Hitachi L200 Series, Instruction Manual

Page: 89 / 280

L200 Inverter
Conf
igur
ing
Dr
iv
e P
a
ra
m
e
ters
3–17
Torque Control Algorithms
The inverter generates the motor output
according to the V/f algorithm selected.
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 00 (constant
torque).
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). You can select either constant torque or reduced
torque V/f control.
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.
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
breakpoint of the boost (point A on the
graph) by using parameters A042 and A043. The manual boost is calculated as an
addition to the standard V/f curve.
Output
A44
V/f control,
constant torque
V/f control,
variable torque
00
01
Inverter Torque Control Algorithms
Constant torque A044 = 00
V
100%
Hz
0
Variable torque A044 = 01
V
100%
Hz
0
Base
freq.
Max.
freq.
Base
freq.
Max.
freq.
f base =
60Hz
Torque boost
A042 = 5
A043 = 3
(%)
V
Hz
100%
5%
30.0Hz 1.8Hz
A
0
(%)