Fuji Electric FRENIC-HVAC User Manual page 386

When the variable torque V/f pattern is selected (F37 = 0 or 3), the output voltage
may be low at a low frequency zone, resulting in insufficient output torque,
depending on the characteristics of the motor and load. In such a case, it is
recommended to increase the output voltage at the low frequency zone using the
non-linear V/f pattern.
Recommended value: H50 = 1/10 of the base frequency
Torque boost

• Manual torque boost (F09)
- Data setting range: 0.0 to 20.0 (%), (100%/Rated voltage at base frequency)
In torque boost using F09, constant voltage is added to the basic V/f pattern, regardless of the
load. To secure a sufficient starting torque, manually adjust the output voltage to optimally
match the motor and its load by using F09. Specify an appropriate level that guarantees
smooth start-up and yet does not cause over-excitation at no or light load.
Torque boost using F09 ensures high driving stability since the output voltage remains
constant regardless of the load fluctuation.
Specify the F09 data in percentage to the rated voltage at base frequency 1 (F05). At factory
shipment, F09 is preset to a level that assures approx. 50% of starting torque.
• Specifying a high torque boost level will generate a high torque, but may cause
overcurrent due to over-excitation at no load. If you continue to drive the motor,
it may overheat. To avoid such a situation, adjust torque boost to an appropriate
level.
• When the non-linear V/f pattern and the torque boost are used together, the
torque boost takes effect below the frequency on the non-linear V/f pattern's
point.
H51 = 1/10 of the voltage at base frequency
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