Ferrites: L changes with current change.
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From: Phil Hobbs on 22 Dec 2009 15:06 On 12/22/2009 3:04 PM, Paul Hovnanian P.E. wrote: > Leon wrote: > >> On 21 Dec, 17:30, Jim Thompson<To-Email-Use-The-Envelope-I...(a)My-Web- >> Site.com/Snicker> wrote: >>> On Mon, 21 Dec 2009 11:23:43 -0600, "amdx"<a...(a)knology.net> wrote: >>> >>>> "Jim Thompson"<To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> >>>> wrote in messagenews:c73vi59928raaaseeo0spcb17vut4ddmpj(a)4ax.com... >>>>> On Sun, 20 Dec 2009 23:34:41 -0600, "amdx"<a...(a)knology.net> wrote: >>> >>>>> [snip] >>> >>>>>> Hey Graham, >>>>>> I reposted a graph from Fred Bartoli on >>>>>> alt.binaries.schematics.electronic, it shows >>>>>> inductance dropping with decreasing drive voltage. It doesn't go low >>>>>> enough >>>>>> though. >>>>>> Mike >>> >>>>> Sonnova gun! I wonder what might be causing that? >>> >>>>> Get out your textbooks ;-) >>> >>>>> ...Jim Thompson >>>> Causing what ? This is my third attempt at finding out if my >>>> postulation >>>> has any merit at all. >>>> I've been told forget it, just build the transformer. >>>> It is just a curiosity for me, I have used the same core at 300 watts >>>> power >>>> levels and at microwatt levels. >>>> Would it have been a better transformer at lower frequencies if I had >>>> added more turns. I don't know and >>>> I have know way to measure microvolts >>>> Note his graph only goes down to 2Vrms, I'd like to see a graph down to >>>> 2 microvolts. >>>> Hey Jim, I'm a little surprised at your response, is Phil rubbing off >>>> on >>>> you? >>>> Have a drink of fine wine on me :-) >>>> Mike >>> >>> I was just pointing out that the effect is not unexpected. Inductance >>> is proportional to B/H. >>> >>> ...Jim Thompson >>> -- >>> | James E.Thompson, CTO | mens | >>> | Analog Innovations, Inc. | et | >>> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >>> | Phoenix, Arizona 85048 Skype: Contacts Only | | >>> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | >>> | E-mail Icon athttp://www.analog-innovations.com| 1962 | >>> >>> Help save the environment! >>> Please dispose of socialism properly! >> >> I've seen a VCO circuit using DC current through a winding on a >> ferrite core to control the frequency. > > http://en.wikipedia.org/wiki/Magnetic_amplifier > > I have a couple of old (discrete transistor) power supplies that use a form > of mag amp to control the voltage output from the main transformer so as to > reduce the series transistor dissipation. > Mag amps are _cool_. Slow, bulky, and heavy, but bulletproof and highly effective. Cheers Phil Hobbs
From: Tim Williams on 22 Dec 2009 15:50 They're not as outdated as you'd think. Ponder this: all ATX power supplies use a power transformer with 5 and 12V windings. Where does the 3.3 come from? Hint: the series inductor that "filters" the 3.3V supply is wound on a metglas toroid! Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "Paul Hovnanian P.E." <paul(a)hovnanian.com> wrote in message news:DvKdnZ5-h5mPu6zWnZ2dnUVZ_jxi4p2d(a)posted.isomediainc... > Leon wrote: > >> On 21 Dec, 17:30, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My-Web- >> Site.com/Snicker> wrote: >>> On Mon, 21 Dec 2009 11:23:43 -0600, "amdx" <a...(a)knology.net> wrote: >>> >>> >"Jim Thompson" <To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> >>> >wrote in messagenews:c73vi59928raaaseeo0spcb17vut4ddmpj(a)4ax.com... >>> >> On Sun, 20 Dec 2009 23:34:41 -0600, "amdx" <a...(a)knology.net> wrote: >>> >>> >> [snip] >>> >>> >>> Hey Graham, >>> >>> I reposted a graph from Fred Bartoli on >>> >>>alt.binaries.schematics.electronic, it shows >>> >>>inductance dropping with decreasing drive voltage. It doesn't go low >>> >>>enough >>> >>>though. >>> >>> Mike >>> >>> >> Sonnova gun! � I wonder what might be causing that? >>> >>> >> Get out your textbooks ;-) >>> >>> >> ...Jim Thompson >>> > Causing what ? This is my third attempt at finding out if my >>> > postulation >>> >has any merit at all. >>> >I've been told forget it, just build the transformer. >>> > It is just a curiosity for me, I have used the same core at 300 watts >>> > power >>> >levels and at microwatt levels. >>> >Would it have been a better transformer at lower frequencies if I had >>> >added more turns. I don't know and >>> >I have know way to measure microvolts >>> >Note his graph only goes down to 2Vrms, I'd like to see a graph down to >>> >2 microvolts. >>> > Hey Jim, I'm a little surprised at your response, is Phil rubbing off >>> > on >>> >you? >>> > Have a drink of fine wine on me :-) >>> > Mike >>> >>> I was just pointing out that the effect is not unexpected. � Inductance >>> is proportional to B/H. >>> >>> ...Jim Thompson >>> -- >>> | James E.Thompson, CTO � � � � � � � � � � � � � � | � � mens � � | >>> | Analog Innovations, Inc. � � � � � � � � � � � � | � � et � � � | >>> | Analog/Mixed-Signal ASIC's and Discrete Systems � | � � manus � � | >>> | Phoenix, Arizona � 85048 � � Skype: Contacts Only � | � � � � � � | >>> | Voice:(480)460-2350 � Fax: Available upon request | � Brass Rat � | >>> | E-mail Icon athttp://www.analog-innovations.com| � � 1962 � � | >>> >>> Help save the environment! >>> Please dispose of socialism properly! >> >> I've seen a VCO circuit using DC current through a winding on a >> ferrite core to control the frequency. > > http://en.wikipedia.org/wiki/Magnetic_amplifier > > I have a couple of old (discrete transistor) power supplies that use a > form > of mag amp to control the voltage output from the main transformer so as > to > reduce the series transistor dissipation. > > -- > Paul Hovnanian paul(a)hovnanian.com > ---------------------------------------------------------------------- > Have gnu, will travel.
From: amdx on 23 Dec 2009 11:33 >> >> Guesses are a waste of time. Either you KNOW or DON'T KNOW ! > > > Thanks Eeyore, finally someone that KNOWS this stuff. > I have a 50 ohm to 200 ohm transformer, 4 turns to 8 turns on a FT37 > toroid of material 75. > I have 2 microvolts driving the 50 ohm primary at 1Mhz. > The effective volume of the core .163 cm^3 > What is the B field? > You will KNOW what other data you need if any (I'd have to guess) so let > me KNOW and I'll > look it up for you. > It sure will be interesting to see how far off my guess was. > > >> At what frequency ? And that's the vector sum of Xj ohms + Rdc ohms by >> the way. > > 1Mhz, Xj=200 Rdc=0.025 > > >>> and the transformer will not work as designed. >>> Since I have never seen this discussed and people build working radios >>> everyday, I'm probably all wrong, but I'm not sure where. >> >> Take the advice and get the Epcos program. It tells you all about >> saturation and change in inductance with >amps. > > I'll look at it, when you calculate the B field quantity, we'll see if > the Epcos program > goes to that low level. > Thanks again for your help, > Mike > > Graham where did you go, To quote you "Either you KNOW or DON'T KNOW !" Three days, no response, does that mean you don't KNOW? Mike
From: Paul Hovnanian P.E. on 23 Dec 2009 14:54 Phil Hobbs wrote: > On 12/22/2009 3:04 PM, Paul Hovnanian P.E. wrote: >> Leon wrote: >> >>> On 21 Dec, 17:30, Jim Thompson<To-Email-Use-The-Envelope-I...(a)My-Web- >>> Site.com/Snicker> wrote: >>>> On Mon, 21 Dec 2009 11:23:43 -0600, "amdx"<a...(a)knology.net> wrote: >>>> >>>>> "Jim Thompson"<To-Email-Use-The-Envelope-I...(a)My-Web-Site.com/Snicker> >>>>> wrote in messagenews:c73vi59928raaaseeo0spcb17vut4ddmpj(a)4ax.com... >>>>>> On Sun, 20 Dec 2009 23:34:41 -0600, "amdx"<a...(a)knology.net> wrote: >>>> >>>>>> [snip] >>>> >>>>>>> Hey Graham, >>>>>>> I reposted a graph from Fred Bartoli on >>>>>>> alt.binaries.schematics.electronic, it shows >>>>>>> inductance dropping with decreasing drive voltage. It doesn't go low >>>>>>> enough >>>>>>> though. >>>>>>> Mike >>>> >>>>>> Sonnova gun! I wonder what might be causing that? >>>> >>>>>> Get out your textbooks ;-) >>>> >>>>>> ...Jim Thompson >>>>> Causing what ? This is my third attempt at finding out if my >>>>> postulation >>>>> has any merit at all. >>>>> I've been told forget it, just build the transformer. >>>>> It is just a curiosity for me, I have used the same core at 300 watts >>>>> power >>>>> levels and at microwatt levels. >>>>> Would it have been a better transformer at lower frequencies if I had >>>>> added more turns. I don't know and >>>>> I have know way to measure microvolts >>>>> Note his graph only goes down to 2Vrms, I'd like to see a graph down >>>>> to 2 microvolts. >>>>> Hey Jim, I'm a little surprised at your response, is Phil rubbing off >>>>> on >>>>> you? >>>>> Have a drink of fine wine on me :-) >>>>> Mike >>>> >>>> I was just pointing out that the effect is not unexpected. Inductance >>>> is proportional to B/H. >>>> >>>> ...Jim Thompson >>>> -- >>>> | James E.Thompson, CTO | mens | >>>> | Analog Innovations, Inc. | et | >>>> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >>>> | Phoenix, Arizona 85048 Skype: Contacts Only | | >>>> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | >>>> | E-mail Icon athttp://www.analog-innovations.com| 1962 | >>>> >>>> Help save the environment! >>>> Please dispose of socialism properly! >>> >>> I've seen a VCO circuit using DC current through a winding on a >>> ferrite core to control the frequency. >> >> http://en.wikipedia.org/wiki/Magnetic_amplifier >> >> I have a couple of old (discrete transistor) power supplies that use a >> form of mag amp to control the voltage output from the main transformer >> so as to reduce the series transistor dissipation. >> > > Mag amps are _cool_. Slow, bulky, and heavy, but bulletproof and highly > effective. Not much space for them left in today's technology. But its sad to see how many people have forgotten about (or never learned) the principles behind this kind of stuff. -- Paul Hovnanian paul(a)hovnanian.com ---------------------------------------------------------------------- Have gnu, will travel.
From: Joel Koltner on 23 Dec 2009 16:17
"Paul Hovnanian P.E." <paul(a)hovnanian.com> wrote in message news:NfGdndkBDcS16K_WnZ2dnUVZ_odi4p2d(a)posted.isomediainc... > Not much space for them left in today's technology. But its sad to see how > many people have forgotten about (or never learned) the principles behind > this kind of stuff. I can understand colleges not bothering with mag amps and toobs and TWTs and what-not in the regular circuits classes anymore, but it sure seems like there should be an elective in bigger colleges for a class on "all the technology you've never heard of...but might just want to know about for certain specialized applications..." OK, maybe a book on the topic would be more like it... there are certainly plenty of books on these older technologies, although nothing that tries to group them all together in one... |