Subject to modifications
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PS3500 N+1 Redundant Power Supply
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4 Temperature considerations
Temperature accelerates the failure mechanism of every electronic component (Arrhenius
criteria). If the operating temperature is increased by 10 °C from its normal operating range,
-25…+45 °C (-11...+113 °F), its expected life is almost cut in half.
Temperature rise depends on dissipated power density. For the same enclosure volume
more power dissipated produces higher temperature rise. For example, a cabinet 600 x
600 x 2000 mm dissipating 300 W with natural convection cooling produces an internal
temperature rise of 10 °C. This should be regarded as an ideal case.
Identify the worst load/temperature environment that the power supply will encounter and
determine the recommended cooling method.
•
Use convection cooling
when the supply load/operating temperature is typically in the
lower part of the diagram and free air circulation is ensured.
•
Use forced cooling
when the supply load/operating temperature is in the upper part
of the diagram for extended periods of time or when a very high system reliability is
required.
Figure 3. Recommended load current per module vs. operating temperature
4.1 Convection cooling
Hot components exchange heat with the surrounding air producing a vertically rising hot
air flow. This determines new cool air intake to cool the component in a natural convection
cooling mode, which is controlled by the intake air temperature and flow.
For good convection cooling, install the equipment with an unobstructed vertical flow
of relatively cool (ambient temperature) air entering from the bottom and flow out at
a higher temperature from the top. To avoid excessive temperature build up, do not
stack power dissipating devices vertically in close proximity.
