ABB ACS560, Firmware Manual

Page: 52 / 514

52 Program features
Sleep and boost functions for process PID control
The sleep function is suitable for PID control applications where the consumption
varies, such as clean water pumping systems. When used, it stops the pump
completely during low demand, instead of running the pump slowly below its efficient
operating range. The following example visualizes the operation of the function.
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
wakeup 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.