HVAC400X – APPLICATION MANUAL
EN2B-0417GE51 R0719
88
P3.1.2.7 U/F RATIO (ID 108)
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 P3.1.2.3 (Zero Frequency Voltage) to the value of
Voltage at Field Weakening Point at a frequency set in Field Weakening Point
Frequency. If a different setting is not necessary, use this default setting.
1
Squared
The voltage of the motor changes from the value of P3.1.2.3 (Zero Frequency Voltage)
to the value of Field Weakening Point Frequency at a squared curve. The motor
operates undermagnetized 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 by using 2 points of reference: voltage at zero
frequency (P1) and U/f mid frequency (P2). The field weakening point (P3) is then set
automatically. This function is used to boost torque at start. After having set the
parameter to programmable, activate ID run to tune the settings.
Fig. 10. Programmable U/f curve
Legend
A.
Nominal voltage of the motor.
C.
Nominal frequency of the motor.
B.
Linear Squared Field weakening point.
When the parameter Motor Type is set to PMM then the U/f curve is automatically set to
linear
.
P3.1.2.8 OVERVOLTAGE CONTROL (ID 607)
You can use this parameter to set the overvoltage controller out of operation. See the description in P3.1.2.9
Undervoltage Control.
U (V)
f (Hz)
P3
P2
P1
ID605
ID606
ID604
B
C
A
