Report examines relationship between coil loss and frequency and heat loss in coil as a function of the magnetic field H. Information is of value to manufacturers of superconducting magnets, motors and generators

Guderjahn, C. A.

Wipf, S. L.

English

NASA Technical Reports Server

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June 1972	 B72-10360 
NASA TECH BRIEF 
Marshall Space Flight Center	 NAL 21011-1111L 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Alternating Current Losses in Superconducting Coils 
A superconducting material wound into a coil, will 
not carry as large a current as tests on shorter lengths 
would suggest. At present, superconductors are clad in 
copper to prevent current reducing instabilities. This is 
an expensive and bulky solution. In order to find a more 
efficient remedy a study was begun, and a report pub-
lished, on the nature of these instabilities. The report 
deals primarily with the technique of exciting the coils 
with an alternating current. A measurement of the heat 
dissipated should lead to a better understanding of the 
mechanism involved in the degradation of the coil. 
First examined was the relationship between coil loss 
and frequency. The conductor used was a composite of 
Nb, Nb 3 Sn and Cu in the form of a tape wound into a 
pancake coil. It was found that dividing the coil losses 
by the current squared (12) and the tape length 
squared helped correlate the data. (However, there is 
no theoretical basis for this correlation.) The figure is a 
sample of the results. Finally, the heat loss in the coil 
was investigated as a function of the magnetic field H. 
In a normal conductor the heat loss would be propor-
tional to 1 2 R (R=Resistance). But in the case of a 
superconductor, the magnetic flux can penetrate the 
conductor to produce eddy currents in the interior of 
the conductor as well as on its surface; thus the heat 
loss will be proportional to 13 or more exactly (Hpeak)3 
When measured, the heat loss in low fields was pro-
portional to (Hpeak)3
 as expected, but it was found 
that in high fields (over 1000 gauss) the heat loss is 
proportional to (Hpeak)3 
Notes: 
1. This information may be of interest to manufacturers 
of superconducting magnets, motors, and generators.
10	 102 
Frequency (Hz)
Coil Loss vs Frequency 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: TSP72-10360 
Patent status: 
No patent action is contemplated by NASA. 
Source: S. L. Wipf and C. A. Guderjahn of

North American Rockwell Corp.

under contract to

Marshall Space Flight Center

(MFS-21 129) 
•
Category 03 
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.
https://ntrs.nasa.gov/search.jsp?R=19720000359 2020-03-17T03:30:01+00:00Z


Alternating current losses in superconducting coils

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