A bifilar winding around the magnetic core of electromagnetic devices suppresses high transient voltages. The winding is alternately spaced vertically and radially from the core to achieve a high coefficient of coupling

Marion, C. W.

English

NASA Technical Reports Server

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Power 
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February 1967	 Brief 67-10031 
NASA TECH BRIEF	 1 
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. 
High Transients Suppressed in Electromagnetic Devices 
1 
1	 S2 
L1 
The problem: 
In the operation of electromagnetic devices such as 
relays and solenoids, high transients are caused by 
rapid field decay upon removal of current to the de-
vices. Previous methods of suppressing these transients 
have been less than ideal in that they resulted in in-
creased size and weight, polarity dependence, and 
increases in contact resistance due to outgassing. 
The solution: 
A bifilar winding around the magnetic core alter-
nately spaced vertically and radially from the core to 
achieve a high coefficient of coupling. 
How it's done: 
An actuation winding W1 about the core is con-
nected to a power supply through a switch S1. A
transient voltage suppression coil W2 is alternately 
wound with its ends connected to form a short cir-
cuited winding. A leg Li projects laterally from the 
base of the core and has a vertical leg L2 extending 
upward to slightly above the top of the core at which 
point a contact assembly C is spring loaded to extend 
laterally above the core. A load is connected in series 
with the device through a switch S2. 
When Si is closed, current flows through W1 creat-
ing a strong magnetic field that pulls C down to con-
tact the core at the same time pulling S2 closed con-
necting the load to the power supply. 
Opening Si de-energizes W1 causing the magnetic 
field to decay rapidly to produce a transient voltage. 
The high coefficient of coupling between Wi and W2 
causes the transient to bleed off through W2 rather 
(continued overicul) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000031 2020-03-11T20:18:58+00:00Z
than seek other dissipative paths. When the magnetic 
field has decayed sufficiently, spring loaded contact C 
returns to the horizontal, opening S2 and removing 
the load from the power supply. 
Notes: 
1. This method affords a simple and inexpensive sup-
pression of high transient voltages that would 
otherwise cause interference in the operation of 
sensitive components adjacent the electromagnetic 
device. 
2. To control the effect on relay release time, it is only 
necessary to select the proper wire size for W2.
3. Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Kennedy Space Center 
Kennedy Space Center, Florida 32899 
Reference: B67-10031 
Patent status: 
This is the invention of a NASA employee and a 
patent application has been filed. Inquiries concerning 
license rights may be made directly to the inventor, 
Mr. Charles Wayne Marion, at Kennedy Space Cen-
ter, Kennedy Space Center, Florida 32899. 
Source: Charles Wayne Marion 
(KSC-66- 13)
. 
Brief 67-10031	 Category 01


High transients suppressed in electromagnetic devices

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