Re: 4000 watt Audio Amp to drive Tesla coil (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 12 Sep 2007 10:26:30 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 4000 watt Audio Amp to drive Tesla coil (fwd)


If you need a cost effective 2.5MA for 5 seconds use 14,000 car batteries 
like the railgun people did.
http://www.arrl.org/rfsafety/lapin/2001/03/28/1/index.html Can't find the 
original reference, sorry.  No doubt they didn't run the railgun on 12 volts 
but used some series/parallel arrangement
You only need 0.0002MA so scale accordingly.

Peter


)
>
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Mon, 10 Sep 2007 10:57:28 -0700 (PDT)
> > From: Timka <tomasdoc2002@xxxxxxxxx>
> > To: tesla@xxxxxxxxxx
> > Subject: 4000 watt Audio Amp to drive Tesla coil
> >
> > Hello all,
> >
> >   Did anyone ever used and audio amp to drive Tesla coil before?
> >
> >   I came across a few mosfet amps on EBay, new but relatively cheap. The
> one I was looking at is rated at 4000 watts bridged output into 4 Ohms 
> load.
> Now, I figured if I would use copper tubing, the resistance wouldn�t be 
> a
> major factor after all.
> >
> >   Another good thing is that I can feed anything into it via signal
> generator or even audio to see how coil behaves.
> >
> >   Now, nasty things that I worry about:
> >
> >   1) It would really suck if I ended up blowing final mosfets due to TC
> secondary kick back and frying internal circuitry, which would be a total
> fiasco and probably would puzzle a lot of clerks at the return department.
> Ad states that amp employs overload protection but whoever designed them
> back in China never envisioned a million volts kickback from an ordinary
> speaker, so I'm not holding my breath there. Any suggestions here?
> >
> >   2) What kind of power supply is needed? In a car amp works off
> alternator and use around...... around a lot of amps! In fact, not every
> alternator can pull a 4000 watts amp as the most of them is in the area of
> 120 amps on average. Here is quick math for 4K watts amplifier:
> >
> >   1 channel with 4000 watts RMS per channel doubled to the account for
> amplifier inefficiency (4000 watts X 2 = 8000 watts), then divided by the
> average output Voltage of an alternator, 13.8 volts (8000 divided by 13.8= 
> 580 amps). Since the average signal requires about 1/3rd of the average
> power in a tone used to drive TC, dividing by 3 (580 amps divided by 3 = 
> 193
> amps). This is the result of the amplifier's approximate average current
> draw.
> >
> >   Soooooooo, how and where in the world do I get a source of 200
> constant amps at 13.8 volts? This is not your average power supply you can
> plug into a wall. I was thinking of getting a car booster/starter 
> a.k.abattery charger, it's the size of small fridge, with 2 fat clammed 
> cables,
> weights about 60lb and probably employs a very large transformer you can 
> use
> to kill your mother in-law that can be plugged into a wall. Another ad
> claims that this car starter can give an instant 300 amps surge or so but
> how about using it for longer than instant or lets say 10 min? Can it pull
> this amp? Of course I can add a few 2 farad audio caps in between, but 
> would
> it be enough?
> >
>
> You don't.. 4kW RMS is probably a bogus spec. (something like "peak
> music power", which has no real meaning)  For one thing, to put 4kW into
> a 4 ohm load takes, let's see.. P=E^2/R 4000*4 = E^2 ->
> Vrms=sqrt(16,000), or about 128 V.
>
> If you buy a "real" multi-kW audio amp, they tend to run off 120 or 240V
> supplies at tens of amps.  Check out the products from, e.g. Techron or
> Crown.  I have a couple Techron 7560s at work, and they're a pretty
> beefy unit.. rack mounted, about a foot tall, etc.  They'll comfortably
> put out a couple kilowatts at 120V, and you can bridge them.  They're
> basically a giant power op amp.  We use them to do things like drive big
> voice coil positioners on shaker tables, simulate power supply
> transients, etc.
>
>
>
>
>