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Transformer Question

Started by Unknown February 2, 2017
On Sunday, February 5, 2017 at 4:01:55 AM UTC+1, John Larkin wrote:
> On Sat, 4 Feb 2017 17:26:28 -0800 (PST), "dcaster@krl.org" > <dcaster@krl.org> wrote: > > >On Saturday, February 4, 2017 at 3:18:22 PM UTC-5, John Larkin wrote: > > > >> >> >as long as you don't want too much isolation. What voltage breakdown do you get with the 2 primaries wouund one directly on the other? > >> > > > > >> John Larkin Highland Technology, Inc > >> > >> lunatic fringe electronics > > > >Don't most dual primary transformers have a layer of insulation between the two primaries? > > > > Dan > > I don't know.
When you don't know, you should not recommend something that is potentially deadly for the OP!
>But they surely have to be insulated enough to withstand > line transients. And of course the 120/240. >
Yes, for a one off test. The reason for the insulation is due to what over voltage category you have for the equipment. For over voltage category II surge pulses (lightning overvoltage) of several kV is normal, and the insulation needs to be able to survive that. Also, the wire insulation degrades over time, and with temperature
> I've done the dual-primary trick many times, and I'm still here. >
Not really an argument Cheers Klaus
On Sunday, February 5, 2017 at 5:20:34 AM UTC+1, John Larkin wrote:
> On Sat, 4 Feb 2017 19:59:52 -0800 (PST), Phil Allison > <pallison49@gmail.com> wrote: > > >John Larkin wrote: > > > >> > >> > >> A dial-primary (120:240 to whatever) transformer makes a good > >> isolation transformer. Use the two primaries and ignore the secondary, > >> unless you have some use for it too. > >> > > > >** Fraid that idea is not safe to recommend - as the two primaries may well be bi-filar wound. > > They can stand 120 and 240 and transients reliably already. It takes a > huge voltage to punch through enameled magnet wire. >
Yes, but several kV surges are normal One other reason for not doing it like that is that during production the wire takes some punishment when winding on the bobbin. The surface can have a lot of minute cracks, which develop over time Cheers Klaus
On Sunday, February 5, 2017 at 5:42:15 AM UTC+1, Phil Allison wrote:
> whit3rd wrote: > > > > > > > Real isolation transformers are tested (briefly) at 3 to 5 kV > > > > > ** Which is not proof of an overall safe design. > > Things like clearances, creepage distances, amount and type of insulation and having thermal fuses built in are *crucial* to achieving acceptable safety. > > The topic is not suitable for arrogant fools like Larkin.
It is legal to test to compliance. See for example EN60335 section 29 But UL and VDE will be in close control of what you are doing Cheers Klaus
On Sunday, February 5, 2017 at 7:21:34 AM UTC+1, Phil Allison wrote:
> John Larkin wrote: > > > > > Transformer winding machines count turns exactly. > > > > > ** I'm sure they do. > > But counting errors still happen for other reasons. >
We do testing on all transformers and CM coils since we have seen transformers wound with incorrect turns. Some transformers, with thick wire can not be machine wound. And you have the manual process of putting the wire on the pin afterwards Cheers Klaus
On Saturday, February 4, 2017 at 11:17:53 PM UTC-5, Phil Allison wrote:
> dca...@krl.org wrote: > > > > > If you are making a 1:1 transformer using a couple of MWT's > > ( MicroWave Tronsformer ), You do not use the secondary windings. > > > > ** THAT is a COMPLETELY DIFFERENT story to what you posted previously. > > YOU need to be WAY more careful with what you post !!!!!!!!!!!!!!! > > W what you posted before was DANGEROUS advice - anyone reading it would think you meant to use the two transformers as they were. > > You need to go back and retract that post NOW. > --------------------------------------------- > > > .... Phil
If you go back and read my previous post, you will see that I never said to use the secondary windings. In fact I did not provide any detailed instructions. I completely agree that using two MWT's as is and connecting the secondary's is really stupid. Dan
On Sun, 5 Feb 2017 02:36:35 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>On Sunday, February 5, 2017 at 5:20:34 AM UTC+1, John Larkin wrote: >> On Sat, 4 Feb 2017 19:59:52 -0800 (PST), Phil Allison >> <pallison49@gmail.com> wrote: >> >> >John Larkin wrote: >> > >> >> >> >> >> >> A dial-primary (120:240 to whatever) transformer makes a good >> >> isolation transformer. Use the two primaries and ignore the secondary, >> >> unless you have some use for it too. >> >> >> > >> >** Fraid that idea is not safe to recommend - as the two primaries may well be bi-filar wound. >> >> They can stand 120 and 240 and transients reliably already. It takes a >> huge voltage to punch through enameled magnet wire. >> > >Yes, but several kV surges are normal > >One other reason for not doing it like that is that during production the wire takes some punishment when winding on the bobbin. The surface can have a lot of minute cracks, which develop over time > >Cheers > >Klaus
Transformers, absent thermal overload or soaking in salt water, are amazingly reliable. Using a dual-primary tranny as an isolation transformer will be no less reliable. If you're really afraid of getting shocked, add a ground fault detector in series with the line input. No, use two in case one fails. Of course, wear a bunny suit and silicone gloves, and have a buddy nearby to administer CPR. Never eat grapes. You can aspirate one and choke to death. Best to avoid all solid food. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Saturday, February 4, 2017 at 10:55:20 PM UTC-5, Phil Allison wrote:
> dca...@krl.org wrote: > > > > Phil Allison wrote: > > > > > > > > > If you really want to spend very little, get a couple of microwave ovens > > > > and use two transformers to make one isolation transformer. > > > > > > > > > > > Those articles require the disassembly ( grinding off weldings ) and rewinding of the transformer. > > You are an utter IDIOT, Dan. > > > ..... Phil
Sorry but to me making one transformer using parts from two transformers implies taking the transformers apart and reassembling to make one transformer. Connecting two transformers together does not make one transformer. If anyone is going to do this, I would not recommend grinding the welds. Using a hacksaw is easier. If you do this you do not have to rewind the transformer. You just slip the secondary winding off one core and replace it with the primaray winding from the other transformer. Dan
On Sun, 5 Feb 2017 02:43:04 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>On Sunday, February 5, 2017 at 7:21:34 AM UTC+1, Phil Allison wrote: >> John Larkin wrote: >> >> > >> > Transformer winding machines count turns exactly. >> > >> >> >> ** I'm sure they do. >> >> But counting errors still happen for other reasons. >> >We do testing on all transformers and CM coils since we have seen transformers wound with incorrect turns. Some transformers, with thick wire can not be machine wound. And you have the manual process of putting the wire on the pin afterwards > >Cheers > >Klaus
A decent transformer shop confirms the count with an AC bridge gadget, direct readout. If anyone made a 120:240 dual-primary transformer, and missed one turn, it would fry when connected to 120 volts. I've never seen that happen, over thousands of transformers. We use 1:1 and 5:1 signal transformers in synchro/lvdt simulators, milli-degree accuracy. The turns ratios are always exact. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sun, 5 Feb 2017 02:28:41 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>On Sunday, February 5, 2017 at 1:28:46 AM UTC+1, John Larkin wrote: >> On Sat, 4 Feb 2017 15:52:41 -0800 (PST), Klaus Kragelund >> <klauskvik@hotmail.com> wrote: >> >> >On Saturday, February 4, 2017 at 9:18:22 PM UTC+1, John Larkin wrote: >> >> On Sat, 4 Feb 2017 11:58:08 -0800 (PST), tabbypurr@gmail.com wrote: >> >> >> >> >On Saturday, 4 February 2017 18:30:34 UTC, John Larkin wrote: >> >> >> On Sat, 4 Feb 2017 09:32:13 -0800 (PST), tabbypurr wrote: >> >> >> >On Saturday, 4 February 2017 17:16:45 UTC, John Larkin wrote: >> >> > >> >> >> >> A dial-primary (120:240 to whatever) transformer makes a good >> >> >> >> isolation transformer. Use the two primaries and ignore the secondary, >> >> >> >> unless you have some use for it too. >> >> >> > >> >> >> >as long as you don't want too much isolation. What voltage breakdown do you get with the 2 primaries wouund one directly on the other? >> >> > >> >> >> Kilovolts, probably. Test it for margin if you plan to float the load >> >> >> way off ground. >> >> > >> >> >that's at odds with my experience of hipot testing transformers. Enamel on enamel failed below 1kV. Unfortunately I don't remember what voltage it managed. Probably over 500v, but that's not a comfortable margin. >> >> > >> >> > >> >> >> It will have more inter-winding capacitance than one of those >> >> >> extreme-expense isolation things. >> >> > >> >> >Yes. I don't know how much shock current that lets through. >> >> > >> >> > >> >> >NT >> >> >> >> I made a twisted pair of #36 magnet wire and applied DC until it >> >> arced. 1400 volts. >> >> >> >> Somebody should test a few ordinary dual-primary transformers for >> >> breakdown. >> >> >> >Relying on testing insulation is venturing on a slippery slope >> > >> >Then you need to do 100% production testing and getting approval from UL or VDE is VERY difficult and time consuming >> > >> >Cheers >> > >> >Klaus >> >> I assume the op wants to hack one isolation transformer for personal >> use. I don't think he intends to get UL or VDE certification. >> >If he does what you say, he is still required to do it according to the standards.
Required? Do you have cops or soldiers in your country who break in and inspect test benches?
> What happens if he gets a visitor that is electrocuted?
How would that happen? Use a GFD if you are afraid of 120 volts. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sat, 4 Feb 2017 22:19:59 -0800 (PST), Phil Allison
<pallison49@gmail.com> wrote:

>John Larkin wrote: > >> >> >> > >> >> >> >> > >> >> >Relying on testing insulation is venturing on a slippery slope >> >> > >> >> > >> >> I assume the op wants to hack one isolation transformer for personal >> >> use. I don't think he intends to get UL or VDE certification. >> >> >> > >> >** But a single point failure of the enamel, likely from excess pressure, >> > a defect or continuous corona discharge over time would make the unit >> > lethal. >> >> 120 volts is no big deal. I wire everything hot. > > >** But you area reckless maniac who treats NG posting as a joke. > > Advising others to do the same as you chose to is criminally irresponible. > > >> >> And 120v is not going to make corona. >> > >** It can, and the secondary side of the tranny can be floating at some higher voltage. > > You advise is criminally reckless. > > > >> >> Don't be such a wuss. >> > > ** Don't be such a cunt. > > > >> >An isolation transformer for bench work on live electronics is a SAFETY device, protecting human life and it is not rational to make or use a hazardous one. >> > >> >Rational advice is not your forte - is it ? >> >> Silly fears sure aren't. >> > > >** More criminal advice for a notorious asshole. > > Larkin is quite proud of being one. > > > > >.... Phil
You can design electronics, or live life, based on fears, or you can make rational assessments of risk and decide what to do. In today's world, thinking works better, because it lets you do things that other people are afraid to do. -- John Larkin Highland Technology, Inc lunatic fringe electronics