6. Control Functions and Parameter Settings
6-34
•
Automatic torque boost function (V/f improved control)
The automatic torque boost function controls voltage boosting and slip compensation using the current
detection value. This allows to improve the motor torque when starting and at the low speed regions.
Critical parameters which performs the automatic torque boost function, will be automatically adjusted
by the Auto-tuning function, allowing that a standard AC motor outputs up to 200% or more starting
torque with 150% current.
-200
-150
-100
-50
0
50
100
150
200
0
25
50
75
100
M otor spee d [% ]
O
u
tput
t
o
rque [
%
]
< standard 3-phase induction motor 1.5kW-4P>
CAUTION
• Even using only manual torque boost, carry out automatic tuning (B19-0 = 1).
• When using automatic torque boost, always carry out automatic tuning (B19-0 = 2).
• The maximum torque is not output instantly. It takes approx. 3 seconds for the maximum torque to
be reached.
• If the motor vibrates abnormally, etc. during Auto-tuning, cancel it and adjust the drive manually.
• If the parameters are with set manually, the motor rotation could become unstable.
• Special motors which the base frequency greatly exceeds the commercial frequency, or motors with
a large constant voltage range, the rotation may be unstable and torque may not be sufficient.
• Check motor temperature if the application requires high torque for a long time
A02-2
Manual torque boost setting [%]
This parameter is automatically set by automatic tuning (V/f control mode).
When setting manually, set the boost voltage at 0Hz as a percentage in respect to the rated
output voltage (B00-3).
