ABB ACS560, Firmware Manual

Page: 68 / 514

68 Program features

Torque control performance figures
The drive can perform precise torque control without any speed feedback from the
motor shaft. The table below shows typical performance figures for torque control.

Power loss ride-through
See section Undervoltage control (power loss ride-through) on page 77 .

U/f ratio
The U /f function is available only in scalar motor control mode, which uses frequency
control.
The function has the following modes:
• Linear
• Squared.
Linear mode
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
Squared mode
In squared mode, 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
t (s)
T
N
= rated motor torque
T
ref
= torque reference
T
act
= actual torque
Torque control Performance
Non-linearity ± 5% with nominal
torque
(± 20% at the most
demanding operating
point)
Torque step rise time < 10 ms with nominal
torque
100
< 5 ms
90
10
T
ref
T
act
T
T
N
(%)