YASKAWA V1000

6 Selecting an External Heatsink
YASKAWA ELECTRIC TOBP C710606 21D YASKAWA AC Drive - V1000 Finless Installation Guide 23
◆ External Heatsink Selection
Figure 5 shows the heat transfer principle from the drive heatsink plate to the heatsink
ambient air.
Figure 5
Figure 6 Thermal Equivalent Circuit
For a given ambient temperature the heatsink plate temperature must not exceed the
maximum allowable value. As the Rθ
HSP
and Rθ
HSP-EHS
are essentially fixed, this condition
must be satisfied with proper heatsink selection.
■ Select an External Heatsink by the Thermal Resistance
Use the formula below to calculate the maximum thermal resistance Rθ
EHS_max
.
Select a heatsink with a smaller thermal resistance than Rθ
EHS_max
. The heatsink height and
width should be close to the drive dimensions. If the selected heatsink has a thermal
resistance that is too high, then choose a heatsink with a different shape (e.g. longer or more
fins). Compare the actual mounting conditions with the ones mentioned for the Rθ
EHS
value
in the heatsink specifications and apply reduction factors if necessary. Also remember that
the heatsink cooling ability can reduce by time due to dirt.
NOTICE: If the heatsink height and width are much larger than the drive heatsink plate dimensions or if
multiple drives are installed on one heatsink, it may be necessary to apply correction factors to the thermal
resistance value given in the heatsink specification. Consult the heatsink manufacturer.
■ Check the Feasibility of a Given Heatsink
If a heatsink is given or the selection is limited by the installation conditions (space available
etc.) use the formula below to calculate the actual heatsink plate temperature.
If T
HSP
is smaller than the maximum allowable heatsink plate temperature, the selected
heatsink can be used. For verification of temperature, refer to Checking and Monitoring
Heatsink Plate Temperature on page 9.
Heatsink plate temperature T
HSP
T
Amb
Heatsink plate thermal resistance Rθ
HSP
Drive
Thermal
compound
Heatsink plate
External
heatsink
P
Loss
External heatsink thermal resistance Rθ
EHS
Thermal resistance between heatsink
plate and external heatsink Rθ
HSP-EHS
T
HSP
T
Amb
Rθ
EHS_max
=
T
HSP_max
- T
Amb
P
Loss
- Rθ
HSP
- Rθ
HSP-EHS
(
)
T
HSP
= P
Loss
࡮ Rθ
HSP
+ Rθ
HSP-EHS
+ Rθ
EHS
) + T
Amb