2.2 Mechanical Installation
42
YASKAWA ELECTRIC
SIEP C710606 44B YASKAWA AC Drive T1000V Technical Manual
■
External Heatsink Selection
shows the heat transfer principle from the drive heatsink plate to the heatsink ambient air.
Figure 2.6
Figure 2.6 Thermal Equivalent Circuit
For a given ambient temperature, the heatsink plate temperature must not exceed the maximum allowable value. As the
R
θ
HSP
and R
θ
HSP-EHS
are essentially fixed, this condition must be satisfied by selecting an appropriate heatsink.
Select an External Heatsink by the Thermal Resistance
Use the formula below to calculate the maximum thermal resistance R
θ
EHS_max
.
Select a heatsink with a smaller thermal resistance than R
θ
EHS_max
.
The heatsink height and width should be close to the drive dimensions. Although the dimensions of a certain heatsink
may match the drive, the thermal resistance may be too high. Instead select a heatsink with a different shape (e.g., longer
fins or more fins) that has an appropriate thermal resistance. Compare the actual mounting conditions with the ones
mentioned for the R
θ
EHS
value in the heatsink specifications, applying reduction factors where necessary. Also remember
that ability of the heatsink to dissipate heat may be reduced over time due to the accumulation of dirt along the heatsink
surface.
NOTICE:
If the heatsink height and width are much larger than the drive heatsink plate dimensions or if multiple drives are installed on
a single heatsink, it may be necessary to recalculate the thermal resistance value given in the heatsink specifications. Consult the
heatsink manufacturer.
Check the Feasibility of a Given Heatsink
Use the formula below to calculate the actual heatsink plate temperature if the selection of the heatsink is limited due to
certain installation conditions (space available etc.).
If T
HSP
is smaller than the maximum allowable heatsink plate temperature, then the heatsink can be used. To verify the
temperature, refer to
Checking and Monitoring Heatsink Plate Temperature on page 40
.
NOTICE:
Due to uneven compound thickness, uneven heat generation across the heatsink plate, or other factors, the actual heatsink
plate temperature (monitored in U4-08) can be slightly different from the calculated value. An oH drive fault may occur if the heatsink
plate temperature exceeds the maximum allowable value.
Heatsink plate temperature T
HSP
T
Amb
Heatsink plate thermal resistance R
θ
HSP
Drive
Thermal
compound
Heatsink plate
External
heatsink
P
Loss
External heatsink thermal resistance R
θ
EHS
Thermal resistance between heatsink
plate and external heatsink R
θ
HSP-EHS
T
HSP
T
Amb
R
θ
EHS_max
=
T
HSP_max
- T
Amb
P
Loss
- R
θ
HSP
- R
θ
HSP-EHS
(
)
T
HSP
= P
Loss
R
θ
HSP
+ R
θ
HSP-EHS
+ R
θ
EHS
) + T
Amb
