ABB ACS320 series, Руководство пользователя

Страница: 121 / 442

Program features 121
Parameter lock
The user can prevent parameter adjustment by activating the parameter lock.
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Settings
Parameters 1602 PARAMETER LOCK and 1603 PASS CODE
PID control
There are two built-in PID controllers in the drive:
• Process PID (PID1) and
• External/Trim PID (PID2).
The PID controller can be used when the motor speed needs to be controlled based
on process variables such as pressure, flow or temperature.
When the PID control is activated, a process reference (setpoint) is connected to the
drive instead of a speed reference. An actual value (process feedback) is also
brought back to the drive. The drive compares the reference and the actual values,
and automatically adjusts the drive speed in order to keep the measured process
quantity (actual value) at the desired level (reference).
The control operates on a 2 ms time level.
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Process controller PID1
PID1 has two separate sets of parameters ( Group 40: Process PID set 1 , Group 41:
Process PID set 2 ). Selection between parameter sets 1 and 2 is defined by a
parameter.
In most cases when there is only one transducer signal wired to the drive, only
parameter set 1 is needed. Two different parameter sets (1 and 2) are used, eg, when
the load of the motor changes considerably in time.
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External/Trim controller PID2
PID2 ( Group 42: Ext / Trim PID ) can be used in two different ways:
• External controller: Instead of using additional PID controller hardware, the user
can connect PID2 output via drive analog output or fieldbus controller to control
a field instrument like a damper or a valve.
• Trim controller: PID2 can be used to trim or fine tune the reference of the drive.
See section Reference trimming on page 106 .