Investigation Into the Effects of Microsecond Power Line ...
Transcript of Investigation Into the Effects of Microsecond Power Line ...
NASA/CR--2000-209906
Investigation Into the Effects of Microsecond
Power Line Transients on Line-Connected
CapacitorsK. Javor
EMC Compliance, Huntsville, AL
Prepared for Marshall Space Elight Centerunder Contract H-29919D
and sponsored by
The Space Environments and Effects Programmanaged at the Marshall Space FLight Center
February 2000
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NASA/CR--2000--209906
Investigation Into the Effects of Microsecond
Power Line Transients on Line-Connected
CapacitorsK. Javor
EMC Compliance, Huntsville, AL
National Aeronautics and
Space Administration
Marshall Space Flight Center • MSFC, Alabama 35812
February2000
NASA Center for AeroSpace Information
7121 Standard Drive
Hanover, MD 21076-1320
(301) 621-0390
Available from:
ii
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161(703) 487-4650
Final Report: Capacitor Transient Potential Tests
EXECUTIVE SUMMARY
An investigation was conducted into the effect of power-line transients on capacitors used by
NASA and installed on platform primary power inputs to avionics. The purpose was to
investigate whether capacitor voltage rating needs to be derated for expected spike potentials.
Concerns had been voiced in the past by NASA suppliers that MIL-STD-461 CS06-1ike
requirements were overly harsh and led to physically large capacitors.
The author had previously predicted that electrical-switching spike requirements representative
of actual power-line transient potentials, durations and source impedance would require no
derating. This investigation bore out that prediction. It was further determined that traditional
low source impedance CS06-1ike transients also will not damage a capacitor, although the spikesthemselves are not nearly as well filtered.
This report should be used to allay fears that CS06-1ike requirements drive capacitor voltage
derating. Only that derating required by the relatively long duration transients in power qualityspecification need concern the equipment designer.
ACKNOWLEDGMENTS
The author wishes to thank Mr. Kurt Mikoleit of the Naval Surface Warfare Center, Dahlgren,
Virginia for the long term loan of a Solar 7399-2 spike generator. This equipment, capable of
delivering 8 MegaWatt pulses at 2 kV, was specially designed for the spike requirements of MIL-
STD-1399 and is not standard equipment in the typical EMI test facility.
Mr. Robert Kapustka of the Marshall Space Flight Center suggested representative bulk
capacitors he has employed as a designer of dc-dc converters. These were pulled from actual
parts bins used for space applications. Mr. Kapustka has been with NASA since the Apolloprogram.
Mr. Mark Nave of Network Appliance suggested that an explosion container be built when using
the Model 7399-2 to stress tantalum electrolytics, since the electrolyte is sulfuric acid. Given
that evidence of explosive forces was found, this was a sound suggestion.
CS06
CUT
DIP
EUT
FET
LISN
MSFC
STS- 1
ACRONYMS
power-line spike susceptibility test requirement (MIL-STD-461/MIL-STD-462)
cable-under-test
dual in-line package (integrated circuit package)equipment-under-test
field-effect transistor
line impedance stabilization/simulation network
(NASA) Marshall Space Flight Center
switching transient simulator
iii
Final Report: Capacitor Transient Potential Tests
1.0 Introduction
This report documents the restllts of a test in which capacitors were subjected to spiked
potentials of varying amplitudes, durations, and source resistances. The work follows the
development of special transient generators which simulate electrical power bus switching
transients._ In addition to the use of these unique generators, two other generators which rneet
the requirements of MIL-STD-461 CS06 and MIL-STD- 1399 were employed to stress the samecapacitors subjected to switching transients earlier.
1. I Purpose
The purpose of these tests is to demonstrate that capacitors connected across primary power
inputs in avionics need not have their voltage rating derated for switching transient-like potential
stresses. It ',viii be shown that it is sufficient to derate capacitor voltage rating for power quality-related surges, which are lower in amplitude, but have longer durations.
1.2 Scope
Six capacitor configurations were evaluated. All capacitors were selected as representative of
those used in spacecraft applications as hold-up or bulk energy storage or line-to-ground filters at
the input to switching power supplies (dc/dc converters). Specifically, these capacitors were
pulled from bins where power supply bulk capacitors are stored at MSFC. Capacitors used on
28 Vdc (Space Shuttle), 120 Vdc (Space Station), and 270 Vdc (X-33) were selected, as well as a
capacitor rated for just 30 Vdc, which was just marginally rated to operate on 28 Vdc.
Cap. Bus Type
A 28 Vdc
B 120 Vdc
C 120 Vdc
D 270 Vdc
E <28 Vdc
F 120 Vdc
Spike sources were as
Potential Volts
0 - 500
0 - 600
0-2500
I .3 Background
Nomenclature Cap Type
tantalum electrolyticM39006/+ 22-0600
M39006/25-0264H tantalum electrolytic
AVX 87106-157 9622A ceramic
AVX 87106-237 9726A ceramic
M39006/ 22-0560
Sprague LC filtertantalum electrolytic
ceramic feedthrough
C #F
140
82
33.6
15.6
WVDC
60
125 2
200
500
300 30
0.2 200
follows:
Source Impedance Ohms Generator Name Manufacturer
50 STS-13 EMC Compliance
1.2 Model 8282- 1 Solar
0.25 Model 7399-2 Solar
The Space Station program imposed a specially tailored CS06 spike (SSP 30237). The tailoringfi)llowed the practice of MIL-STD-461 of the spike potential being twice the nominal line
potential, but ignored the 100 or 200 Volt limit. For Space Station, this resulted in a 240 Volt
spike superimposed on a 120 Vdc bus. There were complaints from some equipment designers
about the severity of this requirement. In 1994, the author presented a paper at the IEEE EMC
iRefcrenccNASA rcport: NASA/('R 1999 209574
2 Two of these capacitors are used in series across the hus to get the propc derating. "[his results in 41 HI"._S'witching Transient Silnulalor - 1
Final Report: Capacitor Transient Potential Tests
symposium that was the result of investigations into this subject (the breadboard spike generatordescribed therein was developed into stand-alone test equipment as described in the footnote 1
report). A 50 _ spike source was developed which more accurately sinmlated switching
transients? It was demonstrated that a small capacitor could effectively filter a 50 _ source
impedance 1 Its spike, but could not filter a 10 ItS, 1 _ source impedance spike from a Solar
Model 8282-1 spike generator, which is the usual test equipment employed for CS06.
This report extends that simple observation into a lull investigation.
2.0 Applicable
Number
MIL-STD-461
MIL-STD-462
MIL-STD-1399
SSP 30237
SSP 30238
NASA/CR-
1999-209574
3.0 Results
Documents
Title
Electromagnetic Interference Characteristics Requirements for Equipment
Electromagnetic Interference Characteristics, Measurement of
Interlace Standard for Shipboard Systems, Section 300A: Electric Power
Electromagnetic Emission & Susceptibility Requirements for EMC
Electromagnetic Techniques (Space Station)
Specification, Measurement, and Control of Electrical Switching Transients
Capacitors were tested as described above. Capacitance of each capacitor was measured prior to
and after spike applications. Pass/fail criterion was the absence/presence of a change in capacity.
3.1 Summary
No bulk or hold-up capacitor tailed at any spike potential generated by either the STS-! 1 its, 50
source or the Model 8282-1 l0 Its, 1 _ source. This included potentials of 500 V peak (spike
plus dc bus) from the STS-I, and potentials of 600 Vdc superimposed on the bus potential
(resulting in peak excursions of 600 Volts above nominal bus potential). Ceramic feedthrough
capacitors were undamaged by the STS-I generated transients, but failed at higher spike
potentials from the Model 8282-1. These spike potentials were, however, above those nonnally
imposed by NASA CS06 limits.
Capacitor E failed at a Solar Model 7399-2 spike source applied potential of 600 Volts for 20 Its.
Amplitude was i.32 kV into a 0.5 _ resistor. The spike source impedance was 0.25 _. It tookahnost four hours to fail the capacitor, with spikes applied at a rate of two pulses per minute.
The original purpose of this investigation was to show that capacitors do not have to be derated
for positive sense (turn-ofl) transients of microsecond duration if they are properly generated.
This means a source impedance reflecting that of real transmission lines, as opposed to the Ohm
or sub-Ohm source i,npedance of the Model 8282-i CS06 spike source. The point here is that if
a plattbrm mission does not subject it to lightning attachments, a low impedance high potential
transient on a power bus is difficult to explain.
-I 50 _ was lhc source impedance lbr a positive going or tt, m-off Iransienl.
was low impedance.
The negative-going or turn-on transient
Final Report: Capacitor Transient Potential Tests
This investigation amply demonstrates this is the case. All the bulk capacitors except capacitor
E were able to load a 500 Volt (transient plus power bus) potential down to a level below their
voltage rating. None of the capacitors showed any degradation either short or long term after
such applications. In fact, the worst case application applied the 500 Volt spike to a 30 Vdc cap
(capacitor E) biased at 28 Vdc (essentially no derating, even for dc) and caused no effect
whatsoever after three hours of spikes at a repetition rate of one pulse per second.
But in addition to this fact, which it was the purpose of this investigation to demonstrate, it was
also found that the CS06 spike caused no damage to any of the capacitors tested. This was a
much more severe test, due to the low source impedance of the Model 8282-1 spike source.
While the spikes were not as effectively filtered, they caused no lasting degradation. All the
tantalum electrolytics got very hot, and capacitor E measured a higher capacitance just after the
test than before the test or after it had cooled off, but this could not be considered an operational
failure, since more capacitance would not cause a problem for a bulk capacitor function. Spike
potentials generated by the Model 8282-1 were capable of damaging the capacitor of Filter F, but
this occurred at potentials well in excess of normal CS06 limits (above 300 Volts spike potential).
Only a kiloAmp source was able to damage the other capacitors. Tantalum electrolytics failed at
kiloVolt/kiloAmp spike levels (20 ]as duration) after repeated spike applications at two pulses
per minute (ppm). Ceramic bulk capacitors failed at the first kiloVolt/kiloAmp spikeapplication.
3.2 Test Methods
Three different test techniques were utilized. They were implemented in order of increasing
severity. The first tests used the EMC Compliance STS-1 switching transient simulators, which
generated a 1 ps, 50 _ source impedance spike. The next test applied spikes from the Solar
Model 8282-1 CS06 transient generator. The last set of spikes were applied from a Solar Model
7399-2 borrowed from the Navy.
3.2.1 Application of Turn-Off Switching Transients
Capacitor value is measured prior to test start, and again at end of spike application. The test is
diagrammed in Figure 1. In Figure 1, CUT refers to capacitor-under-test.
switching
hi-/ o'sco UT c_r°n_ iretrotr
Figure 1: Schematic of switching transient test
The oscilloscope measures potential from line-to-ground at the LISN output. The nominal spike
potential is measured without the capacitor in place, using a 1 or 10 Mfl oscilloscope probe.
The spike is measured again with the capacitor in place. Spikes are imposed at a rate of at least 1
pps. Pictures of test set ups and capacitors are shown in Appendix A.
A characteristic of the STS-1 not previously discovered is that the switching FET has some kind
of protection circuitry which clamps applied potential to just above 500 Volts peak. Regardless
of switched load (V pik_= 50 _'_*lswilchcd) or nominal bus potential, V_otal (: Vbus-{-Vspike) is bounded
3
Final Report: Capacitor Transient Potential Tests
by just over 500 Volts. Thus the spike applied to the 28 Vdc bus was about 500 Volts, but the
spike applied to 120 Vdc was only a little over 400 Volts, and the spike applied to 270 Vdc was
about 300 Volts.
In each case (for each capacitor at each bus potential), the initial spike potential applied was 100
Volts open circuit. The spike potential actually applied to the capacitor was much decreased in
amplitude from the 100 Volts measured open circuit. This spike potential was applied for
several minutes. The capacitor value was measured, found to be unchanged, and the spike
potential increased to 200 Volts. The same process was reiterated until the maximum 500 Volt
spike was applied. At this point, spikes were imposed at a rate of at least 1 pps for over one
hour. At least 3600 spikes are thus applied at the maximum potential to which the capacitors are
exposed and to which they are considered qualified. After this final application, the capacitance
is again measured (and found to be unchanged in all cases). Test data is shown below for the final
500 Volt spike application for each type of capacitor and bus.
3.2.1.1 Test Data
Data 1-1 and 1-2 show the STS-1 50 _ spike unloaded and loaded by a 140 p,F, 60 V rated
capacitor (cap A). This capacitor is typical of one used as a bulk capacitor at the input of a 28Vdc dc/dc converter. The spike was generated by switching a 2 _ load offthe 28 Vdc line. A 14
Amp switched current should have resulted in a 700 Volt spike (14 A • 50 _), but protection
circuitry limited overall (spike plus bus) potential to 516 Volts. The capacitor so loads the spike
that peak spike amplitude (spike + nominal dc bus potential) is less than the dc rating of the
capacitor. No capacitor failure is expected under such conditions. This is the case whenever the
50 _ spike is generated across a capacitor. Therefore switching transient potentials should not
be used to derate capacitor voltages. The switched spike amplitude will not appear across the
capacitor. Demonstrating this was the major goal of this investigation.
In order to show just how benign the switching transient is, the same 500 Volt spike as of Data
1-1 was generated across a 300 pF tantalum electrolytic rated at 30 Vdc (Cap E), while it was
biased at 28 Vdc. The resulting spike is presented in Data 1-3. It is almost identical to the spike
of Data 1-2, except here the peak spike amplitude (spike plus nominal dc potential) exceeds the
capacitor dc rating. Nevertheless, a three hour exposure at one pulse per second resulted in no
observable change in capacitance, and no observed heating.
A 500 Volt spike (switched load = 20 _) was also imposed on capacitors B and C, which were
typical of those used on 120 Vdc power. Capacitor B is two 82 laF, 125 Vdc electrolytics in
series. Capacitor C is a 33.6 pF, 200 Vdc. Data 1-4 is an unloaded spike injected on 120 Vdc.
Data 1-5 shows near complete filtering of Data 1-4 spike across capacitor B after over one hour
of one pulse per second application. The same result was obtained when the Data 1-4 spike was
injected into capacitor C for two hours at one pulse per second (Data 1-6).
A more visible spike appears in Data 1-7, which is the spike of Data 1-4 injected into filter F, a
Sprague threaded LC filter with capacitor value of 0.2 gF. The capacitor was facing the LISN in
this test. Spike amplitude clearly exceeded the capacitor rating of 200 Vdc, but the spike was
applied for two hours at greater than one pulse per second with no change in capacitance.
Data 1-8 shows the 500 V, 50 f_ spike injected onto 270 Vdc. This same spike was injected over
one and one-half hour (at one pulse per second) into capacitor D, a 15.6 pF, 500 Vdc rated
4
Final Report: Capacitor Transient Potential Tests
ceramic. No visible spike was generated or recorded. Note that in any case, the unloaded
switching transient barely exceeds the capacitor D dc rating.
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5
Final Report: Capacitor Transient Potential Tests
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3.2.2 Application ofCS06 - Like Positive Transients
The Solar Model 8282-1 Transient Pulse Generator was used in a MIL-STD-462 CS06-1ike
parallel injection technique (as diagrammed in Figure 2) to inject up to 600 Volt pulses into the
test capacitors. The 10 las spike source impedance was very near 1 _. Data 2-1 and 2-2 show
spike wavetbrms into 5 _ and 1 £) loads respectively. Spike source resistance is given by:
Final Report: Capacitor Transient Potential Tests
RI R2 (V1 - V2) 5_,lf_ (600V- 340V)= = 1.2_
Rsource = V2 R1 - VI R2 340V,5f_ - 600V, lf_
An unloaded source potential of about 700 Volts may also be deduced from this data. The test
set up was identical to CS06 parallel injection with two differences. A MIL-STD-462D LISN
was used in lieu of the MIL-STD-462 suggested 20 laH coil, and the EUT (capacitor) was
connected directly to the Model 8282-1 parallel output banana jacks. Lead lengths were thus
minimized. Pictures of test set up may be viewed in Appendix A.
LISN8282-1
I
Figure 2' Test set up of CS06-1ike parallel spike injection
3.2.2.1 Test Data
The 600 V, 10 bts spike of Data 2-1 was injected on to capacitors B through E, with no test
failures. All tantalum electrolytics got very hot during this test. These tests were run for at least
one hour at one pulse per second. The ceramics were run at 2 pps with no noticeable heating.
One tantalum electrolytic, capacitor E, read 386 laF immediately at test end (very hot), but 316
p.F after returning to ambient temperature. This was not deemed a failure.
The most important result here is Data 2-3. This is the induced spike across the 300 _F, 30 Vdc
rated capacitor (E)biased at 28 Vdc. With absolutely no headroom to spare, this capacitor still
did not fail when the 600 Volt spike was injected. Note that about 600 Amps was flowing at the
peak of the spike waveform in order to result in an applied spike amplitude of 114 Volts (greater
than 700 Volts source potential loaded through 1 _ source resistance down to approximately 100
V). It is quite reasonable to extrapolate from this result that no properly derated tantalum
electrolytic bulk capacitor will be damaged by any low duty cycle CS06 - like spike application.
Because traditional CS06 test procedures mention spike repetition rates of 1 - 10 pps, spike
testing was also performed at 10 pps. An initial trial placed a 600 Volt spike setting across
capacitor A. The Model 8282-1 amplitude was turned all the way clockwise (maximum output).
This yields a spike potential of greater than 600 Volts into 5 f_. Data 2-7 shows the resultant
spike across capacitor A. Spike amplitude actually dropped over the course of an hour long test
to a peak of 96 Volts. This was attributed to an increase in capacitance due to electrolytic fluid
heating. Capacitor A, nominally 140 gF, rated at 60 Vdc, measured 168 btF cold. After one hour
of 600 Volt spike application at 10 pps, the capacitor case was extremely hot and the capacitance
measured 320 gF. This returned to the pre-test value of 168 btF in about four minutes. Figure 3
shows measured post-test capacitance as a function of time, with a superimposed exponential
decrease. Close correlation shows that capacitance decreases exponentially with time:
C(t) = Co ( 1 + e-t), C = capacitance, Co = initial pre-test capacitance, t = time.
which is a solution to Newton's Law of Cooling:
¢?Tz
?t T, T = temperature, t = time.
Final Report: Capacitor Transient Potential Tests
Strong correlation between capacitance and predicted temperature as a function of time indicates
a very high probability of a causal relationship between electrolyte temperature and capacitance.
3-I I I I I I I I I
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Figure 3: Capacitance as a function of post-test time
Having completed a one hour application of a 10 pps 600 V, 10 !as spike to a 60 Vdc rated
capacitor (A), an identical test was performed on a 30 Vdc rated capacitor (E). Data 2-8 shows
the spike applied to capacitor E (recall that Model 8282-1 amplitude is at maximum, yielding
over 600 Volts peak into 5 _). Both capacitors A and E were biased at 28 Vdc for these tests.
Capacitor E gave similar results to A post test, but hot capacitance exceeded the capacitance
meter's range and could not be measured until it was nearly room temperature. Post-test, the
clear plastic coating of both capacitors was discolored by the extreme heating. It is possible that
if the case of such a capacitor were in contact with a printed circuit board (PCB), that damage to
the board could result. However, recall that the applied spike in the above cases was 600 Volts
peak. No CS06-1ike specification calls out such a spike at such repetition rates for an hour.
The same test was performed on capacitor B, the two series tantalums. Capacitor B was biased
at 120 Vdc (Space Station). The applied spike is shown in Data 2-9. Over two hours the
capacitors did not overheat, and immediate post-test capacitance was equal to the pre-test value.
When the 600 Volt, 10 ps, 10 pps spike was applied to ceramic capacitor C, biased at 120 Vdc,
there was no effect. The test was repeated with the bias at 190 Vdc to most severely stress the
capacitor. There was no effect, other than mild temperature rise after a two hour application.
Data 2-10 shows the applied stress to a 5 _ load at 10 pps, while Data 2-11 shows the actual
stress across capacitor C.
The above tests on the tantalum capacitors established a significant safety margin between
typical CS06 requirements and any resultant damage to bulk capacitors. However, the heating
issue may cause concern with respect to nearby circuit elements, including the PCB. Therefore
the above tests were rerun with a 240 Volt spike. This is the highest CS06 spike potential yet
levied on a NASA program. Data 2-12 shows the 240 Volt spike applied to a 5 _ load. Data 2-
13 shows the result when the same spike generator setting as for Data 2-12 is applied to
capacitor E (300 pF, rated at 30 Vdc, biased at 28 Vdc). After one hour of a 10 pps application,
the capacitor was warm, but not too hot to handle. Initial post-test capacitance measured 380
pF, not much different than nominal 315 _tF.
Final Report: Capacitor Transient Potential Tests
Filter F was an L-filter rather than a discrete capacitor. Line-to-ground cap value is 0.2 pF, other
specifications, taken from the RFI TM catalog, are given below.
.O7O± ,010--'_,
\ /FIl4-28 UNF -2A
SPECIFICATIONSOPERATING TEMF_R_TURE -55" "TO .125 C
CIELECTRC lEEr." 2.5 T}MES RATED VOLTAQE
ffJGUL_TION RESISTANCE: 1DOOMEC.TOH_I8
MI_1.@25'C
CONFORI',_ TO _ ,N_PL_,BLE
FtECUIREMENT$ OF tvtL-=-2_{,1
FILTER SLPPLIEO _NIIH LOCKWASH ER & HCX NU't
FINISH HOT _lDER DIP
0001 RE6905-1 L, 25 2DO 125 .1B7 ,3[_....._2.____28 40 60 60 70
i0002 R_6g05-2 L:. .25 200 125 .18/ 375 22 2B 40 60 60 70
No manufacturer specifies filter series inductance, so this had to be measured. A series insertion
loss technique was used. The filter was placed in series between a 50 _ signal source and a 50
spectrum analyzer. No connection whatsoever was made to the filter case, so the capacitor had
no effect on the measurement. A baseline measurement was made without the filter in line, so
that insertion loss could be ascertained. The equation which predicts the insertion loss is:
50
Insertion Loss (dB) = 20 log ( _'x12500+(2r(fL)2 )
Test set-up schematic and equation is plotted below for L = 400 pH, over a 100 to 1100 kHz
range. Test data shows excellent agreement with theoretical insertion loss for 400 pH. Test data
upper trace A is a baseline measurement without the filter in the test circuit. The lower trace B is
due to the insertion of the inductor in series between signal source and receiver.
-10
Choke under tesl
_, I C_5_DA
,
-20RDC:
_= -30©
-40
0.1
%%
0.2 0.3 0.4 0.5
" i
0,6 0.7 0.8 0.9 1 1.1
Frequency MHz
9
Final Report: Capacitor Transient Potential Tests
I0O
"7O
60 ",:'-' / Trace A
50 / TraceB
40 / A -B
30 / Ref
2O
10
0lO0.OOkHz 1.10MHz
Limea_Frequemcy(IDiv= 100.00kHz)
The table below shows the response of the filter to CS06-1ike spikes. Filter F failed from a single
5 or 10 _s at about 450 V spike applied to the inductor end, when biased at 120 Vdc. It could
take the SSP 30237 10 Its 240 Volt pike at 10 pps indefinitely. It failed within two minutes of
350 V 10 _ts spike 10 pps applications on the capacitor end. When spike duration was reduced
from 10 Its to 5 _ts, damage threshold at 10 pps injection
2 minutes to fail at the same rep rate at 420 Volts).
spike duration _ts single pulse failure point Volts
5 464
increased from 350 to 420 Volts (it took
10 pps, 2 minute failure point Volts
420
10 450 350
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Data 2-2: Data 2-t generator setting develops
this spike across 1
10
Final Report: Capacitor Transient Potential Tests
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this spike across capacitor E this spike across capacitor B
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Data 2-6: Data 2-1 generator setting develops
this spike across capacitor D
11
Final Report: Capacitor Transient Potential Tests
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Data 2-9: Maximum generator setting develops Data 2-10: Maximum generator setting
this spike across capacitor B at 10 pps develops 650 V spike across 5 _ at l0 pps
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12
Final Report: Capacitor Transient Potential Tests
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Data 2-14: Model 8282-1 generates a 240 Volt
spike (SSP 30237 CS06) into 5
13
Final Report: Capacitor Transient Potential Tests
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Data 2-15: Filter F response to Data 2-14 Data 2-16: Filter F response to Data 2-14
spike injected into capacitor side spike injected into inductor side (measuredacross capacitor
Filter F provides the best example of how correctly defining a switching transient provides design
relief. Data 1-7 is filter F response to a 50 _ spike of total (spike plus line potential) 540 Volts
(Data 1-4). The applied spike measured 420 Volts (540 - 120 V) open circuit, and would havemeasured 210 Volts into 50 _. Spike amplitude in Data 1-7 is only 116 Volts (236 V - 120 V).
Filter capacitor succeeds in loading the transient potential sufficiently that no damage is done.
Contrast this filter efficiency with what happens when a Model 8282-1 spike is applied to the
same filter F, as shown in Figure 3. Data 2-14 shows a 240 spike (from SSP 30237 CS06)
developed across 5 f_. Data 2-15 shows the same spike applied to the capacitor side of filter F.
The peak potential has increased from that shown in Data 2-14 because the capacitor is a higher
impedance than 5 f_. If the filter is turned around so that the inductor bears the brunt of the
spike, the potential across the capacitor is shown in Data 2-16. Spike potential is reduced from
that measured when injected directly into the capacitor, but it still exceeds the potential the
Model 8282-1 can deliver into 5 _. The inductor is incapable of significantly filtering the spike.
Figure 3:
LISN
Test set up of CS06-1ike parallel spikeor inductor side face the
filter-under-test 8282-1
o'scope__ 7
injection for single filter F. (Either cap side
spike source.)
However, the test set-up of Figure 3 harkens back to the days when a MIL-F-15733 type filter
was installed in just such a line-to-ground configuration because power current was returned
14
Final Report: Capacitor Transient Potential Tests
through metallic platform structure. Nowadays it is much more common to return current on a
dedicated wire, at least until return current exits the equipment enclosure. The test set-up of
Figure 4 is a better model of modern power bus and filter topology.
__t LISN I ._b,4, :rb
rb80 IJF, 125 Vdc
filter-under-test
801JF, 125Vdcj flhllfit_ j_ i 8282-1
I'"'er T I It _1 .--rI filte r F2 ] &scope
Figure 4: Test set up of CS06-1ike parallel spike injection for two filters F in modern power
bus topology.
In Figure 4, the filters F are paralleled by 40 laF of bulk capacitance. This should help to lower
the spike potential across capacitors in filter F, but filter F inductors interfere with that function.
Data 2-17 shows a 450 Volt spike calibrated across 5 f_. This is the potential at which a single
application destroyed a stand-alone filter F. Data 2-18 shows the spike potential when the
setting resulting in Data 2-17 is applied as in Figure 4. For comparison, Data 2-19 shows spike
potential between filters F and the bulk capacitors. Almost the entire spike potential is dropped
across filters F. However in this test configuration the 450 Volt spike did not affect the filters F,
even applied at a rate of 10 pps for several minutes. When the spike potential was increased to
500 Volts (at a rate of 10 pps) it caused filter F capacitor failure in less than one minute.
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spike across filters F in Fig. 4 configuration
Data 2-17:
15
Final Report: Capacitor Transient Potential Tests
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Data 2-19: portion of Data 2-18 spike potential dropped across bulk capacitors
3.2.3 Application of MIL-STD-1399 - Like Positive Transients
The Solar Model 7399-2 Transient Pulse Generator was used in a MIL-STD-462 CS06-1ike
series injection technique (as diagrammed in Figure 5) to inject up to 2000 Volt pulses into the
test capacitors. The source impedance of this generator was measured to be 0.25 f_ (for the 17.5
_ts waveform). Data 3-1 and 3-2 show 17.5 _ts spike waveforms into 10 f_ and 0.5 _ loads
respectively. The equation which gives the spike source resistance is:
Rsource/17.5 =R1 R2 (VI- V2)
V2 R1 - V1 R2
10f_-0.5f_ (1940V - 1320V)
1320V- 10_ - 1920V.0.5_: 0.25 f_
R1R2 (Vl - V2) 10o0.5 (2460-2000)
Rsource63 -- V2R1 - V1R2 = 2000o10- 2460°0.5 = 0.1225
An unloaded source potential of about 2000 Volts may also be deduced from this data. The test
set up was identical to CS06 series injection with only the 7399-2 replacing the Model 8282-1.
The capacitor under test was placed in an explosion chamber in case it failed catastrophically.
Pictures of test set up may be viewed in Appendix A.
Figure 5:
7399-2 cap under test
I 'SCO
',I
cap large compared to CUT
Test set up of CS06-1ike series spike injection
16
Final Report: Capacitor Transient Potential Tests
3.2.3.1 Test Data
The 1320 V spike of Data 3-2 was injected on to capacitor E. Capacitor E is 300 gF, rated for 30
Vdc. The power source bypass capacitor was 3300 pF in order to force the series injected spike
potential to drop mainly across capacitor E. Data 3-3 shows the spike potential as measured
across capacitor E. Note that it is very close to half the potential of the same spike source
applied to 0.5 _. Capacitor E presents a 0.25 f_ load impedance. In turn, this implies a peak
current flow of 5.2 kA in capacitor E. The spike potential of data 3-3 was applied for three
hours (at two pulses per minute, the maximum rate achievable with the 7399-2) with no failure.
At 3:40 into the test, a very large popping sound was heard, the applied spike was very large,
and capacitor E now only measured 1.5 pF. It measured 1.5 gF a day later as well. The hot side
of the tubular capacitor was blackened from arcing. The ground side has a domed characteristic,
as opposed to the healthy capacitor whose flat end cap is that of a cylinder. This is evidence of
high pressure developed in the capacitor. A picture in Appendix A shows capacitor E along side
a "healthy" capacitor A. Although heating must have occurred in order to generate the pressure,
at no time did capacitor E become hot or even warm to the touch, in contrast to the CS06-1ike
spike application, which injected much less current (600 A), but did so 30 to 60 times as often.
A single application of the same spike destroyed capacitor C while biased at 120 Vdc. A picture
and description of the damage is shown in Appendix A. Single applications of the 63 p.s spike
were applied with successively greater amplitudes to capacitor A. Starting at 500 Volts (as
calibrated into a 0.5 _ load) superimposed on 28 Vdc, with 100 Volt increments up to 1 kV, and
200 Volt steps thereafter, it was determined that the single application threshold of damage
occurred at 1400 Volts. At this potential, the post-test capacitance decreased to 1 laF or less
(nominal was 140 laF, pre-test). In case the step-by-step incremental testing had weakened the
capacitor, a fresh capacitor A was also subjected to 1400 Volts, and also failed. Test data 3-6
through 3-15 show samples of calibrated and applied spikes.
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17
Final Report: Capacitor Transient Potential Tests
A 5eC_¢D5 "I=-I:|PRC_E B IV OFF I0'IPROEE
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Data 3-3:2460 V, 63 Its spike across 10 f_
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Data 3-4: Data 3-3 generator setting develops
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Data 3-5 Data 3-1 generator setting develops this spike across capacitor E, which causedeventual failure
18
Final Report: Capacitor Transient Potential Tests
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Data 3-7: Data 3-6 generator setting develops
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Data 3-9:Data3-8 generator setting develops
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Data 3-8:800 V 63 #s spike across 0.5 f_
19
Final Report: Capacitor Transient Potential Tests
_120g'¢ DC
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Data 3-11" Data 3-10 generator setting
develops this spike across capacitor A
_EIIEPATF MERSUR_. PRIttT P,_[HTEF
Data 3-10:1 kV 63 _s spike across 0.5 f_
nL,3gVD{ ]O:IPt,'OFE B I',,'OFF1C-_:IPROBE2F:,us. O I',' ._ i 141".-l,,,F.
.1
AI
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i J_.>.
!
¢ 'li
I
I
I!
I ,1 '
i '; ] 'I
Ii
I
I
I
i;i
I
I
!!
I
Ok :12-"
us
25_V
kV
RISE:-.19.;
u_
,.-n-!;:,7<i.-:___.-C'[I"l<L I V "J. - " l ;
GE'IEF_TE HEASUFE PP.:rIT PRIIYTEF'< "gF_k ";f_i?
Data 3-12:1.2 kV 63 ps spike across 0.5 _2
A 2"_0'4 DC20.us/O I':S II'Ir_E
i
I
I
II-7i
,>%1
'_F_,;.iN. liTUlf_
I0 :IPROBE B 1V OFF IO_ 1 PROBETri_IAJ -201'/
(
D._ I IC__-HE'RATE,tll_t;'._l_'_t_ PP[rlI- PRit_TER
Data 3-13: Data 3-12 generator setting
develps this spike across capacitor A
, dL :i 124, U':i, WEAlll i
_._L; 11.7I V
, M_.TI
i..........6e.EI °ll
' RISE:i -62.4I
Ib5
I
I
i
I
-'.I_.._ HI.R_D
'ii
2O
Final Report: Capacitor Transient Potential Tests
Data 3-14:1.4 kV 63 ps spike across 0.5
! 1:1
I
_401.0
PP[HTEF. JDIEI:,RF: 1,1EA3UPE PR_'I"tT mIt,rer.
Data 3-15" Data 3-14 generator setting
develops this spike across capacitor A.*
* Note that whereas at lower potentials the capacitor A spike potential was roughly half of the
potential applied to 0.5 fL here the capacitor potential has risen to about 70% of the 0.5
potential. This was indicative of the onset of capacitor failure. After application of this spike,
the pre-test nominal capacitance of 140 !aF was reduced to 1 laF.
21
Appendix A
Test Setup Pictures
23
Final Report: Capacitor Transient Potential Tests
Picture 1: 50 _ spike source test set up. Capacitor is connected to LISN power output and
brass bond strap to minimize potential drop across capacitor leads and connections. The power
supply hot output is connected to the back side (power input side) of LISN. A large capacitor
also bypasses the LISN power input to ground, to provide local energy storage. Switched
current is high in magnitude relative to what the power supply can deliver (also there is
inductance/resistance in leads between the supply and LISN). The electrolytic capacitor (on the
order ofmF) has its high side connected to the LISN power input connector using a solder wick
bond strap less than one inch long, and a sheet of thin brass stock from the low side of the
capacitor to the ground plane, providing less than 3:1 length-to-width ratio in the ground path.
The picture above is schematically depicted below (Figure 1 from section 3.2.1):
switching
nL'/ UT transiento'sco generator
24
Final Report: Capacitor Transient Potential Tests
o'scope hotconnection
o'scopeground
tantalum
electrolyticcap-under-test
lowimpedancebond strapconnection
to ground
Cu tape for low impedance bond
Picture 2: Close up of tantalum capacitor connection to LISN output in 50 fl spike test set
up. Capacitor lead length has been minimized by close connection to LISN port and use of brass
bond strap extension of ground plane.
25
Final Report: Capacitor Transient Potential Tests
MIL-STD-462D LISN 50 pH, 50_, 50 A (used as power
supply protection filter only)
Solar Model 8282-1CS06 spike source
ceramic DIP cap-under-test
Picture 3: CS06 parallel injection test set up. The LISN here is a filter protecting the power
supply output from the CS06 spike. Note that capacitor under test is connected directly to
Model 8282-1 parallel output jacks to minimize lead impedance. Figure 2 (from section 3.2.2)
below is a schematic of above test set up:
LISN
26
Final Report: Capacitor Transient Potential Tests
Picture 4: Close up of ceramic capacitor under CS06 spike parallel injection. Minimized lead
length is apparent. Note that ceramic capacitor is configured as a DIP, but all leads on one side
are common. These were interwoven with solder wick and EMI tape to provide very short, low
impedance leads for connection to either LISN terminal and brass bond strap (50 f_ spike test) or
Model 8282-1 parallel output jacks.
27
Final Report: Capacitor Transient Potential Tests
0-270 Vdc power supply
oscilloscope
bypasscapacitor
Solar 6220 CS01transformer
Solar 7399-2 spike source explosion chamber
Picture 5: MIL-STD-1399 series injection test set up. Explosion chamber holds capacitor
under test. Solar transformer is extra protection for power supply, recommended by Solar 7399-
2 instruction manual. For clarity, it is not shown in schematic below (Figure 5 of section 3.2.3):
7399-2 cap under test
,_O'SCOpe_
cap large compared to CUT
28
Final Report: Capacitor Transient Potential Tests
PVC perimeter
Lexan front and back
panel removable forcapacitor access
capacitors-under-test
Picture 6: Close up of explosion chamber with capacitor B (two series 125 Vdc rated
capacitors ganged for Space Station power bus derating) installed.
29
Final Report: Capacitor Transient Potential Tests
good cap A ground side
note end capdeformationdue to highinternal pressure
failed capacitor Eground side up
Picture 7: End view comparison of failed capacitor E with good capacitor A (same package).
Capacitor E is seen to have undergone explosive compression, which, however, was contained by
its case. Capacitor failed open; its failure would not have directly caused other circuit
malfunction, except by its failure to perform its original function.
Picture 8: End view comparison of failed
Capacitor C dielectric has broken into pieces.
the power supply.
ceramic DIP capacitor C with good capacitor.
Capacitor failed short, blowing a 1 Amp fuse in
30
Form ApprovedREPORT DOCUMENTATION PAGE OMBNo.0704-0188
Public reporlthg burden for this cOleCtton of thlormation is estimated to average 1 hour per response, inclt._lingthe time for reviewing instructions,searching existing data sources.gathering and mldrdaJnmg the data needed, and completing and reviewing the collection of irdormatton. Send comments regaKling this burdon estimate or any other aspect ol thiscollection of inlorrnation, including suq_gestk_s for reducing th_sburden, to Washington Headquarters Services, Directorate for Information Operation and Repot(s, 1215 JeffersonDavis Highway, Suite 1204, Adklgton, VA 222024302, and to the Office of Management and Budgel. Paperwork Reduction Project (0704-0188), Washington, DC 20503
1. AGENCY USE ONLY (Leave Blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
February 2000 Contractor Report (Final)4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Investigation Into the Effects of Microsecond Power Line Contract No. H-29919DTransients on Line-Connected Capacitors
6. AUTHORS
K. Javor
7. PERFORMING ORGANiZATiON NAMES(S) AND ADDRESS(ES)
EMC ComplianceP.O. Box 14161Huntsville, AL 35815-0161
9. SPONSORING/MONiTORING AGENCY NAME(S) AND ADDRESS(ES)
George C. Marshall Space Flight Center
Marshall Space Flight Center, AL 35812
8. PERFORMING ORGANIZATiON
REPORT NUMBER
M-961
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
NASA/CR--2000-209906
11. SUPPLEMENTARY NOTES
Prepared for NASA's Space Environments and Effects (SEE) Program
Technical Monitor: R. Kapustka
12a. DISTRIBUTION/AVAILABI LITY STATEM ENT
Unclassified-Unlimited
Subject Category 33Standard Distribution
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200 words)
An investigation was conducted into the effect of power-line transients on capacitors used by NASA and installed on
platform primary power inputs to avionics. The purpose was to investigate whether capacitor voltage ratings needs to
be derated for expected spike potentials. Concerns had been voiced in the past by NASA suppliers that MIL-STD--461
CS06-1ike requirements were overly harsh and led to physically large capacitors.
The author had previously predicted that electrical-switching spike requirements representative of actual power-line
transient potentials, durations, and source impedance would require no derating. This investigation bore out that
prediction. It was further determined that traditional low source impedance CS06-1ike transients also will not damage
a capacitor, although the spikes themselves are not nearly as well filtered.
This report should be used to allay fears that CS06-1ike requirements drive capacitor voltage derating. Only that
derating required by the relatively long duration transients in power quality specification need concern the equipment
designer.
14. SUBJECT TERMS
electromagnetic effects, capacitors, power line transients
15. NUMBER OF PAGES
33
16. PRICE CODE
A03i17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMiTATION OF ABSTRACT
OF REPORT OF THIS PAGE OF ABSTRACT
Unclassified Unclassified Unclassified UnlimitedNSN 7540-01-280-5500 Standard Form 298 (Rev 2-89)
proscribedby ANSIS1d 239"18296-102