7 Advanced Settings
7 - 34
High-function General-purpose Inverter RX2 Series User’s Manual
Precautions for Correct Use
• When the revolution of the motor is hindered by such causes as the braking or the motor lock
caused by foreign objects, such hindrance may cause over current, or the like. When no such
adjustment as ones mentioned above improves the state, checking the portion around the
motor may sometimes improves it.
• If an application of load results in a great amount of change in the inverter’s output frequency
monitor [dA-01], a function to automatically change the frequencies for the overload limiting
function, the momentary-stop non-stop function, the over voltage suppression function may
work depending upon the settings of the functions.
Free V/f control with sensor is used to change the frequency and voltage characteristics when a motor
with an encoder is driven.
The feedback of the encoder signal from the motor allows highly accurate frequency control.
For the adjustment of V/f control (free V/f), see 7-2-3 V/f Control (Free V/f) on page 7-7.
In the V/f control with feedback (FB), a correction of PI control is conducted on the command frequency
for the fed-back frequency to control the motor.
Precautions for Correct Use
• When [CA-90] = 02, Input terminals [A] and [B] are switched to the terminals for feedback
control. When [CA-90] ≠ 02, terminals [EA] and [EB] of the PG option unit are enabled.
•See 7-2-16 Encoder Feedback Control on page 7-37.
Phenomenon Estimated cause(s) Exemplar measures to be taken
The motor speed fol-
lows the command
slowly.
Response of the out-
put is slow and the
change in the fed-back
value is slow.
Increment the proportional (P) gain [Hb170].
The motor operates
unstably.
Response to the
fed-back value is too
quick.
Decrement the proportional (P) gain [Hb170].
Overshoot and/or
hunting occur.
The motor speed oscil-
lates gently.
Response to the inte-
gral operation is slow.
Increment the integral (I) gain [Hb171].
Stabilization of the
operation requires a
long time.
It takes time for the
command value and
the motor speed to be
equal to each other.
Response of the out-
put is slow and the
change in the fed-back
value is slow.
Decrement the integral (I) gain [Hb171].
7-2-14 Free V/f Control with Sensor
()
∙
Kp: proportional gain setting; Ti: integral time; s: operator; ε: deviation
Ki: integral gain setting (Ki = Ti/Kp)
PI control
Control
frequency
Frequency-volt-
age control
Output
frequency
Feedback
Deviation ε
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