Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 52)

Section 2A
Planning Your System Layout
2A-7
Example of Calculating Cabinet Temperature
A design example of a cabinet is given below assuming a component-type
frame incorporating the following:
Main Power Supply (PS1) 225 watts @ 50 0 C
Main Power Supply (PS2A) 130 watts @ 50 0 C
CPU Board 33.5 watts
3-axis Digital Servo module 13.5 watts
The total heat generation (W) for this example would be 47W.
1. Determine a minimum T value for the equation in the
previous section:
a. Estimate the maximum air temperature at the location where the
cabinet will be installed.
b. Subtract this estimate from the maximum internal cabinet temperature
for your application (if you use 55
° C, there is no margin for error).
The difference is the allowable temperature rise in the cabinet (T).
For example, assume a maximum air temperature of 35 ° C and a
desired maximum internal cabinet temperature of 45 ° C, The
value of T would be 45 - 35 = 10
2. Using the W and T values just derived, calculate the minimum heat
radiation surface area, S.
T = W/6S
S = W/6T
= 47/(6 x 10)
= 0.783 sq. meter (8.4 sq. feet)
This result indicates that a cabinet with a minimum of 0.783 m 2
(8.4 ft 2 ) of heat radiation surface is required.
Important: Any cabinet surface in contact with the floor or building wall
is not considered a heat radiation surface in this calculation.
If the resulting cabinet size is prohibitively large, or if the T value
calculated was 10 or more, then the use of a heat exchanger or air
conditioner must be considered. Such designs require more detailed
analysis, beyond that considered within scope of this manual.
Important: The temperature rise value used in this calculation is a
constant. Actual temperature rise will vary depending on the amount of air
flow inside the cabinet.