5.3 Description of Function Codes 5.3.1 F codes (Fundamental functions)
If quadratic-torque characteristics are selected with function code F37, non-linear V/f H50 and H51 are
automatically set. Adjustment may be necessary depending on the motor and load characteristics. On the
other hand, in the event that other than quadratic-torque characteristics are selected with function code
F37, non-linear V/f is automatically disabled.
Recommended value: H50 = 1/10 of the base frequency
H51 = 1/10 of the voltage at base frequency
Torque boost
• Manual torque boost by F09 (Manual adjustment)
• Data setting range: 0.0 to 20.0 (%), (100%/base frequency voltage)
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 Startup and yet does not cause over-excitation at no or light
load. Generally speaking, torque boost is unnecessary (0.0%) with motors of 30kW or higher.
Torque boost using F09 ensures high driving stability since the output voltage remains constant regardless of the
load fluctuation.
Specify the function code F09 data in percentage to the base frequency voltage.
• Precautions when driving an old model IE1 motor
With the 0.75 kW to 22 kW factory default value, a boost amount that ensures a starting torque of
approximately 100% is set for high-efficiency premium motors (IE3), but with the IE1 motor, starting
torque may be insufficient because the boost amount is low. If starting torque is insufficient during the
test run, either adjust the torque manually, or check the appropriate torque boost value with the motor
manufacturer, and set that value. If using a Fuji Electric motor (IE1), by selecting Fuji Electric motor 8-
series by setting P99 to 0, and initializing the motor constants with H03, the torque boost is reset to an
appropriate value.
• 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.
Rated voltage at
base frequency 1
Non-linear V/f
pattern 1 (voltage)
Non-linear V/f
pattern 1
(frequency)
V/f pattern of quadratic-
torque V/f pattern with
non-linear V/f
V/f pattern of quadratic-
torque V/f pattern
without non-linear V/f
Rated voltage at
base frequency 1
Non-linear V/f
pattern 1 (voltage)
Non-linear V/f
pattern 1
(frequency)
Increase output
voltage with Torque
boost 1 (F09)
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