description of parameters
vacon
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2.5 MOTOR
CONTROL
2.5.1
Motor control mode
0 Frequency control:
The I/O terminal and keypad references are frequency
references and the frequency converter controls the output
frequency (output frequency resolution = 0.01 Hz)
1 Speed control:
The I/O terminal and keypad references are speed references
and the frequency converter controls the motor speed
(accuracy ± 0,5%).
2.5.2 U/f
optimisation
Automatic
torque boost
The voltage to the motor changes automatically which makes the
motor produce sufficient torque to start and run at low
frequencies. The voltage increase depends on the motor type and
power. Automatic torque boost can be used in applications where
starting torque due to starting friction is high, e.g. in conveyors.
NOTE!
In high torque - low speed applications - it is likely that the motor
will overheat. If the motor has to run a prolonged time under these
conditions, special attention must be paid to cooling the motor. Use
external cooling for the motor if the temperature tends to rise too
high.
2.5.3
U/f ratio selection
Linear:
The voltage of the motor changes linearly with the frequency in the constant
0
flux area from 0 Hz to the field weakening point where the nominal voltage is
supplied to the motor. Linear U/f ratio should be used in constant torque
applications. This default setting should be used if there is no special
need for another setting.
Squared: The voltage of the motor changes following a squared curve form
1
with the frequency in the area from 0 Hz to the field weakening point where
the nominal voltage is also supplied to the motor. The motor runs under
magnetised below the field weakening point
and produces less
torque and
electromechanical 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.
