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AluminiumElectrolytic

Capacitors

Application Notes

, now part of the Evox Rifa Group, is one

of Europe’s leading manufacturers of Large Can Aluminium

Capacitors. The Evox Rifa Group is a major global capacitor

manufacturer, offering a wide range of technologies and styles

from production facilities in Sweden, UK, Finland, China and

Singapore.

The ISO9001 approved BHC production plant at Weymouth in

the South of England has been successfully manufacturing

Aluminium Electrolytic Capacitors for the most demanding

applications since 1968.

BHC prides itself on its ability to provide a flexible design service

for unique customer requirements. The company has a history of

working alongside design teams, providing the exact solution to

a particular problem, and unrivalled support in the subsequent

application. BHC recognises that its success depends on the future

of its customers and sees itself not only as a supplier of

technologically superior products but as a partner, mutually

striving with our customers for competitive advantage.

The product development and customer service provided by

BHC is backed by a totally integrated, real time information

system that plays an important role in quality, design, and in all

phases of production from planning to control.

The control offered by the use of information systems over the

manufacturing process is only a part of the quality system that

pervades at every level. Quality is the responsibility of every

member of our team with the emphasis placed on “right first time”

and “continuous improvement”. Quality is the link that bonds us

to our customers. We are committed to not only satisfy customers’

current needs, but to improve and develop products in

anticipation of their future requirements.

In formal recognition of this BHC has achieved approval to BS EN

ISO 9001.

Manufacturing competitively priced products of the highest

quality is the cornerstone of our success. If you wish to share in

that success then contact us and see for yourself how we can

provide a solution to satisfy your needs without having to make

do with the closest standard available.

Introduction

This document contains five separate technical articles written to give the equipment designer detailed

information on the application of BHC Components aluminium electrolytic capacitors. It augments the

information already available within the standard product catalogue.

The technical support team at BHC Components are more than happy to offer any additional support that may

be required if the information cannot be found in these notes. To obtain a feasibility of a capacitor for a

particular application, the form at the back of the document should be completed, with as much information

as possible, and faxed to BHC Components.

Balancing Resistors for Voltage Sharing Use of balancing resistors to control the voltage sharing across

each aluminium electrolytic capacitor when they are

connected in series.

Reliability and Failure Rates Guidance on the reliability of the standard product ranges

manufactured by BHC Components Ltd and provide failure

rate data for use in reliability calculations.

Life Expectancy and Thermal Characteristics Explanation of the relationships between ESR, ripple current,

hot-spot temperature and life. Also provides data and

formulae to enable the calculation of life expectancy under

a variety of operating conditions.

Life Expectancy and Rated Ripple Current Details of life expectancy as related to ripple current.

Provides data to enable life expectancy to be calculated with

regard to operating voltage, temperature and ripple current. Flammability Characteristics Details of the tests undertaken by BHC Components with

regard to flammability on both the external and internal

construction of aluminium electrolytic capacitors.

2-4

5-6

7-28

29-41

42-44

Section Page

Balancing Resistors for Voltage Shararing

Introduction

When aluminium electrolytic capacitors are

connected in series it is advisable to use balancing

resistors in order to control the voltage sharing

across each device.

Voltage Sharing Analysis

Consider the following circuit consisting of two

capacitors in series (C1 and C2) with balancing

resistors (R1 and R2) :

C1

C2

R1

R2

Ic1

Ic2

Ir1

Ir2

Vm

V

If a voltage V is applied across this capacitor and

resistor network then, when equilibrium is reached

the currents Ic1, Ic2, Ir1 and Ir2 will flow as shown.

The sum of the currents through the top half of the

network will equal the sum of the currents through

the bottom half of the network, thus :

Ic1 + Ir1 =Ic1 + Ir1 = Ic2 +2 + Ir2 2 (1)

The voltage at the mid point, denoted by Vm, will

be given by :

Vm = I = Ir1 x R1 (2)

Combining equations (1) and (2) gives :

Vm = (Ic2 - Ic1 + Ir2) xVm = (Ic2 - Ic1 + Ir2) x R1 R1 (3)

Furthermore, since Ir2 can be defined as :

R2

Vm)(VIr2

-=

(4)

It can be shown that :

Vm(Ic2 Ic1) R1 R2

(R1 R2)

V R1

(R1 R2)=

- ³ ³

++

³+

(5)

This shows that the mid point voltage Vm is

dependant on the difference in capacitor leakage

current (Ic2-Ic1), the applied voltage V and the

values of the resistors used.

Since the values of the balancing resistors will

normally be equal we can set both R1 and R2

equal to R and simplify the equation to give :

Vm(Ic2 Ic1) R

2

V

2=

- ³+

(6)

This clearly demonstrates that the mid point voltage

Vm deviates from the ideal value of V/2 by an offset

voltage (Ic2-Ic1) x R / 2 which is determined by the

resistor value and the difference in leakage currents

between the two capacitors.

Resistor Tolerance

The effect of different resistor values (varying within

normal tolerance) can be shown by examining

equation (5).

For example suppose the resistors have a ±5%

tolerance and one resistor is on bottom limit and

the other on top limit. We can set R1 = 0.95 x R and

R2 = 1.05 x R which gives :

Vm(Ic2 Ic1) R 0.9975

2

V 0.95

2=

- ³ ³+

³ (7)

In this case the ideal mid point voltage of V/2 is

reduced by 5% and the offset voltage due to

leakage current difference is slightly reduced by a

factor of 0.9975.

2

Balancing Rlancing Resistors for Voltage Shararing

Choice of Resistor Value

Equation (6) can also be rearranged to determine

the value of balancing resistor necessary for a given

set of conditions, thus :

Ic1)(Ic2

V) Vm (2R

-

-³=

(8)

To calculate the maximum resistor value required,

set V to the value of applied voltage and set Vm

to the maximum acceptable mid point voltage,

usually the rated voltage of the capacitor.

The difference in leakage current (Ic2-Ic1) will

depend on the capacitor in use, the temperature

of operation and the eventual voltage that each

capacitor settles to.

If the capacitor leakage currents are measured at

an identical voltage then there will usually be some

difference between the values, one will be higher

than the other.

When placed in the circuit it is important to note

that initially the capacitor with the higher leakage

current will have a lower voltage across it. Since the

leakage current is proportional to the applied

voltage (the lower the voltage the lower the

leakage current), this capacitor will tend to settle to

a lower leakage current.

The opposite will be true for the capacitor with the

higher voltage across it. Since this will reduce the

difference between the leakage currents the mid

point voltage Vm will move closer to V/2.

For practical purposes the difference in leakage

currents at rated temperature can be estimated as :

mA 2000

VCr0.003 ³³

(9)

where Cr is the rated capacitance in µF, and V is

the applied voltage across the pair of capacitors.

The following table gives examples using this

approach.

Cap

µF

Rated

voltage

Ic2-Ic1

mA

V Vm R

3300 450 3.96 800 450 25 kW

2200 400 2.31 700 400 43 kW

470 400 0.53 750 400 95 kW

470 400 0.49 700 400 202 kW

1000 200 0.58 385 200 26 kW

2200 400 2.31 700 400 43 kW

3300 350 2.97 600 350 34 kW

Series / Parallel Capacitor Banks

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.

Option 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.

Option 2 - Common centre connection

Advantages

As the number of capacitors in parallel increases so

the effective capacitance in the top and bottom of

bank will tend to equalise, this will give better

balancing during transient conditions.

Also the average total leakage current for 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 in 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.

Balancing Resistors for Voltage Sharing

Introduction

Voltage Sharing Analysis

Ic1 + Ir1 = Ic2 + Ir2

Vm = Ir1 x R1

Vm = (Ic2 - Ic1 + Ir2) x R1

Resistor Tolerance

3

Balancing Resistors for Voltage Shararing

Revision to TD001 : Balancing resistors for voltage sharing Leakage current difference

The article TD001 has been in use for many years

and over that period a few users have expressed

the opinion that the resistor values are sometimes

on the low side. This is on the safe side as far as

balancing is concerned but does lead to higher,

and possibly unnecessary levels of power dissipation

in the resistors.

The key factor in determining the resistor values is

the difference in leakage current between two

series connected capacitors. The equation (9) given

for this was based on analysis of empirical data and

as such is a good guide to the difference at the

same voltage - we still believe this to be the case.

However, the value required in equation (8), Ic2-Ic1,

represents the difference in leakage currents after

equilibrium has taken place - i.e. at different

voltavoltageses dependant on the final balancing voltage

In other words, we need to know the likely difference

in leakage currents for the same applied voltage

and then adjust this figure according to the level of

offset voltage after the circuit has settled. The final

voltage is unknown, we are trying to calculate it, but

we do know that the change of leakage current vs

voltage follows an exponential curve. So, for

example, a 5% increase in voltage will cause more

than a 5% increase in leakage current and vice

versa. This leads to a self balancing situation

whereby any voltage offset will reduce the leakage

current difference, which in turn reduces the voltage

offset.

For any two capacitors we have defined the max

leakage current difference as equation (9), the

minimum difference is clearly 0. It is impossible to

be precise but we believe that after settling the

difference in leakage current should at least halve

leading to a revised equation (9) as shown below.

Leakage current difference = 0.0015 x Cr x V / 0.0015 x Cr x V / 2000 mA. 2000 mA. Capacitors in banks

When capacitors are used in banks (series/parallel)

with a common centre connection the balancing

resistors can be adjusted in value to account for the

averaging effect on leakage current. In essence the

total leakage current difference between the top

and bottom banks of parallel capacitors will

determine the balance point. The more capacitors

placed in parallel the better the balancing since

individual leakage values become less critical.

For banks of capacitor used in this way we would

recommend using the following equation for the

leakage current difference :

Leakage current difference = 0.0015 x Cr x V / Cr x V / 2000 / Õn mA. n mA.

Where n is the number of capacitors in parallel.

4

Reliability and Faillity and Failure Ratesure Rates

Introduction

The purpose of this technical data sheet is to give

guidance on the reliability of the standard product

ranges manufactured by BHC Components Ltd by

providing failure rate data for use in reliability

calculations.

It is not the intention to describe the mechanisms

which contribute towards the failure of components

nor to discuss the mathematical theory of the

statistics and probability employed.

Many articles have been written on the subject of

reliability and these and other sources should be

consulted for further information.

Reliability

The reliability of a component can be defined as

the probability that it will perform satisfactorily under

a given set of conditions for a given length of time.

Since in practice it is impossible to predict with

absolute certainty how any individual component

will perform, we must utilise probability theory. It is

also necessary to clearly define the level of stress

involved (e.g. operating voltage, ripple current and

temperature) and the duration of time involved.

Finally, the meaning of satisfactory performance

must be defined by specifying a set of conditions

which determine the end of life of the component.

Reliability as a function of time, R(t), is normally

expressed as :

R(t) = e-lt (1)

where R(t) is the probability that the component will

perform satisfactorily for time t, and l is the failure

rate.

Failure Rate

The failure rate is the number of components failing

per unit time. The failure rate of most electronic

components follows a characteristic pattern as

shown in figure 1.

Region (a) is the early failure period, sometimes

called infant mortality, these failures are removed

during the manufacturing process.

Region (b) is the operational or service life, this

period is characterised by an essentially constant

failure rate.

Region (c) is the wearout period and is

characterised by a rapidly increasing failure rate.

The failure rate is normally specified in failures per

hour, e.g. 1 failure per 1 million hours can be stated

as :

1 x 10-6 failures per hour or 0.1 % per 1000 Hours.

Assessment of Failure Rates

Many years of routine endurance testing have

generated millions of component test hours. Most of

these tests are carried out at rated temperature with

full rated voltage and ripple current applied.

Extensive analysis of this data has enabled failure

rates to be established for most product ranges. The

rates are given with a 60% confidence level and

the end of life definition is given below.

End of Life Definition

Catastrophic failure - short circuit, open circuit or

operation of the safety vent.

Parametric failure - capacitance change of more

than ±10%, leakage current greater than specified

limit or ESR increase of more than two times initial

value.

5

Reliablity and Failure rates

Failure Rate Values Voltage Derating

o = x Ku

MTBF = 1 /

Figure 2. Failure Rate vs Core Temperature l

Reliablity and Failure rates

Failure Rate Values

Figure 2 gives the failure rates in failures per 106

hours and the variation with core temperature for

most of the standard product ranges.

Graph (i) ALS10/11, ALS20/21, ALS27/29,

ALP10, ALT10/11, ALP20, ALT20/21,

ALP22, ALT22/23, ALC20, ALC50.

Graph (ii) ALS30/31, ALS40/41, ALC10, ALC40.

Note - for products rated at 85°C the maximum

core temperature is 105°C and for products rated

at 105°C the maximum core temperature is 120°C.

The failure rates for core temperatures between

105°C and 120°C therefore only apply to ALC50,

ALC40, ALS40/41.

It should be understood that the figures quoted in

figure 2 represent the mean failure rates achieved

from a large population of components tested

under controlled conditions.

These components are taken from the normal

manufacturing process and therefore represent

average component performance and build

quality.

As such the figures can only be taken as a guide to

the reliability in any given application since the

actual operational conditions are likely to deviate

significantly from those used in routine testing.

Voltage Derating

The failure rates in figure 2 allow for variation in stre

ss levels due to ripple current and operating

temperature. Figure 3 gives an additional factor Ku

to account for voltage deration.

The operating failure rate (lo) is therefore the rate

((l) from figure 2 multiplied by Ku from figure 3.

lo = o = l x Ku (2)

MTBF

The mean time between failures (MTBF) is simply the

inverse of the failure rate.

MTBMTBF = 1 / = 1 / l (3)

Core Temperature of Capacitor C

l

B

Figure 3. Voltage Factor vs % of Rated Voltage

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100

% of Rated Voltage

Fa

cto

r K

u

6

Life Expectancy and Thermal Chararacacteristics

Introduction

This technical data sheet gives details of the thermal

properties and life expectancy of aluminium

electrolytic capacitors. The relationships between esr,

ripple current, hot-spot temperature and life are

explained, and the data and formulae included will

enable the calculation of the life expectancy under a

variety of operating conditions.

A further technical data sheet, TD004, is also available

which gives details of life expectancy related to the

rated ripple current.

A key aspect of life expectancy calculation is the core

temperature of the capacitor. It is essential to

determine this operating core temperature either by

calculation or by measurement.

In order to simplify matters BHC Components Ltd will

perform life expectancy calculations if full operating

conditions are provided.

Figure 1 gives an over view of the elements involved in

attempting to calculate the life expectancy for a

specific set of conditions.

The first stage is to obtain the operating conditions, i.e.

the ripple currents, voltage, temperature and thermal

conditions.

The thermal resistance from core to ambient is

calculated from factors given later in the article

related to the known conditions inside the equipment.

The esr and ripple current are then used together with

the thermal resistance value to calculate the core

temperature rise. The core temperature may also be

measured directly by means of an internal

thermocouple.

CONSTRUCTION

METHOD (physical style)

CALCULATE Rha

(Thermal resistance from

core to ambient)

THERMAL

CONDITIONS AND

AIRFLOW RATE

Rha

ESR VALUES (for each frequency at

core temperature)

CALCULATE Tr

(Core temperature rise)

APPLIED RIPPLE

CURRENTS (at each frequency)

RATED RIPPLE

CURRENT

Tr MEASURE Tr (internal thermocouple)

LIFE FACTORS (related to product

specification and size)

CALCULATE Le

(Life Expectancy)

AMBIENT

TEMPERATURE Ta

Le END OF LIFE

CRITERIA

RATED VOLTAGE Vr CALCULATE Kv

(Voltage factor)

APPLIED VOLTAGE

Vop

LIFE

EXPECTANCY

FIG 1

7

Life Expectancy and Thermal Chararacteristics

The calculated core temperature is particularly useful

in the early design stage in order to specify the

quantity and type of capacitor required. However,

measurement of the core temperature in the final

equipment provides a useful cross check and is

recommended for all high stress applications.

Finally, using the appropriate factors and end of life

criteria the life expectancy can be calculated. If

desired the effect of any voltage derating can also be

taken into account by multiplying by the voltage

factor.

NOTE - Data regarding the esr of capacitors at various

temperatures and frequencies is not included, but will

be furnished as required. Alternatively the relevant esr

values may be measured directly by the user at the

temperatures and frequencies of interest.

Capacitor Construction

The basic capacitor winding consists of an anode and

cathode foil, separated by tissue paper, wound into a

roll and impregnated with a suitable electrolyte.

Aluminium tabs welded onto the foils connect the

winding to the terminals at the top of the capacitor.

The winding is housed in an aluminium can which is

sealed onto the top with an elastomer seal ring. The

winding is held endwise within the can between the

terminal deck and the base of the can. Larger types

have ribs and spigots on both the underside of the

terminal deck and the base of the can to provide

additional lateral support.

Some designs feature an extended cathode

construction. In these designs the cathode foil is

extended beyond the bottom edge of the winding

and gives good thermal contact to the base of the

aluminium can. This greatly assists heat flow from the

winding to the can and results in a cooler core

temperature for a given power input.

An insulating sleeve and end disc complete the

assembly providing both electrical isolation and

marking detail.

Figure 2 shows the main constructional details for a

typical screw terminal capacitor. Other styles have a

similar construction but have different types of deck

with pcb or solder tags.

Thermal Characteristics

Heat is generated inside the capacitor by the effect of

ripple current which raises the core or hot-spot

temperature above that of the ambient air. Heat is

also generated by the leakage current, however this is

normally small enough to be ignored.

Other circuit components in close proximity will also

contribute to the heating of the capacitor. As will any

mechanical connection to the capacitor, such as the

mounting method, which is at a higher temperature

than the ambient air. Under steady state conditions,

when thermal equilibrium has been reached, the heat

generated will be exactly balanced by the heat lost.

8


Transfer of heat from the winding to the case is mainly

by conduction. The extended foil ensures good

thermal contact of the winding to the base ribs of the

can, whilst the connecting tabs further aid heat flow

via the terminals.

Heat loss from the capacitor case is by convection,

conduction and radiation with the relative proportions

of each being dependant on the mounting method

and ambient conditions.

Radiated heat is governed by the temperature, area

and emissivity of the outer surface of the case. The

convected heat varies with case temperature and

area and can be considerably improved by the use of

forced air cooling.

The conducted heat depends on the mounting

method. Clamp or stud mounting to a suitable plate

or heat sink will give a useful improvement and the use

of heavy bus bars connected to the terminals will also

assist heat loss.

Thermal Equivalent Circuit

Taking into account all the heat transfer mechanisms

described above leads to a rather involved thermal

equivalent circuit for the capacitor, which is far too

complex for practical use.

If we consider only the loss of heat generated within

the capacitor and ignore heat absorbed from

surrounding components and through the mounting

arrangement we arrive at the simplified thermal

equivalent circuit shown in figure 3. In each case the

thermal resistance factors shown are effectively a

lumped combination of conduction, convection and

radiation.

In practice the temperature of the capacitor will vary

significantly between different locations internally and

on the outside surface and so suitable reference

points must be selected. Normally the centre of the

winding and the aluminium base of the can are

chosen, see figure 2.

The method of construction, standard or extended

cathode, will determine the Rhc value. The values of

Rca and Rpa will vary according to the level of airflow,

if any. The value of Rbp will depend upon the

characteristics of the material placed between the

aluminium base of the can and the mounting plate

(i.e. insulating end discs and/or thermal pads) and

also on the pressure holding the capacitor against the

mounting plate.

Thermal Factors

For a given configuration it is possible to fit a

capacitor with thermocouples and measure the

temperatures at the reference points. Then for a

known power input the thermal resistance values can

be calculated as °C per input power.

The absolute values cannot be calculated without

knowing the precise amount of heat lost through each

path. (i.e. the amounts through the base to heat sink,

can wall to ambient air, terminals to busbars etc...).

Core temp

Can temp

Ambient temp

Rhc

Rca

Rbp

Rpa

Thermal resistance factors

Rhc = Hot spot to can

Rca = Can to ambient air

Rbp = Can base to mounting plate

Rpa = Mounting plate to ambient air

Total thermal resistance from hot-spotto ambient air is given by :

Rha = Rhc + 1/(1/Rca + 1/(Rbp + Rpa))

FIG 3

9

Life Expectancy and Thermal Characteristics

Although the individual thermal factors are very difficult

to determine exactly, it is very easy to measure the

core temperature and ambient temperature and

calculate the overall thermal resistance Rha.

Tables 1,2 and 3 show the Rha values for capacitors in

still air and for a selection of airflow rates

The values quoted are based on capacitors in air with

minimal conducted heat loss through electrical

connections and mounting.

ALS30/31 and ALS40/41 products all have extended

cathode construction.

Table 1 Thermal resistance values for ALS (screw terminal) products, no heat sink.

Dia Len Thermal resistance values Rha °C/W

mm mm <1m/s 1.0 m/s 1.5 m/s 2.0 m/s 2.5 m/s 3.0 m/s 3.5 m/s 4.0 m/s 4.5 m/s 5.0 m/s

36 49 11.2 9.91 9.23 8.68 8.27 7.95 7.69 7.50 7.39 7.34

36 52 10.7 9.47 8.82 8.29 7.90 7.60 7.35 7.17 7.06 7.01

36 62 9.57 8.47 7.89 7.42 7.06 6.79 6.57 6.41 6.32 6.27

36 75 8.53 7.55 7.03 6.61 6.30 6.06 5.86 5.72 5.63 5.59

36 82 8.12 7.19 6.69 6.29 5.99 5.77 5.58 5.44 5.36 5.32

36 105 7.09 6.27 5.84 5.49 5.23 5.03 4.87 4.75 4.68 4.64

36 115 6.77 5.99 5.58 5.25 5.00 4.81 4.65 4.54 4.47 4.43

51 62 7.56 6.69 6.23 5.86 5.58 5.37 5.19 5.07 4.99 4.95

51 75 6.5 5.75 5.36 5.04 4.80 4.62 4.47 4.36 4.29 4.26

51 82 6.06 5.36 4.99 4.70 4.47 4.30 4.16 4.06 4.00 3.97

51 105 5.09 4.50 4.19 3.94 3.76 3.61 3.50 3.41 3.36 3.33

51 115 4.79 4.24 3.95 3.71 3.54 3.40 3.29 3.21 3.16 3.14

51 140 4.3 3.81 3.54 3.33 3.17 3.05 2.95 2.88 2.84 2.82

66 67 5.2 4.60 4.28 4.03 3.84 3.69 3.57 3.48 3.43 3.41

66 75 4.75 4.20 3.91 3.68 3.51 3.37 3.26 3.18 3.14 3.11

66 82 4.4 3.89 3.63 3.41 3.25 3.12 3.02 2.95 2.90 2.88

66 98 3.84 3.40 3.16 2.98 2.83 2.73 2.64 2.57 2.53 2.52

66 105 3.64 3.22 3.00 2.82 2.69 2.58 2.50 2.44 2.40 2.38

66 115 3.4 3.01 2.80 2.64 2.51 2.41 2.34 2.28 2.24 2.23

66 140 3 2.66 2.47 2.33 2.21 2.13 2.06 2.01 1.98 1.97

73 115 2.97 2.63 2.45 2.30 2.19 2.11 2.04 1.99 1.96 1.95

77 67 4.3 3.81 3.54 3.33 3.17 3.05 2.95 2.88 2.84 2.82

77 75 3.94 3.49 3.25 3.05 2.91 2.80 2.71 2.64 2.60 2.58

77 82 3.65 3.23 3.01 2.83 2.69 2.59 2.51 2.45 2.41 2.39

77 98 3.16 2.80 2.60 2.45 2.33 2.24 2.17 2.12 2.09 2.07

77 105 3 2.66 2.47 2.33 2.21 2.13 2.06 2.01 1.98 1.97

77 115 2.79 2.47 2.30 2.16 2.06 1.98 1.92 1.87 1.84 1.83

77 140 2.38 2.11 1.96 1.84 1.76 1.69 1.64 1.59 1.57 1.56

77 146 2.29 2.03 1.89 1.77 1.69 1.63 1.57 1.53 1.51 1.50

77 180 1.9 1.68 1.57 1.47 1.40 1.35 1.31 1.27 1.25 1.24

77 220 1.4 1.24 1.15 1.09 1.03 0.99 0.96 0.94 0.92 0.92

91 67 3.5 3.10 2.88 2.71 2.58 2.49 2.40 2.35 2.31 2.29

91 75 3.2 2.83 2.64 2.48 2.36 2.27 2.20 2.14 2.11 2.10

91 98 2.55 2.26 2.10 1.98 1.88 1.81 1.75 1.71 1.68 1.67

91 146 1.85 1.64 1.52 1.43 1.37 1.31 1.27 1.24 1.22 1.21

91 180 1.55 1.37 1.28 1.20 1.14 1.10 1.06 1.04 1.02 1.02

91 220 1.2 1.06 0.99 0.93 0.89 0.85 0.82 0.80 0.79 0.79

10


Table 2 Thermal resistance values for ALP (pcb mounted) products.



35 45 12 10.62 9.89 9.30 8.86 8.52 8.24 8.04 7.92 7.86

35 55 10.5 9.29 8.65 8.14 7.75 7.46 7.21 7.04 6.93 6.88

40 45 11 9.74 9.06 8.53 8.12 7.81 7.56 7.37 7.26 7.21

40 55 9.39 8.31 7.74 7.28 6.93 6.67 6.45 6.29 6.20 6.15

40 65 8.28 7.33 6.82 6.42 6.11 5.88 5.69 5.55 5.46 5.42

40 75 7.18 6.35 5.92 5.56 5.30 5.10 4.93 4.81 4.74 4.70

40 105 5.5 4.87 4.53 4.26 4.06 3.91 3.78 3.69 3.63 3.60

Table 3 Thermal resistance values for ALC (pcb mounted) products.



22 30 24.00 21.24 19.78 18.60 17.71 17.04 16.49 16.08 15.84 15.72

22 40 19.20 16.99 15.82 14.88 14.17 13.63 13.19 12.86 12.67 12.58

25 30 20.00 17.70 16.48 15.50 14.76 14.20 13.74 13.40 13.20 13.10

25 35 17.60 15.58 14.50 13.64 12.99 12.50 12.09 11.79 11.62 11.53

25 40 16.00 14.16 13.18 12.40 11.81 11.36 10.99 10.72 10.56 10.48

30 30 16.00 14.16 13.18 12.40 11.81 11.36 10.99 10.72 10.56 10.48

30 35 14.40 12.74 11.87 11.16 10.63 10.22 9.89 9.65 9.50 9.43

30 40 12.80 11.33 10.55 9.92 9.45 9.09 8.79 8.58 8.45 8.38

30 50 10.70 9.47 8.82 8.29 7.90 7.60 7.35 7.17 7.06 7.01

35 35 10.70 9.47 8.82 8.29 7.90 7.60 7.35 7.17 7.06 7.01

35 40 9.80 8.67 8.08 7.60 7.23 6.96 6.73 6.57 6.47 6.42

35 45 9.20 8.14 7.58 7.13 6.79 6.53 6.32 6.16 6.07 6.03

35 50 8.60 7.61 7.09 6.67 6.35 6.11 5.91 5.76 5.68 5.63

35 60 7.90 6.99 6.51 6.12 5.83 5.61 5.43 5.29 5.21 5.17

35 80 7.40 6.55 6.10 5.74 5.46 5.25 5.08 4.96 4.88 4.85

40 30 11.00 9.74 9.06 8.53 8.12 7.81 7.56 7.37 7.26 7.21

40 35 9.70 8.58 7.99 7.52 7.16 6.89 6.66 6.50 6.40 6.35

40 40 8.80 7.79 7.25 6.82 6.49 6.25 6.05 5.90 5.81 5.76

40 45 8.20 7.26 6.76 6.36 6.05 5.82 5.63 5.49 5.41 5.37

40 50 7.60 6.73 6.26 5.89 5.61 5.40 5.22 5.09 5.02 4.98

40 55 7.30 6.46 6.02 5.66 5.39 5.18 5.02 4.89 4.82 4.78

40 60 6.90 6.11 5.69 5.35 5.09 4.90 4.74 4.62 4.55 4.52

40 80 6.40 5.66 5.27 4.96 4.72 4.54 4.40 4.29 4.22 4.19

40 105 5.90 5.22 4.86 4.57 4.35 4.19 4.05 3.95 3.89 3.86

45 30 10.83 9.58 8.92 8.39 7.99 7.69 7.44 7.26 7.15 7.09

45 35 9.53 8.43 7.85 7.39 7.03 6.77 6.55 6.39 6.29 6.24

45 40 8.63 7.64 7.11 6.69 6.37 6.13 5.93 5.78 5.70 5.65

45 45 8.03 7.11 6.62 6.22 5.93 5.70 5.52 5.38 5.30 5.26

45 50 7.43 6.58 6.12 5.76 5.48 5.28 5.10 4.98 4.90 4.87

45 60 6.73 5.96 5.55 5.22 4.97 4.78 4.62 4.51 4.44 4.41

45 80 6.23 5.51 5.13 4.83 4.60 4.42 4.28 4.17 4.11 4.08

45 105 5.73 5.07 4.72 4.44 4.23 4.07 3.94 3.84 3.78 3.75

50 30 10.66 9.43 8.78 8.26 7.87 7.57 7.32 7.14 7.04 6.98

50 35 9.36 8.28 7.71 7.25 6.91 6.65 6.43 6.27 6.18 6.13

50 40 8.46 7.49 6.97 6.56 6.24 6.01 5.81 5.67 5.58 5.54

50 45 7.86 6.96 6.48 6.09 5.80 5.58 5.40 5.27 5.19 5.15

50 50 7.26 6.43 5.98 5.63 5.36 5.15 4.99 4.86 4.79 4.76

50 60 6.56 5.81 5.41 5.08 4.84 4.66 4.51 4.40 4.33 4.30

50 80 6.06 5.36 4.99 4.70 4.47 4.30 4.16 4.06 4.00 3.97

50 105 5.56 4.92 4.58 4.31 4.10 3.95 3.82 3.73 3.67 3.64

11


Heat Sinking

Substantial improvements in power dissipation can be

achieved by the use of heat sinking at the base of the

capacitor, particularly for designs with extended

cathode.

Table 4 shows some examples of the reduction in Rha

for extended cathode screw terminal capacitors

mounted on a heatsink with a thermal resistance of

0.3°/W.

Note that for condition (d) the aluminium can is in

direct contact with the heatsink and this gives the best

heat transfer but series connected capacitors

cannot then be used on the same heatsink.

(a) No heat sink

(b) With heat sink, standard end disc

(c) With heat sink, thermal end disk

(d) Directly on heat sink, no end disc

Table 4 Effect of heat sinking on Rha

Dia Len (a) (b) (c) (d)

77 105 3 2.34 1.89 1.86

77 146 2.29 1.5 1.1 1.05

Life Expectancy

During the life of the capacitor certain physical and

parametric changes occur. These changes eventually

render the capacitor unusable, either due to thermal

run-away leading to catastrophic failure, or excessive

parametric drift. At higher temperatures degradation

of encapsulation materials may accelerate these

effects.

The reasons behind these changes are many and

complex, and are beyond the scope of this article.

Also, some performance aspects cannot be

predicted and so evaluation of a product’s long term

behaviour must be determined by endurance

testing.

When ripple current is applied to a capacitor the most

important parameter in relation to the life expectancy

is the esr. The value of esr will slowly increase

throughout the life of the capacitor, leading to a

gradual increase in power loss and hence core

temperature rise.

Long term endurance testing, with voltage and ripple

current applied, has established the characteristic

parameter changes which are displayed by each

product family. The typical esr characteristic is shown

below in figure 4.

Esr

increase

Life

Fig 4

Careful study of these curves has enabled the

development of a mathematical model to simulate

the changes in esr which occur under various test

conditions and levels of stress.

Using the initial esr, initial core temperature rise and

the actual operating conditions, the model will

calculate the time elapsed until the defined end of life

is reached.

The life expectancy graphs at the end of this article

incorporate all these factors, and the values quoted

correspond to the end of life definitions stated below.

End of Life Definition

The end of life is defined as being the point at which

any of the following conditions have been reached :

Core temp > 105 °C (85°C products)

> 120 °C (105°C products)

Esr > 2 x initial esr

At the end of life the following conditions will also be

satisfied :

Capacitance change < 10 %

Leakage current < initial limit

12


Basic Formulae

CAPACITOR POWER LOSS

P = I2 x R Watts

I = applied ripple current (A rms)

R = initial typical esr at same frequency (Ohms)

For complex wave forms, sum the individual

power losses at each frequency to give the

total power loss.

i.e. Total power loss for n frequencies is :

P =I(1)2 x esr(1) + I(2)2 x esr(2) + ...

... + I(n)2 x esr(n) Watts

THERMAL RESISTANCE

Capacitor in air :

Rha = Rhc + (Ka x Rca)

Capacitor mounted on heat sink :

Rha = Rhc +1

(Ka x Rca)+

1

(Rbp + Ka x Rpa)

1

èêé

øúù

-

°C/Watt Rhc = thermal resistance of hot-spot to can

Rca = thermal resistance of can to ambient air

Rbp = thermal resistance of can base to mounting plate

Rpa = thermal resistance of mounting plate to ambient air

Ka = Airflow factor

Tables 1, 2 and 3 show calculated values of Rha for a

selection of airflow rates.

CORE TEMPERATURE RISE

Tr = Rha x P °C

CORE TEMPERATURE

Tc = Ta + Tr °C

Ta = ambient air temperature

LIFE EXPECTANCY

Life = Kv x Le (at Ta and Tr) Hours

Le=value from appropriate graph TD003

Kv = voltage deration factor (if used )

Calculation of Life Expectancy

In order to evaluate the life expectancy it is essential

to determine the core temperature accurately, there

are two basic methods :

MeMethod 1 - By calculation of core temper temperature

This method requires detailed knowledge of the

electrical and thermal properties of both the

capacitor and the application.

1 Obtain esr characteristics (esr v temp. and

frequency) by direct measurement or from BHC

Components Ltd.

2 Estimate the core temperature. An approximate

value is required at this stage in order to establish

an esr value.

3 Look up the esr value for the appropriate

temperature and ripple current frequency.

NOTE - Using the typical esr value the typical life will

be calculated, using the max esr the minimum life

will be calculated. The max esr can be taken as 1.2

x typical esr.

4 Calculate the power loss using equation.

5 Lookup the overall thermal resistance of the

capacitor Rha from tables 1, 2 and 3.

6 Calculate the core temperature rise using

equation.

7 Calculate the core temperature using equation.

8 If the calculated core temperature is very different

from the estimated value used initially then repeat

the calculations until the calculated core

temperature and that used in step 3 are similar.

9 Refer to the appropriate graph in TD003 to obtain

the life expectancy.

10 If the capacitor is being operated at a reduced

voltage multiply the life figure by the corresponding

factor Kv (refer to graph in TD003).

MeMethod 2 - By me measurement of core temper temperature

There are many occasions when the capacitor ripple

current cannot easily be defined, or when the thermal

conditions inside the equipment are unknown or too

difficult to specify clearly.

In these cases the accuracy of the calculated core

temperature may have an unacceptably high level of

uncertainty. Under these circumstances the direct

13


measurement of the capacitor core temperature is

recommended, and for this purpose BHC

Components Ltd can supply sample capacitors with

specially fitted internal thermocouples.

1 Using suitable capacitors fitted with thermocouples,

measure the actual core temperature during

operation.

2 Refer directly to the appropriate graph in TD003 to

obtain the life expectancy.

3 If the capacitor is being operated at a reduced

voltage multiply the life figure by the corresponding

factor Kv from the graph in TD003.

Voltage Derating

If capacitors are operated at a voltage below their

rated value then the reduced stress and lower

leakage current will give an improvement in the

service life.

Since leakage current increases with temperature the

benefit of a reduced operating voltage is more

pronounced at higher temperatures. The graphs in

TD003 show values of Kv for products with rated

temperatures of 85°C and 105°C.

Note - the operating voltage should be taken as the

mean d.c. value plus the peak a.c. ripple voltage.

Temperature Measurement of Capacitors

Using suitable samples install the capacitors inside the

equipment. Operate the equipment under the

conditions of interest and allow to stabilise. Measure

both the core temperature Tc and the ambient air

temperature inside the equipment Ta.

Note - when several capacitors are used in a bank it is

quite common for some items to run hotter than

others simply due to their physical position within the

bank.

The ambient air temperature can also show large

variations depending on the position and it may be

necessary to determine the hottest component by

experimentation.

Life Expectancy Graphs

The graphs at the end of this technical data sheet

show the life expectancy for various product ranges.

To use the graphs, find the ambient air temperature

(Ta) on the horizontal scale, then choose the curve

representing the core temperature rise (Tr). Where the

two lines intersect look across to the vertical scale and

read off the life expectancy.

Interpolation will be required when the value of Tr falls

between two curves.

The life expectancy figure should now be multiplied by

the appropriate Kv factor if applicable.

14


Example Life Expectancy Calculation

Consider the following example for an ALS30 series capacitor 4700µF 450 Vdc with case size 77x146 mm and a

rated temperature of 85°C.

Operating conditions : Ambient air temperature Ta = 45°C

DC Voltage (nom) 360 Vdc (i.e. 80% of rated value)

Ripple current I = 39.6 A rms at 300 Hz

Thermal conditions : Airflow rate = 2.0 m/s

Initially assume a core temperature of 65.8°C. The data regarding esr at various temperatures and frequencies is

shown below. For this example the esr at 300 Hz and 65.8°C is 7.5 milliohms.

Fig 3

CAPACITOR POWER LOSS P = 39.62 x 0.0075 = 11.76 Watts

THERMAL RESISTANCE (Table 1) Rha = 1.77 °C/Watt

CORE TEMPERATURE RISE Tr = 1.77 x 11.76 = 20.8 °C

CORE TEMPERATURE Tc = 45 + 20.8 = 65.8 °C

In this example there is no need to repeat the calculations since the calculated core temperature is the

same as the initial estimate.

VOLTAGE FACTOR (80% and 65.8°C) Kv = 1.31

LIFE (Ta=45°C,Tr=20.8°C) Le = 80,750 Hours

LIFE EXPECTANCY (Le x Kv) 80,750 x 1.31 = 105,780 Hours

The life expectancy calculated above is based on the end of life condition where ESR(End of life) = 2 x ESR(initial value).

Also, all of the life expectancy curves featured in TD003 and TD004 are based on this end of life criteria. In this

example, the core temperature at end of life would be Ta + 2Tr=86.6°C as the ESR and power loss would be

double at end of life. The maximum permissible core temperature is +105°C for a capacitor with a maximum

operating temperature rating of +85°C. It is acceptable to operate BHC capacitors to maximum permissible

core temperature. It is clear that in this case, maximum permissible core temperature is reached at Ta + 2.88Tr =

+105°C (i.e. ESREnd of life) = 2.88 x ESR(initial value)).

LIFE EXPECTANCY (Max. core temperature) 162,000 Hours

ESR versus Frequency (4700µF / 450V / ø77 x 146mm)

0

5

10

15

20

25

0.01 0.1 1 10 100

FREQUENCY (KHz)

ES

R (

mW

)

20°C

40°C

85°C

65°C

15

16

Fac

tor K

vFa

cto

r Kv

L i f eLife Expectancy and Thermal Characteristics

17


18


19


20


21


22


23


24



1.0

10.0

100.0

1000.0

40 50 60 70 80 90 100

Ambient Air Temperature Ta (°C)

Tr=0

Tr=5

Tr=10

Tr=20

Tr=30

Tr=40

Life Expectancy ALS30/31/34/35 51mm dia.

1.0

10.0

100.0

1000.0

40 50 60 70 80 90 100


Tr=0

Tr=5

Tr=10

Tr=20

Tr=30

Tr=40

Life Expectancy ALS30/31/34/35 63.5 and 66 mm dia.

25

26


27



28

Life Expepectancancy an and Rd Rated Rd Ripppple Cur Current

Introduction This technical data sheet gives details of the life expectancy as related to the rated ripple current. A further technical data sheet, TD003, is also available which gives details of life expectancy related to esr and thermal conditions. During the life of the capacitor certain physical and parametric changes occur. These changes eventually render the capacitor unusable, either due to thermal run-away leading to catastrophic failure, or excessive parametric drift. At higher temperatures degradation of encapsulation materials may accelerate these effects. When ripple current is applied to a capacitor the most important parameter in relation to the life expectancy is the esr. The value of esr will slowly increase throughout the life of the capacitor, leading to a gradual increase in power loss and hence core temperature rise. Long term endurance testing, with voltage and ripple current applied, has established the characteristic parameter changes which are displayed by each product family. The typical esr characteristic is shown below in figure 1.

Esr

increase

Life

Fig 1

Careful study of these curves has enabled the development of a mathematical model to simulate the changes in esr which occur under various test conditions and levels of stress. Life Expectancy Graphs The graphs in TD004 show the life expectancy for various product ranges. The figures quoted are for capacitors in still air with no heatsinking. To use the graphs, find the ambient air temperature (Ta) on the horizontal scale, then choose the curve representing the ripple current required. Where the two lines intersect look across to the vertical scale and read off the life expectancy. Interpolation will be required when the value of ripple current falls between two curves.

The rated ripple current (Ir) is shown in the catalogue or product data sheet for each individual item. Ripple currents are usually quoted at 100Hz with correction factors for other frequencies. The life expectancy figure from the graph should now be multiplied by the appropriate voltage deration factor Kv, if applicable. End Of Life Definition The end of life is defined as being the point at which any of the following conditions have been reached: Core temp > 105 °C (85°C products) > 120 °C (105°C products) Esr > 2 x initial esr

At the end of life the following conditions will also be satisfied : Capacitance change < 10 % Leakage current < initial limit Voltage Deration If capacitors are operated at a voltage below their rated value then the reduced stress and lower leakage current will give an improvement in the service life. Since leakage current increases with temperature the benefit of a reduced operating voltage is more pronounced at higher temperatures. The graphs in TD004 show values of Kv for products with rated temperatures of 85°C and 105°C . Note - the operating voltage should be taken as the mean d.c. value plus the peak a.c. ripple voltage.

29


30

Fac

tor K

vFa

cto

r Kv

31

Life Expectancy and Rated Ripple Current

32


33


34


35


36


37


38



Life Expectancy ALS30/31/34/35 51mm dia.

1.0

10.0

100.0

1000.0

40 50 60 70 80 90 100


0

Ir

Ir x 1.5

Ir x 2

Ir x 2.5

Ir x 3

Life Expectancy ALS30/31/34/35 63.5 and 66mm dia.

1.0

10.0

100.0

1000.0

40 50 60 70 80 90 100


0

Ir

Ir x 1.5

Ir x 2

Ir x 2.5

Ir x 3

39

Life

Exp

ec

tan

cc

y Le

(K

Hrs

)Li

fe E

xpe

cta

nc

cy

Le (

KH

rs)

TD004 Ammendment 27/11/02Life Expectancy and Rated Ripple Current

TD004 Ammendment BHC Components Ltd.

Life Expectancy ALS30/31/34/35 77 and 91mm dia.

1.0

10.0

100.0

1000.0

40 50 60 70 80 90 100


0

Ir

Ir x 1.5

Ir x 2

Ir x 2.5

Ir x 3

40


41


FlammaFlammability Charbility Characteracteristicsics

Introduction Most plastics and elastomers are combustible i.e. will ignite if an ignition source is applied under suitable conditions of temperature and oxygen level. For most published data, the UL94 Horizontal or Vertical Burning System has been applied. Although useful for comparative values, this test is not practicable, as the ignition characteristics are strongly influenced by the material dimensions, and other materials with which they may be in intimate contact. The results in Table 1 below were obtained by using a Needle - Flame Test, as specified in IEC 695-2-2.

The materials were tested in situ on finished, standard capacitors. The flame was applied at positions and angles which gave maximum ignition capability, see Figures 1 and 2. The flame was applied until well pronounced ignition of the material had commenced. During the test program it became obvious that if no ignition took place within 120 seconds, no further flame application would induce burning.

Table 1 Test results for external capacitorrnal capacitor mater materials ITEM MATERIAL

(orientation Figs 1 and 2) APPLICATION TIME (secs)

IGNITION SELF-EXTINGUISH TIME (secs)

SLEEVING

PVC Polyolefin

180

180

no

no

- -

END DISCS

Phenolic PVC

120

120

no

no

- -

DECKS

Phenolic (Plenco) Phenolic (Vyncolite) Nylon 66 (30% glass) PBT Rubber faced laminate

(a) (b) (a) (b) (a) (b) (a) (b) (b)

120 120

120 120

120 120

100 30

120

no no

no no

no no

yes

yes *

no

- - - - - - 5

10 * -

MOTOR-START CAPACITORS (Plastic cased)

Polycarbonate Polycarbonate Noryl Noryl

(a) (b) (a) (b)

60 10

30 5

yes yes

yes yes

no no

2 sec 2 sec

* Small “stand off” sections on ALP10 style decks only.

42

FlammaFlammability Charbility Characteristics

Wind Elements Under ‘normal’ circumstances the wind element will not be exposed directly to ambient conditions outside the can. In the event of an adjacent fire, the rising internal pressure should rupture the safety vent rather than the can or deck (cover). A relatively small quantity of electrolyte vapour would thus be emitted, and if ignited, would aid the surrounding fire for a short period. However, deck/can rupture can occur if a violent short circuit occurs on the outside of the winding close to the inner case surface. Under this condition the case can rupture before the much slower venting process occurs. Full ejection of the deck, would allow all or part of the wind element to become exposed to air and flames, particularly if mounted horizontally. Additionally, the deck rupturing process could cause a tabbing to can, or tabbing to tabbing short-circuit discharge, providing another possible source of ignition. Two situations thus arise:- 1. Deck rupture followed by short-circuit

discharge which could ignite the winding element.

2. Case rupture could expose the winding

element to adjacent flames. For ignition to occur the temperature of the electrolyte must be at or above its flash point during the application of an ignition source (flame or spark). If the source of ignition is an adjacent fire, the flame must heat the electrolyte in the outer tissue layer to its flash point before burning can commence. The time from flame application to burning is influenced by: ¶ flame temperature ¶ flame size ¶ wind diameter ¶ wind initial temperature ¶ the electrolyte flash point After removal of the applied flame, the induced combustion may continue, the extent and time depending on : ¶ the position of the burning area ¶ the temperature of the flame ¶ the fuel availability (electrolyte)

Table 2 Published dble 2 Published data for ex for externaternal ca capapacitor macitor materials terials MATERIAL LOI

(limiting oxygen index) UL94

PVC 35 - Polyolefin 34 V-2 Phenolic (laminate) 51.3 No data Phenolic (Plenco) 30 V-0 Phenolic (Vyncolite) 53 V-0 Nylon 66 (30% glass filled) 23 HB PBT 20 HB Noryl 32 V-1 Polycarbonate 26 V-2

43

FlammaFlammability Charbility Characteristics

Test Method Flame Flame Needle jet as per IEC 695-2-2, Butane gas. WiWinding Diameter 50-76mm, with no additional tissue overwrap. i.e. current design philosophy. Winding Tempermperature Room temperature (20°C). Flame pFlame position See Fig 3 below.

Table 3 Test resultsTable 3 Test results

Electrolyte type

Application time (secs)

Ignition Self extinguish

time (secs)

Glycol based

60 no -

TableTable 4 Pr 4 Producoducts with glyth glycol bas based electrd electrolyte

Product Range Voltage Range ALC10 10 - 500 Vdc ALC40 10 - 450 Vdc ALP/T10 100 - 450 Vdc ALS10 10 - 450 Vdc ALS30 100 - 500 Vdc ALS40 200 - 450 Vdc

MS/MD (motor-start) 120 - 330 Vac

Flash Point and Flammability

Characteristics Flash Point The lowest temperature at which vapour can be ignited by flame. Flammamability Chararacteristics Extremely flammable Flash point <0°C Highly flammable Flash point 0-21°C Flammable Flash point 21-55°C Combustible Flash point >55°C

44

Technical Enquiry

Please complete the boxes below with as much detail as possible and either fax to:

+44 1305 760670 or complete our on-line enquiry form at http://www.bhc.co.uk.

Contact Details

Name Tel:

Company Fax:

Address Email:

Capacitor Details

Capacitor part

number

(if known)

Capacitance µF Rated V dc

Voltage

Size dia. x l en.

(mm)

Configuration Number of Capacitors:

No in bank No in series No in parallel

Operation details The data below applies to : the whole bank [ ] each individual capacitor [ ]

Ripple currents Hz A rms

Hz A rms

Hz A rms

Hz A rms

Hz A rms

Hz A rms

Hz A rms

Working Voltage

Vdc

Forced air cooling

rate - m/s

Ambient air temperature

°C

Heat sinking

°C/W

Other details (e.g. surge

voltages,...)

Special end of life criteria

( e.g. 2 x initial esr )

Target life requirement Hours

11/02© BHC Components Ltd.

Design - [email protected]

BHC Components Ltd.,20 Cumberland Drive,Granby Industrial Estate,Weymouth,Dorset DT4 9TEUnited Kingdom

Telephone +44 (0)1305 782871Fax +44 (0)1305 760670Email [email protected] site www.bhc.co.uk

aluminium electrolytic capacitors - vsb.czhomen.vsb.cz/.../studijni_opory/appnotes_cap_bhc.pdf ·...

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