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DRSSTC Coupling, power consumption

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zzz_julian_zzz

Mon Nov 19 2012, 02:05AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Hi All,

PROBLEM 1: COUPLING

I just wanted to ask, why the coupling approved by most of all coilers (.18-.19) can't be applied to my DRSSTC due to Pri-Sec Arc Raising? before, I designed this coil for only .17 coupling, it sucks power from my 500VA variac(humming) but I cannot go to higher voltage input approx 170VAC because of the pri-sec arcing and also for VARIAC humming.. the spark length is about 3 feet. My current setup now is for coupling that is 0.15 then the pri-sec arcing disappeared, but in this config, the spark length was also decreased ( for given voltage 170VAC and BPS, its output was only 2.5 ft. And its power consumption is less than 500VA, I think better coupling makes for longer sparks. )
I applied 4 coatings of poly urethane wood varnish. Should I coat it for more?

PROBLEM 2: POWER CONSUMPTION

(I am expecting for 5 ft arc on this coil) powered via 230 VAC/60 Hz mains. For 5ft arcs, the power consumption should be approx ~1200watts, but i think my coil would not suck this high since i can run it on 500 VA variac and it just hums (well this is on 10 BPS i still don't know if this is the same on my max 120BPS) - i don't know how to make my coil suck such power like 1200 watts (computed via john freu formula) Any advice on this matter is HIGHLY appreciated.

PROBLEM 3: CONTROL LOGICS

Specifically, the Hex schmitt inverter gate incoming source from the primary coil feedback CT. The problem is, When i run this coil, the feedback resistor (after the 100nf capacitor) easily burns out. So i decided to remove the resistor and just leave the capacitor alone on the feedbacking circuit. This works pretty well so far, but when arcing (pri-sec) occurs, it automatically damage the IC and the whole system stopped working. If we have, is there a certain formula for a given frequency to get the right capacitance and resistance on the feedbacking circuit to protect the IC or, its just 100nf and a 1k ohms for all specifications??

Here is my MINIcoil Specs:

------------------------------------------ ----------
Secondary Coil Inputs:
------------------------------------------ ----------
Current Profile = G.PROFILE_LOADED
3 = Radius 1
3 = Radius 2
5.5 = Height 1
27.5 = Height 2
1860 = Turns
30 = Wire Awg

--------------------------------------------- -------
Primary Coil Inputs:
------------------------------------------ ----------
Round Primary Conductor
5 = Radius 1
4.9 = Radius 2
2.5 = Height 1
7 = Height 2
9 = Turns
0.25 = Wire Diameter
0 = Ribbon Width
0 = Ribbon Thickness
0.225 = Primary Cap (uF)
0 = Total Lead Length
0 = Lead Diameter

---------------------------------------- ------------
Top Load Inputs:
------------------------------------------ ----------
Toroid #1: minor=4, major=22, height=31.25, topload

----------------------------------------- -----------
Secondary Outputs:
----------------------------------------- -----------
89.5 kHz = Secondary Resonant Frequency
90 degÂ° = Angle of Secondary
22 inch = Length of Winding
84.5 inch = Turns Per Unit
0.0018 inch = Space Between Turns (edge to edge)
2921.7 ft = Length of Wire
3.67:1 = H/D Aspect Ratio
299.031 Ohms = DC Resistance
71785 Ohms = Reactance at Resonance
0.89 lbs = Weight of Wire
127.654 mH = Les-Effective Series Inductance
132.09 mH = Lee-Equivalent Energy Inductance
127.985 mH = Ldc-Low Frequency Inductance
24.772 pF = Ces-Effective Shunt Capacitance
23.94 pF = Cee-Equivalent Energy Capacitance
40.101 pF = Cdc-Low Frequency Capacitance
10.03 mils = Skin Depth
19.457 pF = Topload Effective Capacitance
387.803 Ohms = Effective AC Resistance
185 = Q

----------------------------------------------- -----
Primary Outputs:
----------------------------------------- -----------
71.44 kHz = Primary Resonant Frequency
20.18 % high = Percent Detuned
89 degÂ° = Angle of Primary
23.33 ft = Length of Wire
3.87 mOhms = DC Resistance
0.25 inch = Average spacing between turns (edge to edge)
1.77 inch = Proximity between coils
0 inch = Recommended minimum proximity between coils
22.056 ÂµH = Ldc-Low Frequency Inductance
0.14337 ÂµF = Cap size needed with Primary L (reference)
0 ÂµH = Lead Length Inductance
284.143 ÂµH = Lm-Mutual Inductance
0.169 k = Coupling Coefficient
0.135 k = Recommended Coupling Coefficient
5.92 = Number of half cycles for energy transfer at K
40.67 Âµs = Time for total energy transfer (ideal quench time)

Please help, I need this coil working before Christmas.. Thank you very much in advance!

EDIT: Did you see any faults/wrong values on the numbers from JAVATC that i should be consider and revised from my design? Thanks again!

Steve Conner

Mon Nov 19 2012, 10:16AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The power consumption at 120BPS will be 12 times greater than it is at 10BPS.

What feedback circuit are you using? Many of the early designs are bad. Excessive current from the feedback CT was a known problem.

zzz_julian_zzz

Mon Nov 19 2012, 10:56AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

THanks for the reply Dr. Conner, The PRF@ 10 bps is yes low, but the biggest problem i am experiencing why i cannot increase it is the coupling.. Raising arcs. here is my circuit schematics for feedback. its very very simple. Does increasing the secondary turns of my feedback CT will result in decrease in current? thanks. my ratio as of now is 70:1. I am about to coat another 8 ply of polyurethane carbonate, then i noticed that the tap of my primary as per javatc calculations is 0.5 turns more than the javatc suggests@ 20% lower fres, i think mistuned are one of the cause of raising sparks. thanks. here is my pri-sec coil

Steve Conner

Mon Nov 19 2012, 11:11AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yep, you need more turns on your CT. It is pumping out way too much current, enough to push the +5V rail up and burn out all your ICs.

Normally with that circuit, you use two cascaded CTs of 33 turns, for an effective ratio of 1089:1 (without the hassle of winding 1089 turns

) My PLL circuit uses a single 33 turn CT, but the loading network on the CT secondary is designed to cope with the high current.

I agree, tuning your primary to a higher frequency may help with the racing sparks. However, violent arcing between primary and secondary can sometimes be caused by a bad RF ground.

zzz_julian_zzz

Tue Nov 20 2012, 01:09AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Steve Conner wrote ...

Normally with that circuit, you use two cascaded CTs of 33 turns, for an effective ratio of 1089:1 (without the hassle of winding 1089 turns

HI Dr. Conner,

when we use cascaded CTs isn't that it makes the output phasing of the CT worse?

are you referring to Tune my primary higher than the secondary's Fres? or just tune it a bit higher than of its current fres?

Actually, my RF ground is the roofing of our house, cause its a large sheet of iron, and its connected on the building's metal foundations. Thanks again.

Steve Conner

Tue Nov 20 2012, 10:42AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I don't know what cascaded CTs does to the phasing, but do you want to sit and wind 1000 turns on a small toroid core?

Many people use the cascaded CTs with no problems.

I mean tune the primary a little higher than it is currently. Tune higher in small steps and test at each step to see if the racing sparks have gone away.

Are your building's metal foundations connected to the ground of the AC line too?

zzz_julian_zzz

Thu Nov 22 2012, 05:54AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

yes, our building's metal foundations are connected to earth ground. And Center tap of the secondary windings of our local distribution transformer are also connected to earth grounds. Meaning, that the voltage difference of (1) one of the phase of transformer's secondary with respect to the ground is approximately 110v. Our AC outlet system is 240Vac/60Hz (L-L)/ 120(L-G) Does this have an effect to the performance of the coil and the raising sparks as well? Thanks!

dex

Thu Nov 22 2012, 12:01PM

Registered Member #2566 Joined: Wed Dec 23 2009, 05:52PM
Location:
Posts: 147

what do you mean by "raising sparks"?
arc flashover between primary and secondary winding?

zzz_julian_zzz

Fri Nov 23 2012, 01:39AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Yep, arcing between the two windings. is polyurethane coating will reduce/remove the arcing?

zzz_julian_zzz

Fri Nov 23 2012, 06:44AM

Registered Member #3964 Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332

Yep, arcing between the two windings. is polyurethane coating will reduce/remove the arcing?

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