SIST-TP CLC/TR 50454:2008
(Main)Guide for the application of aluminium electrolytic capacitors
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
Relations
Standards Content (Sample)
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.
---------------------- Page: 1 ----------------------
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
---------------------- Page: 2 ----------------------
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.
__________
---------------------- Page: 3 ----------------------
- 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
---------------------- Page: 4 ----------------------
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
---------------------- Page: 5 ----------------------
- 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
2
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
---------------------- Page: 6 ----------------------
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)
2
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).
---------------------- Page: 7 ----------------------
- 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
R
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.
---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
- 9 - CLC/TR 50454:2008
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.
---------------------- Page: 10 ----------------------
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.
---------------------- Page: 11 ----------------------
- 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.
---------------------- Page: 12 ----------------------
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
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.