Magnetek DSD 412, Техническое руководство

Страница: 85 / 122

DRIVE SETUP
85
there is a finite time required for ARB to
measure unwanted car motion via the
encoder, produce a counteracting motor
torque, and then return the car to the
original position. The reaction time is
controlled by #131, ARB Bandwidth.
The smoothness and time to settle is
controlled by #132, ARB Damping. The
need for ARB starts only when the
elevator brake is actually released, not
when it is told to release. (A subtle
difference in electromechanical timing.)
But the allotted time for ARB to function
will cease as soon as the velocity
reference (internal or external) moves
away from zero speed and crosses the
threshold identified by #133.
a) Ideally, there would be
adequate dwell time after
release of the brake for ARB
settling to occur. But elevator
floor-to-floor time specifications
do not necessarily allow for any
time delay. If the resulting ARB
time is cut short by release of
the velocity reference before
position settling is complete, the
car will begin to accelerate
toward the next landing from
wherever it may be in the ARB
cycle. The position regulator to
speed regulator change-over
will be smooth, but the
repeatability of velocity profile
tracking during acceleration may
be altered by the amount of load
unbalance and the value of the
threshold set in #133. Keep
this setting as low as possible
for best results.
b) If #133 is set too low ARB may
be terminated too early,
particularly when using an
external analog reference. This
will result in elevator rollback
that could have been prevented.
c) If acceleration of the velocity
profile is started and crosses the
threshold set by #133 before
the elevator brake actually
releases, ARB will not function
and may result in elevator roll-
back as acceleration begins.
This, and the jerk or vibration
sometimes felt by passengers
as the motor pulls through the
brake to start the car, is a result
of poor velocity reference
release Vs brake release timing.
With ARB the velocity reference
should not be released to move
away from zero until after the
brake is mechanically released.
Otherwise the ARB feature
cannot work.
4. Anti-Rollback can be used with external
load weighing and pre-torque, as these
features are independent of each other.
If motor pre-torque values are not
precisely correct at the time of starting
the elevator drive, as may occur during
elevator re-leveling, the features of ARB
will intervene to help reduce rollback. If
pre-torque is accomplished correctly,
Anti-rollback will not need to do
anything. However, it can still cause
vibration or oscillation if ARB gains are
set too high.
5. It is not always convenient to use
payload weights during adjustment.
Most elevators are counterweighted
such that an empty car represents an
unbalanced load of 43-57%, with the
counterweight being heavier. If Anti-
rollback works effectively with an empty
car at all landing stops, it should also
perform adequately with full payload
weight in the car. Step 6 in the
adjustment procedure indicates how to
verify and adjust ARB operation with a
full car payload, but it is not always
necessary.
6. Anti-rollback may also be used to hold
the car at a constant position at the end
of an elevator run. Normally this is not
required because the velocity regulator,
E-Reg, will stabilize and hold an
armature current value as necessary to
hold the car at a standstill at the end of
an elevator run. However, turning ARB
back on may be useful to aid car re-level
positioning without first setting the brake
for a total drive re-start. Set #130 to a 2
to re-enable ARB when the car returns
to zero speed at the end of an elevator
run. Zero speed in this case is
measured by the encoder, not the
reference, and defined by #63. ARB
will remain enabled until the drive is
either shut down by removal of Run or
Run-Up/Run-Down or Drive & field
Enable logic signals, or the internal