Free V/F Control With Sensor - Omron RX2 Series User Manual

7 Advanced Settings
Phenomenon
The motor speed fol-
lows the command
slowly.
The motor operates
unstably.
Overshoot and/or
hunting occur.
The motor speed oscil-
lates gently.
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.
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.

7-2-14 Free V/f Control with Sensor

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.
Output
frequency
7 - 34
Estimated cause(s)
Response of the out-
put is slow and the
Increment the proportional (P) gain [Hb170].
change in the fed-back
value is slow.
Response to the
fed-back value is too Decrement the proportional (P) gain [Hb170].
quick.
Response to the inte-
Increment the integral (I) gain [Hb171].
gral operation is slow.
Response of the out-
put is slow and the
Decrement the integral (I) gain [Hb171].
change in the fed-back
value is slow.
PI control
Deviation ε
+
1
( )
Kp 1+
∙
Ti S
-
Kp: proportional gain setting; Ti: integral time; s: operator; ε: deviation
Ki: integral gain setting (Ki = Ti/Kp)
High-function General-purpose Inverter RX2 Series User's Manual
Exemplar measures to be taken
Control
frequency
+
Frequency-volt-
age control
+
M
Feedback