IWFARAD DRY ELECTROLYTIC CONDENSERIkka9
17,141v="rn-ez,:,:x
Hi -Farad Condensers Can BeMounted in Any Position
Hi -Farad Dry Electrolytic Condenserscan be used with perfect
safety in anyposition-upright, horizontal, invertedor at any other
angle.
The mounting rings furnished withHi -Farad condensers are
universal intheir application. With them, Hi-Faradcondensers can be
mounted in uprightor inverted positions above or belowthe subpanel
or mounting base to anydesired amount as shown in the photo-graphs
illustrating the condensersmounted in various positions above
andbelow the phantom view of the subpanel.
Hi -Farad condensers are also standardin size enabling
replacement changes tubemade in practically all types of radio
sets.
.cx"rrce TAR Type TBR TYPO TCR
Mounting Rings foe Hi-Farad Condensers
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otithat either the
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will perhaps be interested to know thatan organization known as
the Instituteof Radio Service Men has been formedfor the purpose of
raising the standardof radio servicing throughout the country.The
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Complete Catalog of Aerovox Products May Be Had Free on Request
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Y.
Manufacturers ofThe Most Complete Line of Condensers and
Resistors in the Radio and Electrical Industries
asm.mRadio Editors of madaSines and nensespenare hereby Piven
per
to reprint inwhole or in parboithproper credit to theAeroviv
Wireless forpotation, the contentsof this issue of theAerovox
Research
Worker.
TheseerowaerthWork is a montlihismemelon of the Aerovorc
tales Corporation.It is published to brW
me Radio Experi-menter and InOneuauthoritativella hand
5$1,,,information on tenden-
b se n and resistances_Re, radio mark.
.senettif
Vol. 4 October -November, 1931 No. 7
The Aerovox Hi -FaradDry Electrolytic Condenser
By the Engineering Department, Aerovox Wireless Corporation[
Prepared and delivered as an address through the medium of a sound
motion picture]
at the Institute of Radio Engineers Fall Meeting, Rochester, N.
Y., November 9-10.
TllE purpose of this paper is to describethe construction and
performance char-
acteristics of the Aerovox Hi -Farad DryElectrolytic Condenser,
the condenserbeing referred to as "dry" to indicate thatit contains
no unabsorbed electrolyte.Such construction eliminates any
possi-bility of leakage of the electrolyte. Thegeneral use of this
type of filter condenserin radio receivers is due to a number
ofMathes of which the following are prob-ably the most
important.
The first advantage, and in these daysmost important one, is its
low cost.
See Fig. 1. An 8 mfd. 500 volt electro-lytic condenser costs a
set manufacturerabout one -sixth as much as a papercondenser of the
same rating.A second advantage, Figs. 2 .d 3, iscompactness and
light weight. For agiven voltage and capacity the electro-lytic
condenser requires a comparatively
THI -FARAD DRYCOSELECTROLYTIC CONDENSER
OF THEONE SIXTH
COST OF PAPER CONDENSER
Fix. i
small amount of space. An mfd. 500volt unit weighs but
approximately100 grams.
A third advantage is the ability toaccurately predetermine the
maximumvoltage the condenser will withstand.
The fourth advantage is its compara-tive immunity to voltage
surges inmoms of its rated peak voltage.These valeblepop
zarezrimarilconydueto
the fact that
WEIGHT3.5 uzS. 3 LBS: 2 OZS.
wag.Fix. 2
denser incorporates an extremely thin filmformed
electrowhemically usually on thesurface of the anode. Its exact
thicknemhas not been accurately determined, butin the case of a 500
volt condenser it isthe order of one hundred thousandthsto one
millionth of an inch thick.
The film formed ori a smooth clean sonface is transparent. Due
to light iMerfer-mice effect, however, the film may some-times
appear to be tinged faintly red,yellow, green or blue, depending
upon thethickness of the film. The meat dielectricstrength of the
film enables it to with-stand high voltages and its thinness
makes
it possible to secure high capacities perunit area. On an
average, each square inchgives a capacity of approximately
0.06mfd.
These dielectric properties of the filmpoteffective only as long
as a positive
ential is applied to the anode. Shouldthe polarity be reversed
the film will notoppose the flow of current and the unitceases to
function as a condenser. Hencethe
toelectrolytic condenser can be
subjected only to uni-directional currents:they are not suitable
in circuits withstraight alternating currents, and ingeneral where
reversal of the polarityoccurs.
During manufacture, the film on thean is formed to a certain
definitevoltage .d electrolytic madensers willoperate safely on all
voltages not exceedingthe forming voltage. As the forming vol.Cage
can be accurately controlled during
SIZE7.5
CUBIC INS.
50ceem NS.
Fig. 3
the manufacturing process, it is easy torate the units correctly
without takingrecourse to large safety factors. This
AEROVOX PRODUCTS ARE BUILT BETTERFilmed in U.S.A. Copyright 1931
by Aorovog Wrieleo Corp.
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emitEROVOX
HIfFARAD DRY ELECTROLYTI CONDENSER_
The Construction ofHi -Farad Dry Electrolytic Condensers
THE foil used for anode and cathode isan alloy of aluminum made
especially
for HiFarad condensers. This aluminumalloy in combination with
our electrolytethat does not attack aluminum precludnaan tendency
for corrosion and facilitiesthey formation of a durable film an
theanode.
The gauze must also be devoid of anyimpurities which may affect
the formingor the operation of the condenser. Twolayers of gauze
later to be impregnatedwith electrolyte, are placed between
thefoils. Not only do the two layers of gauzeabsorb the necessary
amount of electrolytebut the double layer minimizes the dangerof
breakdown in the case of severe over-loads.
Reinforced TabsVital parts of the unit are the tabs which
are reinforced to increase the depend-ability of the condenser
both mechanicallyand electrically. The reinforcement ofthe anode
tab consists of an aluminumstrips uperimposed on and eyeletted
to
Ce.dboerd soxTra P58
the foundation tab, the latter being partof the anode fall
itself. In this manner astrong terminal for the section is
obtained.To prevent corrosion the eyelets used forthe reinforced
tabs are of aluminum.
Corrosion of the tab is also preventeddue to the fact that our
electrolyte. beinga liquid, creeps along the an tab andthereby
tends to maintain a film formationon the tab.
The two foils of the Hi -Farad condenserare staggered or offset,
the edges beingseparated by about one -quarter of an inch.This
patented staggered arrangement isused for several reasons. In the
first place
the electrostatic field is most intensealong the edges of the
foil. Also the film cannot be formed on a sharp edge as
effec-tively as it is formed on a smooth surface.
Tsag G5-8
Therefore, the tendency for increasedleakage currents arcing and
breakdown inthe case of overloads is always greatestalong the
edges. These conditions aretaken care of by the separation
betweenthe edges of the two foils. an exclusivefeature of the Hi
-Farad condenser.
Winding The CondenserThe condenser is made ready for wind-
ing by placing the gauze around the endof the cathode foil. The
anode foil is thenplaced in position and the condenserwound.
The outer area of foil is the cathodeon which there is formed no
film; thisouter layer affords quite complete elm-trostatic
shielding and also aids in thedissipation of any heat generated
withinthe ntht.
ImpregnationAfter the condenser has been wound it
is ready for impregnation in the electro-lyte. The selection,
proportioning andtreatment of the ingredients used in
thepreparation of the electrolyte are all im-portant factors which
determine theproperties of the condenser. An electro-lyte has been
developed which not onlydoes not attack aluminum but which
alsopermits the formation of a hard durablefilm capable of
withstanding high voltage.of remaining stable over a wide range
inLeinriltiar: and which gives extremely
As the electrolyte is a liquid we canthoroughly and uniformly
impregnate the
sections by immersing them for a period oftime in the hot
electrolyte.
The electrolyte used in this condenserhas a relatively high
specific resistance.In general it has been found that elec-trolytes
of low specific resistance arechemically more active and hence
exhibita greater tendency to attack the elec-trodes and produce
corrosion. Corrosionof the anode or mode tab is the mostdamaging
irregularity that can occur.
Neglecting corrosion the life of anelectrolytic condenser
depends upon theability of the electrolyte to retain itsmoisture
content. In the Hi -Farad con-denser a balance is maintained
betweenmoisture lost and moisture gained be-
en solution Is hygroscopic and itreadily absorbs moisture to
make up forthat lost through evaporation or electro-lysis. For
these reasons we End that theamount of electrolyte initially placed
inthe condensers bears little relation to thelife of the condenser.
Electrolytes inmqueous type condensers are non-hygro-
garscopic and cannot absorb moisture to makeup for that lost due
to evaporation andelecrolysis.
These coed one are especially noticeablewhen the condensers are
subjected toemperataena in the order of 140 degreesF. The deciding
tactor is not the amountof moisture. but the ease with which
thewat, is evaporated or decomposed andthe ability of the
electrolyte to reabsorbmoisture. The electrolyte used in
thiscondenser shows a strong tendency tomaintain its moisture
content with thethe result that condensers operated forlong periods
at high tempera.. show noloss ha weight.
EROVO
.4111111-11111111111h9hour period to determine the change
inweight of electrolyte. These figures aregiven in Fig. 5 and show
a gain in weightof approximately 0.03 grams. This gainin weight is
due to the fact that theelectrolyte contains a large percentageof
glycerine which is hygroscopic, and inthis case the absorption of
moisture
used a slight in in weight. Othercondensers did not show the
same changein weight, and on rage the con-densers showed a
negligible change inweight after operation for 1000 I...No change
in weight after 1000 hours ofcontinuous operation at 150 degrees
F.meens that the condenser has an extremelylong life.
This curve of Fig. 5-C also gives in-formation on the leakage.
During prac-tically the entire test the leakage current
For a constant .ode area, the capacityobtained is approximately
inversely pro-portional to the formation voltage. Withour
electrolyte, a total formed anodesurface of 136 square inches gives
a
Tice C5-16
capacity of 8 mfds. when the unit is formedat SOO volts; if the
formation voltage is250, then the same anode area gives acapacity
of 16 mfds. These facts are il-lustrated by the curve, Fig. 6.
Since the capacity depends upon theformation voltage, the
question naturallyarises of the effect which occurs when aunit
formed to a certain voltage is open -
averaged between 50 to 100 microamperes, ated on a low, voltage.
Experience hasor from 4 to 10 microamperes per micro- indicated
that under such conditions thefarad. These low values of leakage
current capacity gradually increases if- the unitare regularly
obtained under conditions of is operated on a voltage lower than
thecontinuous operation. original forming voltage. The change
in
40
Do
25
20
5
10
5
TYPO 15-4
CAPACITY AS A FUNCTION ::MI OF FORMING VOLTAGE MNMN CONSTANT
ANODE AREA ME
1------mol=1...1.-..m
100 200 500FORMING VOLTAGE
Fia. 6
00 500
4
12
0
capacity takes place very slowly, how-ever. To check this poi.,
an 8 mfd. 500volt condenser was placed a,oss a 45volt circuit. The
amit had an initialcapacity of 8 mfds. After operation forthree
thousand hours at 45 volts, thecapacity increased to 13 nafds. This
re-presents the extreme condition since theoperating voltage was
o.y onetenth ofthe initial forming voltage. We canconclude,
therefore, that when units areoperated at voltages somewhat
low,than the forming voltage, the capacitywill increase very
slowly, and that noconsiderable change in capacity will occurover
an operating period of severalthousand hours.
In the test described, the condenserwas actually used as a
by-pass across aC -bias resistance in a receiver. The cur-rent in
the circuit was quite limited, being
Type 054.1
about one mA and this test can there-fore also be taken to show
that thiselectrolytic condenser maintains its cap-acity even when
the die. current is verylimited. We have a number ofinquiries from
engineers who consider that
C.
6
AEROVOXI
8 MFD DRY ELECTROLYTIC CONDENSERLEAKAGE CHARACTERISTICS
LEAKAGE AFTER IDLE SHELF TESTCURRENT
IN MILLI-AMPERES
NE R IDLE FOR 2 PU
CONDENSER IDLE FOR 2 64 HOURS
2
0 2 4 6 8 10 12 14 16TIME IN MINUTES
18 20
Page 6Page 3
@daIII-V01
HI FARAD DRY ELECTROLYTIC CONDENSER
if an electrolytic condenser is used as aby-pass in circuits
where the currentavailable for maintaining formation islimited to
about one mil., that the unitwould gradually deform and cease to
actas a condenser. This test showed that such
effect does not occur, that thedensercon-maintains its
characteristics evenwhen the available current is
extremelysmall.
We have also determined the leakagecharacteristic of the
condenser after Inaperiods of shelf life. The two curves,Fig. 7
give the leakage characteristic afteridle periods of 624 and 2064
hours. Thesecurves represent a very severe test forthe idle periods
were extremely long andin determining the leakage 500 volts dx.
Tn. ES,were applied. and this voltage is coatidee.ably higher
than that to which the con-densers are subjected in the usual
receiver.
It will be noted that these two curvesdiffer but slightly though
they representwidely different idle periods. This in-dicates that
the film structure is quiteperm an Pt and that deterioration,
ifthere be any, takes place very slowly.
14
12
4
2
0
It should be noted that the currentdrops rapidly during the
first thirtyseconds after the voltage was applied.
Effect of TemperatureIt is obvious that if an electrolytic
condenser is to give satisfactory service it
Ty. E54
must be able to withstand both high andlow temperatures. The
test specificationsof many companies include tests at 140degrees F.
with superimposed ac. and nix.Fig, 5 shows that the condenser
givesexcellent performance when continuouslysubjected to such
temperatures. Thecurve. Fig. 8. shows the effect on capacityof
temperatures from zero up to 150degrees 17. At room temperature,
75degrees, the condensers under test havean verage capacity El
',olds. Temper-aturaes above this value cause an increasein
capacity and temperatures below75 degrees cause a decrease in
capacity;this is oho...crime of all types ofcondensers which we
have tested. Itis important to note, however, that thecondenser
remains operative doom belowzero degrees F. due to the fact
thatelectrolyte used has a very low freezingpoint. Subjecting
condensera to tem-peratures helms zero F. and then allowingthem to
return to room temperature hasshown that these low temperatures
haveno permanent effect on the condensercharacteristic.
I I1 II
8 MFD.-I 1
DRY ELECTROLYTAEROVOX
500 VOLTS PEAKC CONDENSER
1
rIVAL IN
CAPACITY- 4111=1111.
,allIV
11
1111GP./ I' CHARACTERS IC CUR ES ON 400 ---.
VOLTS D.C. AFTER ONE NIA ON VOLTAGE_TEMPERATURE AT PLOTTED
POINTSKEPT CONSTANT FOR ONE HOUR
15 50 45 60 75 90 105 120 155 150TEMPERATURE IN FAHRENHEIT
Fie. 8
Efficiency In Filter CircuitsThe following data have brew
obtained
from a number of measurements on titercircuit. using our
electrolytic condenser.These data will show that in filteringaction
the electrolytic condenser is es.sent:lay equal in every respect to
a papercondenser of the same capacity.
In the course of our research on electro-lytic condensers units
of various powerfactors were constructed and we foundthat as the
power factor is reduced bysuitably altering the electrolyte that
thetendency for corrosion to take place isincre.ed, Considerations
of corrosionmake it desirable therefore not to producecondensers of
power factors lower than
Tres ES -80
are needed to give satisfactory results.The curves and data to
be shown indicatethat if the power factor is 20 per centor lower,
the filtering efficiency of anelectrolytic condenser is essentially
equalto that of a paper condenser.
In view of these facts our research wasaimed to design a
condenser that would
ad1111 HI FARAD DRY ELECTROLYTIC CONDENSER III
contain no unabsorbed electrolyte, thatwould have a long life
and be free fromcorrosion. To sacrifice any of these valu-able
properties to obtain a low powerfactor Could hardly be considered
soundengineering.
The tests were made using a standardfilter circuit consisting of
a type 200rectifier, two 8 mfd. condensers and asingle choke coil.
The circuit, see Fig. 9was arranged to use for the first
condenseran 8 mfd paper condenser in seri. withwhich resistors of
various values shouldbe placed to produce a given increase inthe
power factor of the it. Usingthis method the effect on the filter
circuit
Tn. 0-888
could be obtained by using condensersof various power factors.
It was foundthat the filter condensers with Powerfactors up to
about 20 per cent produceextremely small changes in both the
d.c.voltage and the ripple voltage.
If we consider the a.c. ripple voltageacross the first condmser
to be a measure
100
' FILTERING NOEFFICIENCY(oALcuLArEly
40
20
of the filtering action and also considerthat a zero power
factor condenser givesmaximum or 100 per cent filtering action,then
we can calculate the percentagedecrease in filtering action which
resultsfrom the use of condenser of any givenpower factor. The
results of such calcula.
Percentage Increase iv A.C. Ripple,Across First Filter
Condenser,
as a_Fun.ion of Power Factor
E ac for plate=350I load=125 mA
Pace neeIn Peens
0
10
15
20
30
Calculated
AIPPIe0..10
0.1
0.5
1.1
2.0
4.5
0.1
0.8
1.2
1.9
3.9
Table I
tions are shown by Fig. 10. A zeropower factor condenser gives
100 per centfiltering action. As the power factor isincreased the
filtering efficiency dropsvery slowly at first and then much
morerapidly. It will be noted that the curvebegins to bend quite
sharply for powerfactors beyond about 20 per cent. Thedecrease in
filtering efficiency for powerfactors up to 20 per cent is slight
and isin fact so small that for all practicalpurposes it can be
neglected. These cal-
-EFFECT OF POWER FACTOR--ON FILTERING EFFICIENCY-
'
20 40 60 80 100POWER FACTOR IN PERCENT
Fis. 10
600
'Ode OUTPUT
400
300
culated results have been checked ex-perimentally. Table I shows
calculatedend measured data and they both checkquite clearly. The
table brings out onceagain that power factors up to 20 per centhave
a negligible effect on filteringefficiency.
The effect of poorer factor on de.
vesoutput voltage is also extremely small.These cur. Fig. 11
give d.c. outputvoltages of a type 280 rectifier with an 8mfd.
condenser and an an. plate voltage ofMO volts per anode. It will be
notedthat the difference in output with en -
Type E5-8888
densers of aero power fact. and 25 percent power factor is
negligible amountingto only about 1 per cent at a load of about120
mils. It vAll be obvious thereforethat ordinary One voltage
fluctuationnswill cause greater changes in ripple andd.c. voltage
than will be caused by theuse of filter condensers with
powerfactors up to 20 per cent.
-EFFECT OF POWER FACTOR -ON DCOUTPUT VOLTAGE
FOR ZfiRs...
