GE Industrial Solutions QBDW025A0B Barracuda Series - Manual (Page 12)

GE
Data Sheet
QBDW025A0B Barracuda Series; DC-DC Converter Power Modules
36-75Vdc Input; 12.0Vdc, 25.0A, 300W Output
May 9, 2013 ©2012 General Electric Company. All rights reserved. Page 12
Feature Descriptions (continued)
Thermal Considerations
The thermal data presented here is based on physical
measurements taken in a wind tunnel, using automated
thermo-couple instrumentation to monitor key component
temperatures: FETs, diodes, control ICs, magnetic cores,
ceramic capacitors, opto-isolators, and module pwb
conductors, while controlling the ambient airflow rate and
temperature. For a given airflow and ambient temperature,
the module output power is increased, until one (or more) of
the components reaches its maximum derated operating
temperature, as defined in IPC-9592B. This procedure is then
repeated for a different airflow or ambient temperature until
a family of module output derating curves is obtained.
The power modules operate in a variety of thermal
environments and sufficient cooling should be provided to
help ensure reliable operation. Thermal considerations
include ambient temperature, airflow, module power
dissipation, and the need for increased reliability. A
reduction in the operating temperature of the module will
result in an increase in reliability.
Heat-dissipating components are mounted on the top side
of the module. Heat is removed by conduction, convection
and radiation to the surrounding environment. Proper
cooling can be verified by measuring the thermal reference
temperature (TH
1
or TH
2
). Peak temperature occurs at the
position indicated in Figure 17 and 18. For reliable operation
this temperature should not exceed TH
1
=125°C or
TH
2
=105°C. For extremely high reliability you can limit this
temperature to a lower value.
.
Figure 17. Location of the thermal reference temperature
TH.
Figure 18. Location of the thermal reference temperature
TH
3
for Baseplate module.
The output power of the module should not exceed the
rated power for the module as listed in the Ordering
Information table.
Please refer to the Application Note “Thermal
Characterization Process For Open-Frame Board-Mounted
Power Modules” for a detailed discussion of thermal aspects
including maximum device temperatures.
Heat Transfer via Convection
Increased airflow over the module enhances the heat
transfer via convection. The thermal derating of figure 19-
23 shows the maximum output current that can be
delivered by each module in the indicated orientation
without exceeding the maximum TH
x
temperature versus
local ambient temperature (T
A
) for several air flow
conditions.
The use of Figure 19 is shown in the following example:
Example
What is the minimum airflow necessary for a QBDW025A0B
operating at V
I
= 48 V, an output current of 20A, and a
maximum ambient temperature of 60 °C in transverse
orientation.
Solution:
Given: V
in
= 48V, I
O
= 20A, T
A
= 60 °C
Determine required airflow velocity (Use Figure 19):
Velocity = 0.5m/s (100 LFM) or greater.