Control Techniques Unidrive 1 Series User Manual page 25

Safety Product Mechanical
Information Information Installation
Example
To calculate the size of an enclosure for the following:
• Two UNI1405 models
• Each drive to operate at 4.5kHz PWM switching frequency
• RFI filter for each drive
• Braking resistors are to be mounted outside the enclosure
• Maximum ambient temperature inside the enclosure: 40°C
• Maximum ambient temperature outside the enclosure: 30°C
Dissipation of each drive: 190W
Dissipation of each RFI filter: 7.7W (max)
Total dissipation: 2 x (190 + 7.7) = 395.4W
The enclosure is to be made from painted 2mm (0.079 in) sheet steel
having a heat transmission coefficient of 5.5W/m
and two sides of the enclosure are to be free to dissipate heat.
Figure 3-15 Enclosure having front, sides and top panels free to
dissipate heat
H
W
Insert the following values:
T 40°C
int
T 30°C
ext
k 5.5
P 395.4W
The minimum required heat conducting area is then:
395.4
-------------------------------- -
A =
e ( )
5.5 40 30 –
2 2
=7.2m (78ft ) (1m = 3.3 ft)
Estimate two of the enclosure dimensions - the height (H) and depth (D),
for instance. Calculate the width (W) from:
A – 2HD
e
------------------------- -
W =
H + D
Inserting H = 2m and D = 0.6m, obtain the minimum width:
( × ×
7.2 – 2 2 0.6
----------------------------------------------
W =
2 0.6
+
= 1.8m (6ft)
If the enclosure is too large for the space available, it can be made
smaller only by attending to one or all of the following:
• Using a lower PWM switching frequency to reduce the dissipation in
the drives
• Reducing the ambient temperature outside the enclosure, and/or
applying forced-air cooling to the outside of the enclosure
• Reducing the number of drives in the enclosure
• Removing other heat-generating equipment
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Calculating the air-flow in a ventilated enclosure
The dimensions of the enclosure are required only for accommodating
the equipment. The equipment is cooled by the forced air flow.
Calculate the minimum required volume of ventilating air from:
3kP
-------------------------- -
V =
T T
–
int ext
Where:
V Air-flow in m
T
Maximum expected ambient temperature in
ext
enclosure
T Maximum permissible ambient temperature in
int
enclosure
P Power in Watts dissipated by all heat sources in the
enclosure
P
o
------ -
k Ratio of
P
l
Where:
P is the air pressure at sea level
0
P is the air pressure at the installation
I
Typically use a factor of 1.2 to 1.3, to allow also for pressure-drops in
dirty air-filters.
Example
To calculate the size of an enclosure for the following:
• Three UNI3401 models
• Each drive to operate at 6kHz PWM switching frequency
• RFI filter for each drive
• Braking resistors are to be mounted outside the enclosure
• Maximum ambient temperature inside the enclosure: 40
• Maximum ambient temperature outside the enclosure: 30
Dissipation of each drive: 670W
Dissipation of each RFI filter: 12.8W (max)
Total dissipation: 3 x (670 + 60) = 2048.4W
Insert the following values:
T 40°C
int
T 30°C
ext
k 1.3
P 2048.4W
Then:
× ×
3 1.3 2048.4
----------------------------------------- -
V =
40 30 –
3
= 799m / hr (471ft
3 3
(1m / hr = 0.59ft /min)
Advanced Technical
Diagnostics
Parameters Data
3
per hour
3
/ min)
UL Listing
Information
o
C outside the
o
C inside the
o
C
o
C
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