With the new type of NSTs available with the dreaded GFCI circuit built in, I was wondering if there is a way of doing sort of a buffer between a DC rectified NST and the output so that the GFCI wouldn't ever detect an arc that would trip the circuit. Maybe a resistor to a capacitor and then on to the output?
I'm no electrical engineer here, and I hope I'm not way off base, but I've got a nice France 15kv, 60mA NST that I'm hoping to be able to put to use in a demo fusor. I've got a real old 15kv, 30mA NST that I just made a Jacob's ladder out of, but it's at least 50 years old and I don't really want to mess around with trying to rectify it.
Thanks for any help
Todd Massure
NST GFCI "work around"?
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Todd Massure
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David D Speck MD
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Re: NST GFCI "work around"?
Todd,
Some of the new NSTs have the GFCI circuits in an accessible location under the bottom plate. With some careful continuity checking, some experimenters have successfully removed the module from the circuit.
Apparently to prevent just such a dodge, many of the newer NSTs have the GFCI components totally buried within the epoxy fill of the case, beyond any reasonable hope of access.
I have no personal experience with the Franceformers, so I can't tell you for sure about your unit.
Your old boat anchor 15/30 might be more of a sure bet to start with. If it's running the JL, then it should be in good shape to run your fusor.
Dave
Some of the new NSTs have the GFCI circuits in an accessible location under the bottom plate. With some careful continuity checking, some experimenters have successfully removed the module from the circuit.
Apparently to prevent just such a dodge, many of the newer NSTs have the GFCI components totally buried within the epoxy fill of the case, beyond any reasonable hope of access.
I have no personal experience with the Franceformers, so I can't tell you for sure about your unit.
Your old boat anchor 15/30 might be more of a sure bet to start with. If it's running the JL, then it should be in good shape to run your fusor.
Dave
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Jon Rosenstiel
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Re: NST GFCI "work around"?
Hi Todd,
Give the Tesla Coil Mailing List (TCML) archives a search at:
http://www.pupman.com/
Jon Rosenstiel
Give the Tesla Coil Mailing List (TCML) archives a search at:
http://www.pupman.com/
Jon Rosenstiel
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Todd Massure
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Re: NST GFCI "work around"?
I've done a little more searching on the site that Jon suggested (thanks Jon) etc. and I haven't seen that anyone has done the type of thing that I was thinking of. I believe that a typical GFCI (or GFI) circuit is just meant to trip when it senses a sudden peak in current so it seems like something like I suggested might work, however I know that NSTs are meant to only give peak voltage for a short time to initially arc through the gas in a gas tube or "neon" sign to turn the gas to a plasma and then drop to a lower voltage just to maintain the flow in the circuit, so maybe these GFCIs are specifically meant to do that, in which case one wouldn't be able to get more than a few kv out of it except for a second or two without totally disabling the GFCI completely. Hmmmm...... Guess I'll have to keep searching.
Todd Massure
Todd Massure
Re: NST GFCI "work around"?
Todd,
Tesla Coilers often use NSTs to power small to medium sized coils, and often have to deal with a GFCI. There is a lot of collective experience available through the Tesla Coil Mailing List which Jon referred to.
Most tesla coilers depot their NSTs to the extent necessary to get at and remove the GFCI protective circuits. Some have left the circuit in place and claim to have had no problem running their coils without any modification at all to the GFCI. In tesla coil service, even during normal operation the NST is subject to continual arcs through the spark gap, far more violent than the possible arcing in an unstable fusor.
Assuming that both of your NSTs are the conventional type (you'll know because they'll be very heavy) the current is limited by the transformer itself, through the use of magnetic shunts. It is in no way affected by the GFCI, which either trips completely if it detects a ground fault, or doesn't have any effect at all on output current or voltage. (However,I say this without any specific knowledge of the Franceformer units.)
Regarding your suggestion to use an isolation resistor, most people do exactly that by putting a large high voltage resistor between the fusor and the high voltage output of the power supply, to limit current during unstable operation. This is particularly important if a filter capacitor is used on the output of the rectifier.
Your 15/30 NST should work well in a supply for a demo fusor, but if the 15/60 will function, it would definitely be preferable. As the pressure in your fusor drops and the output voltage from the NST climbs, the amount of current available from the 15/60 at any given voltage will be roughly double that of the 15/30. This is not so important at higher pressures, but as you get better vacuum and aim for star mode of operation, the higher current available from the 15/60 NST will be welcome.
If you were to build your rectifier as a separate unit from the transformer, it would be a trivial matter to disconnect one NST and hook up the other. Include the current and voltage measuring resistors in the same unit as the rectifier, and preferably operate the whole assembly under oil.
Good luck!
Ben
Tesla Coilers often use NSTs to power small to medium sized coils, and often have to deal with a GFCI. There is a lot of collective experience available through the Tesla Coil Mailing List which Jon referred to.
Most tesla coilers depot their NSTs to the extent necessary to get at and remove the GFCI protective circuits. Some have left the circuit in place and claim to have had no problem running their coils without any modification at all to the GFCI. In tesla coil service, even during normal operation the NST is subject to continual arcs through the spark gap, far more violent than the possible arcing in an unstable fusor.
Assuming that both of your NSTs are the conventional type (you'll know because they'll be very heavy) the current is limited by the transformer itself, through the use of magnetic shunts. It is in no way affected by the GFCI, which either trips completely if it detects a ground fault, or doesn't have any effect at all on output current or voltage. (However,I say this without any specific knowledge of the Franceformer units.)
Regarding your suggestion to use an isolation resistor, most people do exactly that by putting a large high voltage resistor between the fusor and the high voltage output of the power supply, to limit current during unstable operation. This is particularly important if a filter capacitor is used on the output of the rectifier.
Your 15/30 NST should work well in a supply for a demo fusor, but if the 15/60 will function, it would definitely be preferable. As the pressure in your fusor drops and the output voltage from the NST climbs, the amount of current available from the 15/60 at any given voltage will be roughly double that of the 15/30. This is not so important at higher pressures, but as you get better vacuum and aim for star mode of operation, the higher current available from the 15/60 NST will be welcome.
If you were to build your rectifier as a separate unit from the transformer, it would be a trivial matter to disconnect one NST and hook up the other. Include the current and voltage measuring resistors in the same unit as the rectifier, and preferably operate the whole assembly under oil.
Good luck!
Ben
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Richard Hull
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Re: NST GFCI "work around"?
A GFI will not be an issue with the fusor. It is arcing against ground that creates the trip out as a rule in a franceformer.
I have about 100 Neon transfomrers at my lab. Most are older non-GFI types. The few that are allow me to arc the 15 kv knob to know, but knob to ground trips them every time.
For more data on standard neon transfomers check out the paper that I wrote and which was published in the "files forum"
viewtopic.php?f=19&t=7945#p57349
Richard Hull
I have about 100 Neon transfomrers at my lab. Most are older non-GFI types. The few that are allow me to arc the 15 kv knob to know, but knob to ground trips them every time.
For more data on standard neon transfomers check out the paper that I wrote and which was published in the "files forum"
viewtopic.php?f=19&t=7945#p57349
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Todd Massure
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- Real name: Todd Massure
Re: NST GFCI "work around"?
Thanks Ben.
Richard I did read that post in the files section a few days ago. Lots of great info there.
So Richard, you said that the GFI types are ok to use on a fusor and I'm assuming you are talking about even if they are rectified. Is this because a NST generally won't give enough voltage to arc in a demo fusor?
Here's what happened when I connected the Franceformer to the Jacob's ladder:
As soon as I plugged it in it arced at the smallest part of the gap in between the wires for a second and then stopped, a few seconds later it arced again for less than a second, then a few seconds later it arcs just once, very quickly and then that's it, no more. If I unplug it it starts over again, the same 3 zaps and then nothing. So Richard, it seems to me that I'm having a problem with it triping from knob to knob that you apparently haven't had. Maybe I'll try hooking it back up to the Franceformer, but with the green ground wire left disconnected. Could that be the problem?
Thanks for all the help everyone. I've got a couple of projects in mind for this NST including the demo fusor.
Todd Massure
Richard I did read that post in the files section a few days ago. Lots of great info there.
So Richard, you said that the GFI types are ok to use on a fusor and I'm assuming you are talking about even if they are rectified. Is this because a NST generally won't give enough voltage to arc in a demo fusor?
Here's what happened when I connected the Franceformer to the Jacob's ladder:
As soon as I plugged it in it arced at the smallest part of the gap in between the wires for a second and then stopped, a few seconds later it arced again for less than a second, then a few seconds later it arcs just once, very quickly and then that's it, no more. If I unplug it it starts over again, the same 3 zaps and then nothing. So Richard, it seems to me that I'm having a problem with it triping from knob to knob that you apparently haven't had. Maybe I'll try hooking it back up to the Franceformer, but with the green ground wire left disconnected. Could that be the problem?
Thanks for all the help everyone. I've got a couple of projects in mind for this NST including the demo fusor.
Todd Massure
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Richard Hull
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Re: NST GFCI "work around"?
Todd, You appaernely have a modern all electronic GFI!! The GFI's I have seen are ground fault based and not output current based. This is a new one on me. Forget arcing the thing. Put it under a normal heavy load like a 500k ohm resistor load.
Note a 500K resisitor that will hand the energy is rare now. Rig up something that will just heavily load the device to the full 30 ma. If the GFI doesn't act up then you might be OK for a demo fusor supply.
I know that the clowns afranceformer are just trying to meet ever more stringent codes and save on iron and copper, but it is a sad testament to our times. I might have to up my price on my older neons as they will be collectors items, rare and much sought after soon, it seems. The old supply and demand routine.
I saw three old common 1lb cans of R-12 freon at a hamfest last weekend. I used to buy them by the case for .89 each back in the 80's for my Lincoln collection's A/C systems. The ones I saw were heavilty rusted, but the contents were intact and the price $30.00/can. The three I saw sold finally to a guy for $80.00! Mild discount for quantity.
The good stuff is going, going, gone and replaced by crap.
Richard Hull
Note a 500K resisitor that will hand the energy is rare now. Rig up something that will just heavily load the device to the full 30 ma. If the GFI doesn't act up then you might be OK for a demo fusor supply.
I know that the clowns afranceformer are just trying to meet ever more stringent codes and save on iron and copper, but it is a sad testament to our times. I might have to up my price on my older neons as they will be collectors items, rare and much sought after soon, it seems. The old supply and demand routine.
I saw three old common 1lb cans of R-12 freon at a hamfest last weekend. I used to buy them by the case for .89 each back in the 80's for my Lincoln collection's A/C systems. The ones I saw were heavilty rusted, but the contents were intact and the price $30.00/can. The three I saw sold finally to a guy for $80.00! Mild discount for quantity.
The good stuff is going, going, gone and replaced by crap.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
-
Todd Massure
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- Joined: Thu Mar 11, 2004 12:38 am
- Real name: Todd Massure
Re: NST GFCI "work around"?
Hmmm, it seemed like it was acting kind of odd!
I think it gives those initial bursts just to energize the gas tube in a sign, but that's all it will allow.
So are you suggesting to just try putting a 500k ohm resistor between the knobs and see if it trips?
Not to get too off topic, but I bought several of those cans of R-12 freon right before the ban which I still have. I still own my first car, which is a '65 Barracuda (I'm the second owner too) that has an after market AC unit on it. I decided long ago that I wasn't going to try to resurrect the AC unit, so I still have the R-12. I might have to put it on ebay if it's even legal to sell it(?)
I didn't know what to do with it for a long time, but the "hole in the ozone" seems to be healing or was never an issue in the first place etc......anyway that's a whole 'nuther can 'o' worms that I don't really want to open. This forum is not really meant for that discussion and certainly not in this thread!
Todd Massure
I think it gives those initial bursts just to energize the gas tube in a sign, but that's all it will allow.
So are you suggesting to just try putting a 500k ohm resistor between the knobs and see if it trips?
Not to get too off topic, but I bought several of those cans of R-12 freon right before the ban which I still have. I still own my first car, which is a '65 Barracuda (I'm the second owner too) that has an after market AC unit on it. I decided long ago that I wasn't going to try to resurrect the AC unit, so I still have the R-12. I might have to put it on ebay if it's even legal to sell it(?)
I didn't know what to do with it for a long time, but the "hole in the ozone" seems to be healing or was never an issue in the first place etc......anyway that's a whole 'nuther can 'o' worms that I don't really want to open. This forum is not really meant for that discussion and certainly not in this thread!
Todd Massure
Re: NST GFCI "work around"?
Here is a link to a discussion of the GFI in Allanson neon sign transformers:
http://www.allanson.com/Product%20PDFs/ ... ection.pdf
Page 8 includes a discussion of how the circuit works, and the following page discusses what (apart from ground faults) can cause them to trip. Of course the discussion is oriented toward the Neon Sign industry, but a lot of what they are saying is transferrable to other NST uses as well.
I have no idea how closely the Franceformer GFI resembles the Allanson circuit.
Ben
http://www.allanson.com/Product%20PDFs/ ... ection.pdf
Page 8 includes a discussion of how the circuit works, and the following page discusses what (apart from ground faults) can cause them to trip. Of course the discussion is oriented toward the Neon Sign industry, but a lot of what they are saying is transferrable to other NST uses as well.
I have no idea how closely the Franceformer GFI resembles the Allanson circuit.
Ben