Mitsubishi Electric FR-A700 Series, Technical Manual

Page: 359 / 550

393
PARAMETER
2
P
ARAM
ETE
R
Encoder feedback control is not performed during
acceleration/deceleration to prevent unstable
phenomenon such as hunting and performed when
the output frequency once reaches [set frequency]
±
[speed feedback range].
If the following conditions occur during encoder
feedback control, the inverter operates at the
frequency within [set speed]
±
[speed feedback
range] without coming to trip nor tracking the motor
speed.
• The pulse signals are not received from the
encoder due to a signal loss or the like.
• The accurate pulse signal from the encoder can
not be detected due to induction noise, etc.
• The motor has been forcibly accelerated
(regeneration) or decelerated (motor lock or the
like) by large external force.
For the motor with brake, use the RUN signal
(inverter running) to open the brake. (The brake may
not be opened if the FU (output frequency detection)
signal is used.)
(3) Feedback gain [ Pr. 368 ]
Set [ Pr. 368 Feedback gain ] when the rotation is
unstable or response is slow.
If the acceleration/deceleration time is long, feedback
response becomes slower. In this case, increase the
[
Pr. 368 ] setting.
(4) Overspeed detection [ Pr. 285 ]
If (detection frequency) - (output frequency)
>
[ Pr.
285 ] under encoder feedback control, E.MB1 occurs
and the inverter output is stopped to prevent
malfunction when the accurate pulse signal from the
encoder can not be detected.
Overspeed is not detected when [
Pr. 285 = 9999 ] .
(5) Switching the control method from the
external terminal (RT, X18 signal)
When Advanced magnetic flux vector control, Real
sensorless vector control, or vector control is
selected and [
Pr. 18 = 12 to 20
], use X18 signal to
change to V/F control. When encoder feedback
control is valid, turning X18 signal ON to change to V/
F control becomes invalid, and encoder feedback
control is valid.
Turning RT signal ON changes the control to the
second motor control. Note that if encoder feedback
control is valid and the second motor is selected ([
Pr.
450
≠
9999 ]), turning RT signal ON will not start
encoder feedback control.
When the second motor is not selected ([
Pr. 450 =
9999 ], turning RT signal ON starts encoder feedback
control.
When both X18 signal and RT signal are turned ON,
RT signal has priority.
[Pr. 368]
Setting
Description
[ Pr. 368 ] 1
Although the response becomes
faster, overcurrent or unstable rotation
is liable to occur.
1 [ Pr. 368 ]
Although the response become slow,
rotation becomes stable.
Changing First Motor Control Method
([Pr. 80 = Motor capacity], [Pr. 81 = 12, 14, 16, 18, 20])
X18 signal-OFF X18 signal-ON
Advanced magnetic flux vector
control
with encoder feedback
Real sensorless vector control
*1
Vector control
*1
V/F control
with encoder feedback
*1 Encoder feedback is invalid during Real sensorless
vector control and vector control even if set.
First Motor Control Method Selection
RT Signal-OFF
Second Motor Control Method
RT Signal-ON
[Pr. 450]
Setting
[Pr. 453]
[Pr. 454]
Setting
[Pr. 451]
Setting
V/F control
with encoder feedback
V/F control
with encoder feedback
9999 — —
V/F control
without encoder feedback
Other than
9999
9999 —
Advanced magnetic flux vector control
without encoder feedback
Other than
9999
20, 9999
Real sensorless vector control
*1
10 to 12
Advanced magnetic flux vector control
with encoder feedback
Real sensorless vector control
*1
Vector control
*1
[
Pr. 81 = 2 to 10
] Same control as the first motor
*1
with encoder feedback
[
Pr. 81 = 12 to 20
*2 ] V/F control
with encoder feedback
9999 — —
V/F control
without encoder feedback
Other than
9999
9999 —
Advanced magnetic flux vector control
without encoder feedback
Other than
9999
20, 9999
Real sensorless vector control *1 10 to 12
*1 Encoder feedback is invalid during Real sensorless vector control and vector control even if set.
*2 Turning X18 signal ON selects V/F control. When the X18 signal is not assigned, turning the RT signal ON selects V/F control
as the RT signal shares this function.