22 • vacon
ASFIFF12 High Speed
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108
U/f ration selection
(2.6.3)
Linear:
0
The voltage of the motor changes linearly with the frequency in the constant
flux area from 0 Hz to the field weakening point where the nominal voltage is
supplied to the motor. Linear U/f ration should be used in constant torque
applications.
This default setting should be used if there is no special
need for another setting
.
Squared:
1
The voltage of the motor changes followiing a squared curve form with the
frequency in the area from 0 Hz to the field weakening point where the nomi-
nal voltage is also supplied to the motor. The motor runs undermagnetised
below the field weakening point and produces less torque and electro-
mechanical noise. Squared U/f ratio can be used in applications where
torque demand of the load is proportional to the square of the speed, e.g. in
centrifugal fans and pumps.
Figure 5-1. Linear and squared change of motor voltage
Programmable U/f curve:
2
The U/f curve can be programmed with three different points. Programmable
U/f curve can be used if the other settings do not satisfy the needs of the
application.
Figure 5-2. Programmable U/f curve
Un
ID603
U[V]
f[Hz]
NX12K07
Default: Nominal
voltage of the motor
Linear
Squared
Field weakening
point
Default: Nominal
frequency of the
motor
Un
ID603
ID602
U[V]
f[Hz]
NX12K08
ID604
(Def. 5 Hz)
ID605
(Def. 10%)
ID606
(Def. 1.3%)
Default: Nominal
voltage of the motor
Field weakening point
Default: Nominal
frequency of the motor
