Guide for the application of aluminium electrolytic capacitors

This Technical Report applies to components as described in the scope of the following standards: EN 60384-4 Fixed capacitors for use in electronic equipment;Part 4: Sectional specification;Aluminium electrolytic capacitors with solid (MnO2) and non-solid electrolyte EN 137100 Sectional Specification: Fixed aluminium electrolytic a.c. capacitors with non-solid electrolyte for motor starter applications;Qualification approval The information given in these documents apply to capacitors with non-solid electrolyte but may, in its appropriate clauses, apply to capacitors with solid electrolyte as well. In cases of doubt, the application of this document shall be discussed between the user and the manufacturer of the components.

Leitfaden für die Anwendung von Aluminium-Elektrolyt-Kondensatoren

Guide pour l'utilisation de condensateurs électrolytiques à l'aluminium

Navodilo za uporabo aluminijskih elektrolitskih kondenzatorjev

General Information

Status
Published
Publication Date
20-May-2008
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
09-May-2008
Due Date
14-Jul-2008
Completion Date
21-May-2008

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SLOVENSKI STANDARD
SIST-TP CLC/TR 50454:2008
01-julij-2008
1DGRPHãþD
SIST R040-001:2002
Navodilo za uporabo aluminijskih elektrolitskih kondenzatorjev
Guide for the application of aluminium electrolytic capacitors
Leitfaden für die Anwendung von Aluminium-Elektrolyt-Kondensatoren
Guide pour l'utilisation de condensateurs électrolytiques a l'aluminium
Ta slovenski standard je istoveten z: CLC/TR 50454:2008
ICS:
31.060.50 Aluminijski elektrolitni Aluminium electrolytic
kondenzatorji capacitors
SIST-TP CLC/TR 50454:2008 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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TECHNICAL REPORT
CLC/TR 50454
RAPPORT TECHNIQUE
April 2008
TECHNISCHER BERICHT
ICS 31.060.50 Supersedes R040-001:1998
English version
Guide for the application of aluminium electrolytic capacitors
Guide pour l'utilisation de condensateurs Leitfaden für die Anwendung von
électrolytiques à l'aluminium Aluminium-Elektrolyt-Kondensatoren
This Technical Report was approved by CENELEC on 2008-02-08.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the

Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. CLC/TR 50454:2008 E
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CLC/TR 50454:2008 - 2 -
Foreword

This Technical Report was prepared by the Technical Committee CENELEC TC 40XA, Capacitors.

The text of the draft was submitted to the vote in accordance with the Internal Regulations, Part 2,

Subclause 11.4.3.3 (simple majority) and was approved by CENELEC as CLC/TR 50454 on

2008-02-08.
This Technical Report supersedes R040-001:1998.
__________
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- 3 - CLC/TR 50454:2008
Contents

1 Scope and object .............................................................................................................. 5

1.1 Scope ....................................................................................................................... 5

1.2 Object ....................................................................................................................... 5

2 Normative references ....................................................................................................... 5

3 Terms and definitions ...................................................................................................... 6

4 Protection measures ........................................................................................................ 7

4.1 Handling and tr ans por t .............................................................................................. 7

4.2 Insulation ........................................................................................................................ 7

5 General application limits ................................................................................................ 7

5.1 Polarity - Reverse voltage .............................................................................................. 7

5.2 Voltage ........................................................................................................................... 7

5.3 Temperature range ........................................................................................................ 8

5.4 Ripple current................................................................................................................. 8

5.5 Charge - Discharge ........................................................................................................ 8

6 Storage.............................................................................................................................. 8

7 External pressure ............................................................................................................. 9

7.1 Low air pressure ............................................................................................................ 9

7.2 High air pressure ........................................................................................................... 9

8 Self-recharge phenomenon (dielectric absorption) ........................................................ 9

9 Flammability (passive and active) ................................................................................... 9

9.1 Passive flammability ...................................................................................................... 9

9.2 Active flammability ......................................................................................................... 9

10 Internal pressure and pressure relief device .................................................................10

11 Working electrolytes and contact with an electrolyte ...................................................10

12 Parallel and series connection .......................................................................................11

12.1 Parallel and series connection of capacitors ............................................................... 11

12.2 Balancing resistors for voltage sharing ....................................................................... 12

12.3 Component failure ....................................................................................................... 15

12.4 Back-to-back connection ............................................................................................. 15

13 Clearance and creepage distances ................................................................................16

13.1 Distances inside the capacitor ..................................................................................... 16

13.2 Distances outside the capacitor ................................................................................... 16

14 Capacitor mounting .........................................................................................................16

14.1 General conditions for mounting .................................................................................. 16

14.2 Component preparation ............................................................................................... 17

14.3 Mounting ...................................................................................................................... 17

14.4 Soldering ...................................................................................................................... 18

14.5 Transport and handling of assembled devices ............................................................ 18

15 Cleaning solvents ............................................................................................................19

15.1 General ........................................................................................................................ 19

15.2 Cleaning solvents and process parameters ................................................................ 19

16 Potting and gluing ...........................................................................................................20

16.1 Potting and gluing materials ........................................................................................ 20

16.2 Curing process ............................................................................................................. 20

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CLC/TR 50454:2008 - 4 -

17 Aluminium electrolytic motor start capacitors ..............................................................20

17.1 Connection ................................................................................................................... 20

17.2 Mains voltage and surge .............................................................................................. 20

17.3 Duty cycle ..................................................................................................................... 21

17.4 Discharge resistor ........................................................................................................ 21

17.5 Operating temperature and vibration ........................................................................... 21

17.6 Insulation (capacitor energised) .................................................................................. 22

17.7 Failure mechanism ...................................................................................................... 22

18 Disposal of capacitors ....................................................................................................22

Figures

Figure 1 - Individual balancing resistors ................................................................................................. 11

Figure 2 - Common centre connection ................................................................................................... 12

Figure 3 - Group-balancing resistors ...................................................................................................... 12

Figure 4 - Voltage sharing analysis ........................................................................................................ 13

Figure 5 - Back-to-back connection ........................................................................................................ 15

Figure 6 - Typical motor start arrangement ............................................................................................ 20

Table

Table 1 - Balancing examples ................................................................................................................ 15

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- 5 - CLC/TR 50454:2008
1 Scope and object
1.1 Scope

This Technical Report applies to components as described in the scope of the following

standards:
EN 60384-4 Fixed capacitors for use in electronic equipment - Part 4: Sectional
specification - Aluminium electrolytic capacitors with solid (MnO ) and
non-solid electrolyte

EN 137100 Sectional Specification: Fixed aluminium electrolytic a.c. capacitors with

non-solid electrolyte for motor starter applications - Qualification
approval

The information given in these documents apply to capacitors with non-solid electrolyte

but may, in its appropriate clauses, apply to capacitors with solid electrolyte as well.

In cases of doubt, the application of this document shall be discussed between the user

and the manufacturer of the components.
1.2 Object

Electrolytic capacitors in general – and aluminium electrolytic capacitors in particular –

are an exception in the capacitor field because of the components close interaction of

physics and chemistry. Therefore, aluminium electrolytic capacitors show, in various

aspects, a technical behaviour unaccustomed to the user. That could easily lead to

misapplications and even to endangering of persons and goods. The aim of this

application guide is to minimize these risks by providing detailed information on the

specific peculiarities of the component.
2 Normative references

The following referenced documents are indispensable for the application of this document.

For dated references, only the edition cited applies. For undated references, the latest

edition of the referenced document (including any amendments) applies.

EN 60384-1:2001 Fixed capacitors for use in electronic equipment - Part 1: Generic

specification (IEC 60384-1:1999, mod.)

EN 60384-4:2007 Fixed capacitors for use in electronic equipment - Part 4: Sectional

specification - Aluminium electrolytic capacitors with solid (MnO2)
and non-solid electrolyte (IEC 60384-4:2007)

EN 137000:1995 Generic Specification: Fixed aluminium electrolytic a.c. capacitors

with non-solid electrolyte for use with motors

EN 137100:1995 Sectional Specification: Fixed aluminium electrolytic a.c. capacitors

with non-solid electrolyte for motor starter applications -
Qualification approval
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CLC/TR 50454:2008 - 6 -
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
positive electrode (anode)

aluminium (preferably aluminium foil) of extreme purity which is etched in most cases in

order to increase the electrodes surface and, consequently, the capacitors capacitance

yield
3.2
negative electrode (cathode)

working electrolyte which is a conductive liquid in the case of capacitors with non-solid

electrolyte or a layer of manganese dioxide MnO , conductive organic salt (e.g. TCNQ)

or conductive polymer (e.g. polypyrrole) in the case of capacitors with solid electrolyte

3.3
dielectric

aluminium oxide Al O which is formed on the anode’s surface by an anodizing process

2 3
3.4
contact element for the negative electrode

a high-purity aluminium foil (“cathode foil”) in the case of capacitors with non-solid

electrolyte or silver epoxy on graphite or other conductive connections in the case of

capacitors with solid electrolyte
3.5
separator

layers (preferably of special paper) which separate the anode foil from the “cathode foil”

in the case of capacitors with non-solid electrolyte. The other purpose of these layers is

to retain the working electrolyte
3.6
external insulation

the metallic case of capacitors with non-solid electrolyte is not insulated against internal

capacitor elements as the case may be connected e.g. through the conductive working

electrolyte. Therefore, the capacitors need an external insulation sleeve if electrical

insulation is required
3.7
polarity

electrolytic capacitors are, on principle, polarized components. For special purposes, so-

called non-polar (bipolar) capacitors may be provided. Such special types consist in

principle of an internal back-to-back connection of two basically polarized elements

NOTE Motorstart capacitors are bipolar (see 12.4 and Clause 17).
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- 7 - CLC/TR 50454:2008
3.8
sealing

the internal element of a non-solid electrolytic capacitor is normally encapsulated in an

aluminium case closed with a sealing material which is never perfectly gas-tight.

Because of using a non-solid electrolyte, of which, some constituents are slowly

diffusing through the sealing, the electrical characteristics of the capacitor are changing

gradually over its entire life
4 Protection measures
4.1 Handling and transport
Capacitors are generally housed in a 99,5 % aluminium case giving rise to low
mechanical strength. Shocks must be avoided and manufacturer’s packaging must
always be used to transport capacitors.
4.2 Insulation

Capacitors may be either completely or partially insulated with sleeving. It should be

noted that the capacitor case is not insulated from the cathode terminal.

Axial leaded capacitors have a direct contact between case and cathode terminal. Radial

leaded capacitors have an undefined contact through electrolyte or other parts inside the

case. Dummy pins shall be left potential-free or may be connected to the potential of the

negative terminal. Metal parts other than terminals should never make contact to
conducting tracks or metal parts of other components.
5 General application limits
5.1 Polarity - Reverse voltage
Electrolytic capacitors for d.c. applications require polarization.

The polarity of each capacitor is to be checked both in circuit design and in mounting.

Polarity is clearly indicated on the capacitor. For short periods a limited reverse voltage

is allowed as specified in the relevant specification or by the manufacturer (e.g. 1 V for

capacitors with non-solid electrolyte). Exceeding the specified reverse voltage can

induce damage by causing overheating, over-pressure and dielectric breakdown and

may be associated with open circuit or short circuit conditions – it is the most severe

failure mechanism with aluminium electrolytic capacitors. There could even be a

destruction of the capacitor. Protections are to be used if there are reverse voltage risks

(see Clause 10).
5.2 Voltage

Exceeding the capacitors specified voltage limits may cause premature damage (e.g. by

breakdown with open or short circuit) affecting the useful life. Even destruction of the

capacitor may be the consequence.
5.2.1 Rated voltage

The rated voltage U given in the relevant specification or by the manufacturer is the

value permitted for continuous operation in the rated temperature range.
5.2.2 Surge voltage

For short periods the voltage may be increased up to the surge voltage value according

to EN 60384-4, 4.14, and to manufacturer specification.
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CLC/TR 50454:2008 - 8 -
5.2.3 Transient voltages

The surge voltage value may be exceeded for very short periods or short pulses when in

accordance with the relevant specification or as specified by the manufacturer. A test

method is given in an amendment to EN 60384-4, 4.22.
5.3 Temperature range
The capacitors are to be used within specified temperature range.
Applicable temperature ranges are given in the relevant specifications and/or in

manufacturer’s data. A general principle is: lower ambient temperature means longer

life. Therefore, electrolytic capacitors should be placed at the coolest positions wherever

possible.

Exceeding the permitted temperature causes overheating and over-pressure which can

affect the useful life.
5.4 Ripple current

The sum of d.c. voltage and maximum amplitude of ripple voltage shall remain within

rated voltage and 0 V.

Electrolytic capacitors are not normally designed for a.c. application (see Clauses 1 and

17).

No excessive ripple current must be allowed to pass. Exceeding the ripple current

specification reduces life and can induce overheating and over-pressure. Even
destruction of the capacitor may be the consequence.

The useful life of the capacitor is a function of the r.m.s. ripple current. Temperature,

frequency and cooling conditions are other influences on the useful life.
5.5 Charge - Discharge

Under the conditions defined in EN 60384-4, 4.20, or in manufacturers specifications,

frequent charge/discharge operation is allowed.
Exceeding charge/discharge frequency leads to a high ripple current and induces

damage by overheating and overpressure or breakdown with open circuit or short circuit,

leading to a reverse voltage risk (see 5.1). Even destruction of the capacitor may be the

consequence.
6 Storage

Capacitors should be stored at room temperature, normal atmospheric pressure, low

humidity, and in manufacturers packaging (for more details see EN 60384-1, 4.25).

Storage at elevated temperature (higher than 40 °C to 50 °C) has a negative influence

to leakage current inducing increases up to 10 times the maximum limit where the
capacitors are off duty (see EN 60384-1, 4.25, and EN 60384-4, 4.17).

High humidity and/or high temperature may impair solderability and taping accuracy as

well as the leakage current of the capacitors.

Storage at conditions defined above has a negligible effect on capacitance, tangent of

loss angle or equivalent series resistance, and impedance.
Manufacturers recommendations (reforming procedures, etc.) shall be considered
because long storage may influence the leakage current to increase beyond a
reasonable level.
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7 External pressure
(Not relevant for capacitors with solid electrolyte)
7.1 Low air pressure

Minimum air pressure is 8 kPa for short periods in accordance with EN 60384-4, 4.11.4.

7.2 High air pressure

The maximum operating pressure is dependant upon size and style of the capacitor. It

should be specified by the manufacturer on request. Exceeding the specified value may

damage the capacitor (e.g. destroyed cases, open pressure relief device, short circuit,

etc.).
8 Self-recharge phenomenon (dielectric absorption)

Even if aluminium electrolytic capacitors are totally discharged, these components may

afterwards develop some voltage without external influence. This self-recharge
phenomenon is known as dielectric absorption or as dielectric relaxation.

The capacitor is a non-ohmic conductor and has, therefore, a non-uniform distribution of

the electric field. This is correlated with electric space charges within the dielectric layer.

In the case of open terminals, an increasing voltage is built up in the course of the

electric charges relaxation.

Depending on the capacitor type and its designed voltage, such self-recharge may result

in values (even several tens of volts) which could represent some risk: damage of

semiconductor devices, sparking when by-passing the terminals, and so on.

Therefore, appropriate measures are advisable if such risks are to be avoided. In

particular for capacitors of high capacitance and high electric charge, it is

recommended, for instance, to keep the terminals shorted or to repeat the discharge

before mounting them.
9 Flammability (passive and active)
Aluminium electrolytic capacitors contain materials which may inflame under the

influence of external fire (passive flammability) or in case of a defect of the component

(active flammability). Such flammable parts of the capacitor are for instance: plastic

parts, insulation sleeve, moulding compounds, paper of the capacitors winding element,

in some cases working electrolytes.
9.1 Passive flammability

Under the influence of high external energy, such as fire or electricity, the flammable

parts may ignite. Subclause 4.38 of EN 60384-1 refers to the needle flame test
(EN 60695-2-2 has been replaced by EN 60695-11-5) for testing the passive

flammability of capacitors. The severities and requirements for different categories of

flammability are listed in Table 7 of EN 60384-1. Most aluminium electrolytic capacitors

meet the requirements of category B or C as given in the relevant specifications or by

the manufacturer.
9.2 Active flammability

In rare cases the component may ignite caused by heavy overload or some capacitor

defect. One reason could be that during the operation of an aluminium electrolytic

capacitor with non-solid electrolyte, there is a small quantity of hydrogen developed in

the component. Under normal conditions, this gas permeates easily out of the capacitor.

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CLC/TR 50454:2008 - 10 -

But under exceptional circumstances, higher gas amounts may develop and may catch

fire if sparking occurs at the same time.

As explained above a fire occurrence cannot be totally excluded. Therefore, it is

recommended to use special measures in critical applications (e.g. additional
encapsulation of the equipment for mining applications).
10 Internal pressure and pressure relief device
(Not relevant for capacitors with solid electrolyte).

During the operation of the aluminium electrolytic capacitor with non-solid electrolyte,

some gas develops in the component. Under normal conditions, this small amount

permeates without any problems slowly out of the capacitor. But cases like an overload,

application of reverse voltage, or a malfunction of the capacitor may cause a higher gas

production which cannot be covered by the normal permeation and leads to a
considerable overpressure in the component.

This high internal pressure can lead to the rupture of capacitor body/casing. That is not

too dramatic as long as small capacitors are concerned because the pneumatic energy

is low. For larger types, the relevant detail specifications will indicate that the capacitor

is equipped with a specific pressure relief device (“safety vent”) which opens at a

relatively low pressure and, therefore, limits the above mentioned risk of rupture.

The test of the proper function of this pressure relief device is specified in EN 60384-1,

4.28. The test methods described therein prove whether the pressure relief device

covers the majority of the fault events where the pressure increase is not too extreme.

In rare cases, such as extreme overload or ignition of gas inside the capacitor (through

sparking caused by breakdown), a fully functioning pressure relief device may not react

in time. Therefore, capacitors exposed to such limit conditions must be shielded. The

same apply in case of testing the pressure relief device.

When using the capacitors, care has to be taken that the proper function of the pressure

relief device is not impaired for instance by mounting measures such as clamps or glue

and potting compounds.
11 Working electrolytes and contact with an electrolyte
(Not relevant for capacitors with solid electrolyte).

Capacitors with non-solid electrolyte contain high purity aluminium foils and papers that

are impregnated with a suitable electrolyte. To give the electrolytic capacitor a long and

stable life the ingredients must be very pure. Impurities such as chloride or metals are

not allowed.

The electrolyte is a biodegradable liquid based on a stable solvent with a high boiling

point as the main ingredient. (Common solvents are γ-butyrolactone or ethylene glycol.)

Furthermore the electrolyte consists of an acid base system and other added chemicals

that are dissolved in it. The electrolyte is chemically neutral and contains no PCBs or

other halogenated compounds. It has a low toxicity but prolonged inhalation of vapours

should be avoided.
However it is advisable to avoid contact with the skin or the eyes. Exposure of

electrolyte on the skin shall immediately be treated by rinsing with water. Exposure to

the eyes shall be flushed for 10 min by rinsing with water. Medical attention should be

sought if problems persist. Inhalation of electrolyte vapours or dust particles from

electrolyte shall be avoided. If vapour of electrolyte is present the air in the room must

be ventilated. Smoke from burning electrolyte is irritating but does not contain dioxins or

similar highly toxic substances. If electrolyte gets on cloth it can be washed with water.

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- 11 - CLC/TR 50454:2008
12 Parallel and series connection
12.1 Parallel and series connection of capacitors

Connection of aluminium electrolytic capacitors in series/parallel banks gives rise to the

following considerations.
12.1.1 Voltage sharing between devices

This factor is influenced by the leakage current difference between the individual

capacitors in the chain. It is very important that the leakage current differences are

compensated for at the design stage as fairly small differences can cause problems.

This is normally evidenced at turn on as an overvoltage condition on the components

with the lowest leakage currents and can lead to premature failure.

Depending on the circuit configuration of the bank and failure mode other components

which were initially unaffected could at this stage be subjected to voltages considerably

in excess of the ratings and will also fail.

This leakage current difference is normally controlled by the use of resistors across

each of the individual components or in the case of a common centre connection by only

two resistors.
12.1.2 Circuit configuration

There are two major configurations to consider when constructing a series/parallel bank

of capacitors. The advantages and disadvantages of each are outlined below but the

final choice must be made by the equipment designer:
a) Option 1: Individual balancing resistors
Figure 1 - Individual balancing resistors
Advantages

If one capacitor fails and becomes short circuit then the capacitor in series with it will

almost certainly fail but the other capacitors in the bank should be unaffected.
Disadvantages

More complex construction, many resistors to be fitted. Additional cost of resistors.

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CLC/TR 50454:2008 - 12 -
b) Option 2: Common centre connection
Figure 2 - Common centre connection
Advantages

As the number of capacitors in parallel increases so the effective capacitance at the top

and bottom of the bank will tend to equalise, this will give better balancing during

transient conditions.

Also the average total leakage current at the top and bottom of the bank will become

closer giving improved balancing under steady state conditions.

Only two resistors required. In some cases the difference between the leakage currents

at the top and bottom of the bank may be so small as to render the use of resistors

unnecessary.
Disadvantages

If one capacitor goes short circuit the other half of the bank will be exposed to the full

voltage and may cause several further failures.

Of course, combinations of the above basic configurations are in use too as shown in

Figure 3. Capacitor banks may be subdivided into groups of option 2 (common centre

connection).
Figure 3 - Group-balancing resistors
The consequent advantages and disadvantages of both options apply when using the
circuit diagram as shown in Figure 3.
12.2 Balancing resistors for voltage sharing
12.2.1 Introd
...

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