Tesla primary coil rectification

[Jeg]

Hi to all

After the spark gap in a tesla coil arrangement, i take some bursts at the BPS frequency. Those bursts consists of the oscillation frequency between discharge cap and primary coil which is around 300KHz. In a try to "play" with this signal, i am thinking of rectifying it. The voltage is around 4KV but current is unknown.

My question refers to which kind of diodes may i use so to rectify it without problems. I look for something cheap and capable of handling all these peak currents.

Tnks
Jeg

[gyulasun]

Hi to all

After the spark gap in a tesla coil arrangement, i take some bursts at the BPS frequency. Those bursts consists of the oscillation frequency between discharge cap and primary coil which is around 300KHz. In a try to "play" with this signal, i am thinking of rectifying it. The voltage is around 4KV but current is unknown.

My question refers to which kind of diodes may i use so to rectify it without problems. I look for something cheap and capable of handling all these peak currents.

Tnks
Jeg

Hi Jeg,

You should know the possible peak or normal currents levels involved (considering worst case) and choose diodes accordingly. Price strongly depends on HV reverse breakdown and forward current spec, together with fast speed, see this for instance:
http://www.ebay.com/itm/2CLG-10KV-1A-High-Voltage-Diode-HV-Rectifier-Tesla-Ham-/271096259991 

Some more choices for 10kV diodes (unfortunately up to max 1 A current): http://www.ebay.com/bhp/10kv-diode 

Of course you can search for 5 or 6 kV diodes too.

[Jeg]

Hey Gyula
I am looking for high current ones and i'll fix the desired voltage by making strings. I just don;t know if frequencies around 300-500KHz need special diodes. Will silicon ones make a decent rectification without speed problems? Or i have to look for germanium or others special types!

[gyulasun]

...
I just don;t know if frequencies around 300-500KHz need special diodes. Will silicon ones make a decent rectification without speed problems?

Yes, look for fast and / or super fast diodes, these have less than 80-100 nanosecond reverse recovery time so would not heat just due to the higher frequency involved like an 1N4007 50-60 Hz type. here are some:
http://www.ebay.com/itm/RHRG75120-High-Current-High-Voltage-Fast-Soft-Recovery-Diode-75A-1200V-Qty-2-/171177259669?pt=LH_DefaultDomain_0&hash=item27daf5b295

http://www.ebay.com/itm/RHRG30120-Ultra-Fast-Soft-Recovery-Power-Rectifier-1200V-30A-65ns-Qty-2-/181262817795?pt=LH_DefaultDomain_0&hash=item2a341b1a03

[TinselKoala]

Sounds like a good way to let the magic smoke out of some expensive diodes!

Why in the world would you want to kill that nice 300kHz tank oscillation by rectifying it? The place to rectify a primary Tesla coil circuit is _before_ the sparkgap and tank circuit. Once you have a nice ringing in the tank, you will be wasting half the energy with a half-wave (single) rectifier, and you will kill the oscillation completely with a fullwave bridge.

I'm not saying you shouldn't try it (if you can afford the diode stack you will need to withstand your primary voltage peaks) but I am curious as to the motivation and the expected result.