EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Rick699 on June 10, 2013, 05:20:19 pm
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So to go a little more about it, What would be the best way to get 6.3 volt @ 160 Amps , Continuously in a 12volt mobile application
This is for a large transmission tube.
The voltage must stay within 5% of 6.3volts dc
I was thinking about building a large voltage regulating circuit, But is this the best way?
Is there any ideas out there?
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If you've just got one tube then you'll need a switch mode, if you've a pair of tubes can you run them in series?
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Hi,
This is serious amount of heater (filament power)!! Never mind the heater, where are you going to get the plate (anode) supply from ?
Jay_Diddy_B
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Have the anode figured out, I have special transformers made to run 15volt ac pri , "powered by alternators" that steps up the voltage well into the kv range
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If you've just got one tube then you'll need a switch mode, if you've a pair of tubes can you run them in series?
Yep just have one tube, Switch mode power supply that will run on 12volt dc or are you talking about running a invertor
that will run a 110ac switch mode power supply?
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So to go a little more about it, What would be the best way to get 6.3 volt @ 160 Amps , Continuously in a 12volt mobile application
This is for a large transmission tube.
The voltage must stay within 5% of 6.3volts dc
I was thinking about building a large voltage regulating circuit, But is this the best way?
Is there any ideas out there?
Is there really such a tube design?
The operating filament resistance would be 6.3/160 = 0.04 ohms, which means the cold resistance would be somewhat less, maybe 0.004 ohms? That filament is going to look somewhat like a short circuit, and the wire thickness to convey 160 amps without significant voltage losses is going to be enormous. It is not typical to power 1000 W loads from a 6.3 V supply because of the design challenges involved.
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I've jsut checked the datasheet for a 3cx1500a and that only want's 10.5A at 5V and is good for 1500W of RF. You'll need a very big alternator to power whatever behemoth you're working on.
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What kind of tube takes 160A at 6.3V?? Most of the big transmitting tubes tend to take 5V at a few tens of amps, and I've yet to see a
short circuit welder filament that gulps 160A!
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http://www.g8wrb.org/data/Eimac/4CX10000J.pdf (http://www.g8wrb.org/data/Eimac/4CX10000J.pdf)
http://www.g8wrb.org/data/Eimac/4CX15000J.pdf (http://www.g8wrb.org/data/Eimac/4CX15000J.pdf)
These were in Racal transmitters and they were 3 phase 240V ac.
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http://www.g8wrb.org/data/Eimac/4CX10000J.pdf (http://www.g8wrb.org/data/Eimac/4CX10000J.pdf)
Any tube people know why they couldn't just do 3.2A at 240V or something?
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Yes this is a very large tube "3cx15000a7" The anode will be powered by 4 Leece Neville alternators @ 270amps each
I can add another alternator to get the 6.3 volts but I don't like how the voltage can change per the rpms.
Looking out of the box to find some thing different. Maybe better!
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A good alternator with an AVR board should stay pretty steady on the voltage over a fairly wide rpm range especially if the prime mover is fitted with an electronic governor,A diesel gen set will inherently be more stable on the rpm any way, otherwise generate at a high voltage and use a motor generator set as they used in the old days, whatever you use it is not going to be that portable it will have to be truck mounted.
Out of interest how thick are the filaments in this tube, I have some tungsten rods for tig welding and the 3.2 mm ones will run at about 90 amps go much above 120 amps and they melt.
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Its not a singe filament per se, it is many in parallel. See the attached picture. Its the white 'drum' on the right of the picture. The grid assembly (middle of picture) fits over the filament drum as this is a directly heated cathode valve. The filament supply stud on the bottom of a 4cx10000 is the diameter of your thumb!
Lovely tubes. I sold an old one for US$75 a few weeks ago. The buyer is going to use it in a transmitter so it will 'live' again :)
I have a nice shiny one on a teak plinth as a memento of working on Racal TA1812 10kW transmitters in the good old days. You touch the HT on one of these, you die :scared:
An interesting page on such tubes here:
http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm (http://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm)
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Those look more like some bizarre variation on car parts than electronics. They are beautiful, though. I doubt I'll ever get over the attraction of being able to see the working parts in a tube - that is cool.
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I love electronics and fine engineering. Thermionic tubes satisfy both of those :)
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I did not look into all the details, but I wonder if you could potentially get a 12V power supply (or even the alternator) and associate several of these modules (http://www.ti.com/product/pth08t250w) in series/parallel to get the 6.3V...
I only consider this alternative as I am very crusty in switching PS designs (it's been almost 20 years) - obviously things progressed and a beast like this (http://www.ti.com/lit/ug/slou293c/slou293c.pdf) is possible, but not sure how easy it is to modify it to achieve the specs you need... Maybe it gives you some ideas...
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I did not look into all the details, but I wonder if you could potentially get a 12V power supply (or even the alternator) and associate several of these modules (http://www.ti.com/product/pth08t250w) in series/parallel to get the 6.3V...
I only consider this alternative as I am very crusty in switching PS designs (it's been almost 20 years) - obviously things progressed and a beast like this (http://www.ti.com/lit/ug/slou293c/slou293c.pdf) is possible, but not sure how easy it is to modify it to achieve the specs you need... Maybe it gives you some ideas...
Thanks rsjsouza I am looking in to the modules right now , think that's the way I want to go !
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As there is no practical use for such an installation, it looks suspiciously as if the OP is involved in the seriously stupid activity of CB keydown competitions,where they make ridiculous mobile power amps & (somehow) measure either the power output or signal strength at a remote point.
If the former,have you seen how big a test load is for the power levels they claim?(I've read reports of 50 KW outputs etc----"They're dreaming!")
If the latter,someone with a better antenna would beat a nominally higher power amplifier any old time,but CBers love to kid themselves! ;D
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Good Lord! I didn't know this existed ... check out the pic of the alternators...
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Good Lord! I didn't know this existed ... check out the pic of the alternators...
That's just plain daft, those belts will shred very fast, it would be far better to use one large alternator directly driven from the flywheel with a fenner-flex coupling.
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Or a real Diesel driven Standby power alternator.
They could mount it on a big rigid tray truck,but I guess that wouldn't leave much space for the HT & filament transformers,the blower motor & ducting,& the amplifier itself!
The giveaway with these things is when they start rabbiting on about "Leece Neville alternators".
They all congregate on a car park somewhere in the USA & take turns in "keying down" the heaps of crap on 27MHz (& umpteen harmonics).
The power levels they claim seem very unrealistic to anyone with experience of real high power transmitters.
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:-DD People will always find ways to say "I'm better than you"...
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Or a real Diesel driven Standby power alternator.
They could mount it on a big rigid tray truck,but I guess that wouldn't leave much space for the HT & filament transformers,the blower motor & ducting,& the amplifier itself!
They must have some rules , perhaps everything must fit on a standard class recreational vehicle, be 12V powered, etc. etc... because I started googling around and watching youtube videos yesterday, these guys beef up their suburbans, add 6,8,10 alternators or more (!) and build massive out-riggers to hold arrays of antennas, all on their vehicle.
clearly the best way is to haul a diesel generator, power converters and a transmitter on a flat bed :)
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The thing is,it's illegal!
Not just some newbie getting a slap over the wrist for running a few mW too much on a homemade
gadget ,but full-on "Bubba's new roommate" illegal! ;D
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holy crap, even the harmonics would be stupidly powerful at those ratings.
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I'm still quite dubious about their measurement methods,so the 20 & 50 kW claims are probably horse faeces,but even 5kW with poorly designed amplifiers could cause serious interference on harmonically related bands.