ABB ACS880-01 Series, Firmware Instructions

Page: 45 / 664

ESP program features 45
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Backspin speed observer constraints
Backspin speed measurement is a special drive control mode that requires physical
cable connection to the motor. Therefore, the motor contactor should be closed all the
time for the function to work. If the contact to the motor gets impaired while
monitoring, then manually restart after the connection is restored.
Backspin speed measurement sensitivity has its limitations at slow speeds. The
lowest detectable speed varies (not the same) depends on motor size and can be as
low as 1Hz with 900kW motor. With small motors (1-10kW), the speed detection
routine cannot produce accurate measurement below 4Hz. The general guideline for
the function set up to test speed measurement capacity with each type of motor in
use to assess the lowest feasible speed measurement.
Backspin speed measurement cannot always reliably detect zero-speed crossing
from positive to negative speed and vice versa. The general guideline is to always
have the Restart delay function enabled and active for several minutes after process
is interrupted. It delays the Backspin Speed Observer function to engage, thus giving
system some time to transit from production state to the state of fluid drainage
(typically, being the primary reason for motor to passively back-spin).
With permanent magnet type of motors, backspin speed observer function could
sustain passive monitoring of speeds not greater than half of the motor nominal
speed.
Settings
Parameter group 74 ESP control (page 418 ).