Hitachi SJ7002 Series Instruction Manual page 100

Sj7002 series
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3–16
"A" Group: Standard Functions
V/f Free-setting – The free-setting V/f inverter mode of operation uses voltage and frequency
parameter pairs to define seven points on a V/f graph. This provides a way to define a multi-
segment V/f curve that best suits your application.
The frequency settings do require that
F1 ≤ F2 ≤ F3 ≤ F4 ≤ F5 ≤ F6 ≤ F7; their
values must have this ascending order
relationship. However, the voltages V1
to V7 may either increase or decrease
from one to the next. The example to the
right shows the definition of a complex
curve by following the setting require-
ments.
Free-setting f7 (B112) becomes the
maximum frequency of the inverter.
Therefore, we recommend setting f7
first, since the initial value of all default
frequencies f1–f7 is 0Hz.
NOTE: The using of V/f free-setting operation specifies parameters that override (make
invalid) certain other parameters. The parameters that become invalid are torque boost (A041/
A241), base frequency (A003/A203/A303), and maximum frequency (A004/A204/A304). In
this case, we recommend leaving their settings at the factory default values.
The V/f free-setting endpoint f7/V7
parameters must stay within the more
basic inverter limits in order for the
specified free-setting characteristic
curve to be achieved. For example, the
inverter cannot output a higher voltage
than the input voltage or the AVR
setting voltage (Automatic Voltage
Regulation), set by parameter A082.
The graph to the right shows how the
inverter input voltage would clip (limit)
the characteristic curve if exceeded.
Sensorless Vector Control and, Sensorless Vector Control, 0Hz Domain – These advanced
torque control algorithms improve the torque performance at very low speeds:
• Sensorless Vector Control – improved torque control at output frequencies down to 0.5 Hz
• Sensorless Vector Control, 0Hz Domain – improved torque control at output frequencies
from 0 to 2.5 Hz.
These low-speed torque control algorithms must be tuned to match the characteristics of the
particular motor connected to your inverter. Simply using the default motor parameters in the
inverter will not work satisfactorily for these control methods. Chapter 4 discusses motor/
inverter size selection and how to set the motor parameters either manually or by using the
built-in auto-tuning. Before using the sensorless vector control methods, please refer to
"Setting Motor Constants for Vector Control" on page
NOTE: When the inverter is in SLV (sensorless vector) mode, use B083 to set the carrier
frequency greater than 2.1 kHz for proper operation.
NOTE: You must disable sensorless vector operation when two or more motors are connected
(parallel operation) to the inverter.
Output voltage
V7
V6
V5
V4
V1
V2, V3
B101 to
B113
0
f1
f2 f3
(odd)
B100 to B112
Output voltage
V7
Voltage to output or AVR voltage
V6
B101 to
B113
0
f6
(odd)
B100 to B112
4–69.
Output
frequency
f4 f5 f6 f7 Hz
(even)
Output
frequency
f7
Hz
(even)

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