Hybrid Technology - Rockford Fosgate Power T15kW Installation & Operation Manual

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ESIGN EATURES

Hybrid Technology

By Anthony D'Amore - Rockford Design Engineer
Some people have referred to Ohm's Law (circa 1827) and immediately say this amplifier is impossible. Ohm's Law has been correct for
179 years and I'm sure it will remain correct for many years to come.This technology is in no way breaking Ohm's Law.
The real law that we need to talk about is the 1st law of thermal dynamics or Conservation of Energy.This law states that energy cannot
be created nor destroyed; additionally you can only get the same amount of energy out of a system as the amount of energy that was put
in.This is true for every amplifier including the T15kW.
A quick review of what "Efficiency" means, as I will refer to it later. Efficiency = (Power Out / Power In). Let us take a typical class A/B
amplifier for example. Say it puts out 200 Watts RMS and it takes in 300 Watts to do this. Efficiency = 200/300 = 0.67 or 67%. How do
we know how much power it took in? This is where Ohm's Law is helpful.We knew it took in 23.8 amps to do this at 12.6 Volts. 23.8A *
12.6V = 300W.
Conservation of Energy DOES NOT say "Power In = Power Out". It says "ENERGY IN = ENERGY OUT".What's the difference?
"Power" alone, tells us nothing about length of time,"Energy" does,"Energy" = Power * Time.When you get your electric bill in the mail
they don't charge you for how much "Power" you used, they charge you for how much "Energy" you used, hence the unit "Kilowatt *
Hours".A Kilowatt Hour is a LOT of energy and I doubt we will ever see the unit used in mobile audio.When referring to the T15kW
though we could use the unit Kilowatt * Second, meaning 1 kilowatt for 1 second. However there is already a unit of measure for energy
that is commonly used in the audio world; it is the Joule.A Joule is to energy like the Gallon is to water. It is a quantity of Energy and is
defined as 1 Watt second or 1 watt for 1 second. Ok, I know that is a bunch of info, but to really understand the topic it is necessary.
I suppose we should talk about storing energy now, as in a capacitor.The formula for how much energy a capacitor can store is,
( / * C*V^2).Which reads / times the capacitance (in Farads) times the voltage squared.As an example let's find out how much energy
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is stored in a 1 Farad capacitor that is connected to the +12V system. ( 1 / * 1 Farad * 12 * 12) = 72 Joules or 72 Watt seconds. If you are
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still with me, now we have the knowledge to discuss the operation of the T15kW and its Hybrid Technology (HT).
You cannot put out more power than you take in, or can you? The answer is YES YOU CAN, for periods of time.The HT system in the
T15kW stores a huge amount of energy, well into six figures of Joules. It is capable of this by using the latest technology in capacitors
designed for use in Hybrid Vehicles and large wind turbine electricity generators.The operation of the system is somewhat analogous to
the operation of a Hybrid Vehicle. During some conditions a Hybrid car is running on just electric power, other conditions it runs on just
gasoline power and under 'full throttle' conditions uses both systems.The T15kW has 2 systems in a way. It has the high voltage system,
which is stored in the amplifier, and it has the 12 Volt system from the vehicle.When the T15kW's output power is low it uses power from
the high voltage system to run the amplifier and small amounts of energy from the 12 Volt system to charge the high voltage system.When
output power is relatively high it uses the high voltage system along with some energy from the 12 Volt system.When it is at 'full throttle'
it uses both systems to their capacity, pun intended, to supply the output devices with the maximum amount of current possible.
So how can this work and why doesn't it just 'run out' of energy? The key is that music is very dynamic, meaning it has 'loud' times, like a
kick drum, and relatively 'quiet' times, like...well like anything that is not loud. During the 'loud' times the system releases energy, for
instantaneous efficiency of well over 300%, and during 'quiet' times it absorbs energy, the instantaneous efficiency at this point could be as
low as 0%. Hybrid Technology is an energy management system.The "average" efficiency is still similar to other amplifiers. BUT you must
read the last two paragraphs to understand the big picture.The system in this amplifier was designed so that it could play typical music
continuously at 15 kilowatt levels.After all, this is an AUDIO amplifier we are talking about and audio amplifiers were intended to play
music.With the Hybrid Technology system inside, the T15kW plays music like no other amplifier before it.
The question has been asked,"What about a sine wave, like for an SPL competitor"? The T15kW has plenty of energy to get through a
3 second sine wave burst. However a 5 minute "death match" style competition is not the T15kW's forte.Who wants to torture their
investment like that anyhow?
So why would I design such a system? First of all this amplifier will make your ears smile when you hear it. Or you'll be smiling from ear to
ear, one of the two. Secondly it has the ability to deliver incredible amounts of dynamic power. But maybe more importantly, when getting
into the multi-kilowatt range the power delivery from the 12V system becomes more and more inefficient.The Hybrid Technology system
in the T15kW provides current averaging to help this efficiency problem. Let's talk about why current averaging is useful.
This technology reduces I^2*R losses. I am referring to Ohm's Law by saying that current squared times resistance = power, and in this
case power lost. Let us take a case with any typical amplifier playing music or a sine wave burst for a period of time where half of the time
is 'loud' and half is 'quiet', just to simplify the situation. Let us also pretend that during the 'loud' times the amplifier draws 1000 amps and
during the quiet times it draws 0 amps. Let's assume for a moment that during a 'loud' time, 1000 amps of current are being pulled on a
12 volt system through a 10 foot run of 1/0 AWG cable. Standard resistance for this length of 1/0 AWG cable is about 0.0012 ohms.
Using the formula above for power lost 1000 amps * 1000 amps * 0.0012 ohms = 1200 Watts!!! So during this 'loud' time 1200 watts of
power is being lost on that cable alone, and of course during the 'quiet' time 0 watts of power is being lost since the current being drawn
at that time is zero. Ok, with that said, half the time 1200 watts are being lost and half the time 0 watts are being lost, for an average loss
of 600 watts.
Now let us take that same example with HT's ability to current average for the same period of time. So instead of drawing 1000 amps
when loud and 0 amps when quiet, it draws 500 amps continuously. If we put that number into the formula for power (loss) we will see
something interesting. 500 amps * 500 amps * 0.0012 ohms = 300 watts loss in the cable.The I^2*R losses are cut IN HALF!! So while
the "average" efficiency of the T15kW amplifier itself may be similar to other amplifiers it makes the entire system from battery to
amplifier outputs much more efficient.
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