Eaton PowerXL DB1 Installation Manual page 48

3 Installation
3.3 Assembly
44
The required maximum thermalresistance R
on the power loss P
V
between the temperature T
and the ambient temperature T
temperature difference, the less cooling is required.
The thermal resistance value calculated in this way must also be effective.
If, for example, a heatsink is used with the calculated thermal resistance and
with a larger cooling surface than that of the variable frequency drive, it is
assumed that the effective thermal resistance is greater in this case. In this
instance, you should contact the manufacturer of the heatsink.
In other cases, existing surfaces such as a mounting plate should be used as
cooling surfaces. If the thermal resistance is unknown, measurements can
determine whether the existing cooling type is sufficient. During these mea-
surements, the temperature on thevariable frequency drive cooling surface
must be measured under normal operating conditions (ambient temperature,
motor load, closed control cabinet doors).
The temperature rise will be delayed due to the thermal time constant.
If the temperature exceeds the maximum permitted value, the measure-
ments must be interrupted and cooling improved.
The DB1 variable frequency drive self-monitors its internal temperature and
switches off if required.
The value calculated above for thermal resistance R
mitted value in the relevant application. The lower the thermal resistance, the
lower the temperature on the cooling surface and inside the variable fre-
quency drive.
During installation, it is important to ensure that the cooling air can circulate
adequately and that there are no "hotspots".
DB1 Variable Frequency Drives 09/17 MN040031EN www.eaton.com
of the variable frequency drive and the difference
on the variable frequency drive cooling surface
CP
in the control cabinet. The greater the
AMB
T - T
CP AMB
R =
th
P
V
of the cooling system depends
th
is the maximum per-
th