Sample Calculation Of Thermal Power Loss - Siemens SINUMERIK 840D sl Equipment Manual

Technical specifications
7.3 Ambient climatic and mechanical conditions
Guidelines
If the convection area A [m
then use:
• "Heat dissipation using natural convection and internal turbulence" for hot spots and heat
concentrations in housings subject to space constraints. The total power loss P
thermally critical applications can be determined as follows:
– Current measurement for a 24 V supply voltage
– Power loss P
• Heat dissipation using open-circuit ventilation
7.3.4

Sample calculation of thermal power loss

Calculation of the volumetric flow
The power loss (thermal) dissipated by the components in an operator unit is to be dissipated
using open-circuit ventilation. The volumetric flow V required for this should be calculated at a
difference in temperature of T
①
②
Figure 7-2
Example of heat dissipation with open-circuit air cooling
Calculation of the power loss (including internal power supply unit) of the PCU 50.5 with OP
010S:
PV
OP 010S
PV
PCU 50.5
Calculation of ΔT:
Outside temperature = T
Inside temperature = T
42
] does not suffice for the "heat dissipation using natural convection",
2
[W] = U (24 V) * |measured value in ampères|
Ltot
2
PCU 50.5
OP 010S
Calculation of the heat dissipation, PCU 50.5 with OP 010S
: 4 W
: 48 W
= 45°C
1
= 55°C
2
- T = ΔT ≥ 10K.
1
PV = PV
tot
PV = 52 W (max. 102 W)
tot
ΔT = T
2
ΔT = 10 K
+ PV
OP 010S PCU 50.5
- T
1
Operator panel front: OP 010S
Equipment Manual, 12/2022, A5E50751046B AA
for
Ltot