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Chapter 4
4.2.17 V/F characteristic curve selection
The V/F characteristic curve selection function allows you to set the
output voltage/output frequency (V/f) characteristic.
To switch the V/F characteristic curve selection among the 1st, 2nd,
and 3rd settings, assign function "08" (SET) and "17" (SET3) to
intelligent input terminals. Use the SET and SET3 signals for
switching.
Function code
Data
00
01
02
A044/A244/
A344
03
04
05
(1) Constant torque characteristic (VC)
With this control system set, the output voltage is in proportion to the output frequency within the range from 0 Hz to
the base frequency. Within the output frequency range over the base frequency up to the maximum frequency, the
output voltage is constant, regardless of the change in the output frequency.
Output voltage
(100%)
0
(2) Reduced-torque characteristic (1.7th power of VP)
This control system is suited when the inverter is used with equipment (e.g., fan or pump) that does not require a large
torque at a low speed.
Since this control system reduces the output voltage at low frequencies, you can use it to increase the efficiency of
equipment operation and reduce the noise and vibrations generated from the equipment.
The V/f characteristic curve for this control system is shown below.
Output voltage
(100%)
VC
0
10% of base
frequency
a
Period
:
While the output frequency increases from 0 Hz to the 10% of the base frequency, the output voltage
a
follows the constant torque characteristic.
(Example) If the base frequency is 60 Hz, the constant torque characteristic is maintained within the
output frequency range of 0 to 60 Hz.
Period
:
While the output frequency increases from the 10% of base frequency to the base
b
frequency, the output voltage follows the reduced-torque characteristic. In other words, the output
voltage increases according to the 1.7th power of the output frequency.
Period
:
While the output frequency increases from the base frequency to the maximum frequency, the output
c
voltage is constant.
V/f characteristic
Constant torque characteristic (VC)
Reduced-torque characteristic
(1.7th power of VP)
Free V/f characteristic
Sensorless vector control (SLV)
0 Hz-range sensorless vector control
Vector control with sensor (V2)
Base
Maximum
frequency
frequency
1.7
(f
)
VP
Base
Maximum
frequency
frequency
c
b
Explanation of Functions
Related code
A044/A244/A344: V/F characteristic curve selection,
1st/2nd/3rd motors
b100/b102/b104/b106/b108/b110/b112: Free-setting
V/f frequency (1) (2) (3) (4) (5) (6) (7)
b101/b103/b105/b107/b109/b111/b113: Free-setting
V/f voltage (1) (2) (3) (4) (5) (6) (7)
Available only for A044 and A244
Available only for A044 and A244 (See Section
4.2.96.)
Available only for A044 and A244 (See Section
4.2.97.)
Available only for A044
Output frequency (Hz)
Output frequency (Hz)
4-16
Remarks
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