Beckhoff PS3031-2440-0000, Documentation

Page: 39 / 44

Application notes
PS3031-2440-0000 39 Version: 1.0
4.10 Back-feeding loads
Loads such as braking motors or inductors can feed back voltage to the power supply. This feature is also
known as back EMF. (electromagnetic force).
This power supply is stable and will not malfunction if a load is feeding back voltage to the power supply. It is
irrelevant whether the power supply is switched on or off.
The maximum permissible feed-back voltage is 35 Vdc. The absorbing energy can be calculated according
to the large built-in output capacitor indicated in the output data, see
Output [
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12] chapter
4.11 Use in a tightly sealed enclosure
When the power supply is installed in a tightly sealed enclosure, the temperature inside the housing is higher
than outside. In this case, the temperature inside the housing is considered the ambient temperature for the
power supply.
In the following test arrangement, the device is placed at the center of the housing, and there are no other
heat-generating objects in the housing. The load is placed outside the housing.
The temperature sensor inside the housing is placed at the center of the right side of the power supply at a
distance of 2 cm.
The following measurement results can be used as a reference to estimate the temperature rise within the
housing.
Housing size:
254x180x165 mm Rittal housing, protection class IP66 PK 9522 100, plastic
Input voltage:
230 Vac
Load:
24 V, 32 A; (=80%)
Temperature inside the housing:
57.5°C
Temperature outside the housing:
23.6°C
Temperature increase:
33.9 K
4.12 Installation positions
Installation positions other than the input connections at the bottom and the output at the top require a
reduction of the continuous output power or a limitation of the maximum permissible ambient temperature.
The extent of the reduction influences the lifetime expectancy of the power supply. Therefore, two different
derating curves for continuous operation are provided below:
Curve A1: Recommended output current.
Curve A2: Max. permissible output current (results in about half the lifetime expectancy of A1).