UWE Bristol Engineering showcase 2015

Charles Taylor
BEng (Hons) Electrical/ Electronic Engineering
Project Supervisor
Hassan Nouri
Real Time Fault Analysis of AC Induction Motors
Introduction
Water companies can face large prosecutions and
fines if the water or sewerage quality parameters
goes outside of the consented limits. Any
unforeseen breakdowns in mechanical or electrical
equipment can result in critical items of plant
being left un-operational for periods of time whilst
a repair is carried out, leaving the plant exposed to
potential failures
This project set out to investigate, design and build
an instrument that can monitor real time
condition of plant and to detect potential failures
at their inception.
There are various methods of fault detection
though they often tend to rely on mechanical
instruments which are inherently expensive to fit
and maintain. The use of motor current signature
analysis to carry out real time fault diagnosis is
one that has been widely researched and proven.
Common Faults That Were Identified
Below is a list of common faults that regularly
occur in items of plant in the water treatment
industry.
Electrical Faults
Electrical Over load, nine to ground fault, Line to
line fault, two phase line to ground fault, three
phase line to ground fault, unbalanced supply
voltage, over voltage, under voltage and single
phasing
Pumps Failures
Impellor blockage, Non return valve failure and
Pressure head loss due to pipe burst or rupture
Mechanical Faults
Bearing failure, Motor Unbalanced load or rotor
shaft misalignment
Fault Signature Analysis
In order to be able to identify various current fault
signatures a number of real life experiments on
various pieces of electrical equipment on Wessex
Water’s Sewerage treatment works was set up.
Additionally current signatures were collected on
both healthy and unhealthy equipment and a
comparison made between the two. The
signatures were logged and collected using a
Power Quality Analyser. The data for each test was
then download into Matlab where a Fast Fourier
Transform was carried out to display the current
signature harmonics.
Fuzzy Logic
A hybrid fault identification algorithm was
developed based on the fault identification
method of fuzzy logic but with the added ability to
self learn and back propagate as the Neural
Network does.
Hardware Design
A design by Microchip for a three phase energy
meter with integrated DSPIC was used to become
the Pump Condition Monitor Tool. A PCB was built
to provide three phase 415V voltage and current
signatures .
Software Design
The PCM tool was designed to communicate its
current status, power quality parameters and fault
alarms via Modbus to a Programmable Logic
Controller.. Additionally a Graphical User Interface
was also built to allow the user a detailed insight
into the condition of a pump as it is running.
Project summary
This project set out to investigate, design and
build a system that can monitor real time
condition of pant and to detect failures of
plant at their inception.
The instrument is intended to be used by
utility company's so is required to be able to
communicate via Modbus to a Programmable
Logic Controller
Project Objectives
The objectives of this project were to
investigate a method of carrying out real time
fault analysis of AC induction motors, in
particular the centrifugal pump widely used
by utility company's.
Once a method of fault identification had
been established an instrument needed to be
designed and built that would work on any
centrifugal pump as a stand alone unit, 24
hours a day and that would integrate and
communicate with a Programmable Logic
Controller to alert operational staff of the
need to carry out potentially invasive
maintenances at the faults inception.
Project Conclusion
The project proved to be a good success. A
method of detecting and identifying all of the
faults required was achieved. A instrument
was built that was able to operate on three
phase pumps and detect failures.
The instrument was able to communicate via
Modbus to a Programmable Logic Controller.