On Sunday, February 5, 2017 at 10:54:05 AM UTC-5, John Larkin wrote:>> > 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. >I am not convinced. On a 500 va transformer the amount of voltage per turn is about half a volt. So with one turn difference, I do not think it would fry the transformer. You might be right, but I am sceptical. Dan> -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
Transformer Question
Started by ●February 2, 2017
Reply by ●February 5, 20172017-02-05
Reply by ●February 5, 20172017-02-05
On Sun, 5 Feb 2017 07:08:49 +0000 (UTC), Ralph Barone <ralph@invalid.com> wrote:>whit3rd <whit3rd@gmail.com> wrote: >> >> **note, Tripp-Lite sells "isolation transformers" with the neutral of the secondary >> bonded to ground/case. That is NOT what you want, if you might be poking into a live >> circuit. If the specs mention "Neutral to ground bonding at the secondary" >> it means you can get a shock from isolated HOT to ground. >> > >Yeah, got caught by that one once on a Hammond isolation transformer. >Plugged a scope into the isolation transformer to float it, hooked up the >ground lead of the scope probe and shorted my circuit to ground. As per >CSA, the ground pin in the receptacle of an isolation transformer must be >connected to ground (which kinda ruins the "isolation" function of the >device).We have a Tek TPS2012 scope, fully isolated. It's great. You can clip a probe ground lead to anything. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 5, 20172017-02-05
On Sun, 5 Feb 2017 07:35:09 -0800 (PST), "dcaster@krl.org" <dcaster@krl.org> wrote:>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. > > DanOther than adding some impedance, why is that stupid? -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 5, 20172017-02-05
On Sat, 4 Feb 2017 22:54:24 -0800 (PST), the renowned Phil Allison <pallison49@gmail.com> wrote:> >If you think it must have come fitted inside some flea-bag Chines product - it did not. The tranny was in a Crown Audio (of the USA) professional power amplifier model XLS602. See internal pic. > > http://cdn.avsforum.com/3/38/38365662_vbattach143596.jpegInteresting! Thanks. Indeed I would have guessed that came from some basement Ali manufacturer. Someone at Crown needs a attitude adjustment.> >Understandably, I was very reluctant to buy another example and luckily had on hand a suitable toroidal of Italian manufacture that was close enough in ratings to do the job.Until the Italian company fires their engineers and starts sourcing from the lowest bidder with zero factory inspections or approvals. --sp -- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8
Reply by ●February 5, 20172017-02-05
On 05/02/17 16:48, John Larkin wrote:> 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. > [..]I wish! I'd *expect* transformers to be amazingly reliable, but in my experience they aren't, even under moderately light loads. Jeroen Belleman
Reply by ●February 5, 20172017-02-05
On Sun, 05 Feb 2017 19:28:19 +0100, Jeroen Belleman <jeroen@nospam.please> wrote:>On 05/02/17 16:48, John Larkin wrote: > >> 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. >> [..] > >I wish! I'd *expect* transformers to be amazingly reliable, but in >my experience they aren't, even under moderately light loads. > >Jeroen BellemanI've used thousands of 120:240 power transformers, and none have failed in the field from defects of design or construction. We did have one toroid that ran into saturation, and got hot, at maximum line voltage and 50 Hz, at a UL test lab. The manufacturer had to modify the design; I think they changed the core material. There are no doubt cheap, nasty transformers around; don't buy transformers from chop shops. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●February 5, 20172017-02-05
Den søndag den 5. februar 2017 kl. 19.54.10 UTC+1 skrev John Larkin:> On Sun, 05 Feb 2017 19:28:19 +0100, Jeroen Belleman > <jeroen@nospam.please> wrote: > > >On 05/02/17 16:48, John Larkin wrote: > > > >> 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. > >> [..] > > > >I wish! I'd *expect* transformers to be amazingly reliable, but in > >my experience they aren't, even under moderately light loads. > > > >Jeroen Belleman > > I've used thousands of 120:240 power transformers, and none have > failed in the field from defects of design or construction. We did > have one toroid that ran into saturation, and got hot, at maximum line > voltage and 50 Hz, at a UL test lab. The manufacturer had to modify > the design; I think they changed the core material. > > There are no doubt cheap, nasty transformers around; don't buy > transformers from chop shops. >http://s240.photobucket.com/user/inspector72/media/funny%20stuff/thirdworldarcwelder3.jpg.html
Reply by ●February 5, 20172017-02-05
On Sunday, 5 February 2017 19:07:31 UTC, Lasse Langwadt Christensen wrote:> Den søndag den 5. februar 2017 kl. 19.54.10 UTC+1 skrev John Larkin: > > On Sun, 05 Feb 2017 19:28:19 +0100, Jeroen Belleman > > <jeroen@nospam.please> wrote: > > > > >On 05/02/17 16:48, John Larkin wrote: > > > > > >> 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. > > >> [..] > > > > > >I wish! I'd *expect* transformers to be amazingly reliable, but in > > >my experience they aren't, even under moderately light loads. > > > > > >Jeroen Belleman > > > > I've used thousands of 120:240 power transformers, and none have > > failed in the field from defects of design or construction. We did > > have one toroid that ran into saturation, and got hot, at maximum line > > voltage and 50 Hz, at a UL test lab. The manufacturer had to modify > > the design; I think they changed the core material. > > > > There are no doubt cheap, nasty transformers around; don't buy > > transformers from chop shops. > > > > http://s240.photobucket.com/user/inspector72/media/funny%20stuff/thirdworldarcwelder3.jpg.htmlAfter several minutes of that page loading a vast list of crap but still no picture I gave up. NT
Reply by ●February 5, 20172017-02-05
Den søndag den 5. februar 2017 kl. 21.10.09 UTC+1 skrev tabb...@gmail.com:> On Sunday, 5 February 2017 19:07:31 UTC, Lasse Langwadt Christensen wrote: > > Den søndag den 5. februar 2017 kl. 19.54.10 UTC+1 skrev John Larkin: > > > On Sun, 05 Feb 2017 19:28:19 +0100, Jeroen Belleman > > > <jeroen@nospam.please> wrote: > > > > > > >On 05/02/17 16:48, John Larkin wrote: > > > > > > > >> 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. > > > >> [..] > > > > > > > >I wish! I'd *expect* transformers to be amazingly reliable, but in > > > >my experience they aren't, even under moderately light loads. > > > > > > > >Jeroen Belleman > > > > > > I've used thousands of 120:240 power transformers, and none have > > > failed in the field from defects of design or construction. We did > > > have one toroid that ran into saturation, and got hot, at maximum line > > > voltage and 50 Hz, at a UL test lab. The manufacturer had to modify > > > the design; I think they changed the core material. > > > > > > There are no doubt cheap, nasty transformers around; don't buy > > > transformers from chop shops. > > > > > > > http://s240.photobucket.com/user/inspector72/media/funny%20stuff/thirdworldarcwelder3.jpg.html > > After several minutes of that page loading a vast list of crap but still no picture I gave up. >http://i240.photobucket.com/albums/ff150/inspector72/funny%20stuff/thirdworldarcwelder3.jpg better?
Reply by ●February 5, 20172017-02-05
On Sunday, 5 February 2017 20:28:59 UTC, Lasse Langwadt Christensen wrote:> Den søndag den 5. februar 2017 kl. 21.10.09 UTC+1 skrev tabby: > > On Sunday, 5 February 2017 19:07:31 UTC, Lasse Langwadt Christensen wrote: > > > Den søndag den 5. februar 2017 kl. 19.54.10 UTC+1 skrev John Larkin: > > > > On Sun, 05 Feb 2017 19:28:19 +0100, Jeroen Belleman > > > > <jeroen@nospam.please> wrote: > > > > >On 05/02/17 16:48, John Larkin wrote: > > > > > > > > > >> 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. > > > > >> [..] > > > > > > > > > >I wish! I'd *expect* transformers to be amazingly reliable, but in > > > > >my experience they aren't, even under moderately light loads. > > > > > > > > > >Jeroen Belleman > > > > > > > > I've used thousands of 120:240 power transformers, and none have > > > > failed in the field from defects of design or construction. We did > > > > have one toroid that ran into saturation, and got hot, at maximum line > > > > voltage and 50 Hz, at a UL test lab. The manufacturer had to modify > > > > the design; I think they changed the core material. > > > > > > > > There are no doubt cheap, nasty transformers around; don't buy > > > > transformers from chop shops. > > > > > > > > > > http://s240.photobucket.com/user/inspector72/media/funny%20stuff/thirdworldarcwelder3.jpg.html > > > > After several minutes of that page loading a vast list of crap but still no picture I gave up. > > > > http://i240.photobucket.com/albums/ff150/inspector72/funny%20stuff/thirdworldarcwelder3.jpg > > better?I suspected it might be that pic :) Love it - but he should really be using some cardboard as insulation. The weld appearance suggests he's using a coathanger as welding rod, a sure way to get a lousy weld. NT
