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Bulletin 1606 Switched Mode Power Supplies
21.11. Use at Low Temperatures (-25°C / -40°C)
Please pay attention to the following aspects when operating the unit at low temperatures. Perform tests to verify
suitability in your application.
-
The ripple & noise voltage will increase. For the first minutes after turning on the unit at -40°C, the ripple an
noise voltage can be up to typically 400mVpp depending on load and input voltage. Once the unit heats up,
the ripple & noise voltage will decrease typically to 90mVpp.
-
The start-up delay can be up to 5 seconds. It is a continuous turn-on process without any voltage dips or start-
up attempts.
21.12. Use in a Tightly Sealed Enclosure
When the power supply is installed in a tightly sealed enclosure, the temperature inside the enclosure will be higher
than outside. In such situations, the inside temperature defines the ambient temperature for the power supply.
The following measurement results can be used as a reference to estimate the temperature rise inside the enclosure.
The power supply is placed in the middle of the box; no other heat producing item is inside the box.
Enclosure:
Input:
Case A:
Load:
Temperature inside the box:
Temperature outside the box:
Temperature rise:
Case B:
Load:
Temperature inside the box:
Temperature outside the box:
Temperature rise:
All parameters are specified at 24V, 2.5A, 230Vac input, 25°C ambient and after a 5 minutes run-in time unless noted otherwise.
22
Rittal Type IP66 Box PK 9510 100, plastic, 130x130x75mm
230Vac
24V, 2.5A; load is placed outside the box
40.3°C (in the middle of the right side of the power supply with a distance of 1cm)
21.8°C
18.5K
24V, 2.0A; (=80%) load is placed outside the box
38.6°C (in the middle of the right side of the power supply with a distance of 1cm)
22.1°C
16.5K
Rockwell Automation Publication 1606-RM014A-EN-P — March 2014
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