Cyclic Loads - ABB ACSM1 Hardware Manual

Cyclic loads

If the load cycle is shorter than 10 seconds, the thermal time constant of the heatsink (approximately 80
seconds) can be ignored, and the following simple procedure can be applied to find out whether the
drive can handle the cycle.
1. Determine the rms value (I
2. Determine the maximum instantaneous rms value (I
3. Determine the point (I
If the point falls within the region bordered by a solid line, the load cycle is safe. For I
use the ratings stated for the drive type and switching frequency used.
If the point falls within the shaded area, a more detailed study is required.
I
2peak
I
2max
I
2contxk
The above procedure can also be applied to longer load cycles by dividing the cycle into subcycles no
longer than 10 seconds. If any of the subcycles fail the test, a more detailed study is required.
The DriveSize dimensioning tool available from ABB is recommended for more detailed dimensioning.
) of the output current over the whole load cycle.
2rms
, I ) on the graph below.
2rms 2peak
0.75×I I
2contxk 2contxk
) of the output current during the load cycle.
2peak
I
2rms
73
and I ,
2contxk 2max
Technical data