Torque Control Algorithms; Constant And Variable Torque - Hitachi L300P Series Instruction Manual

3–14
"A" Group: Standard Functions
Torque Control
Algorithms
The inverter generates the motor output
according to the V/f algorithm. Parameter
A044 selects the inverter torque control
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 V/f 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).
• The free-setting curve provides an even more flexible characteristic, but it requires more
parameter settings.
Constant and Variable Torque – The graph below (left) shows the constant torque character-
istic from 0Hz to the base frequency A003. The voltage remains constant for output frequencies
higher than the base frequency.
Constant torque
Output
voltage
100%
0
Base
frequency
The graph above (right) shows the general characteristic for variable torque. The curve may be
best described in three sections, as follows:
a. The range from 0Hz to 10% of the base frequency is the constant torque characteristic.
For example, a base frequency of 60Hz ends the constant torque characteristic segment
at 6Hz.
b. The range from 10% of the base frequency to the base frequency is the variable
(reduced) torque characteristic. The voltage is output in the curve of frequency to the 1.7
power.
c. After reaching the base frequency, the characteristic maintains a constant output voltage
for higher frequencies.
Inverter Torque Control Algorithms
V/f control,
constant torque
V/f control,
variable torque
V/f control, free-
setting curve
Output
voltage
100%
a.
0
Maximum 10% of
frequency base
frequency
A044
00
Output
01
02
Variable torque
b. c.
Base Maximum
frequency frequency