN CAN SHUT DOWN!!!!!

i have the imortal words that NO ONE has ever seen or heard.

arguing with west is like arguing with a 15yr old.
you are talking about the origianal subject but west (the 15yr old) has changed topics and is now arguing something else, meantime you think the topic is still the original subject.

makes me think of the argument with my 15 yr this weekend.
i tell him to get up 5 or 6 times, then through a glass of water on him.
he gets mad at me because he was JUST ABOUT to get up......1/2 an hour after i told him to get up. and yet he cant understand why i had to through water on him.

i have a question for west.

WHAT IS THE CURRENT DRAW OF A BOSCH CD??

Don't take it personally.

I 'm thinking WWEST lives in his own little world where he makes minor alterations the laws of physics as he goes along to explain his understanding. That and he'll find buzzwords and acronyms that barely apply to the situation and act like they are physical laws. He'll never admit he was wrong and of course in later discussion he will use the opposing side if it enhances his argument.

He might be forgetting that the coil is a transformer and the energy is transferred to the spark in the gap. The opposite voltage excursion is caused by the magnetization inductance of the core and stores a minor amount of energy.

I wonder if C16 and R10 make a snubber or if they are there to limit the dv/dt on the anode of the SCR.

not much current flows through those reverse biased diodes or the switched off SCR.

dv/dt.. Yes.

Note that the charge path for the 1.4uF capacitor is through the coil primary (inductive) and therefore the flyback type inverter output rise-time would fairly fast absent the RC snubber.

"..not much current..."

The linked article indicates that in the case of inverter output "bridge" rectification the peak REVERSE current flow (plug fired) will be 8 to 12 amps, brand/model dependent, 1:100 ratio.

In the case of the Bosch OEM the inverter secondary is in the reverse current flow path.

A. The rate of rise of the reverse current is restricted inductively.
B. The inverter secondary's (relatively low) resistance will limit the reverse peak current.
C. The coil's inductance + the primary winding inductance along with the capacitor form a resonant circuit which extends the duration of the reverse current pulse.

Without the loss of the energy to fire the plug a second time there will be more energy to be returned to the capacitor charge, OEM coil ~5mJ, E & I coil ~8mJ.

SmileWavy

Please read the below document, most especially the last paragraph..

"...Now that the capacitor...."

Author concludes, as scope trace indicates, that the capacitor is recharged to -100 volts even though a portion of the energy was used to create a second arc.



http://forums.pelicanparts.com/uploa...1450132174.jpg

Hey WW
If there is 200 volts across C5 and C16 in the above schematic is there the possibility C5 has 1.4 Volts across it and C16 198.6?

The last paragraph refers to a different design where the author is describing the fall from 200V to -100V where indeed the cap discharges to the primary.

In the Bosch design, that half cycle doesn't occur, compare it to the one you posted:

http://i804.photobucket.com/albums/y...psktgjqkw4.png

See? It is truncated.

Instead, the inverter switches on at the top of the 200V and the trace plummets to zero. At this point the cap is negatively charged, it does not get a chance to discharge to the coil as the inverter shorts it out, before charging it again. If it did, you would see the discharge and it would look like the top green trace you posted.

When I said in my PM to you 'I can assure you' it was because I measured it on the scope with our CDI test rig. While I was at it, I also looked at the primary and secondary rise time in detail at 10ns. As you corrected stated, the secondary rise time and firing voltage does change with load (I widened the gap). But, as I have said all along, it does not affect the primary in any way, the rise time is 10ns or thereabout irrespective of load.

How about you do some of your own experiments if you still disagree?

I am very careful about posting on forums, unless I have real world experience of the subject matter. Not just reading stuff but actual real life involvement. My company has been immersed in the design of a brand new CDI unit for the last two years. Although myself and coworkers are MEng EE qualified, I admit power electronics never really featured in our usual line of work. The reason we teamed with a power electronics company was to learn! I like learning and forums are a great way to do that.

I wouldn't dare to comment about building gearboxes, suspension geometry or panel work, all of which I am utterly useless at.

I also prefer the medium of clear English when trying to convey information. 'Blinding folks with science' and technical 'showboating' is just a bit sad really as it serves no purpose. People will look back on this thread and the good information will be lost in a sea of jargon and 'willy waving'.

You are now one of my forum heros - well done! :D

PS - have you ever read any of the past a/c theads - they mirror this one.

Across, as in from the D1 cathode to ground? I'll assume so.

The 2 capacitors are in parallel circuit legs....

At the instant you apply 200 volts via the inverter, yes, you have very little voltage drop across C5, it's a virtual short, with the remainder imposed across the coil primary inductance. C16 would also be a virtual short at this instant, so the majority of the 200 volts would be measured across R10.

Ronnie. This man has brains and humility. A righteous dude.

Technical "showboating". OMG. Six years of wrestling with the "Dub" and even Eric never uttered this term in rebuttal. Spot on.

Clear English when trying to convey info? Yep.

The sad part truly is wwest could be and educator. He is not. I don't get it. Sunset years. Probably well heeled. Needs to beat on Jonny. Needs to beat on Dave or Rick1 or Charlie. Experienced guys. For what end? His ego? Six years worth of ego boosting needed when in his later 70's? He's smart, but he ain't Grady Clay Porsche smart.

Fifty squillion time I (we) have asked Willy to throttle it back. No change.

Why?

How many time would a rational person need to hear this feedback before taking inventory?

Just shift gears, Willy. I know you are the straight man. Be a nice man, instead.

QUOTE OF THE YEAR ON PP:


"WWEST lives in his own little world where he makes minor alterations the laws of physics as he goes along to explain his understanding."

Bobusmaximus, you know the answer (and have said it yourself before); Mr. West likes to mud wrestle regardless of how much he knows about the mud he's rolling in. :)

question for WEST

how much current does a bosch CD draw???

i too have worked on many radars:
MPN-14
TPN-19
GPN-20

ASR-8
ASR-11

he reminds me of a radar tech i use to work with.
he would spout off 7 or 8 impressive bits of radar info but never would work on anything.

I don't know why but this is for Wild Willy on why very little energy is returned to the storage capacitor.

The CDI coil is a transformer. Ideally, a transformer stores no energy. Energy is transferred immediately from input to output.
All physically realizable transformers do store some energy however.

1. magnetizing inductance represents energy stored in the finite permeability of the magnetic core
   
2. leakage inductance.

This is what I think happens.

When the 400 volts is presented to the primary of the transformer the spark starts and uses all the energy in the capacitor. This voltage also starts to charge the magnetizing inductance, the inductor in parallel with the ideal transformer in a model.

When the energy in the storage cap is depleted the magnetizing inductance continues to draw current from the node. This charges the .01 uF snubber capacitor.

When the current drops to zero the SCR shuts off and the fly back takes over and charges everything back up

The question Bob posited in post # 7 requires a non-simplistic response..

We'll get there...

It's ok if we don't get there. It was a really basic question and was not specific to CDI's. Perhaps poor placement by me.

It was an eleven year old with a new Heathkit kind of question by me.