300VDC 6.5A regulator design

You can't supply AC?

Silicon Chip magazine has a (pay for) construction article which might be what you want.

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Just looking at this sentence, seems that this supply has correction inputs where you connect sensing wires from load back to supply and it keeps the voltage constant at load regardless of cable losses with varying load. Check specs of this supply.

************************************************************************* I need the 300V regulator at the end of the cable

HTH

Stanislaw

wrote in message news: snipped-for-privacy@i3g2000cwc.googlegroups.com...

(Note: Valve == tube).

How to modify a surplus PC power supply to produce a 700V or 400V high-voltage rail.

By Leonid Lerner

Valve circuits are not yet dead. While transistors are undoubtedly superior in most applications, the valve still offers several unique advantages. This applies first and foremost to its use in power circuits. There exists a substantial body of opinion that valves outperform transistors in high-quality audio amplifiers, especially in the power output stages. The seriousness of these claims is reflected in the fact that some very reputable manufacturers offer valve amplifiers at the top end of their audio range. For the home constructor, reasonable-quality valve audio amplifiers can be made for a modest outlay using designs available freely on the Internet. These amplifiers are generally based on an EL34 or KT88 valve pair in the output stage, with both valves being readily available in Australia. Another common application for valves is in the output stages of RF power amplifiers. They will operate satisfactorily at frequencies of up to about

30MHz, delivering up to 50W per valve. Their main advantage over RF power transistors, apart from being somewhat cheaper, is that they are much more tolerant of fault conditions. When tuning a new power amplifier design, parasitic oscillations are often encountered which can easily destroy expensive RF power transistors. The valve, however, will live to see another day. Valves are therefore much more suitable for experimentation in new designs. Although valves are readily obtainable, one of the main problems in their exploitation is the lack of suitable power supply transformers. Both the EL34 and KT88 are rated at a maximum plate voltage of 800V, with supply voltages in the order of 500-600V needed to extract maximum power and linearity. However, the only readily available high-voltage power transformers are isolating transformers, which deliver 240V, and magnetron transformers from microwave ovens, which deliver 1500V or more. Clearly, both of these are unsuitable for our application. The easiest way around this is to modify the switchmode power supply of a personal computer (PC), as explored in a previous issue of SILICON CHIP (October 2003). The older AT power supplies are readily available and have now become a surplus item. They are designed to produce about 200-300W, which is in the right ballpark for our application. For little cost, they include a ready-made PC board and almost all of the components we need for a HV switching power supply. Moreover, due to its high operating frequency, the switchmode power supply offers much better regulation and far less ripple than can be obtained from a traditional valve power supply based on 50Hz AC rectification and smoothing. ...

That's a pretty hefty PSU you are looking for. Say 7A @ 300V, that's

2,100W. So you would need a PSU rated at around 2,500W to handle a constant load of 6.5A. You may be able to get away using a slightly lower power output depending upon the load factor and/or duty requirements. Most PSU's rated this high will be AC only input so you should be feeding AC down your 600M line to the point where your PSU is located close to the load. I would also hazard a guess that the single rail 300V DC output would be a custom design so unless you are capable of designing such a beast yourself then it isn't going to be cheap.

This is easily done using a slightly modified off the shelf Active Power Factor Correction module, available from Vicor and others, provided that you maintain the voltage on the input side at less than

280 volts or so. These boost regulators normally supply about 385V, and expect an AC input. However, they will work just fine with DC input, and efficiency will be in the range of 95% if you keep your input voltage near to the output voltage. (You'll get slightly higher efficiency if you jumper across the input rectifier.) The modification will be to change the feedback divider ratio to produce a regulated output of 300V instead of 385V. Paul Mathews

yeah, run a feed back wire to the regulator circuit..

--
"I am never wrong, once i thought i was, but i was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

I'd worry about fire safety: use AC on the long cable, and you can get fuses that will work. At DC, those fuse devices are gonna be a hard part to find.