ABB ACS850 - Page 71

Program features 71
Sleep function for process PID control
The following example visualizes the operation of the sleep function.
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.
Settings
Parameter group 27 Process PID (page 188) and parameter 23.08 Speed additive
(page 180).
t<t
d
t
d
SLEEP MODE
t
wd
t
wd
Motor Speed
t
d
= Sleep delay (27.24)
t
wd
= Wake-up delay (27.26)
Sleep level
(27.23)
STOP START
Actual value
Actual value
Wake-up level
(27.25)
Time
Time
Time
Wake-up level
(27.25)
Non-inverted (source of 27.16 = 0)
Inverted (source of 27.16 = 1)