69
Voltage boost V
min
In the low speed range, the obtained torque is determined largely
by the set voltage boost. If you set V
min
(C016), make sure that the
motor cannot be destroyed by overheat.
Experience tells that self-ventilated standard asynchronous
machines of insulation class B can be operated in a frequency
range up to 25Hz only for a short time with rated current. Therefore
proceed as follows:
• The motor should be operated in idle running.
• Provide a set-value of 4 to 5 Hz.
• The voltage boost should be set such that
− the motor current (C054) does not exceed the rated value
for short-time operation in the low frequency range.
− the motor current (C054) does not exceed 80 % of its rated
value for permanent operation in the low frequency range.
For exact data of the permissible motor current please refer to the
motor manufacturer.
Forced-ventilated machines can be permanently operated with
rated current even in the low frequency range.
Code Parameter Meaning Acceptance
C014 -0-
-1-
linear characteristic
square characteristic
[SH + PRG]
C015 50.0Hz
7.5...960Hz
V/f rated frequency ON-LINE
C016 0.0%
0.0...40%
voltage boost ON-LINE
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