TITLE
An improved fast on line system and method for monitoring and diagnosis of health of
motors (DC) and drives used in stands of rolling mills at any instant of time.
FIELD OF THE INVENTION
The present invention relates to monitoring and diagnosis of electrical/ mechanical
systems of motors and drives in rolling stands of steel rolling mill. More particularly, the
invention is concern about improved fast on line system and method for monitoring and
diagnosis of health of motors (DC) and drives used in stands of rolling mills at any
instant of time.
BACKGROUND OF THE INVENTION
The Rail and Structural Mill (RSM) produces rails and heavy structural of different
dimensions. The mill is divided into five major areas namely Reheating furnaces, Mill
Area, Hot Saw Zone and Cooling Beds followed by the Finishing Groups. The Mill area
is the core area where the blooms are rolled into rails and structurals as per the desired
profile. In order to run the stands at desired speeds and loads, the stands are driven by
very large dc motors.
US 4908775 document discloses that monitoring and analyzing, on an on-line basis, the
fatigue accumulated by components and systems subjected to fluid flow, thermal and
pressure transients, particularly nuclear power plant components and systems. It is based
on calculation of stresses and prediction of life expectancy based on the above mentioned
measured parameters. The invention also claims innovative method for sampling rate
calculation which increases the sampling rate to zoom a phenomenon beyond threshold
level-1 and 2 to maximize storage. However, the proposed invention relates to a different
type of system where rolling of steel products is done in a rolling mill and type of load is
impact loading. In this case, the torque requirement from the motor and associated
mechanical attachments such as spindle, coupling etc. changes suddenly from almost no

load condition to very heavy load. The types of load in the two cases are completely
different. Therefore the parameters being logged by sensors are also different. The
sampling rate in our case is pre-calculated and fixed however we have kept several
options to increase in case the frequency of problem occurrence has gone high.
US 7162312 document discloses that comparing error patterns of plant parameters with
the real time data. Based on statistical techniques "...a mechanism for archiving a
plurality of error patterns that previously occurred in the manufacturing system, the
archived error patterns created by statistical methods; a mechanism for monitoring
manufacturing system data in real-time; and a mechanism for comparing the monitored
data with the archived error patterns in real-time to predict imminent errors likely to
occur in the manufacturing system..." However, it is not mentioned specifically which
techniques are used for creating error pattern library, which statistical methods have been
employed to extract features of error pattern library and method for comparing the two.
US 20030204777 document discloses that Electrical Power Systems, digital power
conversion, distribution and load management system, which are purely electrical in
nature. The invention doesn't give any detail about methodology used for embedding
prognostic and diagnostic abilities in the system.
It is obvious that the dc motors are the most critical equipment for mill and sound health
of these motors is most crucial for the Mill performance. Even though there are several
schemes embedded in the control circuits for motor protection, an online system for
monitoring of motor parameters was essential for analysis of abnormalities in motors and
drive. Further, abnormalities in the stands or operational practices also get reflected in the
motor parameters.
Therefore, on-line analysis of motor parameters also enables getting an insight into
abnormalities in stands and rolling practices. Hence it is required to introduce a fast data
acquisition system with analysis capability for the motors.

OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior
art.
Another object of the present invention is to provide a system for monitoring and
diagnosis of health of motors (DC) and drives used in stands of rolling mills at any
instant of time.
Another object of the present invention is to provide a method for monitoring and
diagnosis of health of motors (DC) and drives used in stands of rolling mills at any
instant of time.
Another object of the present invention is to provide a system and /or method for
acquisition of vital motor parameters at a selectable scan rate ranges from 0.001 to 0.1
million samples per second.
Further object of the present invention is to provide a system and /or method for
preliminary diagnosis utility model for time domain analysis of motor drive tuning.
Yet, another object of the present invention is to provide a system and /or method for
preliminary diagnosis utility model for frequency domain analysis of motor drive.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved fast on
line system for monitoring and diagnosis of health of motors (DC) and drives used in
stands of rolling mills at any instant of time, said system comprising: means for acquiring
plurality of motor parameters; means for determining scan rate of said parameters; means
for selecting said scan rate requirements; and means for analyzing said parameters.
According to another aspect of the present invention there is provided an improved fast
on line method for monitoring and diagnosis of health of motors (DC) and drives used in

stands of rolling mills at any instant of time, said method comprising: acquiring plurality
of motor parameters; determining scan rate of said parameters ; selecting said scan rate
requirements; and analyzing said parameters.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates System Schematic
Fig 2 illustrates Armature Current & Ref. Voltage for Roughing Stand (1D)
Fig 3 illustrates Armature Current & RPM for Intermediate Stand (2D)
Fig 4 illustrates Armature Current & RPM for Finishing Stand (3D)
Fig 5 illustrates Power Spectral Density for Armature Current of Intermediate Stand
Motor (2D)
Fig 6 illustrates Time Frequency Analysis for Armature Current of Intermediate Stand
Motor (2D)
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an improved fast on line system and method
for monitoring and diagnosis of health of motors (DC) and drives used in stands of
rolling mills at any instant of time. There are three rolling stands namely Roughing Stand,
Intermediate Stand, and Finishing Stand_for rolling blooms into rails and structural. The
stands are driven by large DC motors, which are the most critical equipment for mill
operation. The motors are identified as ID for roughing stand, 2D for intermediate stand
and 3D for finishing stand. Even though there are several schemes implemented for
motor safety, there was not any motor performance monitoring system for these critical
motors.
Since these motors are so crucial for RSM performance, it is necessary to install a very
high speed motor data acquisition and analysis system, the data of which can, not only be
used, for post analysis of any abnormal condition and prediction of impending failures in
the motor & drive but also in analyzing problems related to the mechanical components
such as rolls and variations in the operating practices.

With this objective, a very high speed online performance monitoring system has been
installed. The system acquires critical performance parameters such as Armature current,
voltage, motor speed, field current etc. for motors of Roughing, Intermediate & Finishing
stands. The scan rate is calculated using Nyquist criteria and it is found that a sample rate
of 10000 Samples/ sec is sufficient for diagnosis of most of the abnormalities; however
the maximum capability is at 100,000 samples per second. The software development has
been carried out in Labview platform with National Instruments' NI PCI-6250 as main
hardware. A program has been developed in MATLAB to plot frequency spectrum &
power spectral density charts for analysis of the data.
Data sampling rate required (assuming the fastest phenomena of commutator sparking):
w=100 rpm x 360 deg/ 60 sec = 600 deg /sec. Assuming commutator segment at 2deg,
the number of times current reversal and hence contact of commutator with brush edge
would be 300 times per sec. To observe this phenomena, 10-15 times this frequency is
required to be sampled, i.e. 300 Hz x 15 = 4.5 KHz (equivalent to 5 KHz). Therefore
10Khz sampling rate may be covering most of the phenomena of interest. However, if
required 50KHz option can also be tried on experimentation basis.
The Design of Data Acquisition System is to save data at the desired rate and also display
it a cable distance of approximately 100 meters. The disk filling rate is 60 MB/ minute. A
multimode optical fiber cable is used for data transportation and display at user end.
Software for data logging and storage at various scan rates of 100K, 50K, 10K, 5K, 2K &
IK Samples per second is developed in LabVIEW. A proprietary file format of
Lab VIEW is selected for highest compression. The different files are for different motors.
For each motor a composite file having all the five parameters of duration one minute is
created. A Disk management utility is also included for auto deletion of old files when
the disk is filled at 70% level.

A preliminary diagnosis utility model has been developed and installed for calculation of
Power Spectral Density to analyze steady state behavior of 2D motor. A time frequency
analysis has also been done to understand and find a pattern in transient behavior of the
motor.
Experimental Results
A system for fast data acquisition and analysis of motor parameters has been designed
and commissioned for all the three motors of the stands of mill as shown in figure 1. The
system design comprises of two major aspects (A & B) described herein the following.
A. Fast Data Acquisition System:
A Fast Data Acquisition is installed for acquisition of all crucial motor parameters from
the three motors. The parameters are Armature Current, Armature Voltage, Field
Current, Reference Voltage and Angular speed. The DAS system has been built around
data acquisition module PCI-6250 of National Instruments. This card has capability of
acquiring data at a speed of 1.25 M Samples per second (single channel), however it has
been programmed to acquire data in the range of IK - 100K Samples per second with
intermediate options of 2, 5, 10 & 5 OK Samples per second. The programming has been
done in Lab View which provides Data Flow environment instead of Control Flow
environment as provided by high level languages. Also, as the source signals are 150
meters away from user terminal, the analogue signals have been acquired at remote place
and accessed over OFC line to the remote data acquisition system as shown in Figure 1.
Figures 2,3, and 4 shown that features like Data plotting, Auto-deletion of old files upon
70% filling of hard-disk on FIFO basis, portability of data files, zoom function for time-
domain plot, conversion of binary data files to ASCII for compatibility to spreadsheets,
trigger based logging etc. have been considered in design of DAS and implemented.

B. Data Analysis Software:
Algorithms have been developed in MATLAB environment for analysis of data acquired
by Fast DAS. The objective of algorithms is to detect any abnormality in motor, its input
power or mechanical load at an early stage. The approach includes comparison of various
signatures during abnormal condition with templates of healthy condition. The templates
have been generated for various material types (R-52, R-60 & Structurals) & loading
conditions (No Load, Single Load & Double Load). The templates include A) Frequency
domain by calculating and plotting Power Spectral Density (after data preprocessing) as
shown in figure 5; B) Time-Frequency domain by calculating and plotting available
frequency components on a time scale as shown in figure 6; and C) Histogram in time
domain etc.
Though, the identification of presence of abnormal condition can be done through the
algorithms developed, the categorization of the faults can be done based on occurrence of
individual faults and corresponding data pattern.
The invention has been described in a preferred form only and many variations may be
made in the invention which will still be comprised within its true spirit. The invention is
not limited to the details cited above. The structure thus conceived is susceptible of
numerous modifications and variations, all the details may furthermore be replaced with
elements having technical equivalence.

WE CLAIM
1. An improved fast on line system for monitoring and diagnosis of health of motors
(DC) and drives used in stands of rolling mills at any instant of time, said system
comprising:
means for acquiring plurality of motor parameters;
means for determining scan rate of said parameters;
means for selecting said scan rate requirements; and
means for analyzing said parameters.
2. The system as claimed in claim 1, wherein said parameters are selectively
armature current, field current, reference voltage, armature voltage, angular speed,
average load, peak load, transient characteristics during impact loading and
unloading and the like.
3. The system as claimed in claim 1, wherein said scan rate ranges from 0.001 to 0.1
million samples per second.
4. The system as claimed in claims 1 and 2 further comprising preliminary diagnosis
utility model for time domain analysis wherein said selected parameters being
analysed to tune said motor drive tuning.
5. The system as claimed in claims 1 and 2 further comprising preliminary diagnosis
utility model for frequency domain analysis wherein said selected parameters
being analysed for diagnosis of said motor drive.
6. An improved fast on line method for monitoring and diagnosis of health of motors
(DC) and drives used in stands of rolling mills at any instant of time, said method
comprising:
acquiring plurality of motor parameters;

determining scan rate of said parameters ;
selecting said scan rate requirements; and
analyzing said parameters.
7. The method as claimed in claim 6, wherein said parameters are selectively
armature current, field current, reference voltage, armature voltage, angular speed,
average load, peak load, transient characteristics during impact loading and
unloading and the like.
8. The method as claimed in claim 6, wherein said scan rate ranges from 0.001 to 0.1
million samples per second.
9. The method as claimed in claims 6 and 7 further comprising preliminary
diagnosis utility model for time domain analysis wherein said selected parameters
being analysed to tune said motor drive tuning.
10. The method as claimed in claims 6 and 7 further comprising preliminary
diagnosis utility model for frequency domain analysis wherein said selected
parameters being analysed for diagnosis of said motor drive.
11. An improved fast on line system and method for monitoring and diagnosis of
health of motors (DC) and drives used in stands of rolling mills at any instant of
time as herein substantially described and illustrated with the accompanying
drawings.

The present invention relates to an improved fast on line system and method for
monitoring and diagnosis of health of motors (DC) and drives used in stands of rolling
mills at any instant of time. The system comprising means for acquiring plurality of
motor parameters, means for determining scan rate of said parameters, means for
selecting said scan rate requirements, and means for analyzing said parameters. The
method comprising acquiring plurality of motor parameters, determining scan rate of said
parameters, selecting said scan rate requirements and analyzing said parameters.