Circuit limits the turn-on current transient to a specified amplitude and provides a low-impedance path between supply voltage and load after a prescribed time interval. The circuit offers a wide range of flexibility in adjusting peak current and automatic control of the initial peak current

Hallberg, F. C.

English

NASA Technical Reports Server

R(Load) 
October 1968	 Brief 68-10384 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Improved Limiter for Turn-On Current Transient
This circuit limits the turn-on current transient 
to a specified amplitude and provides a low-imped-
ance path between supply voltage and load after a 
prescribed time interval. The circuit offers a wide 
range of flexibility in adjusting peak current and 
time to complete connection to the load. It is more 
compact and lighter than a comparable limiter circuit 
which uses a large choke but which is still not effec-
tive where large load capacities are involved. 
The new circuit automatically controls the initial 
peak current that can flow into a high-capacity 
load when voltage is applied. The load capacity is 
charged in four controllable steps. Peak current 
limiting is controlled by the values of resistors R4, 
R, and R i;. The time for completion of the cycle is 
automatically controlled by the selection of time 
constants R 1 C 1 , R2C, and R:C:. The small choke 
(L) offers a high impedance to small stray-capacity 
charging currents and short-duration voltage changes. 
When power is removed, the sequence of steps is 
automatically ready for the next power turn-on.
In one modification of the basic circuit, a relay 
that is switched on by (SCR) is used to eliminate 
the unnecessary holding or gate current to (SCR). 
In another modification a transistor increases the 
voltage across the relay coil and offers higher gain 
in the last stage than is obtainable with the first 
modification. 
Note: 
Complete technical details may be obtained from:

Technology Utilization Officer 
Goddard Space Flight Center 
Greenbelt, Maryland 20771 
Reference: B68-10384 
Patent status: 
Inquiries about obtaining rights for the commer-
cial use of this invention may be made to NASA, 
Code GP, Washington, D.C. 20546. 
Source: F. C. Hallberg 
(GSC- 104 13) 
Category 0! 
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 free from privately owned rights.
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Improved limiter for turn-on current transient

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