WEG CFW700, Programming And Troubleshooting Manual

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Applications
19
CFW700 | 19-1
19 APPLICATIONS
19.1 INTRODUCTION
The CFW700 has some features that allow better matching the inverter commands to the application. These
features were grouped into a set of applications and can be as simple as the forward and reverse command, or
more elaborated such as a PID controller.
The applications were implemented using the SoftPLC function, in other words, ladder programming applicative
built-in to the CFW700 inverter. It allows the user that has the WLP and the built-in implemented applicative to
change it and use it as an user applicative.
Parameter P1003 allows selecting an application and uploading it to the CFW700. The CFW700 has following
applications built-in:
„
PID Regulator.
„
Electronic Potentiometer (EP).
„
Multispeed.
„
3-Wire Start/Stop.
„
Forward/Reverse Run.
19.2 PID REGULATOR APPLICATION
19.2.1 Description and Definitions
The CFW700 has the PID REGULATOR application that can be used to control a closed loop process. This
application sets proportional, integral and derivative regulator superimposed to the regular speed control of the
CFW700 inverter. Refer to the block diagram in the
figure 19.1 .
The CFW700 will compare the setpoint with the process variable and control the motor speed trying to eliminate
any error and keeping the process variable equal to the setpoint. The setting of the P, I and D gains determines
how fast the inverter will respond to eliminate this error.
Application examples:
„
Flow control or pressure in a pipe system.
„
Temperature of a furnace or oven.
„
Dosing of chemicals in tanks.
The following example defines the terms used by the PID controller.
A pump used in a water pumping system where is necessary to control the pressure of the pipe. A pressure
transducer is installed in the pipe and supplies an analog feedback signal to the CFW700, which is proportional
to the water pressure. This signal is called the process variable, and can be visualized at the parameter P1012. A
setpoint is programmed in the CFW700 via keypad (P1025), through an analog input (such as a 0-10 V or 4-20 mA
signal) or via communication network. The setpoint is the desired water pressure value that the pump is supposed
to produce, regardless of the consumption variations at the pump output at any time.
It is necessary to set the parameter P0221 or P0222 to 7=SoftPLC for the operation of the PID Regulator application.