OK..
since were on the transformers side...
Looking at common amplifiers and such as this one and knowing how important of a role both voltage and amperage are, would it better to get a higher voltage and less amperage or lower voltage and higher amperage ??
I'm looking at in in a way that is easier to transport higher voltage across then high amperage on a circuit board, another fact to look at is that voltage is reverse proportional to amperage. At the same time looking at the frequency spectrum a higher wattage requires a fair amount of current to drive and control a load speaker reliably where if the voltage is too high it might jump in the coil ( specially for those using automotive subwoofers in a home enviroment ) where as if theres too much current you can toast the coil easily.
Either WAY, your SOL.
I have a few friends that use Automotive drivers in custom enclosures and sound very nice if they are powered and matched properly.
Also after hearing my friends "house shaker" im quite suprized of how loud and clear this monster was.
He's using a Memphis MOJO 12" and this thing was just shaking the crap out of everything.
Im almost thinking of doing the same but with 4 x 15's in a ported box
since were on the transformers side...
Looking at common amplifiers and such as this one and knowing how important of a role both voltage and amperage are, would it better to get a higher voltage and less amperage or lower voltage and higher amperage ??
I'm looking at in in a way that is easier to transport higher voltage across then high amperage on a circuit board, another fact to look at is that voltage is reverse proportional to amperage. At the same time looking at the frequency spectrum a higher wattage requires a fair amount of current to drive and control a load speaker reliably where if the voltage is too high it might jump in the coil ( specially for those using automotive subwoofers in a home enviroment ) where as if theres too much current you can toast the coil easily.
Either WAY, your SOL.
I have a few friends that use Automotive drivers in custom enclosures and sound very nice if they are powered and matched properly.
Also after hearing my friends "house shaker" im quite suprized of how loud and clear this monster was.
He's using a Memphis MOJO 12" and this thing was just shaking the crap out of everything.
Im almost thinking of doing the same but with 4 x 15's in a ported box
Then why do higher power transformers need bigger cores? The power is transfered in the magnetic flux in the core. More power = more flux = more core
From wlkipedia:
megajocke:
Then how can the core be responsible for power losses (iron losses)?
wg_ski said:
Well,
i just had a brief discussion with my PCB guy and said he has a source for 100VDC 12000uF at $12 each and then hes got 35A rectifiers with heat sinks on them for $7.50 a piece !!! i told him to get 10 caps in for me and to put 4 bridges aside for me.
Power supply boards are in the works right now along with the output boards ( where the output transistors and drivers will be located ) a total 10 of each and i asked him to work me up a smaller version of the boards with only 12 output transistors (5 PNP & 5 NPN + 2 drivers ) and the other ones are the 22 transistor version ( 10 PNP & 10 NPN + 2 Drivers )
And finally :
So once more I ask. In these large power transformers if you short the output, what limits the output current, copper losses or core saturation? In power transformers the size of the core depends on the amount of power. The price of the transformer depends on the size. Do the manufacturers cheap out and only make the cores big enough to put out the specified power, or do they over size the cores?
So once more I ask. In these large power transformers if you short the output, what limits the output current, copper losses or core saturation? In power transformers the size of the core depends on the amount of power. The price of the transformer depends on the size. Do the manufacturers cheap out and only make the cores big enough to put out the specified power, or do they over size the cores?
cbdb said:
The higher the voltage and amperage requires thicker and more wire to be wound on the core and also lets not forget that some of the "energy" gets dissapated as heat. there isn't such a thing as a true 100% efficient transformer.
Also the big limiting factor is Input Voltage along with Amperage.
Input is proportional to the output minus the losses that is converted to heat.
cbdb said:
Actually its quite simple.
as the voltage passes though the primary winding creates a magnetic field though the core of the transformer that in turn get turned back into la lower voltage, higher current ( since were talking step down transformers ) while passing though your secondary windings.
While the coils are "loaded" there will be some heat generated and is a waste byproduct of the transformer.
PS:
I think your over looking Faraday's Law of inductance.
That might make a better explanation for you.
Adrculda said:
You do not necessarily have to skimp on your 550W into 8 ohms spec. Earlier in this thread I suggested a bridged amplifier with a 1kVA 45V-dual-secondary toroidal transformer per channel.
That will work with 100V filter caps with a safer margin and the build will be easier for a newbie. You can then break the stereo amp down into four seperate, but identical 225W/4-ohm amplifier modules, designing / constructing / operating / debugging only one module to begin with.
Cheers,
Glen
cbdb said:
A coil has inductance. To increase inductance, add an iron core. The core will provide a path for more magnetic lines of force.
Since a transformer is a pair of coils wrapped around a core, the core will act to increase induction in both coils, increasing the efficiency of the process.
Mega said it exactly right - a transformer will still work without a core, just not nearly as efficiently.
G.Kleinschmidt said:
Thanks Glen.
But i have no such intent 🙂
I'm making the other boars as i have a few friends interested in 2 x 5 channel surround amps 😛
I think 2 x 600VA toroids will be plenty for any HT amp driving 120Hz and up and i think it would be safe to say 150W x 5 for that 😉
G.Kleinschmidt said:
That's what I'd do to achieve these power levels. Reduce the risk of electrocution and get away a bit cheaper to boot.
Which part of magnetic flux limiting (the iron can only pass so much magnetic flux) in the core (ie saturation) dont you guys understand. These are not air core, Air dosnt magnetically saturate so stop talking about it. Google transformer core saturation and get educated, then reply.
cbdb said:
Your not making any sense !!
Who was talking about the air ???
Read the whole thing and you might understand it.
And yes...
There's a limit on how much flux a core can carry.
The reason why toroidal transformers are so efficient is that they have the least flux leakage compared to a standard E-core that is a lot easier to manufacture and requires less specialized equipment.
Read this
http://en.wikipedia.org/wiki/Saturation_(magnetic)
Can we agree that a certain x-section area core can only carry so much flux, and the amount of AC current in the windings is proportional to the amount of AC flux in the core.
Then, when the core saturates at high AC power (high load) the saturation will limit the output current. But only if the coil resistances are low enough. Thus my original question. It would seem cheaper (less iron) to limit the power of a transformer with core size rather than wire diameter, but I might be wrong.
http://en.wikipedia.org/wiki/Saturation_(magnetic)
Can we agree that a certain x-section area core can only carry so much flux, and the amount of AC current in the windings is proportional to the amount of AC flux in the core.
Then, when the core saturates at high AC power (high load) the saturation will limit the output current. But only if the coil resistances are low enough. Thus my original question. It would seem cheaper (less iron) to limit the power of a transformer with core size rather than wire diameter, but I might be wrong.
cbdb said:
It would be Impractical as the core is cheaper than the copper itself that is wound on the core. Its not the core that's pricey, but the copper that's on it!
Everyone wants high output in a compact and more efficient package, that's why a lot of PA amplifiers are starting to switch to G or H class and even to D-Class circuitry as there isn't a need for large Toroidal transformers as the circuitry get more complex and more efficient to drive lower loads, and that means less weight to lug around!
But also...
there isn't a sweeter sounding PA amp than an old school class AB :thumbup:
It's a good idea to maximise the economy of your smoothing caps. 63Vdc caps need <=41Vac transformer, 80Vdc caps need <=52Vac transformer, 100Vdc caps need <=65Vac transformer.Adrculda said:
This last recommendation has assumed that the regulation is 3% and the tolerance on your mains supply is +6%.
A 120:65Vac 3% regulation transformer will give ~ 127.2/120 * 1.03 * 65 = 70.97Vac and when rectified and smoothed will give 99.6Vdc when off load. If you buy a 115:65Vac transformer your caps will run at a higher voltage and the risk of failure increases.
cbdb said:
Yes, saturation happens at a specific flux density.
No. For a specific transformer, flux is only dependent on voltage and frequency, see:
http://en.wikipedia.org/wiki/Transformer#Induction_law
That's the relation of voltage, flux and number of turns and the explanation why transformers transform by turn ratio when the same flux is going through both coils.
Current does not matter, the MMF of secondary and primary cancels.
In fact, even if you put the windings on different sides of a square core the flux isn't changed by the current much. This is obvious if you draw up the equivalent reluctance circuit.
Core losses are essentially independent of load, and that's a good reason to keep them low.
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