Torque Control Algorithms; Manual Torque Boost; Constant And Variable (Reduced) Torque - Hitachi SJ200 Series Instruction Manual

3–16
"A" Group: Standard Functions

Torque Control Algorithms

The inverter generates the motor output
according to the V/f algorithm or the intelli-
gent sensorless vector control algorithm.
Parameter A044 selects the inverter algorithm
for generating the frequency output, as shown
in the diagram to the right (A244 for 2nd
motor). The factory default is 02 (intelligent
sensorless vector control).
Review the following descriptions to help you
choose the best torque control algorithm for
your application.
• The built-in V/f curves are oriented toward developing constant torque or variable
torque characteristics (see graphs below).
• Intelligent sensorless vector control (iSLV) calculates an ideal torque vector based on
current motor position, winding currents, and so on. It is a more robust and precise
control method than the V/f control methods. Using the iSLV mode, the inverter
automatically adapts to the electrical characteristics of your motor.
Constant and Variable (Reduced) Torque – The graph below (left) shows the constant
torque characteristic from 0Hz to the base frequency A003. The voltage remains
constant for output frequencies higher than the base frequency. The graph below (right)
shows the general variable (reduced) torque curve. The range from 0Hz to the base
frequency is the variable characteristic.
V
100%
0
Manual Torque Boost – The Constant
and Variable Torque algorithms feature an
adjustable torque boost curve. When the
motor load has a lot of inertia or starting
friction, you may need to increase the low
frequency starting torque characteristics
by boosting the voltage above the normal
V/f ratio (shown at right). The function
attempts to compensate for voltage drop in
the motor primary winding in the low
speed range. The boost is applied from
zero to 1/2 the base frequency. You set the
A044 = 00 Constant torque
Base
Max.
freq. freq.
Inverter Torque Control Algorithms
V/f control,
constant torque
V/f control,
variable torque
Intelligent sensor-
less vector control
(iSLV)
V
A044 = 01
100%
0
Hz
A042 = 5
V
100%
Torque boost
A
5%
0
1.8Hz
A043 = 3 (%)
A044
00
Output
01
02
Variable torque
Hz
Base Max.
freq.
freq.
(%)
Hz
30.0Hz
f base =
60Hz