Title of Invention	A METHOD AND SYSTEM OF PERFORMANCE EVALUATION OF ARC WELDING POWER SOURCE
Abstract	A method of performance evaluation of arc welding power source to control quality level of welding power source comprising the steps of measuring the static and dynamic characteristics of welding power source by measuring the open circuit voltage of the welding power source, measuring are current and arc voltage at different current settings of the welding generator, measuring short circuit voltage and current at different current settings of the welding generator, measuring open circuit voltage are current and arc voltage for voltage stabilizing test, testing load of the said generator for a required time, performing energy efficiency test of welding by measuring input voltage and input current and performing testing for dynamic characteristic by obtaining the required arc stability index, arc ignition index and arc spatter index by processing recorded data of welding voltage and welding current at real time through a data acquisition equipment to ensure quality of welding in a continuous manner.

Title of Invention

A METHOD AND SYSTEM OF PERFORMANCE EVALUATION OF ARC WELDING POWER SOURCE

Abstract

A method of performance evaluation of arc welding power source to control quality level of welding power source comprising the steps of measuring the static and dynamic characteristics of welding power source by measuring the open circuit voltage of the welding power source, measuring are current and arc voltage at different current settings of the welding generator, measuring short circuit voltage and current at different current settings of the welding generator, measuring open circuit voltage are current and arc voltage for voltage stabilizing test, testing load of the said generator for a required time, performing energy efficiency test of welding by measuring input voltage and input current and performing testing for dynamic characteristic by obtaining the required arc stability index, arc ignition index and arc spatter index by processing recorded data of welding voltage and welding current at real time through a data acquisition equipment to ensure quality of welding in a continuous manner.

Full Text	FIELD OF INVENTION: This invention relates to method and system of performance evaluation of arc welding power source to ensure quality of welding in a continuous manner. The invention is related to the filed of welding engineering and in particular to the equipments and power supply for arc welding using electric arc as source of melting. More precisely the work is related to power source that supplies electric current to produce electric arc. Since the range of electric current used for welding is in order of few hundreds of amperes and voltage in few tens, power supplies are exclusively made for this purpose. These power supplies are basically a type of machines but specifically made for welding applications. Maintenance of quality of welding without interruption is a prime need to ensure metallurgical and mechanical characteristics of the welding. The present invention has been developed with this aim by evaluating performance of welding power source, which is unique in itself. PRIOR ART Welding power sources are manufactured in many countries. In most of the developed countries like, US, UK, Germany, Japan etc, they have their own standards. The welding power source manufacturers test their power sources as per their countries standards and deliver them to the buyers. Welding power source is equipment that supplies voltage and current to produce electric arc. This arc is a source of heat for melting the materials to be joined. Continuous and stable arc is essential for achieving good quality welding and welding power source generates this arc. Welding equipment manufacturers test the power sources for electrical characteristics and safety requirements. But welding performance test is not carried out generally. Presently there is no method of testing available for characterizing the welding power source for its welding qualities. This invention provide a systematic methodology for testing static and dynamic characteristics of the welding power sources to determine the stability of arc, ignition characteristics of the arc and the spatter characteristics of the arc. Hence the performance of the welding power source is uniquely evaluated by this procedure. The present invention is aimed at developing method for testing of welding power sources to maintain the quality and the performance characteristics of the welding power sources. According to another object of the invention the present invention develops a equipment installation for testing performance characteristics of the welding power sources. Yet another object of the invention is to evaluate dynamic characteristics of the arc welding power source by a data acquisition system to find out arc stability index, arc ignition index and spatter index thus enabling to secure quality level of the arc welding power source. Though this invention is aimed at testing of welding power source, but it can be used for testing any power sources generating arc. Accordingly to the present invention there is provided a method of performance evaluation of arc welding power source to control quality level of welding power source comprising the steps of measuring the static and dynamic characteristics of welding power source by measuring the open circuit voltage of the welding power source, measuring arc current and arc voltage at different current settings of the welding generator, measuring short circuit voltage and current at different current settings of the welding generator, measuring open circuit voltage are current and arc voltage for voltage stabilization test, testing load of the said generator for a required time, performing energy efficiency test of welding by measuring input voltage and input current and performing testing for dynamic characteristic by obtaining the required arc stability index, arc ignition index and spatter index by processing recorded data of welding voltage and welding current at real time through a data acquisition equipment to ensure quality of welding in a continuous manner. The invention also relates to a system for performance evaluation of arc welding power source to control quality level of the welding power source comprising welding power source maintained for load at voltage, between a current sensor (2) to capture welding current to feed it to a microprocessor (4) through a analog signal conditioner (3), the microprocessor being linked to a computer (5) to evaluate the required static and dynamic characteristics of the welding power source, the said dynamic characteristics being obtained as arc stability index, arc ignition index and arc spatter index by processing recorded data of welding voltage and welding current stored in microprocessor (4) at real time to ensure good quality of welding in a continuous manner. A welding power source is utilized for creating welding arc and carrying out welding operation. Since there are many welding power source manufacturers and each one of them claim that their power source is the best power source, a method is formulated to evaluate the performance of these power sources. A method for performance evaluation of arc welding power sources has been developed for evaluation of given welding power source. The static characteristic tests reveal the performance of welding power source at static condition. Dynamic characteristics are evaluated during welding operation. The following procedure is adopted for measurements of static and dynamic characteristics of the arc welding power source. 1. MEASUREMENT OF OPEN CIRCUIT VOLTAGE OF THE WELDING POWER SOURCE For Welding transformer rectifiers and solid state power sources: The open circuit voltage is measured using a voltmeter, for a given power source. The given power source may be of two types. Either it may of constant current type or it may be of constant potential type. CONSTANT CURRENT POWER SOURCE: There will be a single value for the open circuit voltage. This voltage is measured using a voltmeter and noted down. CONSTANT VOLTAGE POWER SOURCES. There will be a provision for variation of the output voltages. Hence this output voltage is varied by changing the appropriate tap changing switch and the different output voltages are measured using a voltmeter and the values are noted down. FOR WELDING GENERATORS: The generator will be having different output voltage for each current settings. Hence the output current is changed for two different ranges and the list output voltage and the current settings are measured using a voltmeter and noted. The open circuit voltage forms a one point on the point on the static characteristics graph. 2.MEASUREMENT OF ARC VOLTAGE & CURRENT AT DIFFERENT CURRENT SETTINGS Welding is carried out at different pre-determined values of current and the value of the welding voltage and welding current are measured using a voltmeter and one ammeter. These data gives one set of operating points for each setting of welding current. Hence the second set of points for the static characteristics graph is obtained. If the welding power source is rated 400 amperes, then there may be four set of points; one set of points at each 100 amps. 3. MEASUREMENT OF SHORT CIRCUIT VOLTAGE AND SHORT CIRCUIT CURRENT AT DIFFERENT CURRENT SETTINGS. The welding electrode is short circuited at different welding current settings and the voltage and current values are measured, using voltmeter and ammeter. The different current settings chosen can be at 100 amps intervals. This gives the third set of points for each current setting. 4. MAINS VOLTAGE STABILISATION TEST In this test input voltage is varied and output parameters such as OCV, arc voltage and arc current are measured. The input voltage can be varied by using a 3 phase auto transformer. We can choose various input voltages like, 360, 380, 400, 420 and 440 volts. For each of this voltage setting the output voltage is measured and a table is prepared. If there is any variation of the input voltage, how much variation is available in the output voltage is known. 5. LOAD TEST In this test a resistive load, which can take up to 600 amps for 10 minutes is connected at the out put terminals of the power source. The capacity of the equipment to deliver the set current continuously for the required time as per the duty cycle rating is tested. No abnormal temperature raise should be seen during this period. 6. ENERGY EFFICIENCY TEST In this test the welding is done at different current settings and the voltage, output current, input voltage and input current are measured. From this data the no load losses and the efficiency of the power source is estimated. Also the open circuit voltage curve is recorded to know the ripple contents of the output. The no load losses are calculated. The efficiency of the power source= output power/ input power x 100% Output power=arc voltage x arc current Input power= 1.732 x Input voltage x Input current x power factor The input power for Zero output current is known as the no load losses. 7. DYNAMIC CHARACTERISTICS TEST In this test, a data acquisition system captures welding voltage and welding current in real time and the recorded data is processed by a computer through a software and the following index values are calculated and displayed along with the wave form recording. a. Arc stability index b. Arc ignition index c. Spatter index The arc stability index value indicates the stability of the arc produced by the power source under test while ensuring the quality of the welding consumable and the welder, The arc ignition index indicates the re-ignition characteristic of the extinguished arc during short circuits. The spatter index is an indication of spatter produced by the arc during welding. All the above tests are to be carried out in addition to the various type routine tests conducted by different manufactures as per relevant standards. The nature of the invention and its performance will be better explained from the following description in relation to non limiting embodiments with reference to the accompanying drawings, in which Figure 1 is the integrated equipment installation for evaluation of welding power source and Figure 2 represents the dynamic characteristics stability index, ignition index and spatter index of the power source in the graph generated in the screen. Figure 3 is another example of the dynamic characteristics of the power source represented by a graph generated in the screen. Figure 3 is another example of the dynamic characteristics of the power source represented by a graph. Dynamic characteristics of welding power source, plays an important role in determining the quality of weld. Arc ignition, arc stability, and spatter level are the factors that influence the dynamic characteristics of the welding power source. It is therefore necessary to record the arc ignition characteristics, arc stability characteristics and spatter characteristics. For this a microprocessor based data acquisition system and signal conditioners have been designed and developed. The acquired data is then transferred to the personal computer and evaluated. Arc stability is required to be evaluated for arc welding. If the arc current is stable and continuous without any variations, then the arc stability can be said to be 100%. But, invariably, due to inherent nature of arc, during welding the arc current value varies and the stability value drops lower than 100%. When the welding is carried out, whenever the wire touches the plate, the arc extinguishes. If the arc re-strikes immediately within 15 milliseconds, then we can say that the arc ignition is very good. It is found that for a very good power source this re-striking time is 3 milliseconds. If within 15 milliseconds, and within 3 to 5 pulses, the arc re-strikes, the welding power source is said to have a good arc re-ignition capability (Fig-3). If there are no current pulses, then there will be no spatter. The extent to which the deviation is there, to that extent we will have spatter. Hence, the spatter index qualifies the welding power source to be spatter free or not. In fig 1, there is a welding power source (1), which is under test. There are two cables connected to positive and negative terminals of the power source. From the positive terminal, the welding electrode holder is connected. The negative cable is connected to the plate (P) to be welding. The welder will take the electrode holder and fix an electrode and strike an arc on the plate and the welder will move the arc thus carrying out the arc welding. The necessary welding voltage and welding current are supplied by this welding power source. In order to sense the welding current, a low resistance shunt (current sensor) is connected along the negative cable, which is transmitting the welding current from the arc to the welding power source. When this current passes through the shunt, a small voltage signal is produced along the shunt which is transmitted to the microprocessor board (4) through the analog conditioner unit (3). The welding voltage is measured by connecting two wires across the two terminals of the power source. This voltage is also sent to the micro processor board through the analog signal conditioner unit. The data acquired during welding is stored in the memory of the microprocessor. From this it is transmitted to the personal computer (5). In the computer, there is a software which will analyse this welding data and give the values of stability index, ignition index and the spatter index along with the display of the arc welding voltage and current waveform. As in Figs. 2 and 3 when the data of the graph is processed using the requisite software, we will get the result of the calculations for the three indices. By this software the indices are calculated and printed along with the graph. The deviation of the current pulse values from the average current value is calculated as a percentage variation of the current pulses. This percentage can be used as a factor for evaluation of the arc stability for a given power source. If the arc stability index is found above 75 percent, the stability and weld bead formation are satisfactory. From the graph in Fig. 3, it is seen that the thyristor controlled power source is having very good arc stability of the order of 95 for a given current value. During the arc welding, whenever the electrode or the welding wire touches the base plate, the arc extinguishes and the current rises high to clear the short circuit and the arc is re-established. This mechanism is called arc ignition or re-ignition. By recording the arc ignition, or the re-ignition, the time required for the arc to reach stability is calculated. During this period there will be a single pulse or a bunch of pulses before the arc is re- established. Alter conducting several experiments, it is concluded that if the pulse duration is less than 5 millisecs or there are less than 4 pulses within a period of 15 millisecs, the arc ignition characteristics are satisfactory. The difference between the average current and the average current pulse gives the factor which is proportional to the spatter level at given current level. If correct value of choke connected in the welding power source is chosen then this factor is minimum. If the difference is zero then it means that there is no current pulse. It has been established after conducting several experiments that if this difference is large then it means that the current pulses are narrow, the choke value is less and there will be excess spatter. If the ratio of average current pulse to average current is more than 2, then heavy spatter occurs. If the power source is properly designed with necessary chokes there will be no spatter. If the choke value is low then there will be excess spatter. For a given spatter index of 1.1 means that the instantaneous variations in the arc currents are less than 20 percent. Hence in this manner all the information about the arc namely arc ignition, arc stability and arc spatter are evaluated from the dynamic characteristics of the power sources. The invention described as herein above is claimed is in relation to non- limiting embodiments as defined by accompanying claims. WE CLAIM: 1. A method of performance evaluation of arc welding power source to control quality level of welding power source comprising the steps of measuring the static and dynamic characteristics of welding power source by measuring the open circuit voltage of the welding power source, measuring arc current and arc voltage at different current settings of the welding generator, measuring short circuit voltage and current at different current settings of the welding generator, measuring open circuit voltage are current and arc voltage for voltage stabilization test, testing load of the said generator for a required time, performing energy efficiency test of welding by measuring input voltage and input current and performing testing for dynamic characteristic by obtaining the required arc stability index, arc ignition index and arc spatter index by processing recorded data of welding voltage and welding current at real time through a data acquisition equipment to ensure quality of welding in a continuous manner. 2. A method as claimed in claim 1 wherein the static characteristics of welding power source is measured when the welding power source remains at static condition and the dynamic characteristics of welding power source is evaluated for determing quality of weld. 3. A method as claimed in claim in claim 3 wherein the dynamic characteristics are arc ignition characteristics, arc stability characteristics and arc spatter characteristics and the said characteristics are evaluated by determining arc ignition index, arc stability index and spatter index. 4. A method as clamied in claim 5 wherein the said indexes are evaluated in a personal computer microprocessor based data acquisition system and signal conditioners. 5. A method as claimed in claim 1 wherein for evaluation of arc ignition index of the arc the reignition of arc is maintained at 4 pulses within 15 milliseconds. 6. The method as claimed in claim 10 wherein arc stability index is maintained between 75 to 95 for a given current value. 7. A method as claimed in claim wherein to maintain spatter free characteristic of the welding power source the spatter index is maintained at 1.1 8. A system for performance evaluation of arc welding power source to control quality level of welding power source comprising welding power source (1) maintained for load (t) at voltage (v), between a current sensor (2) to capture welding current to feed it to a microprocessor (4) through a analog signal conditioner (3), the microprocessor being linked to a computer (5) to evaluate the required static and dynamic characteristics of the welding power source, said dynamic characteristic being obtained as arc stability index by processing recorded data of microprocessor (4) at real time to ensure quality of welding in a continuous manner. 9. A method of performance evaluation of arc welding power source to control level of welding power source as herein described and illustrated with references to accompanying drawings. 10. A system for evaluations of arc welding power source to control quality level of welding power source as herein described and illustrated with reference to accompanying drawings. A method of performance evaluation of arc welding power source to control quality level of welding power source comprising the steps of measuring the static and dynamic characteristics of welding power source by measuring the open circuit voltage of the welding power source, measuring are current and arc voltage at different current settings of the welding generator, measuring short circuit voltage and current at different current settings of the welding generator, measuring open circuit voltage are current and arc voltage for voltage stabilizing test, testing load of the said generator for a required time, performing energy efficiency test of welding by measuring input voltage and input current and performing testing for dynamic characteristic by obtaining the required arc stability index, arc ignition index and arc spatter index by processing recorded data of welding voltage and welding current at real time through a data acquisition equipment to ensure quality of welding in a continuous manner.

Full Text

FIELD OF INVENTION:
This invention relates to method and system of performance evaluation of
arc welding power source to ensure quality of welding in a continuous
manner.
The invention is related to the filed of welding engineering and in particular
to the equipments and power supply for arc welding using electric arc as
source of melting. More precisely the work is related to power source that
supplies electric current to produce electric arc. Since the range of electric
current used for welding is in order of few hundreds of amperes and voltage
in few tens, power supplies are exclusively made for this purpose. These
power supplies are basically a type of machines but specifically made for
welding applications.
Maintenance of quality of welding without interruption is a prime need to
ensure metallurgical and mechanical characteristics of the welding. The
present invention has been developed with this aim by evaluating
performance of welding power source, which is unique in itself.
PRIOR ART
Welding power sources are manufactured in many countries. In most of the
developed countries like, US, UK, Germany, Japan etc, they have their own
standards. The welding power source manufacturers test their power sources
as per their countries standards and deliver them to the buyers.
Welding power source is equipment that supplies voltage and current to
produce electric arc. This arc is a source of heat for melting the materials to
be joined. Continuous and stable arc is essential for achieving good quality
welding and welding power source generates this arc. Welding equipment
manufacturers test the power sources for electrical characteristics and safety
requirements. But welding performance test is not carried out generally.
Presently there is no method of testing available for characterizing the
welding power source for its welding qualities. This invention provide a
systematic methodology for testing static and dynamic characteristics of the
welding power sources to determine the stability of arc, ignition
characteristics of the arc and the spatter characteristics of the arc. Hence the
performance of the welding power source is uniquely evaluated by this
procedure.
The present invention is aimed at developing method for testing of welding
power sources to maintain the quality and the performance characteristics of
the welding power sources.
According to another object of the invention the present invention develops
a equipment installation for testing performance characteristics of the
welding power sources.
Yet another object of the invention is to evaluate dynamic characteristics of
the arc welding power source by a data acquisition system to find out arc
stability index, arc ignition index and spatter index thus enabling to secure
quality level of the arc welding power source.
Though this invention is aimed at testing of welding power source, but it can
be used for testing any power sources generating arc.
Accordingly to the present invention there is provided a method of
performance evaluation of arc welding power source to control quality level
of welding power source comprising the steps of measuring the static and
dynamic characteristics of welding power source by measuring the open
circuit voltage of the welding power source, measuring arc current and arc
voltage at different current settings of the welding generator, measuring
short circuit voltage and current at different current settings of the welding
generator, measuring open circuit voltage are current and arc voltage for
voltage stabilization test, testing load of the said generator for a required
time, performing energy efficiency test of welding by measuring input
voltage and input current and performing testing for dynamic characteristic
by obtaining the required arc stability index, arc ignition index and spatter
index by processing recorded data of welding voltage and welding current at
real time through a data acquisition equipment to ensure quality of welding
in a continuous manner.
The invention also relates to a system for performance evaluation of arc
welding power source to control quality level of the welding power source
comprising welding power source maintained for load at voltage, between a
current sensor (2) to capture welding current to feed it to a microprocessor
(4) through a analog signal conditioner (3), the microprocessor being linked
to a computer (5) to evaluate the required static and dynamic characteristics
of the welding power source, the said dynamic characteristics being obtained
as arc stability index, arc ignition index and arc spatter index by processing
recorded data of welding voltage and welding current stored in
microprocessor (4) at real time to ensure good quality of welding in a
continuous manner.
A welding power source is utilized for creating welding arc and carrying out
welding operation. Since there are many welding power source
manufacturers and each one of them claim that their power source is the best
power source, a method is formulated to evaluate the performance of these
power sources.
A method for performance evaluation of arc welding power sources has been
developed for evaluation of given welding power source.
The static characteristic tests reveal the performance of welding power
source at static condition. Dynamic characteristics are evaluated during
welding operation. The following procedure is adopted for measurements of
static and dynamic characteristics of the arc welding power source.
1. MEASUREMENT OF OPEN CIRCUIT VOLTAGE OF THE
WELDING POWER SOURCE
For Welding transformer rectifiers and solid state power sources:
The open circuit voltage is measured using a voltmeter, for a given power
source. The given power source may be of two types. Either it may of
constant current type or it may be of constant potential type.
CONSTANT CURRENT POWER SOURCE: There will be a single value
for the open circuit voltage. This voltage is measured using a voltmeter and
noted down.
CONSTANT VOLTAGE POWER SOURCES. There will be a provision for
variation of the output voltages. Hence this output voltage is varied by
changing the appropriate tap changing switch and the different output
voltages are measured using a voltmeter and the values are noted down.
FOR WELDING GENERATORS:
The generator will be having different output voltage for each current
settings. Hence the output current is changed for two different ranges and
the list output voltage and the current settings are measured using a
voltmeter and noted.
The open circuit voltage forms a one point on the point on the static
characteristics graph.
2.MEASUREMENT OF ARC VOLTAGE & CURRENT AT
DIFFERENT CURRENT SETTINGS
Welding is carried out at different pre-determined values of current and the
value of the welding voltage and welding current are measured using a
voltmeter and one ammeter. These data gives one set of operating points for
each setting of welding current. Hence the second set of points for the static
characteristics graph is obtained. If the welding power source is rated 400
amperes, then there may be four set of points; one set of points at each 100
amps.
3. MEASUREMENT OF SHORT CIRCUIT VOLTAGE AND SHORT
CIRCUIT CURRENT AT DIFFERENT CURRENT SETTINGS.
The welding electrode is short circuited at different welding current settings
and the voltage and current values are measured, using voltmeter and
ammeter. The different current settings chosen can be at 100 amps intervals.
This gives the third set of points for each current setting.
4. MAINS VOLTAGE STABILISATION TEST
In this test input voltage is varied and output parameters such as OCV, arc
voltage and arc current are measured. The input voltage can be varied by
using a 3 phase auto transformer. We can choose various input voltages
like, 360, 380, 400, 420 and 440 volts. For each of this voltage setting the
output voltage is measured and a table is prepared. If there is any variation
of the input voltage, how much variation is available in the output voltage is
known.
5. LOAD TEST
In this test a resistive load, which can take up to 600 amps for 10 minutes is
connected at the out put terminals of the power source. The capacity of the
equipment to deliver the set current continuously for the required time as per
the duty cycle rating is tested. No abnormal temperature raise should be
seen during this period.
6. ENERGY EFFICIENCY TEST
In this test the welding is done at different current settings and the voltage,
output current, input voltage and input current are measured. From this data
the no load losses and the efficiency of the power source is estimated. Also
the open circuit voltage curve is recorded to know the ripple contents of the
output. The no load losses are calculated.
The efficiency of the power source= output power/ input power x 100%
Output power=arc voltage x arc current
Input power= 1.732 x Input voltage x Input current x power factor
The input power for Zero output current is known as the no load losses.
7. DYNAMIC CHARACTERISTICS TEST
In this test, a data acquisition system captures welding voltage and welding
current in real time and the recorded data is processed by a computer
through a software and the following index values are calculated and
displayed along with the wave form recording.
a. Arc stability index
b. Arc ignition index
c. Spatter index
The arc stability index value indicates the stability of the arc produced by the
power source under test while ensuring the quality of the welding
consumable and the welder, The arc ignition index indicates the re-ignition
characteristic of the extinguished arc during short circuits. The spatter index
is an indication of spatter produced by the arc during welding.
All the above tests are to be carried out in addition to the various type
routine tests conducted by different manufactures as per relevant standards.
The nature of the invention and its performance will be better explained
from the following description in relation to non limiting embodiments with
reference to the accompanying drawings, in which
Figure 1 is the integrated equipment installation for evaluation of welding
power source and
Figure 2 represents the dynamic characteristics stability index, ignition index
and spatter index of the power source in the graph generated in the screen.
Figure 3 is another example of the dynamic characteristics of the power
source represented by a graph generated in the screen.
Figure 3 is another example of the dynamic characteristics of the power
source represented by a graph.
Dynamic characteristics of welding power source, plays an important role in
determining the quality of weld. Arc ignition, arc stability, and spatter level
are the factors that influence the dynamic characteristics of the welding
power source. It is therefore necessary to record the arc ignition
characteristics, arc stability characteristics and spatter characteristics. For
this a microprocessor based data acquisition system and signal conditioners
have been designed and developed. The acquired data is then transferred to
the personal computer and evaluated.
Arc stability is required to be evaluated for arc welding. If the arc current is
stable and continuous without any variations, then the arc stability can be
said to be 100%. But, invariably, due to inherent nature of arc, during
welding the arc current value varies and the stability value drops lower than
100%.
When the welding is carried out, whenever the wire touches the plate, the arc
extinguishes. If the arc re-strikes immediately within 15 milliseconds, then
we can say that the arc ignition is very good. It is found that for a very good
power source this re-striking time is 3 milliseconds. If within 15
milliseconds, and within 3 to 5 pulses, the arc re-strikes, the welding power
source is said to have a good arc re-ignition capability (Fig-3).
If there are no current pulses, then there will be no spatter. The extent to
which the deviation is there, to that extent we will have spatter. Hence, the
spatter index qualifies the welding power source to be spatter free or not.
In fig 1, there is a welding power source (1), which is under test. There are
two cables connected to positive and negative terminals of the power source.
From the positive terminal, the welding electrode holder is connected. The
negative cable is connected to the plate (P) to be welding. The welder will
take the electrode holder and fix an electrode and strike an arc on the plate
and the welder will move the arc thus carrying out the arc welding.
The necessary welding voltage and welding current are supplied by this
welding power source. In order to sense the welding current, a low
resistance shunt (current sensor) is connected along the negative cable,
which is transmitting the welding current from the arc to the welding power
source. When this current passes through the shunt, a small voltage signal is
produced along the shunt which is transmitted to the microprocessor board
(4) through the analog conditioner unit (3). The welding voltage is
measured by connecting two wires across the two terminals of the power
source. This voltage is also sent to the micro processor board through the
analog signal conditioner unit.
The data acquired during welding is stored in the memory of the
microprocessor. From this it is transmitted to the personal computer (5). In
the computer, there is a software which will analyse this welding data and
give the values of stability index, ignition index and the spatter index along
with the display of the arc welding voltage and current waveform.
As in Figs. 2 and 3 when the data of the graph is processed using the
requisite software, we will get the result of the calculations for the three
indices. By this software the indices are calculated and printed along with
the graph.
The deviation of the current pulse values from the average current value is
calculated as a percentage variation of the current pulses. This percentage
can be used as a factor for evaluation of the arc stability for a given power
source. If the arc stability index is found above 75 percent, the stability and
weld bead formation are satisfactory. From the graph in Fig. 3, it is seen that
the thyristor controlled power source is having very good arc stability of the
order of 95 for a given current value.
During the arc welding, whenever the electrode or the welding wire touches
the base plate, the arc extinguishes and the current rises high to clear the
short circuit and the arc is re-established. This mechanism is called arc
ignition or re-ignition. By recording the arc ignition, or the re-ignition, the
time required for the arc to reach stability is calculated. During this period
there will be a single pulse or a bunch of pulses before the arc is re-
established. Alter conducting several experiments, it is concluded that if the
pulse duration is less than 5 millisecs or there are less than 4 pulses within a
period of 15 millisecs, the arc ignition characteristics are satisfactory.
The difference between the average current and the average current pulse
gives the factor which is proportional to the spatter level at given current
level. If correct value of choke connected in the welding power source is
chosen then this factor is minimum. If the difference is zero then it means
that there is no current pulse. It has been established after conducting
several experiments that if this difference is large then it means that the
current pulses are narrow, the choke value is less and there will be excess
spatter. If the ratio of average current pulse to average current is more than
2, then heavy spatter occurs. If the power source is properly designed with
necessary chokes there will be no spatter. If the choke value is low then
there will be excess spatter.
For a given spatter index of 1.1 means that the instantaneous variations in
the arc currents are less than 20 percent.
Hence in this manner all the information about the arc namely arc ignition,
arc stability and arc spatter are evaluated from the dynamic characteristics of
the power sources.
The invention described as herein above is claimed is in relation to non-
limiting embodiments as defined by accompanying claims.
WE CLAIM:
1. A method of performance evaluation of arc welding power source to
control quality level of welding power source comprising the steps of
measuring the static and dynamic characteristics of welding power
source by measuring the open circuit voltage of the welding power
source, measuring arc current and arc voltage at different current
settings of the welding generator, measuring short circuit voltage and
current at different current settings of the welding generator,
measuring open circuit voltage are current and arc voltage for voltage
stabilization test, testing load of the said generator for a required time,
performing energy efficiency test of welding by measuring input
voltage and input current and performing testing for dynamic
characteristic by obtaining the required arc stability index, arc ignition
index and arc spatter index by processing recorded data of welding
voltage and welding current at real time through a data acquisition
equipment to ensure quality of welding in a continuous manner.
2. A method as claimed in claim 1 wherein the static characteristics of
welding power source is measured when the welding power source
remains at static condition and the dynamic characteristics of welding
power source is evaluated for determing quality of weld.
3. A method as claimed in claim in claim 3 wherein the dynamic
characteristics are arc ignition characteristics, arc stability
characteristics and arc spatter characteristics and the said
characteristics are evaluated by determining arc ignition index, arc
stability index and spatter index.
4. A method as clamied in claim 5 wherein the said indexes are
evaluated in a personal computer microprocessor based data
acquisition system and signal conditioners.
5. A method as claimed in claim 1 wherein for evaluation of arc ignition
index of the arc the reignition of arc is maintained at 4 pulses within
15 milliseconds.
6. The method as claimed in claim 10 wherein arc stability index is
maintained between 75 to 95 for a given current value.
7. A method as claimed in claim wherein to maintain spatter free
characteristic of the welding power source the spatter index is
maintained at 1.1
8. A system for performance evaluation of arc welding power source to
control quality level of welding power source comprising welding
power source (1) maintained for load (t) at voltage (v), between a
current sensor (2) to capture welding current to feed it to a
microprocessor (4) through a analog signal conditioner (3), the
microprocessor being linked to a computer (5) to evaluate the required
static and dynamic characteristics of the welding power source, said
dynamic characteristic being obtained as arc stability index by
processing recorded data of microprocessor (4) at real time to ensure quality
of welding in a continuous manner.
9. A method of performance evaluation of arc welding power source to
control level of welding power source as herein described and
illustrated with references to accompanying drawings.
10. A system for evaluations of arc welding power source to control
quality level of welding power source as herein described and
illustrated with reference to accompanying drawings.

A method of performance evaluation of arc welding power source to control
quality level of welding power source comprising the steps of measuring the
static and dynamic characteristics of welding power source by measuring the
open circuit voltage of the welding power source, measuring are current and
arc voltage at different current settings of the welding generator, measuring
short circuit voltage and current at different current settings of the welding
generator, measuring open circuit voltage are current and arc voltage for
voltage stabilizing test, testing load of the said generator for a required time,
performing energy efficiency test of welding by measuring input voltage and
input current and performing testing for dynamic characteristic by obtaining
the required arc stability index, arc ignition index and arc spatter index by
processing recorded data of welding voltage and welding current at real time
through a data acquisition equipment to ensure quality of welding in a
continuous manner.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=VoiGCPSHcn+5eiRKqDncJw==&loc=wDBSZCsAt7zoiVrqcFJsRw==

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Patent Number

279803

Indian Patent Application Number

246/KOL/2005

PG Journal Number

05/2017

Publication Date

03-Feb-2017

Grant Date

31-Jan-2017

Date of Filing

30-Mar-2005

Name of Patentee

BHARAT HEAVY ELECTRICALS LIMITED

Applicant Address

REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, D J BLOCK 3RD FLOOR, KARUNAMOYEE, SALT LAKE CITY, KOLKATA-700091, HAVING ITS REGISTERED OFFICE AT BHEL HOUSE, SIRI FORT, NEW DELHI-110049

Inventors:

#	Inventor's Name	Inventor's Address
1	VELANI RATCHANNIYA SAMUEL	BHEL TRICHY
2	SIVASANKARAN MANOHARAN	BHEL, TRICHY
3	VICTOR PAUL DANIAL	BHEL, TRICHY

PCT International Classification Number

B23K 9/10

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA