Hitachi S1 Series Basic Manual page 51

S1 series standard inverter
S1inverter also provides multi-point V/F curve. Users can alter the V/F curve outputted by inverter
through setting the voltage and frequency of the three points in the middle. The whole curve consists
of five points starting from (0Hz, 0V) and ending in (fundamental motor frequency, rated motor
voltage). During setup, it is required that 0≤f1≤f2≤f3≤fundamental motor frequency, and
0≤V1≤V2≤V3≤rated motor voltage
S1inverter provides dedicated function codes for V/F control mode. Users can improve the
performance of V/F through settings.
1. Torque boost
Torque boost function can effectively compensate for the low-speed torque performance during V/F
control. Automatic torque boost has been set by default to enable the inverter to adjust the torque
boost value based on actual load conditions.
Note:
(1) Torque boost is effective only under torque boost cut-off frequency;
(2) If the torque boost is too large, low-frequency vibration or overcurrent may occur to the motor, if
such situation occurs, lower the torque boost value.
Output voltage
V
b
Straight-type
Output voltage
100 % V
b
V3
V2
V1
f1
Torque -down V/F curve (1.3
Torque -down V/F curve (1.7
Torque -down V/F curve (2.0
Square-type
Output frequency
f
b
Output frequency
f
f2
f3
b
-46-
th
order)
th
order)
th
order)
Hz