You wrote earlier that it will be pulsed, in connection with power/ heat dissipation concerns which were raised by me.
Hence my question.
50amps into 1.1ohm implies 2.75Kw which is not trivial.
I am aware of that, that's why duty cycle will be 50% or less, but that's irrelevant for my question.
I suppose it's irrelevant if you're not actually planning to make such a device. Even with Duty cycle <50% it is important to know the repetition rate. For e.g. a rep rate of 1 / minute and duty 25% means it is ON for 15 seconds continuously.
You are generating 2750 joules of heat per second, and your coil is capable of dissipating not more than around 40 watts in air with a 50 degC temp differential. You would need some significant additional heat disposal system in place.
Also, to achieve 50 amps, you need at least 55 volts PS.
Just saying
Qustion is about flux density, not heat dissipation, but since you insist on it, how do you think 1Ohm or even 0.5Ohm speaker coils dissipate heat if they are not able to dissipate more than 40 watts as you say.
Most of the energy in the speaker is Ohmic losses, small part of it is reactive losses. So where's the "burning heat" you speak about.
Also, this is wrong.
"For e.g. a rep rate of 1 / minute and duty 25% means it is ON for 15 seconds continuously."
25% DC means just that, out of every cycle only 25% of the time current flows, never 15sec cont.
As for 55V PS why even mention the obvious God knows.
I wrote that your coil can dissipate around 40 watts unassisted.
Speaker coils also do heat up, and special design considerations have to be implemented so that they don't burn up or melt.
I have never heard of 1 ohm / 0.5 ohm speakers.
I am puzzled. Why do you say that 25% of 1 minute is not 15 seconds ?
Simply because you earlier wrote that you were procuring a 48v/ 20A PS for this specific purpose.
... if you ask it at yahoo answers like i did you will get a bunch of conflicting answers.
The one i chose as best said 75% of energy is due to ohmic losses and the rest due to acoustic vibrations (and a tiny amount as radiation).
This implies those 25% of acoustic vibration work is being added to normal ohmic losses which are there whether coils vibrates the membrane or not.
As for my coil it is supposed to work against a fixed PM (neutralizing it), so question is whether coil sees this as work.
Power will be ajdusted to acceptable value by duty cycle and amplitude, i will probably go with less than 50 amps and less than 50% duty cycle.
As for reactance there will be very little as i will drive it at resonant frequency.
Which part of no reactance you don't understand. At resonant frequency, only ohmic losses matter, no inductive or capacitive reactance.
It is not clear what "resonance" you are talking about, or what "capacitive reactance" is there in your setup.
To drive a 10mH inductance from Zero current upto 50 amps using a constant voltage power supply requires ~30mS. How you intend to somehow short circuit the inductance and achieve 50 amps using some mysterious reactance in less time than 30mS is beyond my understanding.
Just saying
Seems you don't understand the meaning of reactance. Which 10mH are you talking about, where did you pull that from.
If driven at resonant frequency, coil's capacitive and inductive reactance cancel out, it behaves as if driven by DC.
XL= 2πfL
XC= -1/2πfC
Z = sqrt(R² + (Xc - Xl)²)
F = 1/6.28(LC)
F = 1/2π√LC
What's confusing you about this simple concept is beyond me.
from here... where the estimate is 8.67mH, which I rounded to 10mH for easy writing.
View attachment 154217
These equations are irrelevant.
LOL inductance of this coil is nowhere near 8.67mH.
Reactance being 0 at resonant frequency is anything but "irrelevant".
I would be interested to know what your estimate is ? I simply used a freely available software to estimate. Maybe you have measured it more accurately ?
If your resonant frequency is below 16 Hz, then this might prove useful. However to achieve resonance below 16 Hz for a 10mH inductor would require a capacitance of 0.01 farads. I doubt this is feasible, and hence I said it was irrelevant.
Inductance for 1 layer of this coil is 50uH, for 17 layers it is ~850uH or 0.85mH.
For calculation i used this website kaizerpowerelectronics.dk/calculators/spiral-coil-calculator/
What are you on about God only knows. 16Hz??
Resonant frequency for this coil is expected to be in range of ~5KHz.
At that frequency coil will behave as pure resistor and thus no-reactance matters very much.
How very interesting. When I applied the same dimensions of your coil to your referred website with Wheeler's formula, I obtained L = 10.132 mH...
I calculate 16 Hz because it takes 30mS to ramp up to 50 amps into 10mH at 60V. bla bla bla
WOW, you actually managed to input few simple values into a simple formula i did not to happen to come accross, simpleton chimp.
Let's see what's the actual resonance. If we take 10mH as actual inductance, resistance 1.1Ohm and assume capacitance to be small due to round wire, let's say 100nF, according to RLC calculator resonance is 5032.92Hz, exactly 5KHz as i assumed.
View attachment 154221
You not only need to learn the difference of inductance and inuductive reactance, you need to go back to kindergarden and start from a scratch, maybe even restart the whole incarnation.
Bye bye and enjoy your bannanas
Let's see what's the actual resonance. If we take 10mH as actual inductance, resistance 1.1Ohm and assume capacitance to be small due to round wire, let's say 100nF, according to RLC calculator resonance is 5032.92Hz, exactly 5KHz as i assumed.
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