Mains wiring question: Sizing buck-boost transformer?

center tap of secondary for 2:1.

Right, it works if you put the windings in series to make an autotransformer,

2:1 voltage ratio, but that's not a 1:1 buck, to play with words.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

center tap of secondary for 2:1.

"Series complimentary".

There is a proper glossary or terms for this, but few have landed on target in all respects as yet.

center tap of secondary for 2:1.

Transformers do what they do, and don't care much about words. Many transformers don't even speak English.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

center tap of secondary for 2:1.

transformers

Yeah? Try wiring it "in series' with the wrong starting lead first.

There are discreet series inductors, and there are series inductors tied together within the same magnetic field.

They DO care about *those* words, turkey.

the center tap of secondary for 2:1.

transformers

That can be done, depending on what you mean by "wrong."

Schematics, with notes and polarity dots, are a better way to convey things like this.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

the center tap of secondary for 2:1.

transformers

like

In transformer speak:

"series complimentary" for "auto-transformer boost configuration".

What your opinion of being "better" hardly has any meaning when an experienced electrician is in the field and needs to have such a thing "conveyed" over an audible phone.

"These days" such a schematic would be easily available online. and is.

And you don't need the notes if the winding start indicators (dots) are there.

And they are also ALWAYS supposed to appear on the physical device as well.

eg: take a isolating transformer and put the secondary in series with the primary, doubles (or halves) the voltage and can still handle full current

T1: 1KVA 120V:120V

___________ | | | * | ____|___ ||| ___| _)|||(_ _)|||(_ 120V _)|||(_ 16?A _)|||(_ _)|||(_ ________)|||(___ | ||| | * 240V | 8?A |___________

• indicates start of winding. As Phil Allison pointed out this only works if you run the windings at their design voltage. As with any transformer if you run it under voltage you get less VA.

--
?? 100% natural 


--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

"John Larkin" Jasen Betts

** Huh ?

It's so obvious.

Primary and secondary in series ( in phase) and the centre is the output.

Supply voltage can now be doubled while the current in each winding is the same.

So a 1kVA 120:120 iso makes a 2kVA 240:120 auto step-down.

... Phil

I must admit, I slip on that one..

+------------ | + | | | + 120AC OUT +---+. ,+---+----------------------+ )|( )|( + +' '+--+----------------------- | | IN/OUT 240AC | | | | +----------+ + IN 240AC

For once Phil, I can say you tripped me up.

Jamie

--QUOTE It's true because you're only using the transformer to "create" 24 volts at the current you wish to draw at 230v. This extra 24 volts is added back into the line voltage.

You can switch flip the leads and subtract voltage too, then the transformer is in buck mode. QUOTE

If you need 20 amps at 230v and start with 208, you need to boost 22volts (208+22=230) x 20 amps = 480VA transformer. A 24 volt transformer rated over 480VA should be fine.

Autotransformers can be confusing, so pretend it's just DC and some batteries.

Let's say you need 24 volts at 10 amps and have a 12 volt battery that can already output 10 amps.

what size power supply do you need to run in series with this battery to get the 24 volts?

just another 12 volts, at at least 10 amps, or a 120 watt power supply. Those wired in series (your battery and the new power supply) will provide 240 watts.

If you already had an 18 volt battery, you'd just need a 6 volt, 10 amp or

60 watt power supply.

The less the voltage adjustment, the smaller then buck/boost transformer rating becomes as it's really not doing all that much work. ======================================= lookup "autotransformer". In this case you have a 2 winding transformer with a 10:1 ratio With 240V applied the secondary will be 24V with a rated current of

1000/24=41.7A If this is connected as a boost autotransformer- the total output voltage would be 240+24 =264V so the output, without exceeding rated output current would be 11KW. only 1 KW (24V*41.7A) is supplied through transformer action and the rest through a direct connection Adjusting to 230V output leads to 11*(230/264)=9.58KW The input voltage would be 207V excluding any voltage drops in the transformer-so 208/230 is close enough. Autotransformers are great for turns ratios near one as there are size and cost advantages. Disadvantage--no isolation between primary and secondary.

Excuse the lack of "quoting" as I am using windows live mail in an emergency- Thunderbird downloads news but then deletes the downloads immediately! New problem- correction not yet found.

Don Kelly cross out to reply

Please view in a fixed-width font such as Courier.

. . . . . . o----------- + . ) . ) . | I ) . | - ) 120VAC . | 2 ) . v ) . ) I . | ---> . 240VAC CT +-------------. . | | . )+ | . ^ ) ----- . | I ) |LOAD | 2X KVA XFMR . | - ) 120VAC ----- . | 2 ) | . ) | . ) | . o-------------------------' . . . .

Per P.A.'s observation:

Please view in a fixed-width font such as Courier.

. . . . . . o----------- + . ) . ) . | I ) . | - ) 120VAC . | 2 ) . v ) . ) I . | ---> . 240VAC CT +-------------. . | | . )+ | . ^ ) ----- . | I ) |LOAD | 2x KVA XFMR . | - ) 120VAC ----- . | 2 ) | . ) | . ) | . o-------------------------' . . . . . I 1 KVA, LOAD KVA,LOAD . KVA,XFMR= 120 x - = 120 x - x --------- = -------- . 2 2 120 2 . . . . I . ----> . ------------- . )+ | . ^ ) | . | ) | . | I ) 120VAC | 240VAC . | ) | . ) | . ) | . | ----- . o-----------+ CT |LOAD | 2x KVA XFMR . | ----- . )+ | . | ) | . 120VAC | I ) | . | ) | . v ) | . ) | . ) | . o-------------------------' . . . KVA, LOAD KVA,LOAD . KVA,XFMR= 120 x I = 120 x --------- = -------- . 240 2 . .

so that Iload=KVALoad/[Vline(1+1/N)], making KVAXfmr=VLine/N x KVALoad /[VLine(1+1/N)]= KVALoad/(N+1) so you can use it with loads up to (N+1)x KVAXfmr , for boost. For buck the factor is VLine(1-1/N), so it can be used up to loads of (N-1)xKVAXfmr. Which makes sense because for the same KVA l oad, the current is greater for buck, but the transformer voltages always r un at line.

Looks like you can squeeze a few extra percentage points out of buck mode b y wiring it like this : Please view in a fixed-width font such as Courier.

. . . . I . ---> . o---------------------------- . )+ | . ) | . 240 ^ I ) | . --- | --- ) N ----- . 1 | N+1 ) |LOAD | N+1 x KVA,XFMR . 1+ - ) ----- . N ) | . | | . 240VAC +------------- . | . )+ . ) . 240 | NI ) . --- | --- ) 1 . N+1 v N+1 ) . ) . ) . o-------------- . . . . . 240 N 240 N KVA,LOAD KVA,LOAD . KVA,XFMR= --- x --- x I = --- x --- x --------- = -------- . N+1 N+1 N+1 N+1 240 N+1 . --- . 1 . 1+ - . N . .

It comes out close enough for a 240 to 208 conversion using standard stepdo wns.

--- "Series complimentary" is nonsensical:

and while it's conceivable that "series complementary" could be used, it's kind of ambiguous.

The correct term is, I believe, "series aiding".

-- JF

Here.. maybe this will help you.

"Series, Phase Complimentary"

Or...

"Series, Phase Opposed"

Winding phase, not electrical phase.

It makes perfect sense... "I believe". I don't know... maybe you are right. Maybe it would be ambiguous to others. I seem to have a mild asperger's thing going... maybe... I doubt it, but I suppose it is possible. I think all this autism stuff is us trying to make the next evolutionary step.

Sit at a winding machine and wind up a few tens of thousands of bobbins. Maybe the terms would then make more sense out of the gate.