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Using Arduino => General Electronics => Topic started by: Joseph3502 on May 25, 2018, 05:10 pm

Title: Help needed with step-up transformer
Post by: Joseph3502 on May 25, 2018, 05:10 pm
Hello. I bought two 277 ballasts at a flea market for $4 last week. I use them in combination with a flyback for a high voltage power supply for wood burning. I have been powering them with 240 volts from my dryer plug. They work, but for one, I don't want to shorten their lives by undervolting them and I want their full power output. I was planning on using a microwave transformer with a 277 volt winding, but quickly figured out that it wasn't feasible because the transformers are inefficient. I was also wondering if i can add extra windings to the primary and eliminate the need for a secondary totally, like the attached picture. Sort of how Variacs have an output of 145 when 120 is supplied(overwinding). Would this work with a transformer like this? Suggestions on how i can get 277 easily from either 120 or 240? Thanks!
Title: Re: Help needed with step-up transformer
Post by: DVDdoug on May 25, 2018, 05:23 pm
Quote
They work, but for one, I don't want to shorten their lives by undervolting them and I want their full power output.
You won't hurt a transformer by running it at lower voltage, but of course you won't get full power.

Power  (Watts) is the product of Voltage X Current, and current depends on the load resistance-impedance (Ohm's Law).     

...I don't know what you're doing or why "wood burning" requires high voltage.
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 25, 2018, 08:21 pm
I was also wondering if i can add extra windings to the primary and eliminate the need for a secondary totally, like the attached picture. Sort of how Variacs have an output of 145 when 120 is supplied(overwinding).
Be very careful with this sort of arrangement.  There is NO ISOLATION!  And, because there is no isolation, it's far easier to receive a lethal dose of current [think ELECTROCUTION] -- especially if you don't know what you're doing.

Suggestions on how i can get 277 easily from either 120 or 240? Thanks!
When you say, 277V, are you talking AC or DC?  Because if it's DC you're after, then consider that 240VAC is an RMS value, and if you full-wave rectify 240VAC, and filter it with an appropriate Capacitance, you'll wind up with:
(240VAC + 1.414) - ~1.4V = 338VDC
That's because you multiply an RMS value by the square-root of 2, to get the Peak voltage value.  And in the case of what you fill get from a full wave rectifier, you gotta subtract the forward voltage drops of the diodes [two in series]. 
BUT, since "240VAC" is an approximate value, subtracting the forward drops merely gives you a "Nominal" voltage.  The actual voltage will vary, depending on what comes down the mains lines.

AND AGAIN: DOING THIS WITHOUT AN ISOLATING TRANSFORMER [and, your Flea Market transformers are NOT isolating] MEANS THIS HIGH VOLTAGE IS NOT ISOLATED, AND THUS IS EVEN MORE DANGEROUS!  And, that's not to say that doing it with an isolating transformer is not dangerous -- it's just a little less dangerous.  You're just less likely to get a shock when you touch surrounding grounded points of conductivity, when the voltage is isolated from mains.
But, I'm unable to advise you on how to achieve what you want to achieve, because I'm just not versed enough on this topic [I'm more of a Digital guy] -- but I wanted to make sure you were aware of the dangers.
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 25, 2018, 08:29 pm
BTW: Here's that diagram the OP provided:

(http://forum.arduino.cc/index.php?action=dlattach;topic=549518.0;attach=259313)
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 25, 2018, 08:37 pm
You won't hurt a transformer by running it at lower voltage, but of course you won't get full power.

Power  (Watts) is the product of Voltage X Current, and current depends on the load resistance-impedance (Ohm's Law).    

...I don't know what you're doing or why "wood burning" requires high voltage.
It's been too long for me to remember the details, but it seems to me there is more to it than P=IE. Especially when you start talking about impedance.
Impedance is a combination of a 90° DC resistive component, and a 180° summation of Capacitive and Inductive reactance.  In this case, there will be very little Capacitive Reactance.  But, Inductive Reactance will certainly play a role.  In which case Power Factor must be considered.  There is a 90° phase shift between Resistance and Inductive Reactance.  Only the Resistive component [in both the load, and in the transformer] is described by the P=IE formula.
Maybe someone else, that knows this subject better, can elaborate (and even, correct, as needed). 
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 25, 2018, 09:20 pm
This is AC I need. It normally comes from a 277/480 three phase transformer by connecting hot to earth (square root of 3) in an industrial setting(schools, factories, large office buildings, etc.). I need some kind of AC supply that outputs around 277 volts AC (plus or minus a couple volts).
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 25, 2018, 09:29 pm
...by connecting hot to earth (square root of 3).
Do you mean connecting hot to neutral?  It seems to me, in my not so educated opinion, that connecting Hot to Earth Ground, is a very bad idea.  Connecting Hot to Neutral is also not such a grand idea, either, unless it's through some sort of load -- otherwise, your transformer windings, and external wires, will be your load, and that usually leads to smoke, fire, sparks, and all manner of pandemonium -- or, at best, a blown fuse or popped circuit-breaker.
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 25, 2018, 09:41 pm
I am sorry I meant to say Earthed-Neutral.
Title: Re: Help needed with step-up transformer
Post by: ted on May 25, 2018, 11:05 pm
P=IE formula.
Maybe someone else, that knows this subject better, can elaborate (and even, correct, as needed).
AC

P = UIcosϕ.
Title: Re: Help needed with step-up transformer
Post by: avr_fred on May 26, 2018, 01:47 am
If they are modern electronic ballasts, raising the the input voltage will do absolutely... nothing. Well, it will reduce the input current but that still means nothing to what you're doing.

Please post a photograph of the device label or an exact make and model. Until you do that, you're just wasting time and effort for... nothing.
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 26, 2018, 05:42 am
It is a Lutron Hi-Lume dimmable and a Sylvania Quicktronic. Both 277. The Sylvania is a magnetic type, and the Lutron is an electronic. The magnetic works fine because it is just a 277 to 600 VACrms step up transformer. It is just underpowered by about 37 volts. The electronic one, however, will not start because it's not getting the correct voltage. It is more sensitive to input voltage. It needs 277 volts ± a couple of volts.
Title: Re: Help needed with step-up transformer
Post by: ted on May 26, 2018, 03:41 pm
https://www.google.ca/search?rlz=1C1AFAB_enCA475&biw=1440&bih=744&tbm=isch&sa=1&ei=tF8JW_byCMqfjwSmgZf4CQ&q=microwave+transformer+wood+burning+circuit&oq=microwave+transformer+wood+burning+circuit&gs_l=img.3...426174.443375.0.445701.21.21.0.0.0.0.108.1703.20j1.21.0....0...1c.1.64.img..0.0.0....0.zZQ_VFm6W08#imgrc=YHrDirMS8iTjxM: (https://www.google.ca/search?rlz=1C1AFAB_enCA475&biw=1440&bih=744&tbm=isch&sa=1&ei=tF8JW_byCMqfjwSmgZf4CQ&q=microwave+transformer+wood+burning+circuit&oq=microwave+transformer+wood+burning+circuit&gs_l=img.3...426174.443375.0.445701.21.21.0.0.0.0.108.1703.20j1.21.0....0...1c.1.64.img..0.0.0....0.zZQ_VFm6W08#imgrc=YHrDirMS8iTjxM:)
Title: Re: Help needed with step-up transformer
Post by: ted on May 26, 2018, 03:45 pm
https://www.youtube.com/watch?v=mNlQD8OwHb4 (https://www.youtube.com/watch?v=mNlQD8OwHb4)
Title: Re: Help needed with step-up transformer
Post by: avr_fred on May 26, 2018, 07:55 pm
You could create a boost transformer with a 100va or so (I doubt you need any more than that) 120/240 to 24 vac control transformer. You just connect the secondary in series with the primary and run it as an autotransformer. If it had dual 120 primaries, you put all three coils in series and power it with 120 for an output of 120+120+24=264 volts. It will have to be phased correctly otherwise it will buck rather than boost. Trial and error will get you there, just test unloaded with a voltmeter. That's about the best you can do with commonly available parts.

Hopefully you can get a transformer for really cheap or borrow one to test because it probably will not make much of a diffference in the burn. Ballasts are a poor choice since they are designed to limit current. A byproduct of that behavior is that the output voltage drops off in order to maintain a constant current. The only way to increase the voltage is to increase the resistance of the wood - which means dry it. This the opposite of what you really want. Translation? Ballasts don't work for the purpose and I don't think jacking the input voltage up is going to make any difference. The moisture content of the wood is going to determine the voltage.

A repurposed transformer from an old, big microwave (modern ovens don't have transformers) is a better choice since it's a straight step up transformer without the inherent current limiting. If you overload it, yes the voltage will drop when the core reaches saturation but you don't want to let that happen since that will let the smoke out.

Put big Powerstat/Variac (at least 6 but 10 amps ideally) on the input to control the voltage/power and you'll have voltage to burn ;-)
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 29, 2018, 04:56 am
I actually started out with the microwave transformer. I feel uncomfortable using the microwave transformer because it can deliver 1 amp at 2kv. They also run on full saturation mode and trip my breaker every two minutes. The ballast only pulls 0.43 amps when completely shorted so I don't have to worry about blowing breakers. I am currently looking for a neon sign transformer for it, but until then, I only have flyback transformers. They are good because they don't deliver a whole bunch of current. The ballasts are good too because they don't push a whole lot of current into the flyback and burn it up. A ballast is perfect for my application. Woodburning uses a mixture of baking soda and water soaked into the wood to make it more conductive. As for the 277 supply, could I pick up a 120/240 to 24vac at my local home Depot or Lowe's or my electrical surplus store or would I have to order it? If I supply 24vac to it's secondary to get 240 then have another transformer with a 32 volt secondary wired in series with the 240 volts to make 272 volts?
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 05:39 am
1. Use tap water without baking soda - what are the results ?
2. reduce voltage applied to transformer, halogen lamp 500W in series with transformer.
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 05:55 am
. The ballasts are good too because they don't push a whole lot of current into the flyback
what flyback

Typical ballast is just inductor when starter is on the heating elements increase the temperature inside the tube in the moment when going off the flyback spike igit the vapor in the tube then applayed voltage to tube is 110 V.
So the balast is not some kind of transformer or autotransformer.

Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 05:56 am
(https://qph.fs.quoracdn.net/main-qimg-9919c522bf50a62aad6abeb7871f1680-c)
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 06:00 am
electronic ballast is producing high voltage

(http://www.xinshilighting.com/Admin/upload/Pro/Electronic-Ballast-XP-E118H-4.jpg)
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 06:17 am
(http://www.edisontechcenter.org/lighting/Fluorescent/FluorLampStartupquartz900.jpg)


1. Filament electrodes are preheated and glow red
2. The Cathode begins to ionize argon gas surrounding it
3. This lamp is powered by AC power, so the cathode switches to the other side and you see the left side begin to ionize, the other side (now the anode) stays warm and ionized
4. The left side cathode warms to full and both sides are warmed up
5. The ballast provides a high voltage kick which instantly ionizes the entire tube to a high level of brightness


6. The lamp returns to normal voltage and its warmth has vaporized all the mercury, the lamp operates as normal
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 08:46 am
Why you stick with 277 volts, for your application voltage is not critical, try 240 V.
Your ballasts 50W can deliver only 150mA of high voltage, I think you need much more.
Low resistance is causing overloading the ballasts and drop 277V mayby to 100V
 
Microwave transformer is a 1000W

trip my breaker every two minutes = a lot of current you taking from transformer perhaps 2000W - 15A breakers ?

Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 29, 2018, 10:09 pm
Yes the MOT trips the breaker often and on a 20 amp breaker. The transformer gets very hot in a matter of minutes and so hot it burnt my hands. It runs solely on saturation. It is inefficient and even when I turn it down with my 30 amp variac, it still gets somewhat hot and the output voltage is a little too low. It works, but takes about 5 minutes per 6 inches to burn. Even when the voltage is lowered, there still is too much current. A ballast is sort of like a transformer because it outputs around 600 volts AC open circuit. I know it is more like an inductor, because it limits current, but. I know this reply is all random, but I'm trying to answer everybody. :)
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 10:24 pm
It is something wrong with your transformer - it is getting warm when is on load ?
or too much water
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 10:30 pm
google - wood burning microwave transformer - images
Title: Re: Help needed with step-up transformer
Post by: ted on May 29, 2018, 10:45 pm
https://www.youtube.com/watch?v=PWUALAJBFdw (https://www.youtube.com/watch?v=PWUALAJBFdw)

https://www.youtube.com/watch?v=1UY0pbsHPHk (https://www.youtube.com/watch?v=1UY0pbsHPHk)

there is a lot youtube
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 30, 2018, 02:34 am
I am sorry, but the microwave transformer is out of the question. For one, I'm not comfortable using it. Two, I already took the secondary out to try to get 277 out. The only way I'm using the MOT is if I can figure out how to get 277 from it.
Title: Re: Help needed with step-up transformer
Post by: ted on May 30, 2018, 02:48 am
how much you have now ?
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 30, 2018, 03:11 am
OK, caveat: I have no experience with wood burning with electricity [you're creating Lichtenberg Figures, correct?]

But, just based on Electronics: if the Microwave Transformer is getting hot, and popping the circuit breaker, then that means the resistive path is allowing too much current to flow.  There are two things that can cause too much current:

So, either use less baking soda [or whatever it is that you are using to make the water more conductive], OR a lower voltage [which, clearly, is what you're trying to do]


BUT, maybe by adjusting the conductivity of the water, by using less "ionizing agent", you can get some success with the microwave transformer -- i.e. get away with using more voltage.
Title: Re: Help needed with step-up transformer
Post by: ted on May 30, 2018, 03:28 am
That what I suggested i post # 15, but he is stick with 277V and 50W.
Good luck.
Title: Re: Help needed with step-up transformer
Post by: Joseph3502 on May 30, 2018, 04:21 am
Well the problem is I don't have one now. I have tried different ratios of baking soda and water on wood, and they all work okay. It all depends on the wood. If it is a hardwood, it needs to be more baking soda and vice-versa. I am trying to get as close to 277 as I can get. I do not have 240 in the garage and if I want 240 I have a homemade cord that I run into my laundry room that plugs into my 30 amp 240 volt dryer plug. To make matters worse, we have a main circuit panel and 2 subpanels in the basement that have no spaces left. And where I live, there is constantly a load of laundry in the dryer. The worst part is we have a main circuit panel and 2 subpanels in the basement that have no spaces left, so I can't even run a 15 amp 240 volt line to the garage even if I wanted to. Ideally, I wanted to get 240/277 at about 0.5 amps from a standard 120 volt outlet. Even if I can get 240 from a standard 120 outlet I'd be happy. 277 would be better though. One thing is that I need it to be a transformer, not an electronic country converter for American to European plugs.
Title: Re: Help needed with step-up transformer
Post by: ReverseEMF on May 30, 2018, 07:10 am
How about these ideas: