Mitsubishi Electric FR-A700 Instruction Manual page 319

Parameter
Stopping characteristic of motor
When parameters are used to run the motor, the internal command pulse frequency and motor
speed have the relationship as shown in Fig. 6-39, and as the motor speed decreases, pulses
are accumulated in the deviation counter of the inverter. These pulses are called droop pulses
(ε) and the relationship between command frequency (f0) and position loop gain (Kp: Pr. 422)
is as represented by the following expression.
fo
ε
= ------ - pulse
Kp
204800
ε
------------------- - pulse
=
When the initial value of Kp is 25 s
Since the inverter has droop pulses during running, a stop settling time (ts) is needed from when
the command has zeroed until the motor stops. Set the operation pattern in consideration of the
stop settling time.
ts = 3
When the initial value of Kp is 25 s
The positioning accuracy Δε is (5 to 10) × Δl = Δε [mm]
Position command acceleration/deceleration time constant (Pr. 424 )
● When the electronic gear ratio is large (about 10 or more times) and the speed is low, rotation
will not be smooth, resulting in pulse-wise rotation. At such a time, set this parameter to
smooth the rotation.
● When acceleration/deceleration time cannot be provided for the command pulses, a sudden
change in command pulse frequency may cause an overshoot or error excess alarm. At
such a time, set this parameter to provide acceleration/deceleration time.
Normally set 0.
FR-A700 EC
[ ]
[ ] rated motor speed (
25
1
× ------ - s [ ]
Kp
)
−1
, the droop pulses (ε) are 8192 pulses.
−1
, the stop settling time (ts) is 0.12s.
Position control by vector control
6 - 139