6
Digidrive SK Technical Data
www.leroy-somer.com Issue Number: a
2 Derating curves and losses
2.1 Derating curves
N
The de-rating curves are based on the results of heatruns that are carried out to measure temperatures at various key points (components) within the
drive at different switching frequencies / loads /ambient temperatures: These key points are things like:
•
Heatsink
•
Bridge rectifier
•
IGBTs
•
DC bus capacitors
•
Various electrolytic capacitors
•
Various resistors
•
etc.
It is not always the heatsink temperature that is the limiting factor for the de-rating curves.
At 3 and 6kHz, the limiting factor tends to be capacitor temperatures.
At 12 and 18kHz, the limiting factor tends to be the heatsink temperature.
At 3 and 6kHz, operating outside the de-rating curves will cause some of the capacitors within the drive to run outside of their maximum operating
temperature and this could lead to the drives design operating lifetime being reduced.
At 12 and 18kHz, operating outside the de-rating curves will cause the heatsink temperature to increase and may cause the drive to trip on Oht2. If
the auto-switching frequency change is enabled (Pr
5.35
= 0 [by default]), the drive will automatically decrease the switching frequency when the
heatsink temperature rises above pre-determined levels to reduce the heatsink temperature. When the drive switches down the switching frequency,
the drives display will flash 'hot'.
It is important that operating within these de-rating curves is observed.
Figure 2-1 Digidrive SK Size A 0.25kW derating curve
NOTE
0
0.5
1.0
1.5
2.0
10
40
30
20
60
50
Ambient Temperature (
o
C)
3kHz
6kHz
12kHz
18kHz
Output
current (A)
