ABB ACH550-01, Руководство пользователя

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266 Parameter listing and descriptions
ACH550 User's Manual
PID controller
–
Advanced
The ACH550 has two separate PID controllers:
1. Process PID (PID1) and
2. External PID (PID2).
Process PID controller (PID1)
Process PID (PID1) has two separate sets of parameters:
• Process PID (PID1) set 1, defined in
Group 40: PROCESS
PID SET 1 , and
• Process PID (PID1) set 2, defined in Group 41: PROCESS
PID SET 2 .
The user can select between the two different sets by using
parameter 4027
PID
1
PARAM SET
.
Typically two different PID controller sets are being used when
the load of the motor changes considerably from one situation to
another.
External PID controller (PID2)
External PID (PID2), which is defined in Group 42: EXT/TRIM
PID , can be used in two different ways:
• Instead of using additional PID controller hardware, External
PID can be set to control a field instrument like a damper or a
valve through outputs of the ACH550. In this case, parameter
4230
TRIM MODE
has to be set to value 0 (default value).
• External PID (PID2) can be used as an additional PID
controller to Process PID (PID1) to trim or fine-tune the
speed of the ACH550.
An example of the trimming is a return fan that follows the speed
of the supply fan. As the return fan needs to run faster or slower
than the supply fan in order to create under- or overpressure,
correction factors to the supply fan speed are needed. External
PID (PID2) can be used in the return fan for ACH550 to provide
these corrections.