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Thermal design
Introduction
Attention needs to be paid to thermal design-in for
LED-modules and drivers to ensure optimum
performance and life time of the luminaire. The critical
thermal management items for the LED module are set
out in this chapter in order to facilitate the design-in. If
these thermal items are taken into account, this will
help to ensure optimum performance and lifetime of
the LED system.
Relevant definitions are explained along with guidance
on how
and where to measure the temperatures.
Key Definitions:
Module temperature: This is the temperature measured
at the specified Tcase or Tc point of the module. This
temperature is directly related to the LED junction
temperature, which is the critical parameter for
operation.
Ambient temperature: This is the temperature of the air
surrounding the luminaire in the test environment or
application. The module and driver temperature
increases, by approximation, linearly with the ambient
temperature. This relation can be used to predict
module and driver temperatures at a different ambient
temperature.
Tc nominal: This is the module temperature at which
the performance is specified.
Tc life: This is the module or driver temperature (equal
or higher than Tc nominal) at which the lifetime of the
module (e.g. lumen maintenance of LxxByy) is
specified.
Tc max: This is the maximum module or driver
temperature
(equal or higher than Tc life) to stay within safety limits.
This temperature must not be exceeded, even in case
of fan failure. The specified Tc nominal, Tc life, and Tc
max are listed in the relevant datasheets that can be
found on our website
philips.com/oem
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Design-in Guide - LEDFlex S system
Test Requirements
Measurements shall not be taken until the luminaire has
stabilized thermally, i.e. temperatures are changing at a
rate less than 1 °C per hour (see also the relevant
clauses in IEC 60598-1). For ANSI/UL 8750 the test is to
continue until constant temperatures are obtained. A
temperature is
considered constant if:
a) The test has been running for at least 3 hours, and
b) Three successive readings, taken at 15-minute
intervals, are within 1°C (1.8°F) of one another and are
still not rising.
Module T ambient
The LEDFlex S is a self-cooling product when
used between an ambient temperature of -35 to 50
degrees Celsius, and the light beam of the LEDFlex S is
not covered.
Module Tcase point location
The tc point is located on the accessible silicone surface
of the LEDFlex S module. The thermocouple can be
attached with a high temperature glue or Kapton tape.
Indication of Tc measuring point
Driver Tcase point location
The Tcase point on the driver is indicated by a point or
an asterisk with the Tc caption. Please refer to the driver
datasheet for the exact location. For the thermal
measurements a thermocouple can be attached with a
high temperature glue or Kapton tape.
November 2021
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