34 • vacon description of parameters
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7
109 U/f optimisation
(2.5.2)
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.
EXAMPLE:
What changes are required to start with load from 0 Hz?
♦ First set the motor nominal values (Parameter group 2.1).
Option 1
: Activate the Automatic torque boost.
Option 2
: Programmable U/f curve
To get torque you need to set the zero point voltage and midpoint voltage/frequency (in
parameter group 2.6) so that the motor takes enough current at low frequencies.
First set par. ID108 to
Programmable U/f curve
(value 2). Increase zero point voltage
(ID606) to get enough current at zero speed. Set then the midpoint voltage (ID605) to
1.4142*ID606 and midpoint frequency (ID604) to value ID606/100%*ID111.
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 condi-
tions, special attnetion must be paid to cooling the motor. Use external
cooling for the motor if the temperature tends to rise too high.
110 Nominal voltage of the motor
(2.1.5)
Find this value U
n
on the rating plate of the motor. This parameter sets the voltage at the
field weakening point (ID603) to 100% * U
nMotor
.
111 Nominal frequency of the motor
(2.1.6)
Find this value f
n
on the rating plate of the motor. This parameter sets the field
weakening point (ID602) to the same value.
112 Nominal speed of the motor
(2.1.7)
Find this value n
n
on the rating plate of the motor.
113 Nominal current of the motor
(2.1.8)
Find this value I
n
on the rating plate of the motor.
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