On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote:> Can I use this for 220V input and 380V output? > > https://www.ebay.com/itm/255681909221 > > This should give me around 400V to 450V full bridge rectified DC.You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?
Swapping transformer I/O
Started by ●July 1, 2023
Reply by ●July 1, 20232023-07-01
Reply by ●July 1, 20232023-07-01
On Sat, 1 Jul 2023 05:07:53 -0700 (PDT), Eddy Lee <eddy711lee@gmail.com> wrote:>47uF 400V cap.If you feed the 220/380 V transformer with something that even remotely looks like 220 Vrms and rectify the output with a bridge rectifier, the idle (no load) voltage will be the peak voltage or about 530 V. I would suggest using a capacitor rated for 600 V.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 9:53:36 AM UTC-4, John Larkin wrote:> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid> > wrote: > >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee > ><eddy7...@gmail.com> wrote in > ><c944dcc8-8559-4276...@googlegroups.com>: > > > >>Can I use this for 220V input and 380V output? > >> > >>https://www.ebay.com/itm/255681909221 > >> > >>This should give me around 400V to 450V full bridge rectified DC. > > > >450 / sqrt(2) = 318 > >318 - 220 = 98 > > > >Only 100 V extra needed! > > > >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318 > >So less copper / money / weight needed. > >In phase that is :-) > Autotransformer mode, but no isolation. > > One concern about cheapish transformers is copper loss. Some people > design transformers with minimal copper and assume a high temperature > rise. Signal Transformer used to be famous for selling "soft" > transformers; I think they used high temperature varnish. > > If such a transformer is used to rectify to DC, one may see an > unexpected high DC voltage at low loads and bad regulation after that. > And figure it might get hot at full load. Rectifying into a capacitor > makes all that worse.Signal had a separate line of "rectifier" transformers designed to support current peaks in rectification. Standard regulation was 10% and core temperature rise was something like 40oC at rated. My experience with them is everything always worked to specification. For excellent isolation in addition to only a few p's coupling capacitance, their split bobbin design is unbeatable.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote:> On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote: > > Can I use this for 220V input and 380V output? > > > > https://www.ebay.com/itm/255681909221 > > > > This should give me around 400V to 450V full bridge rectified DC. > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps?0.5A to 2A. I can put in multiple 100W Ts.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 6:53:36 AM UTC-7, John Larkin wrote:> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid> > wrote: > >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee > ><eddy7...@gmail.com> wrote in > ><c944dcc8-8559-4276...@googlegroups.com>: > > > >>Can I use this for 220V input and 380V output? > >> > >>https://www.ebay.com/itm/255681909221 > >> > >>This should give me around 400V to 450V full bridge rectified DC. > > > >450 / sqrt(2) = 318 > >318 - 220 = 98 > > > >Only 100 V extra needed! > > > >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318 > >So less copper / money / weight needed. > >In phase that is :-) > Autotransformer mode, but no isolation. > > One concern about cheapish transformers is copper loss. Some people > design transformers with minimal copper and assume a high temperature > rise. Signal Transformer used to be famous for selling "soft" > transformers; I think they used high temperature varnish. > > If such a transformer is used to rectify to DC, one may see an > unexpected high DC voltage at low loads and bad regulation after that. > And figure it might get hot at full load. Rectifying into a capacitor > makes all that worse.Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity. I will be driving it from both sides, but not at the same time.
Reply by ●July 1, 20232023-07-01
On Sat, 1 Jul 2023 10:39:25 -0700 (PDT), Eddy Lee <eddy711lee@gmail.com> wrote:>On Saturday, July 1, 2023 at 6:53:36?AM UTC-7, John Larkin wrote: >> On Sat, 01 Jul 2023 04:39:14 GMT, Jan Panteltje <al...@comet.invalid> >> wrote: >> >On a sunny day (Fri, 30 Jun 2023 20:55:08 -0700 (PDT)) it happened Eddy Lee >> ><eddy7...@gmail.com> wrote in >> ><c944dcc8-8559-4276...@googlegroups.com>: >> > >> >>Can I use this for 220V input and 380V output? >> >> >> >>https://www.ebay.com/itm/255681909221 >> >> >> >>This should give me around 400V to 450V full bridge rectified DC. >> > >> >450 / sqrt(2) = 318 >> >318 - 220 = 98 >> > >> >Only 100 V extra needed! >> > >> >So basically you can use a 220 to 100 V transformer in series with the 220 to get to 318 >> >So less copper / money / weight needed. >> >In phase that is :-) >> Autotransformer mode, but no isolation. >> >> One concern about cheapish transformers is copper loss. Some people >> design transformers with minimal copper and assume a high temperature >> rise. Signal Transformer used to be famous for selling "soft" >> transformers; I think they used high temperature varnish. >> >> If such a transformer is used to rectify to DC, one may see an >> unexpected high DC voltage at low loads and bad regulation after that. >> And figure it might get hot at full load. Rectifying into a capacitor >> makes all that worse. > >Question is whether they are symmetrical from either side (primary/secondary) in efficiency and load capacity. I will be driving it from both sides, but not at the same time.Sure, a transformer works either way.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 1:35:53 PM UTC-4, Eddy Lee wrote:> On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote: > > On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote: > > > Can I use this for 220V input and 380V output? > > > > > > https://www.ebay.com/itm/255681909221 > > > > > > This should give me around 400V to 450V full bridge rectified DC. > > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps? > 0.5A to 2A. I can put in multiple 100W Ts.When you correct for magnetics regulation and filter (capacitor) losses, Vsecondary,RMS= 0.71 x 450 VDC / 0.95 = 340 VAC RMS, and the I secondary,RMS= 3 x 2 A= 6A. So that's a 340 x 6 =2 kVA transformer. Those corrections are based on a middling w x C x RL = 20, where w=377 line radian frequency, C= filter capacitor, RL= load resistor 400 VDC/2A= 200 Ohm, and an assumption of 10% transformer regulation with an approximate 340 VRMS, making for an equivalent series output impedance of Rs= 34 V/6A= 6 Ohm. Ripple factor, ratio of RMS ripple to DC output will be about 4% or 14VRMS. wCRL too small and it gets sloppy, ripply, and less predictable, too large and you get excessive diode current peaks and surges. Your call. This is an iterative process based on a process and associated curves published in 1943 by O.H. Shade and pretty much used ever since. None of this precise. That would be Figures 7.4 thru 7.7 in this handbook: https://frank.pocnet.net/other/sos/TexasInstruments_TheVoltageRegulatorHandbook_1977.pdf None of the above addresses line variation which can be pretty bad worst case.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 1:35:53 PM UTC-4, Eddy Lee wrote:> On Saturday, July 1, 2023 at 8:24:59 AM UTC-7, Fred Bloggs wrote: > > On Friday, June 30, 2023 at 11:55:14 PM UTC-4, Eddy Lee wrote: > > > Can I use this for 220V input and 380V output? > > > > > > https://www.ebay.com/itm/255681909221 > > > > > > This should give me around 400V to 450V full bridge rectified DC. > > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps? > 0.5A to 2A. I can put in multiple 100W Ts.The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd. Buy a high efficiency switcher.
Reply by ●July 1, 20232023-07-01
On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote: >> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote: >> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote: >> > > Can I use this for 220V input and 380V output? >> > > >> > > https://www.ebay.com/itm/255681909221 >> > > >> > > This should give me around 400V to 450V full bridge rectified DC. >> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps? >> 0.5A to 2A. I can put in multiple 100W Ts. > >The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd. > >Buy a high efficiency switcher.High voltage output switchers are rare. PFC modules output around 400 DC and lots of power, but aren't isolated.
Reply by ●July 1, 20232023-07-01
On Saturday, July 1, 2023 at 5:35:56 PM UTC-4, John Larkin wrote:> On Sat, 1 Jul 2023 14:06:23 -0700 (PDT), Fred Bloggs > <bloggs.fred...@gmail.com> wrote: > > >On Saturday, July 1, 2023 at 1:35:53?PM UTC-4, Eddy Lee wrote: > >> On Saturday, July 1, 2023 at 8:24:59?AM UTC-7, Fred Bloggs wrote: > >> > On Friday, June 30, 2023 at 11:55:14?PM UTC-4, Eddy Lee wrote: > >> > > Can I use this for 220V input and 380V output? > >> > > > >> > > https://www.ebay.com/itm/255681909221 > >> > > > >> > > This should give me around 400V to 450V full bridge rectified DC. > >> > You'll never know from that fantasy, fake advertisement. What is the load you're putting on the 400-450 VDC in Amps? > >> 0.5A to 2A. I can put in multiple 100W Ts. > > > >The foregoing was meant to show that a 60 Hz magnetics approach is kinda absurd. > > > >Buy a high efficiency switcher. > High voltage output switchers are rare.Not anymore. China makes them a commodity: https://idealplusing.en.made-in-china.com/product/EdjGBQbxgzkH/China-Hot-Sale-220V-110V-AC-to-400V-500V-600V-700V-DC-1000W-Switching-Power-Supply.html Pointless to read the specs, but it sounds right.> > PFC modules output around 400 DC and lots of power, but aren't > isolated.
