Program features 77
Example: The drive controls a pressure boost pump. The water consumption falls at
night. As a consequence, the process PID controller decreases the motor speed.
However, due to natural losses in the pipes and the low efficiency of the centrifugal
pump at low speeds, the motor would never stop rotating. The sleep function detects
the slow rotation and stops the unnecessary pumping after the sleep delay has
passed. The drive shifts into sleep mode, still monitoring the pressure. The pumping
resumes when the pressure falls under the predefined minimum level and the wake-
up delay has passed.
The user can extend the PID sleep time by the boost functionality. The boost
functionality increases the process setpoint for a predetermined time before the drive
enters the sleep mode.
Wake-up level
(Setpoint - Wake-up deviation [40.47])
t < t
sd
Motor speed
Actual value
STOP
t
sd
= Sleep delay (40.44)
Sleep level
(40.43)
START
Wake-up delay
(40.48)
t
sd
Setpoint
Time
Sleep boost step (40.46)
Sleep mode
Sleep boost time (40.45)
Time
Time
Non-inverted
(40.31 = Not inverted (Ref - Fbk))
Wake-up level
(Setpoint + Wake-up deviation [40.47])
Actual value
Time
Inverted (40.31 = Inverted (Fbk - Ref))
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