Mitsubishi Electric FR-A700 Technical Manual page 358

2.19.2 Encoder feedback control [Pr. 144, 285, 359, 367 to 369]
This controls the inverter output frequency so that the
motor speed is constant to the load variation by detecting
the motor speed with the speed detector (encoder) to feed
it back to the inverter under V/F control and Advanced
[Pr.] Name
144 Speed setting switchover
Overspeed detection
285
frequency
*1
Encoder rotation
359
direction
Speed feedback
367
range
368
Feedback gain
Number of encoder
369
pulses
*1 When performing vector control with the FR-A7AP or FR-A7AL, this parameter changes to speed deviation excess detection
frequency (For details, refer to page 294).
(1) Setting before the operation
[Pr. 144, 359, 369]
When performing encoder feedback control under V/
F control, set the number of motor poles in [Pr. 144
Speed setting switchover] according to the motor used.
When [Pr. 144 = 0, 10, 110] and run the inverter, fault
E1 to E3 occurs.
When [Pr. 144 = 102, 104, 106, 108], the value
subtracting 100 is set as the number of motor poles.
[Pr. 144] is used to change the monitor display
increments. Refer to page 343 for details.
When operating Advanced magnetic flux vector
control and encoder feedback control together, the
[Pr. 144] setting is invalid and the [Pr. 81 Number of
motor poles] setting is valid.
Set the rotation direction of the encoder and number
of pulse using [Pr. 359 Encoder rotation direction] and
[Pr. 369 Number of encoder pulses]. Encoder feedback
control can not be performed when the setting of
encoder rotation
operation is enabled.) Encoder rotation direction can
be checked with the rotation direction display of the
parameter unit.
In encoder feedback control, inverter output is
controlled by the encoder at motor side. When
performing encoder feedback control by the encoder
at machine side by using FR-A7AL, convert the
number of encoder pulses at machine side to the
number equivalent for the motor side, and set the
value to [Pr. 396 Number of encoder pulses ]. When
encoders at motor side and machine side differ, set
the same rotation direction as the motor side to [Pr.
359 Encoder rotation direction].
Initial
Setting Range
Value
0, 2, 4, 6, 8, 10, 102
4
104, 106, 108, 110
0 to 30Hz
9999
9999
1
0 to 400Hz
9999
9999
1 0 to 100
1024 0 to 4096
direction is wrong. (Inverter
magnetic flux vector control. Slip compensation of [Pr. 245
to Pr. 247] is invalid.
Plug-in option FR-A7AP or FR-A7AL is necessary.
Set the number of motor poles when performing encoder
feedback control under V/F control.
If (detected frequency) - (output frequency) ≥ Pr. 285 during
encoder feedback control, the inverter fault (E.MBI) is provided.
Overspeed is not detected.
0
1
Set the region of speed feedback control.
Encoder feedback control is invalid
Set when the rotation is unstable or response is slow.
Set the number of pulses of the encoder.
Set the number of pulses before multiplied by four.
(2) Selection of encoder feedback control [Pr.
367]
When [Pr. 367 Speed feedback range ≠ 9999], encoder
feedback control is valid.
Using the set point (frequency at which stable speed
operation is performed) as reference, set the higher
and lower setting range. Normally, set the frequency
converted from the slip amount (r/min) of the rated
motor speed (rated load). If the setting is too large,
response becomes slow.
Speed feedback range
Set value
(Set command)
[Example]
When the rated speed of the motor (4P) is1740 r/min/60Hz
Slip amount Nsp = Synchronous speed - rated speed
Frequency fsp equivalent to the slip amount
Nsp
of motor poles
fsp =
392
PARAMETER
A700 )
(A700
Description
A
Encoder
Clockwise direction as viewed
from A is forward rotation
CCW
A
Encoder
Counter clockwise direction as
viewed from A is forward rotation
Driven load
= 1800 - 1740 = 60 (r/min)
×
the number
×
60 4
=
120 120
CW
Regeneration
load
= 2(Hz)