A suitable electroyte has been formulated for aluminium electrolyte capacitor and its performance was

studied over a temperature ranged- 2S0C to+ 85Oc The dirnatic, eledrical cheraderisitics and the life

endurrance test d the capacitor using the devekped eledrdyte wem tested according to IS1 specification

and the results are disarsse

Kanagaraj, D.

Narasimhan, V.L.

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&tin of Electrochemistry 2 (3) May-June. pp. 281-282 ELECTROLYTE FOR ALUMINIUM ELECTROLYTIC CAPACITOR D RANAGAR# d VL NARASLMHAN Chtd Eleetrochemial Raarch htitutc. M u &  - 623 006 ABSTRACT A suitable eledmlyte has been fonnukd fa aluminium eledmlyk capecitor and its performance was studied anwa tempendure ranged- 2S0C to+ 85Oc The dirnatic, eledrical cheraderisitics and the life endurrance test d the capacitor using the devekped eledrdyte wem tested according to IS1 specification and the are disarssed A U electronic equipentr d at kaat a fer ckctrdytic upviton For the fabrication d electrdytic Qpdta, formal .Id etcbrd utbalefoild~uireddzcur~withkdr~w~iotoallnitby h g a p c i t o r ~ i n b c h w c c n t h c m . ? h e r r o r m d n n i t i a ~ t o b e  ~withaf i lmfofmingd&trdyteal led*imprrgut ine  dectmlm to produce tLrlar up.dta. Thedec lrdyterrrat iJ lycmrLbdaaiomgmupabkd~ oxide film prfarMy f- otnte whaliaed a prt i J ly  neuhalired with ammonia or an amimdidved io a suitable solvent mcb u dyad, amidea br Nabrtituted amida and adding phosphate or phapbite or both t o r e d u c e t h e l ~ c a r r e n t  d theupvi tor .  Glyd b a d  dectrdytes kcaw higbly Viaanu at low tempatlrrr- Marewer the electrolyte is Unrt.ble .Id lllldalpa reaction dwing the life d the upvita. Above 70°C, water in the datrolyte reacts with the didectric oxide hlm leading to poar pchmuax d t h e  upuitor. Amide or N-aubatituted unide bucd datrdyte rttwL the &ala uaed for the IpbriePtiondcPpuitorandnrrdrrpkirllrvpbardewtdTdlolld neoprme rubber which are &vdy costly. To obviate these d i d v a n t a p  attempt was mde to devdop a glycol b a d  electmi te which cao have improved performance in the tempeature d" -of-25 Cto+85°Candthesestu&aarerepoltedinthiap.pa.The lpcial electrolyte had the following composition : Ethylme glycol Diethanolamine 50g by wt Butyric acid 208 by wt log by wt Methanol log by wt Sodium &-hydrogen phosphate 0.4g by wt 20 g of diethonalamine and 10 g of butyric acid were heated to 55O C - 60O C for 5 min. followed by addition of 50gof ethylene glycol and the mixture wol heated to 105OC and maintained at that temperature for 10min. to expel water. 0.4g of sodium dihydrogen phosphate was added. After cooling the mixture to room temperature, log of methanol was added. Tbe rd&ance of the electrolyte was measured at 25OC using codactivity bridge The maistance was 200 oh- The electrolyte waa then kept inride the Thennotnr The miatance of the electrolyte was measured maintaining the da iml  tanpemture for 15min. The resistance of the electrolyte at -30°C wm 7550 ohm. To study the performance chuutaiatia, c l i c  t a t .  and mdwnce tert wan carried out after fabricating capacitor d rating 25V, 50Mm) impregnated with the electrolyte m per IS : Specification 43 17 - 1967. Five c a p i t o n  were atudicd for ach tat More starting the teat, the components were charged to the rated voltage for IOmin. and at themd of this period, the ledcage current, power factor and the capacitance were measured at a hquency of 50 Hz uring a capacitance bride applying an rc. vol- but not exceeding0.5 volts r.m.a. Table 1 giva the capacitance, power factor and leakagecurrent at +2S0 C Avrding to the npecification, the CV product gmaier tho 1000, the leak- a p  current rhsll not exceed 0.03CV + 20pA which ia equivalent to 57.5pA. the tol- of the rste capacitance value ahall not exceed - 20 to + 100% and the tangent of the law angle at frequency 50 Hz not to exceed 35. From the data in the Table, one fin& that the maximum change in capacitance value ia + 25% and power factor 0.15 and leakage current at the maximum 7 M .  ?be valuer are well within the specification. Table I : Pertomunce at low temperalure 1 2 3 4 5 Idriel nod* ol mom l cmpmtw (25" C) Csp.city GF) 60 58 54 62 FO Power kctor  0.085 0.085 0.150 0.095 0.1 15 Leakage current @A) 4.5 7.0 3.5 3.5 2.5 A t  low lnnpnalure of - 3 4  C Capacity (cF) 49 45 44 52 38 Power factor 0.30 0.43 0.37 0.32 0.29 Lealuge current (pA) 1.0 1.5 Nil 1.0 Nil F i d  reading at roon *ahwe (25O C) C q m t y  (PF) 58 59 54 63 48 Power factor 0.080 0.085 0.1 10 0.095 0.100 leakage current (pA) 3 2 2 4 3 Kanagaraj and Narasimhan - Eledrolyte for aluminium eledrolytic capacitor DRY HeAT TEST This test was carried out to determine whether the electrolyte system is suitable for high temperature opemtion. The components tested at + Z 0 C  were mounted on an insulating board capable of withstanding + 85°C and was placed in a hot chamber. the temperatum of which was maintained by a control with a tol-ce of f I "C and direct heat radiation from the heating elements to the capaciton was avoided. The capacitors +ere kept at that temperature for 16hn applying the rated voltage. At the end of the period while still at + U°C. the upwitPaa. power factor and I+ current were m d  and tabulated in Table IL The leakage current accordin6 to the specification should not exceed 4 times the initial d u e  (%PA). After the conclusiw of the teat, the upwitaoce was only 13 pF which is well within the specification and no seepap of the electrolyte and any sign of corrosion of the container o c c d  Table 11 : Petfomce at high -re COLD TEST At the end of the teat, the compmmts were removed from the clumber and allowed to remain under atmospheric d t i w r  for r&ovay. for a period of 1-2 hn. The capacitors were immediately subjected to cold test in the thermostat which is capable of maintaining -30°C with a tdesancc of *2-C. The temperature was nuint.ined at - 25-C for two houn and the cap.citon were kept under load during this yposumoAt the cod of the period the components were m d  while stdl at - 25 C for upacit.ncc. power factor and leakage c-t valuer The ratio of impedance at low temperature (- z 0 C )  to the mom b r m p r r h u c  vu calculated which should not exceed by a &tor of 2. The compol~ota w e  removed fmm the ch& and allowed to mnain under mrmpl atmospheric condition for recovery for 1 112 h n  and the water droplet. w the container w&e wiped and agaio kept for not lest than m e  hour or more than two h- The upPritaoce vu measured after recovery from cdd cycle which should mt exceed 5% ofthe initial value. From the values given in Table I, &e chaqpE in the ratio of impdaace calculated is not more than I .4 timer ofthe limit Ip&i6ed and the chuy in capacitance was within 4% of the p r e v i d y  maaucd value without my seepage of the electrdyte d no damage vu observed w visual inrpectim ENDURANCE TEST Another bat& of five capaciton were mounted on an insulting b o d  and the values of capacitance, power factor and leakage current were measured. In order to provide free ventilation, the capacitors were placed in the teat chamber in such a manner that no apadtor is within 25 mm of any other capacitor. The temperatum of the test chamber was kept at + 85OC such that the ambient temperature of the capacitor under no circumstances exceeds the upper catepry temperature. All the capacitors were protected from the direct heat hum the h d n g  elements and circulation of air was provided within the chamber w that the tempenturn difference in any part of the chamber does not exceed f 3OC. During the entire conditioning period, the upwiton were subjected to an ac voltage of approximately ainuroidol wave form at a frequency of SO to 60 d s  superimposed on a d.c voltage such that the rated ripple current was applied to the capacitor and the peak vol- equalled the nted vd-. At the cod of the test period of 10M hn, the upwiton were allowed to remain d e r  standard ncovery period of 1 6 h .  The capacitance was visually examined for seepage of the e l a l y t e  or other visual damrgc. Acanding to the specification, leakage cumat should not exceed 57.5p.4 and the upwitamx change must be within 15% of the previously  value and thepower factor 1.3 times the limited value of 0.35 and ratio of impedance change &er the endurance teat to the initial value should not exceed 2 times. From the test values'tabulated in Table UI, the capacitaoce d u e  changes only 12% and leakage cumnt at the maximum 1OpA as against 57.5 pA with the impedance change of 1.13 times only. Table 111: Endurance test Six capedton, wem subjected to 1000 hn. l ie test at the rated temp. of 85 OC. The rated voltage of 25 V D.C. was a p p l i i  throughout the life test SI. No. Initial value before mm 1 0 M h . a t 8 5 " C d  of startiq the experiment maintaining for another 16 hrs. capad- at '25°C Capacity Power kakage Capacity Power Leakage (PF) factor current factor c-t (PA) (PA) 1 48 0.055 1 47 0.080 10 2 54 0.070 3 51 0.105 3 3 58 0.080 2 52 0.090 3 4 54 0.075 4 48 0.170 2 5 56 0.065 2 50 0.080 1 6 54 0.075 2 53 0.090 2 CONCLUSION Bulletin d Eledrochemistry 2 (3) May-June. 1986 282 

Electrolyte for aluminium electrolytic capacitor

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