lørdag den 1. juli 2023 kl. 23.35.56 UTC+2 skrev John Larkin:> 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.there's one in the inverter, likely something like this: https://www.tehnomagazin.com/Power-supply/24v-to-220v-inverter-1000W-schematic-diagram.jpg
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 15:06:47 -0700 (PDT), Fred Bloggs <bloggs.fredbloggs.fred@gmail.com> wrote:>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.At least it's CE!
Reply by ●July 1, 20232023-07-01
upsidedown@downunder.com wrote:> 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.That hardly provides any margin. Use two 450 volt caps in series with equalizing resistors in parallel. -- MRM
Reply by ●July 1, 20232023-07-01
John Larkin wrote: ----------------------------> Eddy Lee > > >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. >** But makers nominate the primary and secondary for good reasons. The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. ...... Phil
Reply by ●July 2, 20232023-07-02
On Sat, 1 Jul 2023 19:32:12 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:>John Larkin wrote: >---------------------------- >> Eddy Lee >> >> >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. >> > >** But makers nominate the primary and secondary for good reasons. > >The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. > > > > >...... PhilAny winding can magnetize the core. The primary is the one you decide to put power into and the secondary is the one you elect to take power out of. 2-winding power transformers are usually designed for equal copper loss on both windings. So are thermally symmetric. Sometimes some windings are insulated better than others. What other catches might there be?
Reply by ●July 2, 20232023-07-02
John Larkin wrote: ------------------------------> >> > >> >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. > >> > > > >** But makers nominate the primary and secondary for good reasons. > >The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. > > > > Any winding can magnetize the core. The primary is the one you decide > to put power into and the secondary is the one you elect to take power > out of.** The maker tells you which is which because they have adjusted the windings ( number of turns and wire gauges) accordingly.> 2-winding power transformers are usually designed for equal copper > loss on both windings. So are thermally symmetric. > > Sometimes some windings are insulated better than others. > > What other catches might there be?** As I mentioned, which winding carries the I mag plus the turns ratio have been adjusted by makers to compensate for the full load voltage drop. Reverse the makers intended roles and those built in compensations operate in the opposite directions. You may have to seriously de-rate the transformer in order to use it that way, mains frequency transformers under 100VA are the most affected. ...... Phil
Reply by ●July 2, 20232023-07-02
On Sat, 01 Jul 2023 21:27:42 -0700, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:>On Sat, 1 Jul 2023 19:32:12 -0700 (PDT), Phil Allison ><pallison49@gmail.com> wrote: > >>John Larkin wrote: >>---------------------------- >>> Eddy Lee >>> >>> >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. >>> >> >>** But makers nominate the primary and secondary for good reasons. >> >>The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. >> >> >> >> >>...... Phil > >Any winding can magnetize the core. The primary is the one you decide >to put power into and the secondary is the one you elect to take power >out of. > >2-winding power transformers are usually designed for equal copper >loss on both windings. So are thermally symmetric. > >Sometimes some windings are insulated better than others. > >What other catches might there be?Those (380/220 V), 400/230 V or 690/230 V transformers are typically used with big three phase motors running with delta feed only (no neutral available). If some ordinary small 230 V loads, such as local control panels or lights, are needed close to the motor, just connect the small transformer primary between two phases pf the 400 V or 630 V delta feed. The secondary 230 V feeds low power mains equipment, with possibly grounding the cold end of the secondary, if local regulations demand it. Industrial gear are usually designed for well below absolute maximum ratings to ensure long lifetime. Swapping primary and secondary should not be an issue, unless you load the transformer with 100 % or more as in some consumer electronics cases. I guess similar transformers for the US market are 480/120 V for three phase 480 V delta motor systems.
Reply by ●July 2, 20232023-07-02
On Sat, 1 Jul 2023 23:07:24 -0700 (PDT), Phil Allison <pallison49@gmail.com> wrote:>John Larkin wrote: >------------------------------ >> >> >> >> >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. >> >> >> > >> >** But makers nominate the primary and secondary for good reasons. >> >The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. >> > >> >> Any winding can magnetize the core. The primary is the one you decide >> to put power into and the secondary is the one you elect to take power >> out of. > >** The maker tells you which is which because they have adjusted the windings ( number of turns and wire gauges) accordingly. > >> 2-winding power transformers are usually designed for equal copper >> loss on both windings. So are thermally symmetric. > >> Sometimes some windings are insulated better than others. >> >> What other catches might there be? > >** As I mentioned, which winding carries the I mag plus the turns ratio have been adjusted by makers to compensate for the full load voltage drop. Reverse the makers intended roles and those built in compensations operate in the opposite directions. >That's easy to think through. Power transformer models are simple and easy to reverse.>You may have to seriously de-rate the transformer in order to use it that way, mains frequency transformers under 100VA are the most affected.A 100 VA transformer is happy moving 100 VA in either direction.
Reply by ●July 2, 20232023-07-02
Mike Monett VE3BTI <spamme@not.com> wrote:> upsidedown@downunder.com wrote: > >> 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. > > That hardly provides any margin. > > Use two 450 volt caps in series with equalizing resistors in parallel.Plus two reverse polarity diodes. -- MRM
Reply by ●July 2, 20232023-07-02
John Larkin wrote: ------------------------------> >> >> > >> >> >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. > >> >> > >> > > >> >** But makers nominate the primary and secondary for good reasons. > >> >The primary supplies the magnetising current, which can be significant, plus is wound to allow for voltage drop at the secondary under full load. If the roles are swapped, there are several changes that can catch the unwary. > >> > > >> > >> Any winding can magnetize the core. The primary is the one you decide > >> to put power into and the secondary is the one you elect to take power > >> out of. > > > >** The maker tells you which is which because they have adjusted the windings ( number of turns and wire gauges) accordingly. > > > >> 2-winding power transformers are usually designed for equal copper > >> loss on both windings. So are thermally symmetric. > > >> Sometimes some windings are insulated better than others. > >> > >> What other catches might there be? > > > >** As I mentioned, which winding carries the I mag plus the turns ratio have been adjusted by makers to compensate for the full load voltage drop. Reverse the makers intended roles and those built in compensations operate in the opposite directions. > > > That's easy to think through. Power transformer models are simple and > easy to reverse.** But real transformers are not so simple.> >You may have to seriously de-rate the transformer in order to use it that way, >> mains frequency transformers under 100VA are the most affected.> A 100 VA transformer is happy moving 100 VA in either direction.** JL has such simple faith in overly simple models. I wonder why ? ...... Phil
