Thermal Properties Of The Heat Sink; Thermal Resistance - BONFIGLIOLI active Installation Manual

4

Thermal properties of the heat sink

The heat in the frequency inverter due to the energy dissipation of the electronic com-
ponents (rectifier and IGBT) must be dissipated to a heat sink via the cold plate of the
frequency inverter.
The capacity to dissipate this heat mainly depends on the size of the heat sink surface,
the ambient temperature and the heat transmission resistance. An increase of the heat
transmission rate can only be realized to a certain extent by increasing the surface of
the heat sink. An additional increase of the heat dissipation by increasing the heat sink
is not possible.
The frequency inverter should be mounted with the cold plate on a heat sink with the
lowest thermal resistance possible.
4.1
The thermal resistance R
heat sink temperature and the ambient temperature, referred to the energy dissipation
of the frequency inverter. The ambient temperature to be considered refers to the
immediate environment of the frequency inverter.
Max. permissible heat sink temperature of the frequency inverter
Ambient temperature of the cold plate of the frequency inverter
Difference between the maximum heat sink temperature and the
ambient temperature (T
Energy to be dissipated by the heat sink
Note:
For the max. permissible thermal resistance R
tion P , refer to the following table. The thermal resistance R
v
vin per Watt (K/W). Additionally, the thermal radiation of the frequency inverter is
indicated.
11/06

Thermal resistance

is calculated from the difference between the maximum
th
-T )
k max U
During installation, the following items must be considered in order to mini-
mize the thermal resistance:
The installation surface must at least be as large as the cold plate sur-
-
face.
The contact surface must be plane and have a good thermal conductiv-
-
ity.
The thermal limits of the frequency inverter and the cold plate must be
-
considered when determining the dimensions.
T − T
k max u
R =
th
P
v
and the device-specific energy dissipa-
th
T = 75 °C
kmax
T = 35 °C
U
ΔT = 40 K
P = depends on
v
type
is given in the unit Kel-
th
9