Torque Control Performance Figures; Power Loss Ride-Through; U/F Ratio - ABB ACS560 Firmware Manual

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.
Torque control
Non-linearity
Torque step rise time < 10 ms with nominal


Power loss ride-through

See section Undervoltage control (power loss ride-through)


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
Performance
± 5% with nominal
torque
(± 20% at the most
demanding operating
point)
torque
T
(%)
T
T
N
ref
100
T
90
10
< 5 ms
T = rated motor torque
N
T = torque reference
ref
T = actual torque
act
on page 77.
act
t (s)