5.3 Recommendations for reducing the wattage in discharge lamps. Osram HQI-E 150 W/NDL CL
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ing the course of the service life. Lamps of differing geometries and filling also show different resonance frequencies. A reduction in wattage also changes the resonance frequencies due to the change in plasma temperature.
The PTo with squarewave operation and optimised ignition runs the POWERBALL HCI ® lamps ideally down to 60% of the lamp output (rated value). No significant negative effects arise even when the output is reduced to 85% of the rated output.
5.3 Recommendations for reducing the wattage in discharge lamps
Even when operated at between 85% and 60% of the rated output, this does not negatively effect the failure rate. However, increasingly the lamps have a slightly green touch and the colours may deviate from each other (colour spread).
5.3.1 Metal halide lamps:
Operation of OSRAM POWERSTAR HCI ® (cylindrical burner) and OSRAM HQI ® lamps with reduced power is not permitted as this can cause considerable colour deviations, much poorer luminous flux maintenance and shorter service lives
The luminous flux drops slightly more throughout the service life in dimming mode than when operated at
100% on the PTo. This effect can be reduced if the lamps are operated via a combination of dimming and
100% operation.
Dimming causes a reduction in light output and colour change.
Basically it is possible to dim POWERBALL HCI ® .
While the higher thermal load capacity of the round ceramic arc tube permits an improved dimming behaviour in terms of luminous efficacy and colour rendering compared to metal halide lamps with quartz arc tube or with the normal cylindrical ceramic tube, dimming still causes a shift in the chromaticity coordinate.
Dimmed lamps show a greater drop in light output and wider colour spread throughout the service life.
It is important to avoid these effects for interior lighting. They are more apparent when operated on conventional control gear than on electronic control gear.
OSRAM therefore recommends not to reduce power with currently available lamps on conventional control gear or for indoor lighting.
The type of dimming has a great impact on the results.
It is recommended to use only adjustable Electronic ballasts with squarewave operation and to completely avoid dimming via reducing the supply voltage or leading-edge or trailing-edge phase dimmers. It is not possible to guarantee that dimmed lamps will be able to meet the product properties.
In any case, the lamp should run for at least 15 minutes with 100% wattage after being switching on so that the lamp can light up correctly.
A warranty regarding lifetime can only be given when approved POWERBALL HCI ® units (cf. online catalogue) on the POWERTRONIC ® PTo are dimmed.
Operation of POWERBALL HCI ® on the
POWERTRONIC ® PTo:
The combination of POWERBALL HCI ® and
POWERTRONIC ® PTo allows energy-saving operation everywhere where optimised colour rendering is not important, for example outdoor lighting.
Squarewave operation is recommended for dimming.
For outdoor lighting: optimised operation of the approved POWERBALL HCI ®
POWERTRONIC ® PTo.
on the
There is no warranty for dimmed POWERBALL
HCI ® . A warranty regarding lifetime can only be given when approved POWERBALL HCI ® units (cf. online catalogue) are dimmed on the
POWERTRONIC ® PTo.
5.3.2 Dimming of other discharge lamps
High pressure mercury lamps:
These lamps can be dimmed to 50% of the rated wattage, whereby they must be started up with 100% wattage. Dimming is possible by voltage reduction, phase control and amplitude modulation.
High pressure sodium lamps:
It is possible and allowed to reduce the power of all
VIALOX ® NAV ® down to 50% of the lamps rated values without impact on the service life
• via step switching by changing to inductive control gear with the next lower rating or
• via step switching with additional inductance, whereby in both cases electronic power switches must be used.
When reducing the power, ensure that the lamps are started and operated at their rated values for approx.
10 minutes before dimming.
It is not permitted to reduce the power by leading edge phase control or reducing the mains voltage.
OSRAM recommends the electronic ballast
POWERTRONIC ® PTo for dimming operation.
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