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Overvoltage on transformer secondary

Started by Unknown November 28, 2017
On Tuesday, November 28, 2017 at 7:12:40 PM UTC-5, Steve Wilson wrote:
> George Herold <gherold@teachspin.com> wrote: > > > On Tuesday, November 28, 2017 at 12:46:52 PM UTC-5, > > anti...@math.uni.wroc.pl wrote: > >> > Do you have a link to article, or is it in his trouble shooting book? > >> > then give a page number. > > >> I followed links that Steve Wilson gave: > > >> http://www.introni.it/pdf/Bob%20Pease%20Lab%20Notes%20Part%208.pdf > > >> The specific text is in third paragraph on page 28 (using .pdf page > >> numbers). > > > Thanks, maybe my Xmas gift can be some sort of e-reader. > > > Otherwise, I've hardly read any of that... lucky me. :^) > > > George H. > > Just curious, why do you need an e-reader to view a PDF file? How do you > read datasheets that are usually in PDF format?
Oh, I wanted to curl up with B. Pease (and others) in bed and read them as I go to sleep. I might even walk around and read one. (You'll find me with my nose in a book, more often than not.) George H.
> > What operating system do you run that doesn't have a pdf reader available? > > If it's Windows, have you tried PDF Xchange? It runs on XP and later: > > https://www.tracker-software.com/product/pdf-xchange-viewer > > If it's Linux, there should be a multitude of PDF readers available. I use > the HP device manager for the HP 3050A Deskjet. This installs on Ubuntu > 10.04, and has an excellent built-in PDF reader. > > I never use it to print anything, but it has an excellent scanner that can > output PDF files. As usual for HP, it had a very low price and was further > marked down for clearance. Irresistable. It was one of the more sane > purchases I have ever made.
On Tuesday, November 28, 2017 at 9:17:16 PM UTC-8, P E Schoen wrote:
> "Martin Riddle" wrote in message > news:s2es1dt2bqsu2ngljgfn04j0inbahdaekv@4ax.com... > > >> Yep, in high power transformer based supplies you can get core > >> saturation.
> > Forgot to mention 'Core walking' is a somewhat milder case. Capacitive > > coupling can alieviate that.
> I think one company's circuit breaker test set incorporated a gradually > changing phase firing on the controller to demagnetize the core. But IIRC it > had to be done after the breaker tripped.
There's similar trickery used in magnetic chucks, so they respond to switching OFF by releasing their cargo promptly.
On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highland_snip_technology.com> wrote: > >> On Tue, 28 Nov 2017 14:51:06 +0000 (UTC), antispam@math.uni.wroc.pl >> wrote: > >>>I his article about troubleshooting () Bob Pease writes: >>> >>>: If the power line switch was turned off at exactly the wrong time of >>>: the cycle, the flux in the transformer steel core could be >>>: strored at high level. Then, if the line power switch was >>>: reconnected at exactly the wrong time in the cycle, the flux >>>: in the transformer would ontinue to build up until the >>>: transformer saturated and produced a voltage spike of 70 to 90V on >>>: its secondary. > >>>Possibility of saturation is well-known. However, getting voltage >>>spike on secondary due to saturation looks strange: > >>>1) saturation means that high current in primary gives only tiny >>> increase of flux. SEM is proportional to derivative of flux, so SEM >>> is limited. In fact, high current in primary is because SEM is to >>> small to oppose line voltage. >>>2) Ignoring stray inductance SEM on the secondary is transformer >>> constant times SEM on the primary. Ohmic losses mean that >>> SEM on primary is lower than voltage on the primary, SEM on >>> secondary is higher than voltage on secondary. I would expect >>> similar effect from stray inductance. > >>>So I do not see how saturation can lead to overvoltage on secondary. > >> Not on the half-cycle that saturates the core. But maybe on the next >> opposite-sign half cycle, the one that yanks the core out of >> saturation. > >> That will happen when there is a lot of magnetizing (actually >> demagnetizing) current. > >Instead of speculating, the correct procedure would have been to measure >the pulse with a scope, something that Bob P. should have done in the first >place.
I've seen it happen, big voltage spikes when a sine wave drove a saturating inductor. -- John Larkin Highland Technology, Inc lunatic fringe electronics
John Larkin <jjlarkin@highlandtechnology.com> wrote:

> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote: > I've seen it happen, big voltage spikes when a sine wave drove a > saturating inductor.
What kind of news client do you have that can pick up a post two and a half months old?
On Sat, 10 Feb 2018 20:24:30 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote: >> I've seen it happen, big voltage spikes when a sine wave drove a >> saturating inductor. > >What kind of news client do you have that can pick up a post two and a half >months old?
What client do you have that can't access a few years' worth of Usenet? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Saturday, February 10, 2018 at 2:38:23 PM UTC-5, John Larkin wrote:
> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote: > > >John Larkin <jjlarkin@highland_snip_technology.com> wrote: > > > >> On Tue, 28 Nov 2017 14:51:06 +0000 (UTC), antispam@math.uni.wroc.pl > >> wrote: > > > >>>I his article about troubleshooting () Bob Pease writes: > >>> > >>>: If the power line switch was turned off at exactly the wrong time of > >>>: the cycle, the flux in the transformer steel core could be > >>>: strored at high level. Then, if the line power switch was > >>>: reconnected at exactly the wrong time in the cycle, the flux > >>>: in the transformer would ontinue to build up until the > >>>: transformer saturated and produced a voltage spike of 70 to 90V on > >>>: its secondary. > > > >>>Possibility of saturation is well-known. However, getting voltage > >>>spike on secondary due to saturation looks strange: > > > >>>1) saturation means that high current in primary gives only tiny > >>> increase of flux. SEM is proportional to derivative of flux, so SEM > >>> is limited. In fact, high current in primary is because SEM is to > >>> small to oppose line voltage. > >>>2) Ignoring stray inductance SEM on the secondary is transformer > >>> constant times SEM on the primary. Ohmic losses mean that > >>> SEM on primary is lower than voltage on the primary, SEM on > >>> secondary is higher than voltage on secondary. I would expect > >>> similar effect from stray inductance. > > > >>>So I do not see how saturation can lead to overvoltage on secondary. > > > >> Not on the half-cycle that saturates the core. But maybe on the next > >> opposite-sign half cycle, the one that yanks the core out of > >> saturation. > > > >> That will happen when there is a lot of magnetizing (actually > >> demagnetizing) current. > > > >Instead of speculating, the correct procedure would have been to measure > >the pulse with a scope, something that Bob P. should have done in the first > >place. > > I've seen it happen, big voltage spikes when a sine wave drove a > saturating inductor.
That kinda defines how to make a flux gate magnetometer. Going one way (out I think) is bigger cause of the dL/dt term. George H.
> > > -- > > John Larkin Highland Technology, Inc > > lunatic fringe electronics
John Larkin <jjlarkin@highlandtechnology.com> wrote:

> On Sat, 10 Feb 2018 20:24:30 GMT, Steve Wilson <no@spam.com> wrote:
>>John Larkin <jjlarkin@highlandtechnology.com> wrote:
>>> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote:
>>> I've seen it happen, big voltage spikes when a sine wave drove a >>> saturating inductor.
>>What kind of news client do you have that can pick up a post two and a >>half months old?
> What client do you have that can't access a few years' worth of > Usenet?
I can go back hundreds of thousands of posts. It's picking the desired one that is the problem.
On Sat, 10 Feb 2018 20:57:59 GMT, Steve Wilson <no@spam.com> wrote:

>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> On Sat, 10 Feb 2018 20:24:30 GMT, Steve Wilson <no@spam.com> wrote: > >>>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >>>> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote: > >>>> I've seen it happen, big voltage spikes when a sine wave drove a >>>> saturating inductor. > >>>What kind of news client do you have that can pick up a post two and a >>>half months old? > >> What client do you have that can't access a few years' worth of >> Usenet? > >I can go back hundreds of thousands of posts. It's picking the desired one >that is the problem.
It's only a newsgroup. It doesn't matter. -- John Larkin Highland Technology, Inc lunatic fringe electronics
John Larkin <jjlarkin@highlandtechnology.com> wrote:

> On Sat, 10 Feb 2018 20:57:59 GMT, Steve Wilson <no@spam.com> wrote:
>>John Larkin <jjlarkin@highlandtechnology.com> wrote:
>>> On Sat, 10 Feb 2018 20:24:30 GMT, Steve Wilson <no@spam.com> wrote:
>>>>John Larkin <jjlarkin@highlandtechnology.com> wrote:
>>>>> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote:
>>>>> I've seen it happen, big voltage spikes when a sine wave drove a >>>>> saturating inductor.
>>>>What kind of news client do you have that can pick up a post two and a >>>>half months old?
>>> What client do you have that can't access a few years' worth of >>> Usenet?
>>I can go back hundreds of thousands of posts. It's picking the desired one >>that is the problem.
> It's only a newsgroup. It doesn't matter.
Are you on your period all the time, or only on days ending in "Y"?
On 02/10/2018 03:57 PM, Steve Wilson wrote:
> John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> On Sat, 10 Feb 2018 20:24:30 GMT, Steve Wilson <no@spam.com> wrote: > >>> John Larkin <jjlarkin@highlandtechnology.com> wrote: > >>>> On Tue, 28 Nov 2017 23:50:25 GMT, Steve Wilson <no@spam.com> wrote: > >>>> I've seen it happen, big voltage spikes when a sine wave drove a >>>> saturating inductor. > >>> What kind of news client do you have that can pick up a post two and a >>> half months old? > >> What client do you have that can't access a few years' worth of >> Usenet? > > I can go back hundreds of thousands of posts. It's picking the desired one > that is the problem. >
Try turning on threading. In Thunderbird, Nov 27 is only four or five screenfuls back. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com