2.3.2. Measuring luminaires for T5 lamps
Before measuring the light output ratio of a luminaire, the T5
Extreme Temperature lamps should be in a stable condition. The
following steps must be taken:
• To bring the lamps to a stable condition, operate the lamps for
approximately 100 hours
• Wait for 12 hours with the lamps turned off
• Measure the top lumen output of the lamps in the photometer
with a measurement time of approximately 15 minutes
• For measuring the total Phi-T curve, a temperature step of
1°F/hr must be applied, starting at a low temperature and going
to a high temperature
2.4.Thermal luminaire design and ballast lifetime
The ballasts for T5 VHO and T5 HO have a T_case max of 194°F
(90°C). To maximize the lifetime and to minimize the failure rate of
the ballast, the ballast should be placed inside the luminaire at a point
where the measured T_case is lowest.
The time after which 10% of the ballasts have failed is called
the constant failure rate. For a T5 VHO and HO ballast in normal
operation, this constant failure rate is approximately 50,000 hours
at a fixed specified case temperature (194°F). A temperature
increase of approximately 18°F halves this lifetime (thus, 212°F gives
25,000 hrs), while approximately 18°F lower doubles this figure
(176°F gives 100,000 hrs).
2.4.1.Thermal hints and tips
There is an increasing trend towards higher wattages and lumen
outputs in fluorescent lighting, leading to higher internal
temperatures of luminaires.
Every luminaire is different (difference in materials, dimensions,
applications, requirements, etc) so there is not just one simple
solution which helps to prevent overheating of the internal luminaire.
These hints and tips provide some ideas on how to deal with heat
management inside a luminaire.
In the case of T5 VHO, the minimum distance between the lamp
and the reflector must be at least 10mm. Adapting existing T5
luminaires (<54W) for T5 VHO requires more adjustment than
just changing the lamp holders and ballasts.
OEM Design Guide
Philips T5 VHO and HO Extreme Temperature Lamps and Ballasts
5
