Philips Electromagnetic Lamp manual Ballast specification and marking

5 1.4 Types of ballasts

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.

1 5 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 1500 V,
- tw and Δt (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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