How many ways for rectify hv

[Tomata]

How many ways are for rectifying high voltages like 5kv 100ma to 30kv20ma AC to DC?

[Jetijs]

You can use HV diodes for this. If you can't get them, just use several low cost 1000V diodes in series. Use fast ones. UF5408 are good, they are rated 1000v 3A, just solder 30 of them in series and you will have one monster diode rated for 30kV at 3A, should do just fine. Another way is using different electrode materials at spark gap, they will work like a galvanic cell, just with higher voltages. For example I have tried tungsten and aluminum, I noticed that if I put HV + to tungsten and - to aluminum, I need way bigger voltages to jump the same gap as I need if the polarity is reversed (or maybe it was the other way around) anyway, it works like a diode, but I don't know how effective, diodes are a better way. Microwave oven diodes are also a good way, they are usually rated 12kV at 500mA, but they are more expensive.

[Tomata]

Thank you Jetis,
so diodes is one way ,the easy one.

What you mention with the electrode materials at spark gap is very interesting.I need to find more information about this.

I read about tube rectifiers for high voltage also.Is tubes efficient and practical for this kind of voltage?

Iam wondering how they was rectifing ac to dc before they invent todays diodes and tubes.

[HairBear]

Mercury arc valve

From the wiki...

A mercury arc valve (mercury vapor rectifier) is a type of electrical rectifier used for converting high-voltage or high-current alternating current (AC) into direct current (DC). Rectifiers of this type were used to provide power for industrial motors, electric railways, streetcars, and electric locomotives, as well as for high-voltage direct current power transmission. They were the primary method of rectification before the advent of semiconductor rectifiers such as diodes and gate turn-off thyristor (GTOs).

[Shanjaq]

What about something like this? Inquorate's Magnetic Diode, rectifying 30kv!

YouTube - c30kv magnetic diode proof of concept

[boguslaw]

Tesla patent.But with HF it might be costly to find a good core.

[Tomata]

Thanks,
i order a rectify valve to give it a try but the magnetic diode it looks very interesting.I will try that also.
@boguslaw
Which patent?

[boguslaw]

Thanks,
i order a rectify valve to give it a try but the magnetic diode it looks very interesting.I will try that also.
@boguslaw
Which patent?

Don't remember now, just search google patents for Tesla patent converting AC into DC.

[Tomata]

I got the tube 705WA but need help on how to connect it as this is my first tube and need help not to destroy it.



I find a pdf file with data and cant understand how to.

http://www.scottbecker.net/tube/sheets/084/3/3B24WA.pdf

What iam guessing is the points 3 and 1 are the filament and those must be powered with 5Volts/5Amps.Is that right?

What should connect on point number 2 and 4 and is the top metal "hut" on the tube used in any way?

[WeThePeople]

I got the tube 705WA but need help on how to connect it

What i am guessing is the points 3 and 1 are the filament
and those must be powered with 5Volts/5Amps.
Is that right?

What should connect on point number 2 and 4
and is the top metal "hut" on the tube used in any way?

These are nice old buggers,
I just spotted a matched pair on eBay for about $40.

Most are only aware of lower voltage units like the 5U4GB, etc.

A lot of rectifier tubes use one of the heater terminals as the cathode lead also,
but this design uses a dedicated cathode lead that is also a center-tap on the heater.

So yes, heater voltage goes to one 1 & 3,
2 is the center tap on the heater AND cathode,
and 4 has no connection on it.
(See attached pinout pic)

So measure the three active leads for the highest resistance reading,
that would be terminal 1 and 3 for the heater.

The resistance to the remaining pin will be half of that reading
from both heater pins because it is center tapped.

I state this to you, so you can confirm internal wiring,
and blow out your pretty new toy, heheh...

That pin (2) is the cathode, the cap on top of the tube is the anode (Plate)
You know the silicon equivelant as this:

Anode ---|>|--- Cathode

It takes five volts direct current at about five amperes to pins 1 & 3 for the heater,
that is the specifications for this, back in the day of type "A" 90-volt plate batteries.

But you can use AC too if you bring it up slowly and determine the correct amount,
I suspect at that heavy a filiment it will be about 3.75-VAC for proper operation.

Put a steady 5-VDC in while in a dimly lit room to get your reference visual,
then match that with slowly inceasing AC voltage to match the brightness.

The filiment will last a lot longer on AC...

Put your alternating voltage to be rectified to pin 2 on the base,
collect your rectified positive voltage from the "top-hat" pin (Plate).

These will take about 30-KV peak inverse voltage across it,
and supply a hefty 100-milliampere of rectified current.

You may see ratings as high as 400-milliampere (0.4-Ampere),
but try to keep it under 150-milliampere for tube longevity,
and under 360-milliampere for the better three pin unit...

Also, the four pin has a full top hat the uses the later standardized cap,
and of course the standard large-pin'd obligitory four pin rectifier base.

But they can be found with a three pin base and a wire lead cap instead,
with a thoriated tungstene cathode from General Electric (DLA MIL-PRF-1/1159D).

(See attached Alternate Packaging pic)

[Tomata]

This is simple and detailed explanation easy for me to understand.Thank you for your time.

Put your alternating voltage to be rectified to pin 2 on the base,
collect your rectified positive voltage from the "top-hat" pin (Plate).

One more question,maybe naive but,
If i want to collect a negative voltage ?

[WeThePeople]

One more question, maybe naive but,
If i want to collect a negative voltage ?

First, I came back to edit my post to include the obvious to most folk,
but as it is a safety issue, I thought best to add a note on this.

When I said to observe the current through the rectifier section,
I find that I did not denote WHERE to do this sampling of data.

Put your meter in the path of the lead closest to earth ground,
don't put it in the cathode or anode leads at 30+KV !

put it in the return path that is closer to earth gorund,
as most meters are limited to about 600-V isolation.

As to your question, reverse provided data.

Supply AC to top cap, harvest negative from pin-2 at base.

Another safety tip is that the supplied heater voltage is subject to these extreme voltages too.

You cannot just use some wall-wart to provide them !

If it is a transformer (as example),
it must respect the total circuits PIV of 30-KV isolation to be safe !

For testing, and as a prototype jig, I recommend batteries.

Your in an area where an oversight like this can cause harm sir.

[Tomata]

The tube still working fine.
Now i had got 4 diodes 40kv 1amp and i would like to ask what is the best solution to protect the diodes from destroying ?I will use it to rectify a 15kv 60ma nst and sent paulses to a coil or a spark gap.

I already these days burned a channel from the function generator and destoyed one nst...so i dont need any more losses.