Mitsubishi Electric FR-A700 Instruction Manual page 383

Parameter
S-pattern acceleration/deceleration B (Pr. 29 = 2)
When a setting of "2" is entered frequency changes are executed with an S-pattern. For exam-
ple, if a drive is accelerated from 0 to 30Hz and then re-accelerated to 50Hz then each accel-
eration sequence (i.e. the first sequence from 0 to 30Hz and the second from 30Hz to 50Hz) will
be executed with an S-pattern. The time for the S-pattern is not longer than that for linear accel-
eration (refer to Fig. 6-82). This prevents jolts in drive operation, for example for conveyor belt
and positioning drive systems.
f1
f2
Backlash measures (Pr. 29 = 3, Pr. 140 to Pr. 143)
What is backlash?
Reduction gears have an engagement gap and have a dead zone between forward rotation and
reverse rotation. This dead zone is called backlash, and this gap disables a mechanical system
from following motor rotation.
More specifically, a motor shaft develops excessive torque when the direction of rotation
changes or when constant-speed operation shifts to deceleration, resulting in a sudden motor
current increase or regenerative status.
To avoid backlash, acceleration/deceleration is temporarily stopped.
Set the acceleration/deceleration stopping frequency and time in Pr. 140 to Pr. 143.
Fig. 6-83: Anti-backlash measure function
NOTE
Setting the backlash measures increases the acceleration/deceleration time by the stopping
time.
FR-A700 EC
S-pattern acceleration/
deceleration C
Time
Pr. 13
Fig. 6-82:
Characteristic for parameter 29 = 2
t
Pr. 140
P r. 1 4 1 Pr. 143
Acceleration and deceleration
Pr. 142
Time
I001527E
6 - 203
I000017C