Pump And Fan Control (Pfc) - ABB ACS580 Firmware Manual

114 Program features
Settings
• Menu - Primary settings - PID
• Parameter 96.04 Macro select
• Parameter groups
(page 272).
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Pump and fan control (PFC)

The Pump and fan control (PFC) is used in pump or fan systems consisting of one
drive and multiple pumps or fans. The drive controls the speed of one of the
pumps/fans and in addition connects (and disconnects) the other pumps/fans directly
to the supply network through contactors.
The PFC control logic switches auxiliary motors on and off as required by the
capacity changes of the process. In a pump application for example, the drive
controls the motor of the first pump, varying the motor speed to control the output of
the pump. This pump is the speed regulated pump. When the demand (represented
by the process PID reference) exceeds the capacity of the first pump (a user defined
speed/frequency limit), the PFC logic automatically starts an auxiliary pump. The
logic also reduces the speed of the first pump, controlled by the drive, to account for
the addition to the total system output by the auxiliary pump. Then, as before, the PID
controller adjusts the speed/frequency of the first pump in such a way that the system
output meets the process needs. If the demand continues to increase, the PFC logic
adds further auxiliary pumps, in a similar manner as just described.
As the demand drops, making the speed of the first pump fall below a minimum limit
(user defined as a speed/frequency limit), the PFC logic automatically stops an
auxiliary pump. The PFC logic also increases the speed of the drive controlled pump
to account for the missing output of the stopped auxiliary pump.
Autochange
Automatic rotation of the start order, or Autochange functionality, serves two main
purposes in many PFC type setups. One is to keep the run times of the pumps/fans
equal over time to even their wear. The other is to prevent any pump/fan from
standing still for too long, which would clog up the unit. In some cases it is desirable
to rotate the start order only when all units are stopped, for example to minimize the
impact on the process.
The Autochange can also be triggered by the Timed function (see page 118).
Interlock
There is an option to define interlock signals for each motor in the PFC system. When
the interlock signal of a motor is Available, the motor participates in the PFC starting
sequence. If the signal is Interlocked, the motor is excluded. This feature can be used
for informing the PFC logic that a motor is not available (for example due to
maintenance or manual direct-on-line starting).
(macro selection)
40 Process PID set 1 (page 261) and 41 Process PID set 2