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Re: [TCML] Rectifying methods



Hello Dennis,

I think you don't have understood the function of a DC - Teslacoil. You first should work through Richie Burnetts website and learn whats happening in a DC - Charging circuit and why you have to use a DC charging inductor. To start with a DC system in teslacoiling is not the best idea because it is much more complicated than an AC system, you need a well built DC charging inductor and also a well engineered Rotary Spark gap with adjustable speed and very good dwell time, especially in the power levels you want to use.

Stefan

----- Original Message ----- From: "Dennis Eriksson" <teravolt@xxxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, December 03, 2010 11:39 AM
Subject: RE: [TCML] Rectifying methods



The input voltage to the rectifier is only about 4000VAC, which would make 10000VDC in the primary circuit (12-pulse rectifier). So far, the only commercial diodes I have managed to find are low voltage/power rated, such as those found in household electronics. These are insufficient, as I would require thousands of them. On eBay I found these

http://cgi.ebay.com/50x-6Amp-1KV-High-Voltage-High-Current-Rectifier-Diode-/130461406786?pt=LH_DefaultDomain_0&hash=item1e601b1642

Which are ought to be somewhat similar to the ones you are referring to, am I right? Perhaps these would be suitable in the rectifier, but would they be able to resist the tremendous current from the tank capacitor when the spark gap fires? Or is it not a problem at all? I have no education in electronics worth mentioning, I built my first coil at the age of thirteen, and has continued ever since, so there is plenty of experience though.


Date: Thu, 2 Dec 2010 16:52:17 -0800
From: jimlux@xxxxxxxxxxxxx
To: tesla@xxxxxxxxxx
Subject: Re: [TCML] Rectifying methods

Dennis Eriksson wrote:
> First of all, please show indulgence to my writing, as english is not
> spoken as a primary language.
>
> Hello fellow coilers!
>
> Years ago, I began constructing my very last tesla coil, a magnifier
> set to do nothing but entertain and educate the students in my
> hometown. I didn't have time to make it pretty, as I only had 6
> months until dealine. However, it was completed and operational. Set
> to operate at 20kW single phase current, capable of 80kW, it was to
> be the most powerful tesla coil in this part of the world. As the day
> of the show arrived, it became clear that there was nowhere to plug
> it in, and the show was cancelled. Ever since I have failed with
> everything, education, jobs et.c. Now is the time to finish it.
>
> I have decided to convert it into a DC powered coil, with the
> advantage of using polyphase current through a rectifier, but at
> these high power levels, common rectifying methods are insufficient.
> I have primarily been considering mercury arc valves and
> electromechanical converters, but none seem apt in this application.
> I need to know if there are anyone out there who knows how to rectify
> my current, or have done it in the past.


What voltage are you working at? I would think that standard
semiconductor rectifiers would work perfectly well. 80kW at 20-30kV is
nothing special. It's only a few amps, after all.

There are many commercial vendors of high voltage, high current
rectifiers, if that's the route you want to take (they're used in high
power transmitters, for instance)

If you want to build yourself.. the basic technique is to string
multiple lower voltage diodes in series. These days, the part to part
consistency is so good, you don't need to use resistors or capacitors in
the string (and, in fact, there are good reasons not to).

You could probably just use 1n5408s, which are 3A 1000PIV units, but
you'd need to string 25-30 in a row for 20kV (you want to have a few
extras) so it's a lot of soldering.

You might want to take a look at the NXP (Philips) BYX101-BYX104 series,
all 9-10 kV parts..

the 101G is 400mA average forward current (in oil)
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