GE
Data Sheet
QPW050/060 Series Power Modules; DC-DC converters
36-75Vdc Input; 1.2Vdc to 3.3Vdc Output
October 5, 2015 ©2012 General Electric Company. All rights reserved. Page 18
Thermal Considerations with Baseplate
The baseplate option (-H) power modules are
constructed with baseplate on topside of the open frame
power module. The baseplate includes quarter brick
through-threaded, M3 x 0.5 mounting hole pattern,
which enable heat sinks or cold plates to attaché to the
module. The mounting torque must not exceed 0.56 N-
m (5 in.-lb.) during heat sink assembly. This module
operates in a variety of thermal environments; however,
sufficient cooling should be provided to help ensure
reliable operation.
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. The
thermal data presented here is based on physical
measurements taken in a wind tunnel.
Heat-dissipating components are mounted on the
topside of the module and coupled to the baseplate with
thermal gap material. Heat is removed by conduction,
convection and radiation to the surrounding
environment. Proper cooling can be verified by
measuring the thermal reference
temperature (T
ref
).
Peak temperature (T
ref
) occurs at the position indicated
in Figure 51. For reliable operation this temperature
should not exceed 95ºC temperature threshold.
Figure 51. T
ref
Temperature Measurement Location
for QPW-H baseplate option
The output power of the module should not exceed the
rated power for the module as listed in the Ordering
Information table.
Although the maximum Tref temperature of the power
modules is 95 °C, you can limit this temperature to a
lower value for extremely high reliability. 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. Following derating figures
shows the maximum output current that can be
delivered by each module in the respective orientation
without exceeding the maximum T
ref
temperature
versus local ambient temperature (T
A
) for natural
convection through 2m/s (400 ft./min).
Note that the natural convection condition was
measured at 0.05 m/s to 0.1 m/s (10ft./min. to 20
ft./min.); however, systems in which these power
modules may be used typically generate natural
convection airflow rates of 0.3 m/s (60 ft./min.) due to
other heat dissipating components in the system. The
use of Figures 2 - 4 are shown in the following example:
Example
What is the minimum airflow and heat sink size
necessary for a QPW050A0F-H operating at VI = 48 V, an
output current of 30A, and a maximum ambient
temperature of 70 °C in transverse orientation.
Solution:
Given: VI = 48V
Io = 30A
TA = 70 °C
To determine airflow (V) and heatsink size (Use Figures
52 - 53):
There are couple of solution can be derived from below
derating figures.
1) Baseplated with 0.25” heatsink in natural
convection (V= 0 m/sec) environment.
2) No baseplate required when operated with
airflow of 200 LFM (V = 1m/sec).
T
ref
