Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Pulsed mode
Date: Feb 25, 11:05 pm
Poster: Ely Silk

On Feb 25, 11:05 pm, Ely Silk wrote:

>As regards insulation break down....WRONGO...Just the opposite! Pulsed discharges of 2us at 20kv with low impedance, (high energy capability), will break down insulation that would easily withstand continuous 20kv DC operation for years!!!! It is at the very core of how a Tesla coil can produce such long arcs and why lightning doesn't need the teravolt potentials calculated to make the cloud to earth leaps! Instead, lightning is merely in the millions of volt range and makes it long trip to ground in a rapid series short microsecond stepped leaders. The leaders heat and pre-ionize the air ahead of the stroke. Such would be the case here too. The insulation would have to be incredibly beefy to pulse a system.

Well, not exactly. Referring to "HIGH-POWER ELECTRONICS" by Sarjeant and Dollinger (Chapter nine dealing with Transformer Insulation in high-voltage air core pulse transformers) it appears that if the high-voltage pulses are short (say 1 microsecond or less) and if there is an adequate time between pulses so that discharge paths have a chance to dissipate, one can greatly exceed the electric strength of materials. A short enough pulse will allow perhaps twice (or more) the normal DC voltage to be applied.

What you say above is correct for slower pulses at a high pulse repetition rate -- that is, what you would encounter in working with Tesla discharges.