John Larkin wrote: ------------------- >> >BTW, what is the source of this and similar rules of thumb (e.g. equal > >copper and core losses)? Logic says that one should always design for > >minimal total losses, given the economic constraints. > > > > Best regards, Piotr > > I don't think transformers are usually designed for equal core and > copper losses. >** The condition for *max efficiency* IS when Cu and Fe losses are equal but this only affects the energy bill you have to pay. For all other purposes, throughput or VA rating is what matters for a given size and cost. Filling the available winding space with copper and operating the core close to its saturation limit results in the most economical transformer. Transformer "efficiency" is a variable, depending on load. "Rated efficiency" is quoted at full load. .... Phil
transformer thermals
Started by ●August 4, 2020
Reply by ●August 6, 20202020-08-06
Reply by ●August 6, 20202020-08-06
On Wednesday, August 5, 2020 at 6:36:17 PM UTC-7, Phil Allison wrote:> whit3rd ...> > > > It is going to be hotter with AC. > > > > > > Hardly any. > > > > Iron lossses due to eddy currents and hysteresis aren't insignificant. > > > > ** They are with GOSS tape wound into a toroid. > > > > It this for variable frequency use? > > Those iron losses are frequency-dependent. > > it might take a bunch of testing to characterize. > > ** No it wont. > > JL's tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage.Iron losses are zero with DC testing, and certainly not 'lower' at all higher frequencies. Core magnetization goes down with frequency, but losses go UP when the secondary doesn't draw current. And, the core shape determines the magnetization profile, at higher frequencies it's unclear whether the entire core shares the induction (so the behavior at 4 kHz ought to be tested... at 4 kHz.
Reply by ●August 6, 20202020-08-06
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.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. 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.>> > 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? >> > > ** 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.Could be- I have no references for core loss in small toroidal tranformers handy. It should be fixed though and less than the losses needed to magnetize the core with no load, so yeah, the 20 + 6 looks ok. 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.> > Regulation about 8%. > > Toriods are very simple. > > > .... Phil
Reply by ●August 6, 20202020-08-06
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? 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?
Reply by ●August 6, 20202020-08-06
Phil Allison <pallison49@gmail.com> wrote:> Piotr Wyderski wrote: > > =============================== >> > >> > I think people design transformers for >> > equal copper loss in the primary and secondary >> >> BTW, what is the source of this and similar rules of thumb (e.g. equal >> copper and core losses)? Logic says that one should always design for >> minimal total losses, given the economic constraints. >> > > ** The source is simple calculus that finds the minimum or maximum in a curve. It's also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings. > > The issue with tape wound toriodals is their very sharp saturation > curves - forcing the designer to keep away from that condition. Hence > their low contribution to heat from the core. > > Commercial toroidals are made using a clever machine passing wire > through the centre hole - this sets a limit on the amount of copper that > can be used.It looks like they could dump more copper on the typical toroidal transfomer. The diameters for large ones get huge, with gigantic empty holes in the middle. The stacking factor, if that's the right term is terrible on most toroids. Not sure why this is though. They seems to scale the wide and thin vs. taller with more copper stuffed in the hole and around the rest of it. >> I know of one amplifier designer who at my suggestion had the winder use > his machine for the primary and wind the secondary by hand in order to > fill the hole almost completely. This almost doubled the amount of > copper used. > > Along with a bit of fan cooling, the result was a 3kW rated amplfier > that used a 1kW size transformer core.Was the core really more than 3x oversize?
Reply by ●August 6, 20202020-08-06
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. 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. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 6, 20202020-08-06
On Thu, 6 Aug 2020 06:41:36 +0000 (UTC), Cydrome Leader <presence@MUNGEpanix.com> wrote:>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. > >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. 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.No, I'm assuming zero core losses, but figure the copper loss will double if I have 10 amps RMS AC into the primary and load the secondary to get there. That's probably close. Any decent power transformer runs cold at rated voltage and no load. Core losses can be ignored. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 6, 20202020-08-06
On Thu, 6 Aug 2020 07:08:33 +0000 (UTC), Cydrome Leader <presence@MUNGEpanix.com> wrote:>Phil Allison <pallison49@gmail.com> wrote: >> Piotr Wyderski wrote: >> >> =============================== >>> > >>> > I think people design transformers for >>> > equal copper loss in the primary and secondary >>> >>> BTW, what is the source of this and similar rules of thumb (e.g. equal >>> copper and core losses)? Logic says that one should always design for >>> minimal total losses, given the economic constraints. >>> >> >> ** The source is simple calculus that finds the minimum or maximum in a curve. It's also kinda obvious that if the primary and secondary run at different temps then you have one heating the other. Same goes for core and windings. >> >> The issue with tape wound toriodals is their very sharp saturation >> curves - forcing the designer to keep away from that condition. Hence >> their low contribution to heat from the core. >> >> Commercial toroidals are made using a clever machine passing wire >> through the centre hole - this sets a limit on the amount of copper that >> can be used. > >It looks like they could dump more copper on the typical toroidal >transfomer. The diameters for large ones get huge, with >gigantic empty holes in the middle. The stacking factor, if that's the >right term is terrible on most toroids. Not sure why this is though. They >seems to scale the wide and thin vs. taller with more copper stuffed in >the hole and around the rest of it. >Iron is cheaper than copper. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 6, 20202020-08-06
whit3rd is a Fuckwit wrote: ================================> Phil Allison wrote: > > > > > > It this for variable frequency use? > > > Those iron losses are frequency-dependent. > > > it might take a bunch of testing to characterize. > > > > ** No it wont. > > > > JL's tranny is rated for 50/60Hz and will work fine with lower losses at any higher frequency. Core magnetisation goes DOWN with rising frequency for a given primary voltage. > > Iron losses are zero with DC testing, >** Huuuuh ??? Massive stupid red herring, from a desperate LIAR !!> Core magnetization goes down with frequency, but losses go UP when the secondary doesn't draw current.** Complete BOLLOCKS !!!!> And, the core shape determines the magnetization profile,** On which planet is that faintly relevant here ? What a LYING pile of shit you are. Fucking oxygen thief ... Phil
Reply by ●August 6, 20202020-08-06
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. Maybe on on planet Claire where know nothing jerks like you come from. ..... Phil
