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9.3.12
Derating behavior with increased pulse frequency
Description
To reduce motor noise or to increase output frequency, the pulse frequency can be
increased relative to the factory setting.
The increase in the pulse frequency normally results in a reduction of the maximum output
current (see "Technical data/current derating depending on the pulse frequency").
During commissioning of the drive, the behavior at overload is automatically adjusted in such
a way that the pulse frequency is variably reduced so that the required output power can be
provided.
Properties:
● The reaction to overload depends on the setting of parameter p0290:
– p0290 = 0: Reduce output current or output frequency
– p0290 = 1: No reduction, shutdown when overload threshold is reached
– p0290 = 2: Reduce the output current or output and pulse frequency (not using I²t).
– p0290 = 3: Reduce the pulse frequency (not using I²t)
● p0290 = 2: On overload, the pulse frequency (and consequently the output frequency) is
first reduced until it has dropped to the rated pulse frequency; then the output frequency
is reduced if overload continues to persist.
The rated pulse frequency is half the inverse value of the current controller cycle:
0.5 x 1/p0115[0].
● Reduction of the pulse frequency is executed in whole multiples based on the rated pulse
frequency (5 kHz -> 2.5 kHz -> 1.25 kHz or 4 kHz -> 2 kHz).
● After entry of the maximum speed in p1082, the system automatically calculates whether
the pulse frequency is sufficient for the entered maximum speed; if necessary the pulse
frequency is increased automatically to a value that is necessary for this.
On overload, this new pulse frequency will no longer be fallen below even when p0290 =
2 or 3; the downstream reaction (reduce output current or switch off) will be triggered.
Exceptions:
● With an activated sine-wave filter (p0230 = 3, 4), this behavior is not permitted because
the factory set pulse frequency (2.5 kHz or 4 kHz) must not be changed through this
measure. Consequently in this case the selection possibility for the parameter p0290 is
limited to "0" and "1".
Activation of the variable pulse frequency
During commissioning, the parameter p 0290 is automatically set to "2". This activates pulse
frequency reduction under overload.
Converter cabinet units
Operating Instructions, 11/2017, A5E36652151A
Functions, monitoring and protective functions
9.3 Drive functions
529
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