Bank uses commercially available high-energy-density capacitors for energy storage and silicon-controlled rectifiers for switching. Low voltage design employing solid-state switching is utilized in lieu of conventional gas discharge switching

Michels, C. J.

Posta, S. J.

English

NASA Technical Reports Server

May 1973	 B73-10171 
NASA TECH BRIEF Lewis Research Center	 & 
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be directed to the Technology Utilization Office, NASA. Code KT. Washington. D C 20546 
Compact 20-Kioampere Pulse-Forming-Network Capacitor Bank 
A compact high-current pulse-forming-network (PFN) 
capacitor bank has been developed using commercially 
available high-energy-density capacitors for energy storage 
and silicon-controlled rectifiers for switching. A low 
voltage design employing the solid-state switching is 
utilized in lieu of the conventional gas discharge 
switching. 
1—Low voltage charging power supply 
• 
PF\-capacitor bank assembly. 
A prototype PEN capacitor bank, shown in the figure, 
is rated at 1 .25 kilojoules and provides rectangular pulse 
current waveforms for periods of 125 microseconds at a 
peak current of 20 kioamperes. The complete assembly is
mounted on a 0.91 meter (3 foot) cart. This bank has a 
capacity of 2500 microfarads distributed equally among 
five stations. Each station consists of five parallel-
connected capacitors rated at 100 microfarads and 2500 
volts dc. Inductance is obtained from a 10-turn solenoid 
consisting of a 3.81 cm (1.5 in) by 0.317 cm (0.125 in) 
copper strip wound with a 10.2 cm (4 in) inside diameter 
on a 6.35 cm (2.5 in) pitch. Each two-turn section of the 
solenoid provides inductance for one capacitor station. 
Four parallel-connected silicon controlled rectifiers 
mounted on a common convection-cooled heat sink serve 
as the switch assembly. 
Forward current among the four silicon controlled 
rectifier (SCR) units is equalized to within 10 percent 
during both turn-on and conductance by: (1) matching 
the forward characteristics of each SCR, (2) applying a 
strong gate trigger to each unit, (3) mounting the SCR's 
perpendicular to and centered about the axis of the PFN 
solenoid, and (4) equalizing resistive and inductive paths 
to each SCR. 
The modular design and construction provides 
capability for extending the length of the rectangular 
pulse current waveform to any length or multiples of 
length by adding more stations. 
The PFN capacitor bank shown is a prototype of a 10 
kilojoule/i millisecond bank to be built for use in plasma 
studies. The design is especially suited for powering 
low-impedance (5 to 25 milliohm) arcs such as those 
employed in laser and fusion oriented pulsed plasma 
sources, pulsed solar simulators, and MPD-arc thrusters. 
Notes: 
I. This PFN capacitor bank design can also be utilized in 
compact precise pulsed power sources for welding, 
intense magnetic fields, plasma torches, and arc 
vacuum deposition of metallic coatings. 
2. Documentation may be obtained from: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B73-10171
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that Such use 
Government nor any person acting on behalf of the United States
	 will be tree from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000171 2020-03-17T07:11:10+00:00Z
Patent Status: 
NASA has decided not to apply for a patent. 
Source: S.J. Posta and C.J. Michels 
Lewis Research Center
(LEW-1 2009)
. 
. 
B73-10171	 Category 01


Compact 20-kiloampere pulse-forming-network capacitor bank

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