Transmission Line Delay for Nanosecond Pulse Arc Current Limiting
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Solution Overview
Problem
Nanosecond pulsed power sources face damage from load arcing due to high short-circuit currents reflected back to the generator, which can destroy circuitry, particularly in high-voltage applications like nsPEF therapy.
Innovation Solution
Utilizing long transmission lines with distributed inductance and transmission line delay to prevent damage by ensuring the transmission cable length is greater than half the maximum pulse duration divided by the characteristic pulse speed, thereby allowing the generator to switch off before reflected pulses reach it.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage nanosecond pulses are delivered to the load, then therapeutic effect is achieved, but load arcing occurs causing damage to the pulse generator
Solution Approach 1:
The transmission line length is specifically designed to provide a time delay that allows the pulse generator to complete its nanosecond pulse delivery and begin recovery before the reflected arc current returns. This preliminary configuration of the transmission line dimensions prevents the harmful reflected current from reaching the generator during its vulnerable switching period.
Solution Approach 2:
The transmission line acts as an intermediary element between the pulse generator and the load. By carefully selecting its length to exceed the critical threshold (L > c×τ/2), it mediates the interaction by delaying the reflected current waveform, allowing the generator to safely complete its operation cycle before the harmful reflection arrives.
2Reliability
If transmission line length is increased to prevent reflected current damage, then pulse generator protection is improved, but pulse waveform distortion increases
Solution Approach 1:
The invention optimizes the transmission line length parameter within a specific range (L > c×τ/2) to achieve the desired protection effect while minimizing waveform distortion. By carefully controlling this dimensional parameter, the system achieves generator protection without excessive pulse broadening or amplitude loss.
Solution Approach 2:
The transmission line length is set to exceed the minimum critical value (c×τ/2) by a margin that provides sufficient protection while avoiding excessive length that would cause unacceptable waveform distortion. This partial action approach achieves just enough delay to protect the generator without over-correcting to the point of degrading pulse quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents damage to the pulsed power source by dispersing and attenuating high currents, maintaining system reliability and performance without significant pulse waveform distortion.
Implementation Method 1
using transmission lines (e.g., coaxial cable, twisted pair or parallel pair cables) between the pulsed power source and the load having a length that is relatively long, and in particular, greater than half of the maximum pulse duration divided by the characteristic pulse speed on the cable
Implementation Method 2
the transmission cable length is greater than half the maximum pulse duration divided by the characteristic pulse speed, thereby allowing the generator to switch off before reflected pulses reach it
Data Source
AI summary
Described herein are apparatuses and methods for applying high voltage, high current, sub-microsecond (e.g., nanosecond range) pulsed output to a biological material, e.g., tissues, cells, etc., while preventing damage from load arcing. Some of the apparatuses and methods described herein may limit the load and pulsed power source current in case of load arcing significantly by using a transmission line (e.g., coaxial cable, twisted pair or parallel pair cables) between the pulsed power source and the load having a length configured to achieve this goal.