Magnetek DSD 412, Техническое руководство

Страница: 83 / 122

DRIVE SETUP
83
Using Anti-Rollback (ARB)
Elevator rollback occurs when an elevator
motor drive is started and the brake is
released but the hoist motor has not yet
developed enough torque to prevent gravity
from moving the car. The car may move up
or down depending on the overall balance of
equipment and payload. Velocity regulators
normally used for speed regulation will
eventually detect unwanted movement and
react to halt the car. But there will be a
position error accumulated during that
process that can represent many inches of
unwanted car movement relative to the
landing. This effect is most noticeable with
low friction gear-less elevators. It may be
totally masked by the friction of an elevator
driven through worm gears. Rollback by
itself does not pose any hazards, but it does
give an uneasy, out of control feeling to
passengers. In many installations brake
release timing is adjusted so that the brake
is released just as the car begins to
accelerate toward the next landing to mask
the rollback effect. This often results in jerky
starts as the brake linings release. The
correct countermeasure is to weigh the car
just as the doors close to determine the
degree of gravity unbalance, then pre-torque
the motor so that when the brake is released
all forces are balanced. This method is very
effective, but does require expensive
calibrated load weighing equipment.
The purpose of the Magnetek Anti-rollback
feature is to help prevent rollback on
elevators that do not use load weighing or
do not use the motor pre-torque capability
provided by the Magnetek drive. It uses a
double integrator (type 2) regulator when
operating at zero speed to hold the elevator
car at an average speed of zero and to
regulate a constant position as the brake is
released. When the velocity reference
leaves zero speed to accelerate the car
toward the next landing, the active velocity
regulator is switched to be E-Reg to
precisely track (follow) the velocity reference
profile. Be aware that this anti-rollback
feature works from encoder/tachometer
signals. So there must and will be some
movement in order for the feature to
function, but the position error generated by
elevator movement will recover. The
bandwidth gain of the system will determine
how much movement will occur. Several
new operating options and adjustments are
provided. Refer to the individual
descriptions for Drive Functions #130 - #132
and #63.
Set-Up And Tuning Of Anti-Rollback
(ARB)
1. The ARB function uses adjustment
settings #41 (Per Unit Inertia), and #42
(speed regulator Stiffness). These
settings and others are critical for good
performance of the E-Reg velocity
regulator. The first step for good ARB
performance is to disable ARB by
setting #130 to 0 (zero) and to tune all
other E-Reg adjustments for a smooth
ride and good floor-to-floor elevator
performance. Be sure that the car
weight and counterweights have been
adjusted to be at the final values.
Follow the suggested procedures for
tuning E-Reg as listed in this Tech
Manual. Ignore elevator rollback while
adjusting primary elevator performance
features. If rope resonance exists, also
adjust the notch filter for minimum
interference. Then tune up ARB last as
necessary to prevent elevator rollback
with an unbalanced payload.
2. After all other adjustments are
satisfactory, set #130 to a 1 to enable
ARB when starting an elevator run. Set
up the following initial ARB adjustment
values. Be sure to read ADJUSTMENT
HINTS and CAUTIONS listed below.
a) Set #131, ARB Bandwidth, to 2
times the setting in #40.
b) Set the initial value of #132,
ARB damping, to 0.5.
c) If the drive will be using an
internally generated velocity
reference or serial link
commands (#110 set to
2
or
3
)
set #133, ARB Speed
Threshold to 0.0%. If the drive
will be using an
external
analog
velocity reference (#110 set to
1
), set #133 to 0.5%.
3. With the car empty at a convenient
landing, prepare to start the elevator
drive, call for zero velocity from the car
controller via the normal way, release