U/F Ratio; Flux Braking - ABB ACS580 Firmware Manual

Settings
Parameter group 37 User load curve


U/f ratio

The U/f function is only available in scalar motor control mode, which uses frequency
control.
The function has two modes: linear and squared.
In linear mode, the ratio of voltage to frequency is constant below the field weakening
point. This is used in constant torque applications where it may be necessary to
produce torque at or near the rated torque of the motor throughout the frequency
range
In squared mode (default), the ratio of the voltage to frequency increases as the
square of the frequency below the field weakening point. This is typically used in
centrifugal pump or fan applications. For these applications, the torque required
follows the square relationship with frequency. Therefore, if the voltage is varied
using the square relationship, the motor operates at improved efficiency and lower
noise levels in these applications.
The U/f function cannot be used with energy optimization; if parameter
optimizer is set to Enable, parameter
Settings
• Menu - Primary settings - Motor - U/f ratio
• Parameter 97.20 U/F ratio


Flux braking

The drive can provide greater deceleration by raising the level of magnetization in the
motor. By increasing the motor flux, the energy generated by the motor during
braking can be converted to motor thermal energy.
Motor
speed
Flux braking
(page 258).
97.20 U/F ratio
(page 314).
No flux braking
t (s)
is ignored.
T
Br
T
(%)
60
40
Flux braking
20
No flux braking
Program features 105
45.11 Energy
= Braking torque
Br
= 100 Nm
f (Hz)