Transient voltage detection circuit measures voltage excursions and recovery times resulting from step-load changes applied to a combination alternator-voltage regulator

Perz, D. A.

English

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S-2	 S-i 
Al 
Galvanomet 
(OscilIograp 
[1
November 1968	 Brief 68-10513 
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. 
Method for Measuring Alternator Voltage Transients 
A transient voltage detection circuit was built to 
measure voltage excursions and recovery times result-
ing from step-load changes applied to a combination 
alternator—voltage regulator. The circuit mainly con-
sists of a three-phase full-wave bridge, zener diodes 
to step down the voltage, and an oscillographic re-
corder. 
As shown in the figure, the three alternator phase 
voltages (1- 11 L,, L 3) are fed into a three-phase. full-
wave bridge (CR-I through CR-6). The direct current 
output is dropped down b y 36 volts for each zener diode
(CR-7 through CR- I 1). The total voltage drop is de-
termined by switches S-I and S-2. S-I and S-2 are 
necessary to short out two zener diodes in those cases 
where the load applied to the alternator is sufficient 
to cause a voltage undershoot which falls below the 
total breakover voltage of the zener diodes in series. 
If this were allowed to happen, the zener diodes would 
no longer conduct and the galvanometer would not 
follow the voltage excursion. Resistor R-1 is used to 
assure sufficient current through the bridge at all 
times. This ensures linear operation of CR-I through 
(continued overleaf) 
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=19680000469 2020-03-12T06:02:53+00:00Z
CR-6. Resistors R-2 and R-3 are used for the cali-
bration of the oscillograph. 
Notes: 
I. The circuit is an inexpensive, fast AC—DC con-
verter. It can be of particular use when testing 
three-phase systems or high-voltage DC systems 
where oscillographic data is needed. 
2. The most important feature of this circuit is that 
it has a very small, insignificant time constant be-
cause no reactive components such as step-down 
transformers are Used. Therefore, the time response 
data is inherently more accurate.
3. Documentation for the innovation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: B68-10513 
Patent status: 
No patent action is contemplated by NASA. 
Source: Dennis A. Perz 
(LEW-1 0373)
. 
. 
Brief 68-10513	 Category 01


Method for measuring alternator voltage transients

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