APA501
AMPSS
™
Astec Modular Power Supply System
Series Highlights
•Horizontal, Vertical and Low Profile fin options
•Full range of mounting accessories
Heatsinks for Power Modules
Technical Reference Manual
Series
Rev. 01 Jan 96
AMPSS
®
Reference Manual
Table of Contents
1
Contents
Heatsinks ............................................................................ 3
"60" Size Heatsink Dimensions & Characteristics............................................4
"80" Size Heatsink Dimensions & Characteristics............................................7
Thermal Design Process and Example .......................... 11
Rev. 01 Jan 96
AMPSS
®
Reference Manual
AMPSS
® Accessories
3
Heatsinks
Heatsinks for
AMPSS
modules are available in a
variety of sizes and fin orientation. Mounting kits
and thermal pads are also available. The table
below shows the options available for "80" and "60"
module sizes.
A heatsink mounting kit provides the most conven-
ient way to mount the heatsink to the module and
then mount the assembly onto a circuit board
12
AMPSS
modules may be retained by their input and
output pins only, or may be fixed to the board using
bolts screwed into the tapped studs which are
provided as part of the mounting kit. In both cases
the studs provide clearance between the module and
the circuit board to facilitate PCB cleaning opera-
tions.
Note: baseplate and heatsink must be connected to
protective earth
Description Model Number Dimensions Free air therma
l
inches mm resistance
Heatsink, "60" size, vertical fin. APA501-60-001 2.26x2.32x0.6 57.5x59x15 3.8˚C/W
Heatsink, "60" size, horizontal fin APA501-60-002 2.26x2.32x0.6 57.5x59x15 3.9˚C/W
Heatsink, "60" size, vertical fin. APA501-60-003 2.26x2.32x0.9 57.5x59x22.5 3.3˚C/W
Heatsink, "60" size, horizontal fin APA501-60-004 2.26x2.32x0.9 57.5x59x22.5 3.7˚C/W
Heatsink, "60" size, vertical fin. APA501-60-005 2.26x2.32x1.5 57.5x59x37 2.8˚C/W
Heatsink, "60" size, horizontal fin APA501-60-006 2.26x2.32x1.5 57.5x59x37 2.8˚C/W
Heatsink, "60" size, low profile APA501-60-007 2.25x3.50x0.5 57.2x89x12 3.6˚C/W
Heatsink, "80" size, vertical fin. APA501-80-001 4.53x2.32x0.6 115x59x15 2.7˚C/W
Heatsink, "80" size, horizontal fin APA501-80-002 4.53x2.32x0.6 115x59x15 2.4˚C/W
Heatsink, "80" size, vertical fin. APA501-80-003 4.53x2.32x0.9 115x59x22.5 2.2˚C/W
Heatsink, "80" size, horizontal fin APA501-80-004 4.53x2.32x0.9 115x59x22.5 2.0˚C/W
Heatsink, "80" size, vertical fin. APA501-80-005 4.53x2.32x1.5 115x59x37 2.0˚C/W
Heatsink, "80" size, horizontal fin APA501-80-006 4.53x2.32x1.5 115x59x37 1.7˚C/W
Heatsink, "80" size, low profile APA501-80-007 4.55x3.50x0.5 115.6x89x12 2.2˚C/W
Thermal Pad, "60" size APA502-60-001
Thermal Pad, "80" size APA502-80-001
Mounting Kit, Tapped Studs APA503-00-001
Mounting Kit, Solder Studs APA503-00-002
Mounting Kit, Tapped Studs APA503-00-007
for low profile heatsink
Mounting Kit, Solder Studs APA503-00-008
for low profile heatsink
Spring Sockets (20 cont. 15pwr) APA504-00-001
Rev. 01 Jan 96
AMPSS
®
Reference Manual
4
Heatsinks
APA501-60-002
APA501-60-003
57.50 (2.26)
59.00 (2.32)
24.0 (0.9)
50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
APA501-60-001
"60" Size Heatsink Dimensions & Characteristics
57.50 (2.26)
59.00 (2.32)
15.0 (0.6) 50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
57.50 (2.26)
59.00 (2.32)
15.0 (0.6) 50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
Forced Convection for APA501-60-001 at 100W Output
0
0.5
1
1.5
2
2.5
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-60-002 at 100W Output
0
0.5
1
1.5
2
2.5
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-60-003 at 100W Output
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
AMPSS
® Accessories
5
APA501-60-004
57.50 (2.26)
59.00 (2.32)
37.0 (1.5)
50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
APA501-60-005
APA501-60-006
57.50 (2.26)
59.00 (2.32)
24.0 (0.9)
50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
57.50 (2.26)
59.00 (2.32)
37.0 (1.5)
50.80 (2.00)
4.0 (0.16) 12.0 (0.47)
48.26 (1.90)
ø 3.80 (0.15)
Forced Convection for APA501-60-005 at 100W Output
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-60-006 at 100W Output
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-60-004 at 100W Output
0
0.5
1
1.5
2
2.5
3
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
6
Heatsinks
50.80 (2.00) 19.10 (0.75)
4.47(0.18)
48.26 (1.90)
AA
57.2 (2.25)
45°
63.0 (2.48)
89.0 (3.50)
ø7.5 (0.30) (4X)
ø3.8 (0.15) (4X)
ø4.2 (0.17) (4X)
4.0 (0.16) ± 0.1
12.0
(0.47) 4.2 (0.17)
3.5 (0.14)
Section A-A
APA501-60-007
Forced Convection for APA501-80-007 at 200W Output
0
0.5
1
1.5
2
2.5
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
AMPSS
® Accessories
7
"80" Size Heatsink Dimensions & Characteristics
115.0 (4.53)
59.0 (2.32)
15.0
(0.6)
50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
115.0 (4.53)
59.0 (2.32)
15.0
(0.6)
50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
Forced Convection for APA501-80-001 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-80-002 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
APA501-80-001
APA501-80-002
Rev. 01 Jan 96
AMPSS
®
Reference Manual
8
Heatsinks
APA501-80-003
APA501-80-004
Forced Convection for APA501-80-003 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-80-004 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
115.0 (4.53)
59.0 (2.32)
22.5
(0.89)
50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
115.0 (4.53)
59.0 (2.32)
22.5
(0.89)
50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
AMPSS
® Accessories
9
Forced Convection for APA501-80-005 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Forced Convection for APA501-80-006 at 200W Output
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
APA501-80-005
APA501-80-006
115.0 (4.53)
59.0(2.32)
37.0 (1.5) 50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
115.0 (4.53)
59.0(2.32)
37.0 (1.5) 50.80(2.00)
4.0 (0.16) 12.0 (0.47)
106.68 (4.20)
ø 3.80 (0.15)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
10
Heatsinks
APA501-80-007
50.8 (2.00) 19.1 (0.75)
4.47 (0.18)
106.68 (4.20)
AA
115.6 (4.55) ±0.2
45°
Section A-A
63.0 (2.48)
89.0 (3.50)
ø7.5 (0.30) (4X)
ø3.8 (0.15) (4X)
ø4.2 (0.17) (4X)
4.0 (0.16) ± 0.1
12.0
(0.47) 4.2 (0.17)
3.5 (0.14)
Forced Convection for APA501-80-007 at 200W Output
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 200 400 600 800 1000
V air (LFM)
Thermal Resistance Baseplate to Ambient (˚C/W)
Rev. 01 Jan 96
AMPSS
®
Reference Manual
AMPSS
® Accessories
11
Thermal Design Process and Example
Temperature & MTBF
APMSS
modules are designed to be able to run at
baseplate temperatures of 100°C in the case of the
AM80 series and 85°C for other series. However, for
normal operation the modules should not be run at
the maximum allowable temperature since the Mean
Time Between Failures (MTBF) will reduce sharply
as temperature increases. For example, an
AM80-300L-050F40 operating at 5V@40A output,
with a baseplate temperature of 50°C, has an MTBF
of over one million hours. If the temperature is
doubled to 100°C this figure drops to 155,000 hours.
The following rules should be followed to ensure
reliable operation -
• At the maximum system ambient tempera-
ture the APMSS
baseplate temperature
rating should not be exceeded.
• At the normal system ambient operating
temperature the APMSS
baseplate tem-
perature must be low enough to meet MTBF
requirements.
The Thermal Design Process
1. Determine heat generated by module from its
losses. The minimum efficiency at relevant line
and load conditions should be used in calculat-
ing the losses.
2. Determine maximum baseplate temperature
rise to stay within module temperature rating
at maximum system ambient.
3. Define maximum system baseplate tempera-
ture to meet MTBF in normal system operating
conditions or at the temperature at which the
MTBF is specified.
4. Select/design heatsink and airflow require-
ment.
5. Test using the
APMSS
imbedded TEMP-MON
feature which allows direct and convenient
monitoring of baseplate temperature. (BM/AM/
AL/AK Series)
Thermal Design Example
This example is for the following parameters:
• Single 5V AM80 module used in a distributed
power system.
• Average load 30A (150 Watts)
• Normal operating ambient temperature 25°C
• Maximum ambient temperature 60°C
• MTBF required - 800,000 hours (from system
requirements)
• Efficiency measured at 83% (Efficiency =
Output power/ Input power)
1. Heat generated = Power Out x [(1/Efficiency)-1]
= 150 x [(1/0.83)-1]
= 31 Watt
2. Maximum baseplate temperature 100°C (from
AM80 specifications).
⇒ At 60 °C (max. ambient temp.) the maximum
baseplate temperature rise is 40°C.
3. To achieve 800,000 hours MTBF, baseplate
temperature must not exceed 61°C.
⇒ Maximum baseplate temperature rise (from 25°C
operating ambient) is 36°C.
4. Choose the lowest temperature rise of ➁ or ➂ i.e.
36°C.
The cooling system must dissipate 31 Watts with a
maximum baseplate temperature rise of 36°C.
⇒ Thermal resistance = 36/31 = 1.16°C/Watt.
To ensure good thermal contact Astec recommends
the use of Thermstrate® thermal mounting pads.
Thermal resistance of the Thermstrate® interface
between baseplate and heatsink is 0.1°C/W.
For this example (overall thermal resistance 1.16 °C/
W) the heatsink thermal resistance should be a
maximum of 1.06°C/W. A 10% safety margin is
desirable so a heatsink achieving 0.95°C/W is
chosen.
To achieve this level of cooling using natural convec-
tion would require an very large heatsink. It would
therefore be better to employ forced air cooling. A
thermal resistance vs air flow characteristic should
be referenced to determine the required airflow for
the heatsink you are using.
Rev. 01 Jan 96
AMPSS
®
Reference Manual
12
Heatsinks
Tips on installation of
AMPSS
modules
1.Ensure that the module/heatsink interface
smooth, flat and free of debris. Always use either
thermal grease or APMSS thermal pads.
2. Fit modules and other heat generating devices at
the top of the cabinet where possible.
3. Stagger modules to improve cooling and facili-
tate even heat distribution between modules.
4. Avoid blocking the airflow to the modules with
other components.
5. Use a heatsink with fins running vertically for
natural convection cooling.
✖
✓
AIRFLOW AIRFLOW
AIRFLOWAIRFLOW
EUROPE
ASTEC EUROPE LTD.
Astec House, Waterfront Bus. Park
Merry Hill, Dudley
West Midlands
DY5 1LX
U.K.
Tel : 44-1384-842211
Fax : 44-1384-843355
NORTH AMERICA
ASTEC AMERICA, INC.
5810 Van Allen Way
Carlsbad, CA 92008
USA
Tel : 760-930-4600
Fax : 760-930-4700
For further information contact :
ASIA
ASTEC ASIA
6F., China Dyeing Works Building
382-392 Castle Peak Road
Tsuen Wan
N.T.
Hong Kong
Tel : 852-2437-9662
Fax : 852-2402-4426
APA701-VRM Rev. 04 May 97
