Selection
number
Selection name Description
0 Linear
The voltage of the motor changes linearly as a function of the
output frequency. The voltage changes from the value of
P3.1.4.6 (Zero Frequency Voltage) to the value of P3.1.4.3
(Voltage at Field Weakening Point) at a frequency set in
P3.1.4.2 (Field Weakening Point Frequency). Use this default
setting if a different setting is not necessary.
1 Squared
The voltage of the motor changes from the value of P3.1.4.6
(Zero Frequency Voltage) to the value of P3.1.4.2 (Field
Weakening Point Frequency) at a squared curve. The motor
operates undermagnetised below the field weakening point
and produces less torque. You can use the squared U/f ratio
in applications where the torque demand is in relation to the
square of the speed, for example in centrifugal fans and
pumps.
2 Programmable
It is possible to program the U/f curve with 3 different points:
the zero frequency voltage (P1), the midpoint voltage/
frequency (P2), and the field weakening point (P3). You can
use the programmable U/f curve at low frequencies if it is
necessary to have more torque. You can find the optimal set-
tings automatically with an identification run (P3.1.2.4).
C
B
E
D
A
Un
U[V]
f[Hz]
ID603
ID602
Fig. 38: Linear and squared change of the motor voltage
A. Default: Nominal voltage of the motor
B. Field weakening point
C. Linear
D. Squared
E. Default: Nominal frequency of the motor
PARAMETER DESCRIPTIONS VACON · 225
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