MCO 305 Design Guide
__ Functions and Examples __
50
MG.33.L4.02 – VLT
®
is a registered Danfoss trademark
The chart below shows a stopping movement that begins from a
negative
velocity and a very high decelera-
tion. (It is a deceleration because the speed is slowing down.) However, because the initial deceleration is
so high, the motor is unable to stop without overshooting 0 velocity and ‘coming back’.
So the curve starts with a deceleration ramp-down
segment (using JERKMIN4) to slow the deceleration
as much as possible before reaching 0 velocity. At
0 velocity, the "deceleration" becomes an
‘acceleration’" because the direction has changed.
Hence, the curve continues by ramping-down the
acceleration (using JERKMIN2) until it gets to 0
acceleration. The motor is now at a constant posi-
tive velocity and so the curve will finish in the
normal way with a deceleration ramp-up segment
(using JERKMIN3), a constant deceleration seg-
ment (very short in this example), and a decele-
ration ramp-down segment to 0 velocity (using
JERKMIN4).
Changing to a Constant Velocity
This chart shows a movement that begins from a
positive constant velocity and increases its speed
to a higher positive constant velocity. This curve
consists of an acceleration ramp-up segment (using
JERKMIN), followed by a constant acceleration
segment (at maximum acceleration), and finally an
acceleration ramp-down segment to constant
velocity (using JERKMIN2). Note that the decelera-
tion JERKMIN3 and JERKMIN4 values are not used
because there is never any deceleration.
This chart shows a movement that begins from a
high positive constant velocity and decreases its
speed to a lower positive constant velocity. This
curve consists of a deceleration ramp-up segment
(using JERKMIN3), followed by a constant decele-
ration segment (at maximum deceleration), and
finally a deceleration ramp-down segment to
constant velocity (using JERKMIN4). Note that the
acceleration JERKMIN and JERKMIN2 values are not
used because there is never any acceleration.
Summary of Contents for MCO 305
Page 4: ......