It definitely seemed like one of those hammer-nail situations. Like writing "software" within an Excel spreadsheet for tasks where the complexity justifies what most people call a "programming language."
Is the VA a function of output voltage, as in the lower output voltage source has a higher VA rating than the higher voltage output source? That doesn't make any sense.
Power loss in a wire goes as current squared.
If I had four identical windings stacked up, and could deliver, say,
120V at 1 amp when they are in series, that's 120 VA to the customer. If it has 1 ohm per winding, the total secondary copper loss would be 4 watts. Voltage loss is 4 volts total out of 120.If I use only one winding to get 120 VA at 30 volts, there would be 4 amps in that chunk of wire. 16 watts loss. Voltage loss is 4 out of
If I used 4 windings in parallel to get 30 volts, I'm back to 4 watts total loss. 1 volt lost.
A transformer is most efficient and economical if you use all that expensive copper all the time in a balanced way.
My class D amps can theoretically output 600 watts each. I can buy a kilowatt main power supply. The thing that limits the specs of a channel, or of the whole box, is the size and cost of the output transformers.
A few dollars worth of relays keeps the channel output at my 120 VA spec on all voltage ranges.
Yes. I've done something similar. When I first got out of college with a g ood dose of two courses in classical control theory I was hired in an engin eering company that engineered and constructed various steel mill plants (e .g. coke oven, blast furnace and stove changing controls). Thinking I could put LaPlace transforms and open & closed loop response theory into practic e, I was shocked to run into reality - everything was controlled by ladder logic. With a crash course in ladder logic in evenings and weekends, and l everaging designs from previous work, I was able to design the control logi c for sequencing the stoves for a blast furnace. It consisted of two 8'x6' enclosures full is 'control relays' arranged horizontally one next to each other, estimating 50 relays/row and about 10-12 horizontal rows with pandu it wireways between them. In addition to producing the schematics, I had to produce the wiring diagrams to be used in the shop for assembly, and then design the knife switch and light 'simulation panel." On what fun it was c hecking it out. The next version of the control system was based on discrete logic, DEC 'K series' logic, which I designed and wire wrapped because the techs didn't k now about wire wrapping till after I walked them through it. Version 3 of the control system was based on a new technology called PLC's (Programmable logic controllers' which basically emulated ladder logic base d on a intel 4004 and some ancillary discrete logic and I/O signal conditio ning. the I/O was binary, no analog...yet. I needed to design some logic to make a decision based on the division of settings from two sets of 3-dig it thumbwheels on a control panel. I ended up designing and implementing a divider in relay logic. While not as complex as a phone switching system, the stove changing logic was very complex for its time. Now the same thing could be done with a PL C the size of a shoe box and the I/O rack in a 2'x3' enclosure. A classmate of mine went to work for Bell Labs and ended up working on ESS3 and 4. For a look at a fascinating rotary switch which was the corner sto ne of the phone network switching, see:
Provided the windings are identical, which is kind of a brave assumption. You need special windng techniques to achieve that.
The transformer yes, but the whole system -- not necessarily.
I have never seen a switcher with a bridge rectifier at the output. A copper-wasting center-tapped full wave is the standard.
Best regards, Piotr
Here you have some:
-- -TV
No, I need a specification and a normally-competant transformer manufacturer. I have those.
Many commercial power transformers have dual primaries and dual secondaries, spec'd to be used in series or in parallel. People who wind power transformers don't randomize turns counts.
Adding gratituous transformer loss doesn't help.
Bridge rectifier?
Not in my box. But my simulated alternator output will often drive a bridge rectifier+capacitor, with a shunt regulator somewhere.
Turn count is one thing, wire length is another. Much harder to make identical. I'd use 4 twisted wires and wind the secondary(-ies) with that rope, then untwist the endings.
Best regards, Piotr
My transformer will resemble this one
but I'll have one primary and four secondaries.
That Hammond part works fine with any combination of connections. The voltage imbalance between windings is parts per million.
Specifically, about 5 PPM at 400 Hz. Hard to measure.
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