Forums

transformer thermals

Started by Unknown August 4, 2020
Phil Allison <pallison49@gmail.com> wrote:
> Cydrome Leader is an IDIOT wrote: > > ================================ > > >> >> >> >> > So I ran it for a few hours with 10 amps DC in the primary. Temp rise >> >> > was about 26C in free air. I think people design transformers for >> >> > equal copper loss in the primary and secondary, so temp rise would >> >> > double when loaded in the system. >> >> >> >> What about the heat generated by losses in the secondary? >> > >> > >> > ** Doubles the temp rise - as JL just claimed. >> >> It sounded like the double the heat assumption was from the 50% of losses >> being in the iron, when the transformer is used with AC. > > ** You on drugs ?? > > >> Even if you >> double the primary resistive loses to account for the secondary, the core >> is still being left out. That's how I read it. > > ** JL neglected it as he knows it is trivial. > > >> >> As for the PF has no effect statement, I've never really understood the >> point on the VA in and VA out ratings on some toroidal transformers. >> Isolation transfomers are usually marked in a more sensible way like >> "input 120VAC 8.4A, output 120VAC 8.0A". While these are safe use ratings, >> it still doesn't answer the question about efficiency at no to full load. >> You can only guess the worst case heat losses. >> > > ** My god you are stupid. > > Max heat loss happens at max load, always.
Wow, you're finally catching up. Now go ahead and re-read my comment about the sillyness of VA in and VA out ratings on small toroidal transformers.
legg <legg@nospam.magma.ca> wrote:
> On Thu, 6 Aug 2020 16:41:03 -0700 (PDT), Phil Allison > <pallison49@gmail.com> wrote: > >>legg wrote: >> >>========== >> >> >>> For windings, it's a 'fill factor'. >>> >>> If you check the ratio of copper vs air in the inner >>> diameter of a toroid, as the fill approaches a certain >>> percentage, you'll see a diminishing return for agravated >>> difficulty in fabrication. >> >>** Cost is everything in manufacture. >> >>But as here like to consider what physics allows, it is clearly a fact that filling a toroidal with as much copper as possible maximises the VA for a given core. >> >>This IS the practice for all other types of core shape. >> >>Most toroidals are low and flat - again not optimum but liked by many customers. Same goes for R-cores and U cores which result in low height products. >> >> >> >>.... Phil > > Those last few turns also have the longest length > per turn, further diminishing their 'return'. > > The 'practice' is to assume a fill factor of less > than 80%, to allow for insulation, wire shape and > cover. For mains voltage wall thickness, creepage > spacing, and bobbin tolerancing, it's even worse. > > Toroids depend upon 3xlayer film overlapping weave for > reinforced layering and core or outer wrap, though > some cores use fitted caps at the expense of efficiency. > > Low and flat toroids are a 'style' (at the expense of > efficiency) - the most efficient physical ratio being > roughly 2.2:1 / OD:H. > > High frequency stuff . . . . > > RL
How would you rate this cutie? https://www.overunity.com/7833/thane-heins-bi-toroid-transformer/dlattach/attach/48359/image/ I didn't look at the site, but it's clearly some free energy nonsense project. Maybe the entire thing spins on a tesla turbine or overbalance wheel. I like how it's the most complicated way to come up with a three legged tape wound core.
Cydrome Leader is a retarded NUT case wrote:


===========================================
> > > > ** You on drugs ?? > > > > > > ** My god you are stupid. > > > > Max heat loss happens at max load, always. > > Wow, you're finally catching up. >
** I'm way ahead of morons lie you.
> Now go ahead and re-read my comment about > the sillyness of VA in and VA out ratings on small toroidal transformers.
** You never made any. .... Phil
On Sat, 8 Aug 2020 05:54:48 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>jlarkin@highlandsniptechnology.com wrote: >> On Thu, 6 Aug 2020 06:57:07 +0000 (UTC), Cydrome Leader >> <presence@MUNGEpanix.com> wrote: >> >>>jlarkin@highlandsniptechnology.com wrote: >>>> On Wed, 5 Aug 2020 01:21:10 -0700 (PDT), Phil Allison >>>> <pallison49@gmail.com> wrote: >>>> >>>>>Cydrome Leader is Funny: >>>>> >>>>>======================= >>>>>> >>>>>> > So I ran it for a few hours with 10 amps DC in the primary. Temp rise >>>>>> > was about 26C in free air. I think people design transformers for >>>>>> > equal copper loss in the primary and secondary, so temp rise would >>>>>> > double when loaded in the system. >>>>>> >>>>>> What about the heat generated by losses in the secondary? >>>>> >>>>> >>>>>** Doubles the temp rise - as JL just claimed. >>>>> >>>>> >>>>>> > https://www.dropbox.com/s/ylm8dc1e14dwv7y/P900_Xfmr_Thermal.jpg?raw=1 >>>>>> > >>>>>> > https://www.dropbox.com/s/5b55ybfoq2pkp9v/P900_Xfmr_Thermal_2.jpg?raw=1 >>>>>> >>>>>> You can even see on the label (looks sort of like a Noratel) the input is >>>>>> 266VA and output is rated 240VA. So depending on power factor at full >>>>>> load, it could be upto 26 watts of loss, although I doubt a toroid that >>>>>> size would have such a poor efficiency. The iron losses will surely be >>>>>> less than 50% on a toroid. Maybe the maker can tell you the ratio? >>>>>> >>>> >>>> This transformer was made for us by Amgis. I specified it so I know >>>> the ratios: 1 : 1.4 : 1.4 : 1.4 : 1.4. We have a relay board that >>>> switches the secondaries to get four output voltage ranges. >>> >>>Are these ratios exact or is there a fudge factor for losses at rated >>>load? >> >> Exact turns ratio. We know the other parameters: wire resistance, mag >> inductance, leakage inductance, SRF, saturation. We plug all that into >> the system Spice model. > >How did that work out? Did you give rought specs and the then the >manufacture provided full expected specs?
Pretty much. I specified the voltages, power levels, turns ratio, frequency range, and suggested a stock Hammond part as being about the right size and mounting. The Hammond part guided me as to what was reasonable; I didn't have to do any real magnetics calculations, just scale that transformer a little. They responded with a more detailed spec with resistances, inductances, wire colors, things like that. That looked good so I told them to go.
> >> Just curious. Retired transformer designer friend seemed to spend a >>>bit of his time trying to get "the facts" from customers to make designs >>>that would actually work under load. The stubborn customers would get full >>>production runs of stuff that met specs, but didn't work for the >>>application. >>> >>>>>** PF has no effect - VA is all that matters, effectively just the RMS current. Iron losses are a watt or so per kg or iron. I mag is tiny. >>>>> >>>>>So 20 watts copper loss, 6 watts for iron. >>>>> >>>>>Regulation about 8%. >>>>> >>>>>Toriods are very simple. >>>>> >>>>> >>>>>.... Phil >>>> >>>> Unloaded, the AC operating primary current is essentially zero, so I >>>> don't think core loss is significant. >>>> >>>> As an alternator simulator, voltage increases with frequency, which >>>> keeps Imag low on the low end. >>>> >>>> It's a weird application. We specialize in weird. >>> >>>Was amgis friendly about making samples? >> >> Not free samples, but I didn't ask for that. We placed a PO that >> included a few first-articles for verification, with the rest shipped >> on approval. > >Sounds reasonable.
I'd used them before, and the production requirement was real, so that was a good way to work with them. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
On Thu, 6 Aug 2020 03:57:22 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

>Cydrome Leader is an IDIOT wrote: > >================================ > > >> >> >> >> > So I ran it for a few hours with 10 amps DC in the primary. Temp rise >> >> > was about 26C in free air. I think people design transformers for >> >> > equal copper loss in the primary and secondary, so temp rise would >> >> > double when loaded in the system. >> >> >> >> What about the heat generated by losses in the secondary? >> > >> > >> > ** Doubles the temp rise - as JL just claimed. >> >> It sounded like the double the heat assumption was from the 50% of losses >> being in the iron, when the transformer is used with AC. > >** You on drugs ??
I am! -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard