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ARC STARTER AND STABILIZER - COMPLETED

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Newton Brawn

Thu Apr 14 2011, 12:44AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Yes, I agree that the pulse frequency is higher, in the range of megahertz. The discharge of the cap through the coil produce a momentary oscillation that finishes as soon the cap is discharged.

More precise:
Coil inductance = N^2 n D^2 / (18D + 40D) =
= 10^2 x 1^2 /( 18 x 1 + 40 x 4.7) = 0.49uH

Pulse frequency = 1/(2 x pi x (L xC)^1/2 =
= 1/ (2 x pi x(0.49 x 0.02)^1/2 = 1.6mHz

This pulse is the result of fast discharge of the cap through the air gap and primary air core coil.
As soon the cap is discharged, the oscillation stop and the rectifier and the 330kohm resistor starting to charge the cap. This charging takes time.
The time required to charge the cap to 63% of its full voltage is dictaded by the RC constant, this case 6.6miliseconds.
I considered the transistor circuit strong enough to charge the cap easilly.
Since a good practice is set the gap 50~~70 % of cap full voltage, the repetition of each oscilation is in the range of 5 ~~10 ms.
All above are a theorectical manipulation. Small deviations may occurs.

Regards

EDIT: please note that the above calculation applies only to the TRANSISTORIZED circuit posted by Ash Small on april 10.

Newton Brawn

Fri Jul 22 2011, 04:55PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi !
Please see the EDIT note posted by Newton doing clarifications on the last post.
Regards

Ash Small

Fri Jul 22 2011, 05:10PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I've recently been reading about the 'loose coupling' that transfers energy from the primary to the secondary. Is it possible to work out how many oscillations it would take to transfer all the energy from each charging of the capacitor to the secondary.

I appreciate that the secondary circuit isn't tuned to the primary, so any advice regarding this would also be appreciated.

(I have now got the HV TIG welder here, I'm just building a new rectifier before I start using it/modifying it again.)

Newton Brawn

Thu Nov 17 2011, 03:24AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi !

Just to reply some emails regarding the spark gap construction.

See attached picture of the parts used in the Arc Starter

At right you can see the spark gap using a pvc pipe and 2 mild steel bolts. This spark gap was used in the begining of the development of the circuit, it works very well. It should be noted that the energy dissipated is very low, due to only two syncronized pulses in each period of 60Hz. No temperature rise was noted.

Any questions, let me know .

Regards

Newton

Rick

Sat Dec 24 2011, 08:59AM

Registered Member #4220 Joined: Sun Nov 20 2011, 12:11AM
Location:
Posts: 6

Newton:

I hope you'll entertain a question from one who isn't highly knowlegeable about electronics. I'm trying to duplicate your arc starter circuit and have built the components per your descriptions. I'm now trying to make the sssg but am confused by the two wiring diagrams. The sssg diagram shows the aircore coil as part of the sssg, but the diagram of the whole circuit shows it between the RL and CD. Could you please clarify this for me? Also, is the RL resistor the one shown in the sssg diagram mounted on an angle going into the pot? Thank you.

Rick A

Newton Brawn

Tue Dec 27 2011, 08:47PM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi Rick A !

Thanks for your review and comments !
You are 1000 % correct.
My mistake is re " consistence of information" .

If L1 is appearing in the drawing des_arc_starter_and_stabilizer_r2.pdf
it shall not appear in the drawing des_sssg_schematics_r2.pdf.
The duplication of information allways generate confusion.

The L1 function is limit the di/dt during of discharging of CD to avoid damage in the SCR. L1 is not critical, 5 to 12uH is ok. The important is to be in series with CD and SCR anode.
In assembling or in electrical wiring, you can assembly L1 following the first drawing or as shown in the second drawing. ( or even adding TWO air core inductors, one L1 following the first dwg, and a second air core inductor as shown in the second draring ! - the circuit will work fine.)

You wrote:

The sssg diagram shows the aircore coil as part of the sssg, but the diagram of the whole circuit shows it between the RL and CD.

Not really, the air core inductor is shown in both drawings in serie with CL, CD, LP,and SSSG. So, the L1 functin off limiting SCR di/dt is enforced.

Also, is the RL resistor the one shown in the sssg diagram mounted on an angle going into the pot?

As shown in the drawings the position of RL is correct. RL mission is to limit the CL inrush current when you connect the circuit in the 230V line.
Let me know more doubts, I will be happy in provide answers
Regards
Newton

Rick

Fri Dec 30 2011, 07:23AM

Registered Member #4220 Joined: Sun Nov 20 2011, 12:11AM
Location:
Posts: 6

Newton:

Thank you for the clarification. I'm just afraid to wire things up wrong and fry some of the components.

I'm also wondering if this circuit will work OK on 120 volts. As I understand it, your 220v is a 220v live wire and a neutral, whereas ours in the US is two 120v live wires 180* out of phase and a neutral, so I can only get a true 220v by running my 120 through a step-up transformer. We'll see!

Rick A.

Newton Brawn

Thu Jan 12 2012, 12:56AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

Hi Rick A.

Do not worry !

SINGLE PHASE SUPPLY SITUATION:
(The power outlet in your shop is 120 or 220~240V, or 125-0-125V, 220V at the lines, 50~60 Hz)
Since the arc starter is connected in the same power line of the buzzbox, the arc starter spark will be sinchronyzed with the buzzbox. Also the arc starter spark will be delayed of 25=35 degreees, provinding the proper ignition of the main arc.

As published the circuit works fine in 120V, Try it . If the spark at the gaps are less than 2.00mm you may increase the pulse energy:
1- the capacitor CD could be 0.94 uF (two 0.47 in parallel ) or one 0.94 x 2000V from a microwave oven.

2- the primary coil of T1, may have a tap at the 18th turn. for better voltage ratio.

Let me know the progress of the construction, send pics of your machine!

Regards

Newton

Redstone

Thu Jan 26 2012, 04:01PM

Registered Member #2578 Joined: Sun Dec 27 2009, 09:21PM
Location: USA Utah
Posts: 31

proper ignition? why would it matter? maybe if your running under current and have to keep it starting. but other wise who cares. misfires will work right?

Newton Brawn

Sat Jan 28 2012, 01:36AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

D Rosey:

The concept of the apparatus:
1 - The buzzbox is a 50~75Vac transformer with high serial reactance in order to control the welding current. The buzzbox provides 60Hz main power to the welding arc. Under some conditions (very low welding current, operator"s hability) the welding arc stinguish, interrupting the welding process. Also, as the buzzbox supplies AC current that cross zero current at 120 times per second, the welding arc also may be interrupted 120 times per minute.

2- When the arc starter is coupled with the buzzbox, the arc starter provides 120 pulses per second superimposed upon the buzzbox supply. These pulses are enough to start the ignition of the main arc after each zero current pass. This assure the main arc stays alive producing heath for the welding.
The pulses provided by the arc starter are 10-15kV, 1-2 microseconds, VERY LOW energy 0.005J, in such way that you may touch the welding electrode without fill the electric shock.

A more detailed information you may read at US Patent # 2880376.

Any concern, let me know.

Regards

Newton

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