Hitachi SJ Series User Manual page 225

Chapter 12
12.9.6 Manually adjust torque
Ｑ
• To improve the delayed start of the motor from the
start of the operation.
• To improve the small torque at low speeds.
Ａ
• Raise the output voltage by adding an extra voltage
in order to achieve a higher torque at low speeds
than otherwise.
• In the V/f control, no special correction is
conducted to control the motor. Accordingly, at low
output voltages, the resistance component and/or
the wiring in the motor will cause the voltage drop,
which in turn lowers the voltage applied to the
motor. Manual boost corrects the voltage and
thereby improves the lowering of the torque at the
low-speed range.
e.g.) When [Hb140] = 02, the boost works only for the
forward revolution of the motor.
Output
voltage (%)
Backward-
100
revolution
[Hb141]
Base frequency
(100%)
Parameter
Item
Torque boost operation
mode selection
Amount of manual torque
boost
Manual torque boost break
point
Forward-revolution
Output
frequency
[Hb142]
Base frequency
(100%)
Parameter
[Hb140]
[Hb141] 0.0~20.0(%)
[Hb142] 0.0~50.0(%)
12-9-8
！
• Be sure not to cause an over excitation of the
motor when raising the set value for the manual
torque boost. Boosting increases the flow of the
current, which may burn the motor.
• The target of the torque boost is the V/f control of
induction motors. (except the free V/f)
• As the amount of manual torque boost [Hb141], set
the proportion thereof to the motor rated voltage
[Hb106] (= 100 %). The set value is the maximum
amount to be added at manual torque boost break
point [Hb142].
• As the manual torque boost break point [Hb142],
set the proportion of the frequency at that point to
the base frequency [Hb104] (= 100%).
Data
00 Disabled
01 Always enabled
02 Enabled only for forward revolution
03 Enabled only for backward revolution
Setting the maximum amount of torque boost
for the motor's rated voltage [Hb106] at the
time of setting the manual torque boost break
point.
Set, as the break point, the proportion of the
boost amount to the base frequency [Hb104]
Inverter Function
Description