# Need Help With HV Diode

#### Livingwaters

Joined Mar 4, 2008
16
Hello group,

I need help with protection diodes. I am running app. 34,000 volts @ 0.83 amps. DC at intervals. I want to join the current flow with 110 volts @ 20 amps AC steady. What value diodes would I need to keep the 34 Kv from running back through the 110 line circuit??

To make this a little clearer..... The 110 volts will be flowing, or, on constantly, The 34,000 volts will be pulsed, or on/off, on/off etc.

Thanks In Advance for the help!
Livingwaters

#### Davidpostlethwaite

Joined Mar 2, 2008
12
what the heck are you up to?
let me get this straight, you're trying to connect a 34,000V supply to a 110V supply? are they both AC? if so, are they the same frequency and phase? In theory a triac could be used to pulse power and not allow back feed. finding one at that rating will be hard! stacking diodes is another way (droppind the Voltage across many HV diodes).
If you can elaberate on the project I might have a couple of ideas.
Sounds dangerous whatever it is!

#### beenthere

Joined Apr 20, 2004
15,819
We need more explanation about this proposed circuit. On the face of it, placing a 34KV DC potential onto a 120VAC line is just asking for big problems - the insulation simply will not handle that potential. What is the application?

#### scubasteve_911

Joined Dec 27, 2007
1,203
IMHO, No offense, but someone that is working with this sort of power and potential should already know what he is doing.. Even if someone had answered the question and it seemed well-grounded, then you are still putting yourself and perhaps others at risk by taking someone's word for it.

I would either ask an expert in the field, then understand what you're dealing with, then try to do it very safely. Or, hire a consultant that deals with these matters.

Steve

#### Livingwaters

Joined Mar 4, 2008
16
We are experimenting with supplying a plasma spark within an internal combustion engine.

The concept is to adjust the voltage and amps to achieve this without burning anything up, and more importantly, hurting someone.

Remember that the 34,000 volts is from an automobile ignition coil at only 0.83 amps.

The 110 volts @ 20 amps is placed within the circuit via an inverter AC. This is not grounded to the car except at the plug base. So, the arc is made only when the 34Kv makes it's way to the spark plug. This is achieved by the rotation of the rotor within the distributor.

My question is what value diodes would I need to keep the current from running back and frying the inverter. I know there is an equation for this. Thought you guys could help me with that.

Best Regards,
Livingwaters

#### thingmaker3

Joined May 16, 2005
5,084
This is achieved by the rotation of the rotor within the distributor.
New tech for old, old car?

Choose the diode the same way you would for any other application - pick one with breakdown voltage in excess of your need.

#### nanovate

Joined May 7, 2007
666
You might need to look at a gas discharge tube or spark gap.