Philips Electromagnetic Lamp User manual

Main ballast functions
In chapter 2.1 of this Guide:General aspects,section 2.1:Main ballast
functions,the main functions of ballasts have been described.The term
‘ballasts’ is generally reserved for current limiting devices,including
resistors,choke coils and (autoleak) transformers.Other pieces of
auxiliary equipment are compensating capacitors,filter coils and
starters or ignitors.Some systems use an additional series capacitor
for stabilisation.
With the components summed up,all control functions which are
necessary to operate standard fluorescent lamps can be carried out.
Special arrangements,including sequence start,constant wattage or
dimming circuits will not be described in this Guide,as such circuits
are more and more being replaced by the modern high-frequency
(HF)systems.
Stabilisation
In section 3.2:Stabilisation,the need for current stabilisation in
fluorescent lamps has been described,resulting in the following two
formulae:
Ilamp = (Vmains -Vlamp)
/
Zballast
and: Plamp =Vlamp .Ilamp .αlamp
where Ilamp = the current through the lamp
Vmains = the mains voltage
Vlamp = the voltage across the lamp
Zballast = the impedance of the ballast
Plamp = the power of the lamp
αlamp = a constant called lamp factor
From these formulae it can be concluded that the power of the lamp
(and therefore the light output) is influenced by:
- the lamp voltageVlamp,which in turn is highly dependent on
the operating temperature (see section 5.3.12:Ambient and operating
temperatures) and on the lamp current,according to the negative
lamp characteristic (see section 3.2:Stabilisation).
- the lamp current Ilamp,which is dependent on the mains voltage (see
section 5.3.13:Effects of mains voltage fluctuations),the lamp voltage
and the linearity of the ballast impedance.
In order to avoid undesirable variations in light output as a consequence
of mains voltage fluctuations,the lamp voltage must be not more
than approx.half the value of the mains voltage (100 to 130V) and the
impedance should be as linear as possible.
Ignition and re-ignition
In chapter 3:Lamps,section 3.3:Ignition,the need for ignition of a
fluorescent lamp has been described.
ELECTROMAGNETIC LAMP
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13
BALLASTS
12
107
CONTROL GEAR

In the case of electromagnetic control gear,a combination of preheating
and a high ignition peak is obtained by using a normal choke ballast
and a preheat starter or an electronic ignitor.
Energy is supplied to the discharge in the form of electrons.The lamp
current,just like the mains voltage,is sinusoidal,with a frequency of
50 or 60 Hz.If the energy flow is zero (at lamp current reversal) the
lamp stops burning and in theory would have to be re-ignited.
This could be done by supplying additional energy to the electrodes
via a higher lamp voltage,the way it is done when initially starting the
lamp.But from the moment the lamp has reached its stationary
condition,the lamp voltage is constant.
And yet,in practice the lamp does not extinguish at current reversal.
Why not?
The phase shift introduced by the inductive element of the ballast
ensures that the mains voltage is not zero at that moment.Because of
the inductive properties of choke coil ballasts a phase shift ϕoccurs
between the mains voltage and the lamp current (see Fig.102).So,at
the moment of current reversal the lamp voltage would be equal to the
mains voltage,since the voltage over the ballast is nil.The difference
(gap) between the mains voltage and the average lamp voltage as a
consequence of the phase shift ensures proper re-ignition of the lamp
at the moment the current passes the point of reversal (zero-pointA
in figure).
Types of ballasts
1 Resistor ballasts
Current limitation by means of resistor ballasts is a very uneconomic
form of current limitation,because in the resistor electrical energy is
dissipated in the form of heat.Nevertheless,until the advent of
electronic circuitry,use of a series resistor was the only way of stabilising
fluorescent lamps operated on DC,for example the‘TL’R lamp (see
Fig.103).For stable operation on a resistor ballast,it is necessary that
the supply voltage be at least twice the lamp voltage under operating
conditions.This means that 50 per cent of the power will be
dissipated by the ballast.A considerable improvement in efficiency
can,however,be achieved by using a resistor with a very pronounced
positive temperature characteristic (an ordinary or specially
constructed incandescent lamp serves well for this purpose).
A temperature-dependent resistor compensates for variations in the
lamp current resulting from variations in the mains voltage,which means
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Fig. 102. Phase shift between supply voltage
and lamp current (and lamp voltage) in a
discharge lamp with an inductive ballast. In
the case shown, the supply voltage is
sufficiently high for re-igniting the lamp after
every current reversal.
1.3 Ignition and re-ignition
V, A
t
A
VmIlVl
gap
ϕ

that the no-load voltage need be no more than 25 to 30 per cent
higher than the lamp voltage.This is also the proportion of the power
dissipated by the ballast compared to the total circuit power.
2 Capacitor ballasts
A capacitor used as a ballast causes only very little losses,but cannot
be used by itself,as this would give rise to very high peaks in the lamp
current wave form at each half cycle.Only at very high frequencies
can a capacitor serve satisfactorily as a ballast.
3 Inductive ballasts or chokes
Choke coils are frequently used as current limiting devices in
gas-discharge lamp circuits (see Fig.104).They cause somewhat higher
losses than a capacitor,but produce far less distortion in the lamp
current at 50 Hz.Moreover,in combination with a switch starter,they
can be made to produce the high voltage pulse needed to ignite the
lamp.
In practice,a choke ballast consists of a large number of windings of
copper wire on a laminated iron core.It operates on the self-inductance
principle.The impedance of such a ballast must be chosen in
accordance with the mains supply voltage and frequency,the lamp type
and the voltage of the lamp,to ensure that the lamp current is at the
correct value.In other words:each type of lamp requires for each supply
voltage its own choke as a ballast with a specific impedance setting.
Heat losses,occurring through the ohmic resistance of the windings
and hysteresis in the core,much depend upon the mechanical
construction of the ballast and the diameter of the copper wire.
The right ballast for a given lamp and supply voltage should be chosen
by consulting documentation and/or ballast markings.
The Philips standard range of ballasts is for supply voltages of
220/230/240V and for frequencies of 50/60 Hz.
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Fig. 103. Schematic diagram of a
fluorescent lamp operated on a resistor
ballast in a DC circuit.
Fig. 104. Schematic diagram of a
fluorescent lamp operated on a choke
ballast in an AC starter circuit.
1.4 Types of ballasts
+
-
‘TL’ R
I b
Il
La
BVl
Vm
+
-
+-+-
0
S

The most important value for stabilisation is the ballast impedance.It
is expressed as voltage/current ratio in ohm (Ω) and defined for a
certain mains voltage,mains frequency and calibration current (normally
the nominal lamp current).
Chokes can be used for virtually all discharge lamps,provided that
one condition is fulfilled:the mains voltage should be about twice the
arc voltage of the lamp.If the mains voltage is too low,another type
of circuit should be used,like the autoleak or constant-wattage circuits.
The advantages of a choke coil are:
- the wattage losses are low in comparison to those of a resistor,
- it is a simple circuit:the ballast is connected in series with the lamp.
Disadvantages of a choke coil are:
- the current in a lamp with choke circuit exhibits a phase shift with
respect to the applied voltage,the current lagging behind the voltage
(see also section 5.3.4:Power factor correction).
- a high starting current:in inductive circuits the starting current is
about 1.5 times the rated current.
- sensitivity to mains voltage fluctuations:variations in the mains
voltage cause variations in the current through the lamp.
Ballast specification and marking
There are two ways of selecting the right ballast for a certain lamp
and/or to compare various ballasts:
1) the ballast marking,
2) the manufacturer’s documentation.
As all ballasts have to comply with the norm IEC 920/921 some data
has to be marked on the ballast and other data can be mentioned in
the documentation.
On the ballast can be found:
- marks of origin,such as the manufacturer’s name or trade mark,
model or reference number,country of origin,production date code,
- rated supply voltage and frequency,nominal ballast current(s),
- type(s) of lamp with rated wattage,
- type(s) of ignitor with wiring diagram and peak voltage if this
exceeds 1500V,
- twand ∆t (see section 5.1.6),
- max.cross-section of mains or lamp cable;e.g.4 means 4 mm2,
- symbols of the officially recognised certification institutes,such as
VDE,SEMKO,SEV,KEMA,if applicable;CE marking for safety,
- in case of an independent ballast:the symbol ;an independent
ballast is a ballast which is intended to be mounted separately outside
a luminaire and without any additional enclosure,
- a symbol like top if there are mounting restrictions,
- F-marking if the ballast fulfils the IEC F-requirements;that means
it is suitable to be mounted directly on normally flammable surfaces,
-TS,P-marking or if the ballast is thermally protected
(* = thermo-switch temperature in degrees Celsius),
- indication of terminals:L for single phase,N for neutral, for
protective earth (PE), for functional earth,
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1.4 Types of ballasts

- rated voltage,capacitance and tolerance of separate series capacitor.
In the documentation can be found:
- weight,
- overall and mounting dimensions,
- power factor (λ,P.F.or cos ϕ),
- compensating capacitor value and voltage for λ= 0.85 or 0.9,
- mains current nominal and during running-up,both with and
without power factor correction,
- watt losses (normally in cold condition),
- description of version,e.g.open impregnated,‘plastic’ encapsulated,
potted or compound filled.
This information suffices to find the right ballast for a certain
application.Additional information can be obtained on request or can
be found in special application notes.Philips ballasts are designed for
use with IEC standardised fluorescent lamps.
Maximum coil temperature twand ∆T
A ballast,like most electrical components,generates heat due to its
ohmic resistance and magnetic losses.Each component has a
maximum temperature which may not be exceeded.For ballasts it is
the temperature of the choke coil during operation that is important.
The maximum permissible coil temperature twis marked on the
ballast.Coil insulating material,in combination with lacquer,
encapsulation material etc.,is so chosen that below that temperature
the life specified for the ballast is achieved.A twvalue of 130 ºC is usual
nowadays with a coil insulating class F (150 ºC) or class H (180 ºC).
Under standard conditions,an average ballast life of ten years may be
expected in the case of continuous operation at a coil temperature of
twºC.As a rule of thumb,a 10 ºC temperature rise above the twvalue
will halve its expected life (see Fig.105).If,for instance,the operating
temperature is 20 ºC above the twvalue,one may expect a ballast life
of 2.5 years of continuous operation.If no twvalue is marked on the
ballast,a maximum of 105 ºC is assumed for the coil temperature.
As the ballast normally does not function continuously,the actual life
of the ballast can be very long.It also takes some hours before the
thermal equilibrium is reached in the ballast,which again increases the
practical ballast lifetime.
To verify the twmarking,accelerated lifetime tests are done at ballast
temperatures above 200 ºC for 30 or 60 days.
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Fig. 105.The nominal life of choke coils
in relation to the permitted rated
maximum operating temperature of a
ballast winding tw, dependent on
insulation material:
a) class A: tw105 ºC,
b) class E: tw120 ºC,
c) class F or H: tw130 ºC.
1.5 Ballast specification and marking
250
200
150
100
0,1
1,0
10
temp. (°C)
t (years)
(c)
(b)
(a)
16

Another value marked on the ballast is the coil temperature rise ∆t.
This is the difference between the absolute coil temperature and the
ambient temperature in standard conditions and is measured by a
method specified in IEC Publ.920 (EN 60920).Common values for ∆t
are from 50 to 70 degrees in steps of 5 degrees.
The coil temperature rise is measured by measuring the ohmic
resistance of the cold and warm copper coil and using the formula:
∆t = {(R2- R1)/R1} .(234.5 + t1) - (t2- t1)
or: tc= R2/R1 .(t1+ 234.5) - 234.5 (IEC 598-1Appendix E)
where R1= initial cold coil resistance in ohm
R2= warm coil resistance in ohm
t2= ambient temperature at measuring R2in Celsius
t1= initial ambient temperature at measuring R1in Celsius
tc= calculated warm coil temperature in Celsius
∆t=t
c
- t2in Kelvin
The value 234.5 applies to copper wire;in case of aluminium
wire,the value 229 should be used.
So a ballast marked with tw130 and ∆t 70,will have the specified 10
years average life in continuous operation at standard conditions at an
ambient temperature of 130 - 70 = 60 ºC.When the ambient
temperature around the ballast is higher,a shorter ballast life has to
be accepted or sufficient air circulation or cooling has to be applied.
The so-called ambient temperature mentioned in this chapter is not
the room or outside temperature,but the temperature of the micro-
environment of the ballast.Built into a luminaire or ballast box the air
temperature around the ballast is higher than the outside ambient
temperature.This higher temperature has to be added to the coil
temperature rise ∆t to find the absolute coil temperature:tc= t2+ ∆t.
Additionally,a third temperature figure can be mentioned on the ballast:
the ballast temperature rise in abnormal conditions,again measured
according to specifications like EN 60920.In short:it is the winding
temperature rise at 110 per cent mains voltage when the glow-switch
starter,belonging to the system,is short-circuited.
The marking of the three temperature markings should be :
∆t ** / *** / tw*** with * = figure
Example:∆t 70 / 140 / tw130.
Watt losses
Ballast losses normally are published as‘cold’ values,meaning that the
ballast is not energised or only very shortly before and the ballast
winding is at ambient temperature (25 ºC).In practice the ballast will
reach more or less the marked ∆t value and then the copper resistance
is approx.25 per cent higher than in the‘cold’ situation.Therefore the
‘warm’ losses in practice will be 10 - 30 per cent higher than the
published values.
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1.6 Maximum coil temperature twand ∆T

As in some applications the power consumption is of prime importance,
there are low-loss ballasts for the major lamp types‘TL’D 18,36 and
58W ( BTA**L31LW).The 18 and 36W LW ballasts are bigger than the
standard types,resulting in lower ballast temperatures and 25 to
30 per cent less ballast watt losses.Due to practical restrictions the
BTA 58L31LW type could not be made bigger.The 15 per cent lower
ballast losses are the result of a better iron lamination quality,while
the ballast temperatures are only slightly lower than those of the
standard types.
Main starter function
Fluorescent lamps do not ignite at mains voltage.To ignite the lamps,a
starter is applied to preheat the lamp electrodes and to give a peak
voltage high enough to initiate the discharge.
So in fact there is only one basic function for a starter:to deliver the
ignition voltage to start the discharge in a fluorescent lamp in a proper
way.After ignition the starter has to stop producing ignition peaks.This
can be obtained by sensing the lamp voltage or lamp current and/or
by a timer function.
Starter types
There are two types of fluorescent lamp starters:
1 Glow-switch starters
The glow-switch starter consists of one or two bimetallic electrodes
enclosed in a glass container filled with noble gas.The starter is
connected parallel across the lamp in such a way that the preheat
current can run through the lamp electrodes when the starter is closed
(Fig.106).At the moment of switching on the mains voltage, the total
mains voltage is across the open glow-switch starter.This results in a
glow discharge starting between the bimetallic electrodes of the
starter.The glow discharge causes a temperature increase in these
bimetallic electrodes,resulting in the closure of the electrodes of the
starter.During this closure the lamp electrodes are preheated by the
short-circuit current of the ballast.After closure the temperature of
the starter electrodes decreases and the starter re-opens.At the
moment of re-opening,the current through the ballast is interrupted,
causing a peak voltage over the lamp electrodes high enough for lamp
ignition.This peak voltage depends on the inductance of the choke,
the level of the short- circuit current and the speed of the opening of
the glow-switch electrodes.In formula:
Peak voltage:Vpeak = L dI/dt
The minimum specified peak voltage depends on the type and is between
800 and 900V.
If the lamp electrodes are not yet hot enough or the peak voltage is
not high enough,the glow-switch starter will resume the whole
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STARTERS
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1.7 Watt losses

starting process again until the lamp ignites.If the lamp will not ignite
(end of life) the starter will continue producing peaks (flickering) until
the mains voltage is switched off or until the electrodes of the glow-
switch starter stick together.In the latter case the short-circuit
current is continuously running through the lamp electrodes,which
can be seen at the glowing lamp ends.
Once the lamp is properly ignited,the lamp voltage is too low for a
glow discharge between the starter electrodes.So these electrodes
stay‘cool’ and in open position.
A capacitor across the starter electrodes prevents radio-interference
of the lamp.
There are five types of glow-switch starters,specified for a certain mains
voltage and/or lamp wattage ( S2-10-11-12-16).There are also resettable
glow-switch starters:SiS2,Si S3 and SiS10.These starters switch off
after a certaintime in case the lamps do not ignite and have to be
reset manually by a push button.Switching the mains supply does not
reactivate a switched-off resettable starter.
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Fig. 106.Working principle of a glow-
discharge starter circuit.
1.The heat from the discharge in the
starter bulb causes the bimetallic
electrodes to bend together.
2.When the bimetallic electrodes make
contact, a current starts to flow through
the circuit, sufficient for preheating the
electrodes of the fluorescent lamp.
3.The bimetallic electrodes cool down
and open again, causing a voltage peak,
which ignites the fluorescent lamp.
2.2 Starter types
0
0
0

2 Electronic starters
In principle the electronic starter or ignitor is working in the same
manner as the glow-switch starter.But now the switching does not
come from bi-metallic electrodes,but from a triac.
The electronic circuit in the starter gives a well-defined preheat time
(1.7 sec) for the lamp electrodes and,after the preheat,a well-defined
peak voltage,which ensures optimum lamp ignition.The heart of the
electronic starter is a customized integrated circuit,containing the
intelligence of the product.It makes the starter switch off after seven
unsuccessful ignition attempts,so it is called‘flicker free’.
The electronic starter also contains an over-heating detection by
means of a PTC resistor,to switch off in case the starter becomes
too hot (e.g.with a short-circuited ballast).This second stop function
resets after approx.4 minutes.
The electronic starter extends the lamp lifetime up to 25 per cent on
account of the well-defined preheat time.The exact digital timing makes
the electronic starter independent of mains voltage fluctuations.
In the Philips programme there are two types of electronic starters:
one in the canister of the glow-switch starters (two-pin types S2-E and
S10-E Perform version),and one in a plastic housing (four-pin type ES08).
Lifetime
The lifetime of fluorescent lamp starters is expressed in the number
of switches.
At present the glow-switch starters have a lifetime of 10 000 switches
or more,while the electronic starters have a lifetime of 100 000 switches
or more.
Components
A customer primarily needs a solution to his lighting requirements.
Basically,he needs two things to obtain an installation which completely
fulfils his specifications:a design and components.To make sure that
the installation works properly under all circumstances,the right
components must be chosen and selected in combination with each
other.
In principle the following components are required in a lighting
installation:
- lamps,
- lampholders,
- luminaires,
- gear (ballasts,starters),
- compensating capacitors,
- cabling,
- fusing and switching devices,
- filter coils (if necessary),
- dimming equipment (if possible and required).
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SYSTEMS
115
2.2 Starter types

Information about lamps can be found in the lamp documentation,
where also the type of lampholder or lamp cap is mentioned.Be sure
to use the appropriate lampholder,as there are many different types.
Lamp types with different wattage are in principle not interchangeable
in a certain circuit,even though they may have the same lamp cap and
do fit in the same lampholder.
In some lamp types the glow-switch starter is incorporated in the
lamp base (2-pin version PL).In the SL family the total electric circuit
is incorporated with the lamp in the outer shell (see Fig.107).
In the luminaire documentation,information can be found on which
lamp types can be used.When installing other than specified types,
electrical,thermal or lighting problems will arise.In the luminaire
documentation it can also be found if the gear is incorporated in the
luminaire and what the cable entries and connections are.
In the gear documentation,information can be found about the
electrical terminals and the electrical diagrams.Also the value and the
voltage range of capacitors is mentioned here.
The remaining system-related components and subjects mentioned
above will be described in the following sections.
Capacitors
Two types of capacitors are possible in fluorescent lamp circuits.One
type is the parallel compensating capacitor for power factor
improvement,connected across the mains.The second type is the series
capacitor which also determines the lamp current.
Series capacitors are used in capacitive or duo circuits.
In installations with fluorescent lamps of more than 25W,capacitors
are necessary for power factor correction,as the power factor of an
inductively stabilised circuit is only approx.0.5.Power factor
compensating capacitors are connected across the mains supply voltage
(parallel compensation) between phase and neutral (220/240V).
In the relevant ballast documentation figures can be found for the
capacitor value in microfarad (µF) for a certain combination of lamp
and supply voltage to achieve a power factor of ≥0.9.
Every user can in fact create his own solution for obtaining the necessary
capacitance.
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Fig. 107.The circuit of an SL lamp
consists of the following components:
1. Discharge tube,
2. Starter,
3. Capacitor,
4. Ballast,
5.Thermal protector.
3.1 Components
L
N
mains 
supply
1
3
2
4
5