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LAN_403

loveHV

Mon Mar 30 2009, 03:42PM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

i've made some SSTC's lately but i now want a new challenge a SGTC, i have a tesla coil secondary 50cm long and 10cm in diameter, about 800-1000 windings.

i have everything to build my tesla coil except one thing, the powersupply.

i can't get an NST

so there are 2 options remaining

- a MOT

- and a ZVS flyback

but a MOT scares the hell out of me when you calculate the current flowing trough your body when you should accedently come in contact with it, and isn't 2kV a bit low ?

a ZVS flyback can't deliver 500W, wat would be the minimum power my coil would need.

so i don't know what to use as my powersupply for my TC any advice is certainly welcome

Robert2

Mon Mar 30 2009, 04:04PM

Registered Member #1773 Joined: Tue Oct 21 2008, 06:56PM
Location: Poland
Posts: 93

You can make ~3,2 KVDC with mot and good power diodes and some hv cap MOC . You can make 30-40VDC with mot and supply zvs witf two flyback range connect but when use ZVS you have problem with rezonans cap... When you use mot 3,2kv you had problems with spark gap. sorry for my bad english

theju

Mon Mar 30 2009, 04:47PM

Registered Member #1445 Joined: Tue Apr 15 2008, 01:25PM
Location: Germany
Posts: 24

if u want to use a ZVS driven flyback the biggest porblem will be the "high" voltage compared with the mot
10kV with a ZVS is no problem, also over 500W link

if u use a mot you could get problems with the spark cap if ypu donÂ´t use a rotary, and with the flyback your capacitor must resist higher voltages

both can handle over 500W so iÂ´ts your decision what to take :P

Dr. Dark Current

Mon Mar 30 2009, 05:32PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

If you want 10kV at good power you will need to rewind your TV transformer. NO flyback will take 500W continous, they will just overheat. 200W continouos seems doable for some types but rewinding it for 10kV shouldn't be too big problem.

loveHV

Mon Mar 30 2009, 06:14PM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

ok i'd like to keep my options open 2 things look very interesting to me

- rewinding that flyback, i still have an old B&W tv flyback that i could rewind but,how many turns on the secondary, and does it need to be a multilayer coil, and does it need to be in oil to avoid insulation problems or would polyuthurane varnish work also ?

- is it possible to current limit the primary of the MOT with a 500W halogen bulb, and then double the voltage, i have 3MOC's and 2 7.5kV 1A diodes

also MOT's draw a lot of reactive current is it possible to use a power correction capacitor to lower the reactive current and to increase the cos phi ?

Tribologist

Tue Mar 31 2009, 01:34AM

Registered Member #1879 Joined: Mon Dec 22 2008, 04:11AM
Location:
Posts: 40

What about a oil burner ignition transformer? 10kV at 23mA Next to free at your local recycling center.

Ulf

Dr. Slack

Tue Mar 31 2009, 07:06AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

You say an SG TC, but you haven't specified whether the traditional AC supply, or a semi-resonant DC supply, and fixed or rotary SG.

If you go for DC RSG, then a MOT can be just about right. Feed a pair of voltage doublers in opposition (or a quadrupler, but that's less efficient, and means higher voltages from ground) to get >~10kV DC, then this nearly doubles with the inductor in the charging process to give around 20kV on the tank cap, which is completely usable.

Suggest strategy for the MOT, put insulation round it and devise safe working practices so that you don't come into contact with it, even accidently.

Littlew

Tue Mar 31 2009, 08:41AM

Registered Member #1448 Joined: Sat Apr 19 2008, 01:16PM
Location: Russia/Moscow
Posts: 21

use old mots(bigger ones). You can use one old MOT with voltage multipler, or 2 old MOTs.
But remember - MOT is very dangerous.
For first time u can use NST or transistor inverters

loveHV

Tue Mar 31 2009, 11:34AM

Registered Member #1854 Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88

a oil burner ignition transformer i have some of the ones that i have are electronic ones.

i also read that those ignition transformers can only supply the power needed for a coil for about 5 min, then they get really hot, but i can try to get one.

about the voltage of the powersupply, i will make my cap's with PVC pipe as my dielectric material and around it aluminum foil and in it salt water. i don't know the breakdown voltage of PVC but i guess it could withstand about 40kV. but will it withstand the tesla coil ?

also what kind of tesla coil outputs most sparks ?

DC charging, AC charging... RSG,Static SG ...

LithiumLord

Tue Mar 31 2009, 12:38PM

Registered Member #1739 Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261

Hehe, depends of what output levels you are aiming for ;) Apparently the most optimal is DC resonant charging mode with synchronous gap, but again - you have to be ready to give what it takes ;)

>But remember - MOT is very dangerous.
For first time u can use NST or transistor inverters

Don't spread the local urban legend here - how much time did you die because of a MOT hit? ;) Safety-wise SGTC is always a certain death in an idiot's hands, and there's no difference between any of the supplies listed above. Btw I wouldn't recommend solid-state PSUs because they are nearly pointless - why designing a resonant charging circuit, sparkgap mechanics and a powerfull supply when you can just make the invertor electronics alone (read: "DRSSTC") and get a better output due to decreased circuitry loss ;)

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