Program features 79
Switching frequency
The drive has two switching frequencies: reference switching frequency and
minimum switching frequency. The drive tries to keep the highest allowed switching
frequency (= reference switching frequency) if thermally possible, and then adjusts
dynamically between the reference and minimum switching frequencies depending
on the drive temperature. When the drive reaches the minimum switching frequency
(= lowest allowed switching frequency), it starts to limit output current as the heating
up continues.
For derating, see chapter Technical data, section Switching frequency derating in the
Hardware manual of the drive.
Example 1: If you need to fix the switching frequency to a certain value as with some
external filters, set both the reference and the minimum switching frequency to this
value and the drive will retain this switching frequency.
Example 2: If the reference switching frequency is set to 12 kHz and the minimum
switching frequency is set to the smallest available value, the drive maintains the
highest possible switching frequency to reduce motor noise and only when the drive
heats it will decrease the switching frequency. This is useful, for example, in
applications where low noise is necessary but higher noise can be tolerated when the
full output current is needed.
Settings
Parameter 97.01 Switching frequency reference and 97.02 Minimum switching
frequency (page 280).
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