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V/f characteristics
The EQ7 series of inverters offers a variety of V/f patterns and torque boosts, which include V/f patterns suitable
for variable torque load such as general fans and pumps and for constant torque load (including special pumps
requiring high starting torque). Two types of torque boosts are available: manual and automatic.
Variable torque V/f pattern (F37 = 0)
Linear V/f pattern (F37 = 1)
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
H51 = 1/10 of the voltage at base frequency
Torque boost
Data setting range: 0.0 to 20.0 (%) (100%/Rated voltage at base frequency)
• Manual torque boost (F09)
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 per F09 ensures high driving stability since the output voltage remains constant regardless of the
load fluctuation.
• Specifying a high torque boost level will generate a high torque, but may cause overcurrent due to
over-excitation at no load which can overheat the motor. To avoid this, 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.
(F09)
(F09)