Design and Implementation of PLC-Based Monitoring Control System for Three-Phase Induction Motors Fed by PWM Inverter


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Introduction

With the rapidly changes on industries and
information technologies in recent years, some
traditional bulk electronic appliances have to be
monitored for a long time. All of their control devices
such as communication interfaces gradually enter the
Intemet information era. The control of all equipment
has been performed through the use of computers.
Most equipment uses PLC to connect with
computers to monitor each load and electricity
consuming devices. Programmable Logic Controllers
(PLC) are widely used in industrial control because
they are inexpensive, easy to install and very flexible
in applications.


PLC as a System Controller

Programmable logic controllers are modular,
industrially hardened computers which perform
control functions through modular input and output
(I/O) modules. The modularity of PLC allows the
user to combine generic I/O modules with a suitable
controller to form a control system specific to his is
most simply understood needs. The operation of a
controller by envisioning that it repeatedly performs
three steps:


Control System of Induction Motor

The software models generated in the Software
Requirements Analysis phase of the development
project are refined and embellished in the design
phase of the project. This phase involves making
implementation decisions such as the interfacing
between different software modules, the break down
of software across multiple processors, assigning inputs
and outputs to I/O cards, etc. PLC software, once
written must be easy and intuitive to follow.


Results

The system was tested during operation with varying
loads including tests on induction motor speed control
performance and tests for trip situations. The PLC
monitors the motor operation and correlates the
parameters according to the software.


Conclusion
Successful experimental results were obtained from the
previously described scheme indicating that the PLC can
be used in automated systems with an induction motor.
The monitoring control system of the induction motor
driven by inverter and controlled by PLC proves its high
INTERNATIONAL JOURNAL OF SYSTEMS APPLICATIONS, ENGINEERING & DEVELOPMENT
Issue 3, Volume 2, 2008
accuracy in speed regulation at constant-speedvariable-
load operation.