Honeywell SmartVFD HVAC2 Applications Manual page 125

U / f ratio
There are three selections for this parameter:
0 = Linear:
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 field weakening point
voltage is supplied to the motor. Linear U
/ f ratio should be used in constant torque
applications. See Figure "Linear and
squared change of motor voltage" on
page 126.
This default setting should be used if
there is no special need for another set-
ting.
1 = Square:
The voltage of the motor changes follow-
ing a squared curve form with the fre-
quency in the area from 0 Hz to the field
weakening point where the field weaken-
ing point voltage is also supplied to the
motor. The motor runs under magnetised
below the field weakening point and pro-
duces less torque, power losses and elec-
tromechanical 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.
125 31-00108—07