Digidim 505 : Technical information : Page 34

HF-ballast

The life span spread of an HF-ballast. After 50,000 hours, at least 90 % of all HF-

ballasts work if the temperature of the control gear’s tc-point (reference point) does

not exceed the manufacturer’s deﬁned value for that life span.

Terminology

Warm start

Correctly optimised ignition of ﬂuorescent lamps, where the cathodes at the ends of

the lamp are preheated to the right temperature, allowing controlled discharging to

take place. This creates the best conditions for maximising the uorescent lamps life

span.

Cold start

Igniting ﬂuorescent lamps without preheating the cathodes, causes the cathodes’

emissions-material to be consumed quicker. The advantage this oers is smaller and

less expensive electronic control gear. These are suited only for industrial premises, and

places, where uorescent lamps are not switched on and o more than once or twice

a day.

Nominal voltage

The operating voltage is stated on the luminaire label. Normally, HF-ballasts work

without problems within ±10 % uctuation of the nominal voltage. Check the voltage

is correct. Too high or too low can damage the electronics. Most HF-ballasts also work

with direct voltage. Please contact us for this type of operation.

Harmonics

Harmonics are distortions of the mains voltage’s waveform caused by non-linear loads

on the mains. Harmonics give rise to distorted currents, high magnetic elds and inter-

ference to sensitive electronic apparatus. Computers, frequency converters, standard

compensated luminaires are large harmonic producers. The guideline value for com-

puters is approximately 80 % THD, standard luminaires approximately 20 % THD and

HF-ballasts about 10 %. Low quality HF-ballasts can be large producers of harmonics.

THD

Total Harmonic Distortion.

Operating frequency

is the discharge current’s frequency in the uorescent lamp. In luminaires with mag-

netic ballasts this equals the mains frequency 50 Hz. HF-ballasts convert the mains

frequency to approximately 25–50 kHz. The luminaire’s eciency is also improved by

approximate 10 % in this case. As the operating frequency also modulates light, this

can cause problems with infrared detectors used in alarm systems and lighting control.

The problem can however be avoided through the right choice of HF-ballast.

Cathode

Also called electrode. The cathodes at each end of the uorescent lamp are made of

tungsten laments, coated with beryllium oxide. When heated, electrons are released

which maintain the lamp’s discharging current. Incorrect temperature on the cathodes

shortens the lamp’s life span. This occurs primarily with dimming when the ﬂuorescent

lamp output drops, which can seriously shorten the lamp’s life span. This is avoided by

using high quality HF-ballasts.

Life span HF-ballasts

The life span of the HF-ballast is, like other electronic equipment,

limited. It is determined by, among others, component selection,

mains uctuations, ignition rate and rst and foremost the ambient

temperature inside the luminaire. The electronic components’ fault

frequency causes failures on a few HF-ballast during the rst hours

of operation. HF-ballast faults then occur evenly over a period of

time, like uorescent lamps.

The life span and function can be jeopardised by incorrect handling

during installation. The HF-ballast can be destroyed by:

Incorrect measuring of the insulation resistance.•

Current peaks caused by machinery at the workplace. •

Over temperature, if the luminaire is used in a space with in-•

creased temperature (normal temp. > 25 °C). The luminaires’ ta

(max permitted ambient temperature) is in most cases 25 °C, but

luminaires with heightened ta are available.

The life span of the HF-ballast, as previously described, is dependent

in part on the ambient temperature. Normally there is a tempera-

ture control point (tc-point) on the HF-ballast, which should be

checked when the ballast is positioned in the product in question.

The tc-max varies between manufacturer and type and denes the

highest permitted temperature to prevent damage to the ballast.

HF-ballasts with a high tc-max are not necessarily better than

models with a low tc-max. The HF-ballast manufacturer may have

chosen to place the reference point at a cool or warm position on

the HF-ballast.

The life span of an HF-ballast is stated at a specic temperature

on the tc-point. Sometimes this corresponds with tc-max, but it

can also be stated at a lower temperature. Manufacturers usually

state 50,000 hours as the life span with a maximum depreciation of

0.2 %/1000 hours, which corresponds to a 10 % dropout.

The cooler the tc-temperature, the longer the life span. A rule of

thumb is that a 10° reduction in temperature on the tc-point dou-

bles the life span while a 10° increase in temperature halves this.

HF-ballasts for demanding environments, HF Industry

HF Industry is a ballast designed for use in rugged and demanding

environments. Examples are industrial environments where:

mains voltage transients are a problem•

the atmosphere is dustier than normal•

the atmosphere is slightly more humid than normal•

heavy vibrations occur•

The HF-ballasts are designed for a life span of 100,000 hours (10 %

depreciation) under the condition that the temperature is kept

below specic levels (according to the spec. for the HF-ballast).

They are also designed with IVG (Intelligent Voltage Guard) which

both warns and protects against overvoltage and undervoltage. The

HF-ballasts are also designed to withstand mains voltage transients

up to 4 kV. The more robust HF-ballast oers longer maintenance

intervals, which reduces maintenance costs to a minimum.

Ballasts are not available in HF-dim or in slimline designs, which

means they cannot be used in all luminaires. The ballasts are pri-

marily intended for products in industrial environments, products

that are usually equipped with high lamp outputs and where there

is physical space for the HF-ballasts. The use of these HF-ballasts in

other types of luminaires, for example oce luminaires, does not

normally give any advantages compared to using HF-std.

For product ranges, please refer to the industrial luminaires chapter.