FIELD OF INVENTION:
The invention relates to an automated testing system, which is an integrated system for testing the single-phase Inverter and the UPS systems. The present invention proposes an apparatus for controlling the testing of inverter/ UPS with a programmable logic controller that includes a plurality of inputs and a plurality of outputs.
In a production facility where hundreds and thousands of units are produced to meet the demand of the market, it is a big challenge to maintain the standard and quality of the final products. A testing standardization needs to be maintained in order to deliver a quality product which meets its stated specification.
However, it requires a number of skilled operators with in-depth knowledge of the testing process and product to maintain such standards. Still because of the nature of work which involves repetitive steps of testing a possibility of human error or negligence can not be neglected. Along with this the complete process is dependent on the ability and skill level of the operator. Therefore, considering the need of the highly skilled operator all the time and the potential hazard that any power electronics equipment carry with it, it becomes quite essential to ease the dependence on the manual labor by creating an automated testing system to test the products without any human intervention.
RELATED ART:
US patent 6,262,569 and 5,821,742 discloses a portable energy meter test system for testing energy meters and other related instrumentation on-site. The test system utilizes waveform generating circuitry to generate and transmit electrical waveforms to an energy meter to be tested, and sensing circuitry for sensing electrical characteristics corresponding to the transmitted electrical waveform. The test system includes a processor for evaluation and control of the testing procedure. A graphic touch screen is coupled to the processor for displaying information about the energy meter and the test options to the user and it allows the user to control the testing process by touching the screen. This invention specifically deals with the testing system for the energy meter under user controlled test conditions.
US patent 7,343,558 discloses methods and systems for measuring a device under test. A first test instrument is connected to a programmable logic device, which is configured to comply with the interface specifications of the first test instrument. A second test instrument, having interface specifications that are different from the interface specifications of the first test instrument, is connected to the programmable logic device. The programmable logic device is configured to comply with the interface specifications of the second test instrument. This invention deals with the test setup for testing electronic devices such as an application specific integrated circuit (ASIC), a system on chip (SOC), a microprocessor or any other semiconductor device.
US Patent 6,035,263 and Publication No KR100294204B shows a device for testing a product. It includes a programmable logic controller (PLC) for loading or unloading a mechanical part of a test target product at a regular position suitable to a test environment; a personal computer (PC) for performing bi-directional communication

through communication ports by generating a test control signal in order to test the test target product. This invention discloses a system for testing a product using the bidirectional communication port of personal computer. In this patent computer is an integral and important part of the system, which controls the complete process and increases cost of the system.
US Patent 6,064,948 discloses a tester to be used with a device under test. It includes a processor, a signal timing editor to create representations of signal waveforms and associated times and a test program executable on the processor that schedules events based on information from the signal timing editor. The test program schedules different delays for the events to compensate for variations in time delays between different signals coupled to the device under test. This system is specifically designed for the testing of electronic circuits such as DRAMS, SDRAM etc. It does not test the complete product, instead it tests memory devices with the help of programmable logic devices.
US Patent 6,324,485 describes an application specific automated test equipment system for source synchronous bus interface devices. A native interface board is provided to interface an automated test unit and a device under test. The invention relates to the automated test equipment and more specifically to an apparatus for testing source synchronous bus interface devices. This patent uses source synchronous bus interface RAMBUS in which clock signal is transmitted alongside data to create a point-to-point interface to test integrated circuits device. This patent is specific to the testing equipment of integrated circuit devices and does not test a complete product.
In US publication No 20070101215, an intertwined test specification (ITTS) is used for controlling Automated Test Equipment (ATE) to apply a sequence of stimulus signals to a device under test (DUT) during a stimulus run and to validate returned response signals during a validation run. The ITTS has response validation scripts intertwined with stimulus invoking scripts where the response validation scripts are conditionally executed during the validation run but not during the stimulus invoking run. Response signals are logically associated with unique stimulus identification codes so that appropriate response signals can be matched with corresponding validation scripts even if the response signals are returned out-of-order to the ATE or to a response-logging unit interposed between the ATE and the DUT. The invention relates to the automated testing of devices specifically to the device under test that can output responses in an order other than that in which corresponding input stimuli were sent.
US publication No 20070291906 discloses a test system. It comprises of a test processor, which determines an operational status, such as a fault status, for a unit under test. This invention deals with the testing of electronic boards or assemblies following TCA (telecom computing architecture). Therefore, it only targets to specific type of systems in telecom.
Reference is to be made to an article by Hewson et.al, IEEE, Feb 2000. This article describes the design and development of a high-performance test facility to be used for the off-site commissioning and performance

evaluation of commercial AC inverters. This article describes a test facility. It comprises of a dynamic mechanical loading rig capable of emulating both linear and non-linear systems. Such a facility provides platform for commissioning an inverter-motor drive combination for a specific application before transporting the drive to site. Alternatively, the facility can be employed as a demanding programmable loading system for research and development projects in novel non-linear speed and position control algorithms. This article deals with the testing set up for motor drives inverter by testing it for different type of load characteristics generated by a torque controlled dynamometer load emulator. This is specific to the motor drives and their testing.
With all the above discussed restrictions or limitations it is required to have an improved testing system for testing inverter and ups systems with PLC based control and various sensing circuits. The present invention is provided with a PLC based control card integrated with variable voltage and frequency source and programmable load for testing inverter and ups systems. The specification and the type of the test to be carried out according to the product under test are fed to the system through computer/ single board computer /touch screen the control section process the information and then executes the testing. At the end of testing the system generates a detailed report of the test carried out and the specification against which the system was tested. Then, this information can be transferred to the PC locally or remotely. PC records this information and generates reports. Unlike already available automation techniques which are complex in nature and require skilled operators to carry out the process, its functionality is very simple and doesn't require a highly skilled operator. The best an operator is required to do is to make a few connections and start the process. The rest is done by the Unit itself.
OBJECT OF THE INVENTION
It is the primary object of the present invention to overcome above said problems and limitations. More specifically, it is an objective of the present invention to provide a performance analyzer and failure detection system for an inverter/UPS, capable of detecting a failure, measuring other parameters and generating reports.
Another object of the present invention is to propose an improved and efficient integrated system for testing single-phase inverter and UPS systems.
Still another object of the invention is to reduce the cycle time to carry out the functional testing of a single product and standardize the testing process.
Yet another object of the present invention is to give a better insight towards the complete record of number of products tested during a day by provide the data logging that ensures the availability of the data for all the tested products, that can help in improving the production process.
Yet another object of the present invention is to propose a novel PLC based system along with different kind of sensors such as CT's (current transformer) and PT's (potential transformer) and meters such as AC voltmeters frequency meters, THD meters, input output VA and Watt meters, power factor meters and different kind of loads such as resistive load, inductive load and rectifier non linear load used in testing, for controlling,

performing the testing along with an integrated computer with dedicated software for monitoring and report generation.
Another object of the present invention is to provide user programmable settings for controlling the testing procedure timings and testing set points through a configuration file. It provides programmable settings for specification for which the product is to be
tested.
Still another object of the present invention is to reduce human intervention in the testing of the system so that the error due to human negligence can be eliminated and the testing can be made independent of the operator's competence. Since the technical specifications of the products are already fed in the Programmable logic control inside this embedded system, therefore there is no control of the operator on the testing process and the chances of the operator missing/skipping any process is eliminated. The system also reduces the testing time to increase production efficiency.
Yet another object of the present invention is to connect different types of loads to the product under test for complete testing with the help of PLC. The various loads include resistive load, inductive load and rectifier load. It also provides user programmable settings for various configuration and value of load to be connected to the products.
Further object of the present invention is to generate a complete report of the test conducted and store that report in a printable format with the help of a dedicated monitoring and controlling software provided along with the system.
Yet another object of the present invention is to provide remote monitoring and control facility of the testing through Ethernet and wireless connectivity etc. The testing can also be monitored and controlled remotely with the help of internet.
STATEMENT OF INVENTION
According to this invention there is provided an automated testing system comprising of a programmable logic controller based main control panel integrated with a plurality of meters to read input/output parameters, a controlled variable voltage and frequency source connected to product under test, output of which is connected at load feeder where loads according to the test and rating of the product under test are connected.
SUMMARY OF THE INVENTION
These and other objectives of this invention are accomplished by providing a PLC based automated testing system which includes PLC based measurement and controlling system along with combination of various types of load and a computer for monitoring and controlling. The user first set up the system according to the requirement of the testing which is followed by testing of product under test by the system automatically.
The system is designed for the testing of the inverter and UPS systems. All the system parameters such as AC input output voltage, input output current, frequency and total harmonic distortion for voltages, battery voltage, charging current, discharging current,

system efficiency, power factor, overload time and short circuit are measured and displayed as well as logged in the test report.
The product testing takes place in sequential manner where different test conditions are applied to the product and its output parameters are measured and compared with the expected range of values in that particular condition.
Various control schemes are used for performing tests such as mains mode test, mains high cut, mains low cut, no load test, full load test, over load test and short circuit test.
In an embodiment of the present invention, the variable mains source is obtained from the PLC based servo control. The main control panel sends the command to servo control to set the required voltage to the product.
The complete testing can be supervised centrally and there is no need to supervise the production lines individually and in person. The whole process can be monitored remotely on a single/multiple PCs depending upon the communication protocol selected.
In an embodiment of the present invention, PC receives the data from the system through RS 232/RS 485/USB and other user interface devices.
The foregoing as well as additional objects features and advantages of the invention will be more readily apparent from the drawings and their detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig 1 shows a block diagram of an embodiment of an automated testing system for
inverter/UPS according to the present invention;
Fig 2 shows the overall view of the functionality of the PLC section of the Automated
Testing system
Fig 3 depicts the interface of the system with the PC.
Fig 4 depicts the interface of the system with the 'product under testing'.
Fig 5 shows the interface of the system with the Load bank.
Fig 6 shows the circuit diagram of the PLC based servo control section of the system.
Fig 7 depicts the charging current sense section of the product under test.
Fig 8 depicts the load current sense section of the product under test.
Fig 9 depicts the input and output AC current sense section of the system.
Fig 10 depicts the Supply section of the system.
Fig 11 A- 11 G shows various testing schemes.
FIG. 12 depicts a flow chart outlining the software program procedures for a typical visit
to the computer by the user, according to the present invention;

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
Reference may be made to FIG. 1 indicating a block diagram showing overall view of the functionality of the system i.e. PLC based Testing system 1 and its interface with the product under testing & the computer. The block diagram of the system shows the important sub systems. The main control panel 2 controls the complete operation of the system. It is based on the advanced PLC technology. Various meters are also integrated into main panel to read the input/output parameters. A controlled variable voltage and frequency source 3 is used as input source to the product under test 4. The main control panel 2 also controls this source. The output of the product under test is connected at the load feeder 5 where loads according to the test and rating of the product under test 4 are connected. The main control panel 2 controls how much and what type of load is to be connected to the system under test 4. The main control panel 2 reads all the input and output parameters of the product under test 4 and displays it on the connected computer 6.
The main control panel 2 then compares the products 4 output with the reference output and makes a decision if the product under test 4 is performing correctly or not. The user according to the product under test 4 can program the reference signals. The system also takes care of the charging of the battery bank 7 connected so that it remains in good condition for the product testing.
Fig 2 gives the overall view of the functionality of the PLC section of the system i.e. Automated Testing system. The programmable logic controller 201 directs the process through signals at the outputs in response to input signals at the inputs.
The supply section 202 consists of a switch mode power supply with input as mains supply. It provides supply to all the sections of the system. The main PLC block 201 is interfaced with the Input modules 203 for interfacing with input parameters and directing the output for controlling the testing operation. The analog signal-conditioning block 204 consists of circuits for interfacing various input signals of the system such as input output AC currents, voltage, battery voltage and current, input output frequency etc. The graphic terminal screen 205 is provided to display the test results and various user configurable test settings. The main PLC block 201 is also interfaced with the various power meters 206 to measure input and output power for system efficiency calculation as well as Total harmonic distortion calculation. Based on the input signals and test settings, the main PLC controls 201 the servo controlled voltage source 207 and the load block 208 through input output modules 203 for various test condition.
All the test information is also displayed on the connected desktop computer, SBS (single board computer) or any other smart panel 209 where it is stored in a database and final test report is generated for the testing carried out.
Now, reference may be made to Fig 3 depicting the interface of the system with the PC 209. The PC 209 receives the data from the system through RS 232/RS 485/USB interface. With the help of the Graphical User Interface, the operator observes the system parameters and status. The parameters like I/P & O/P voltages, THD, frequencies and ac

current, battery parameters like battery voltage, charging & discharging current, O/P parameters like percentage of load and total power of system in VA and watts are displayed on the GUI screen 301. Also, all the parameters which comprise the technical specifications of the said systems e.g. input voltage, frequency, charging current and inverter parameters like no load voltage & current, full load voltage & current, overload voltage and current, O/P frequency, protection conditions like short circuit are displayed on the screen along with their status. In case of any communication failure, there would be a message on the screen indicating such notifications. This interface also lets the operator to give the print command to the control section which further dictates the printer to generate a test report of the tested product. The test report thus generated can be sent along with the tested product. A example of the test report generated is shown in Fig 13. A copy of this can be retained for production record. The data sent to the PC along with the 'product under testing' status and the overall status of the products tested so far, gets stored in a file and in database with the product's name & tested date in the PC 209 for further analysis as well as a record purpose. Using a bar code reader, the bar code printed on the product may also be read in so that it can be compared against the product results at a later stage. The system also has a provision of web based remote monitoring and control of the testing process.
Fig 4 depicts the interface of the system with the 'product under testing' 4. The 'product under testing' is connected to the battery bank 7 for its operation whilst the main is supplied from servo controlled voltage source/ variable voltage frequency source 3. The main PLC module 201 monitors the input and output parameters through input output modules connected 203. The analog signals are passed through interfacing and signal conditioning block 204 to the I/O modules 203. The output of the 'product under testing' 4 is connected to the load block 5 with the help of contactors. The Main PLC 201 is configured according to the user-configured settings for the product under test 4. Depending on the type and capacity of the product, it loads the 'product under testing' 4 to carry out the testing.
The load block 5 is connected to the I/O module 203 and a proper load is applied by operating a combination of relay in the load bank 5.
Fig 5 depicts the interface of the system with the Load bank 5. The load bank comprises of several types of loads i.e. resistive load 501, Inductive load 502 and rectifier load 503. It is connected to the main PLC 201 through I/O module 203. Depending on the type of the 'product under testing' 4, its rating and type of tests specified in the configuration. A combination of relays 504 are operated to configure the amount of load to be connected at the output of the product 4 with the help of contactors. The system selects the desired type and amount of load 5 related to the particular type of product 4.
The main PLC block 201 through the analog signal conditioning circuit interfaced 204 to the I/O module 203 monitors the output parameters of the product 4.
Fig 6 depicts the servo control variable voltage source 207, which acts as the mains

source for the product under test 4. The main PLC 201 control board reads the desired voltage levels to be applied for various tests from the configuration settings in the software and sets the output voltage of the servo 207 accordingly.
Fig 7 depicts charging discharging current sense for the system. The current is measured with the help of a shunt 701 in series of the battery wire 702. Voltage drop across the shunt 701 is amplified using an mV/V 703 amplifier and given to the PLC 201 and also displayed on the meter.
Fig 8 depicts the input AC current sense section. The ac currents are measured with the help of current transformers (CT) connected at the input of the system.
Fig 9 depicts the load current sense. The load AC current is measured with the current transformer (CT) 801 connected at the output of the system.
Fig 10 depicts the supply section of the system, which consists of a switch mode power supply 1001 which is powered from the mains supply 1002. Power supply for all the components of the system is generated from this supply.
Fig 11 A is a scheme for AC High/Low cut and recovery. In this test the low and high cut and recovery of the product under test 4 are verified.
To achieve this, the main control panel 201 sends the command for gradually lowering the voltage of the variable voltage source 3 that is connected at the input of the product under test 4. The product under test 4 is monitored to check at what input voltage it switches from the mains mode to the inverter mode. After this condition is detected the voltage of the variable source3 is increased gradually and the voltage at which the product 4 recovers and switches back to mains mode is recorded. If this low cut and recovery voltage are within the specified range then the product 4 is passed else or it is declared as failed in low cut and recovery.
Similarly, the high cut and recovery of the product 4 are tested. First the voltage of the variable source 3 in increased and the voltage at which the inverter goes into high cut and switches into inverter mode is recorded, after that the voltage is reduced gradually and the voltage at which the product recovers from high cut and switches back to mains mode is recorded as high cut recovery voltage. These values are then compared with the specified range of values to test the product.
Fig 11B is a scheme for measuring charging current. The charging current to the battery when the product is operating in mains mode is measured with the help of current sensors 1101. The main control system 201 first supplies the mains to the product under testing 4, when the charging current stabilizes after some time the current is monitored continuously, if it remains within the specified limits the charging current is declared as passed and next testing sequence is started.

Fig 11C is a scheme for checking minimum and maximum output voltage and the frequency in inverter mode at full load. The output voltage and frequency of the inverter 4 at full load are measured by operating the product in inverter mode. The main control unit 201 removes the input mains from the product under test 4 so that the product 4 operates in inverter mode. The output load is increased to the specified value for the products 4 full load then the output voltage and the frequency is recorded. These parameters are now compared with the specified limit of the voltage and frequency for asserting whether the product 4 is ok or not.
Fig 11 D is a scheme for testing at full load and total harmonic distortion (THD) calculation. The THD of the output of the product is also measured in order to find if there are any harmonics present in the output of the inverter. The product is operated in the inverter mode and a specified full load 5 is applied at the output of the product 4. The output voltage of the product is monitored and total harmonic distortion is calculated. The test can be performed on different types lo load such as resistive load 501, inductive load 502, rectifier load 503 or any combination of the three loads so that the output distortion of the product can be tested in various practical load condition.
Fig 11 E is the scheme for testing overload condition of the product. The overload condition for the product is tested in a sequential manner with the specified time for the overload. The specified overload conditions are applied and the products output is monitored for the time specified for overload shutdown at the specified load. If the product detects an overload condition, it turns off its output in the specified time.
Fig 11 F shows the scheme for testing short circuit protection and is performed at the output of the product with the help of contactors 504. The main control unit operates as a contactor 504 to short circuit at the output of the inverter. The output of the inverter is observed in order to see whether the product performs short circuit protection and turns off its output immediately. If the product applies the protection for short circuit, then it is passed in a short circuit test.
All the tested parameters and results are displayed on the computer attached and also logged within a database. The test report is generated with all the results and can be printed with the attached printer.
Fig 12 is the flow chart outlining the software program procedures for operation of the system. The SCADA (Supervisory Control and Data Acquisition) software is presently written in Microsoft Visual Basic but the same can as well be written in Java or other equivalent programming languages. A typical sequence of tests for the device under test
is as follows:
1
2
"> _■>
4 5 6 7 8 EXAMPLE:
Low-voltage cut test and recovery test
High-voltage cut test and recovery test
Mains Testing
Charging Current test
No load test
Testing under various loads
Overload test
Short-circuit test

INVERTER TESTING REPORT 3.5 KVA 48V
01:48:12 PM 7/12/2008
INVERTER NO LOAD
PARTICULARS SET POINT CURRENT VALUE
VOLTAGE = 210V-230V 220.000
FREQUENCY = 49.5-SO.SHZ 50.000
BAT-VOLT = 46.0V-58.0V 48.250
BAT-CURRENT = 1.2A-2.0A 1.500
MAINS PRESENT
PARTICULARS SET POINT CURRENT VALUE
VOLTAGE-MAINS = 210V-230V 227.000
VOLTAGE-INVERTER = 210V-230V 228.000
BAT-VOLT CHARGING = 37.0V-57.0V 51.900
BAT-CURRENT CHARGING = 11.0A-14.0A 12.000
VOLTAGE RECOVERY ON MAINS PRESENT
PARTICULARS SET POINT CURRENT VALUE
LOW CUT VOLTAGE = 130V-150V 147.000
LOW CUT RECOVERY VOLTAGE = 140V-165V 165.000
HIGH CUT VOLTAGE = 270V-290V 278.000
HIGH CUT RECOVERY VOLTAGE = 260V-280V 260.000
100% LOAD TESTING 2400W
PARTICULARS SET POINT CURRENT VALUE
OUTPUT VOLTAGE = 19SV-220V 212.000
OUTPUT FREQUENCY = 49.7-50.5HZ 50.090
OUTPUT CURRENT = 10.0A-12.0A 10.866
BAT-VOLTAGE = 46.0V-52.0V 49.200
BAT-CURRENT = 5J.ft4-6J.ft4 55.800
OUTPUT WAVEFORMTHD = 2.1%-4.0% 3.500
INVERTER PF = 1.0 1.000
LOAD IN VA = 2400 VA 2349.593
LOAD IN WATTAGE = 2400 WATT 2349.593
EFFICIENCY = 83.906 %
/50% LOAD TESTING 3600W
PARTICULARS SET POINT CURRENT VALUE
OUTPUT VOLTAGE = 170V-210V 179.000
OUTPUT CURRENT = 15.0A-18.0A 16.276
OUTPUT FREQUENCY = 49.5-50.5HZ 50.090
BAT-VOLTAGE = 46.0V-52.0V 47.400
BAT-CURRENT = 65.0A-tfJ.A4 79.110
INVERTER PF = 1.0 1.000
LOAD IN VA = 3600 VA 2962.954
LOAD IN WATTAGE = 3600 WATT 2962.954

SHORT-C1RCUIT TESTING
PARTICULARS SET POIN CURRENT VALUE
OUTPUT VOLTAGE = 0.0V 0.000
OUTPUT FREQUENCY = OHZ 0.000
The foregoing is meant to illustrate the invention but not to limit. Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.

WE CLAIM:

An automated testing system comprising of a programmable logic controller based testing Rig having a main control panel integrated with a plurality of meters to read input/output parameters, a controlled variable voltage and frequency source connected to product under test, output of which is connected at load feeder where loads according to the test and rating of the product under test are connected.
2. An automated testing system as claimed in claim I wherein said control panel controls how much and what type of load is to be connected to the product under test.
3. An automated testing system as claimed in claim I or 2 wherein said control panel reads all the input and output parameters of the product under test and displays it on the connected device such as computer.
4. An automated testing system as claimed in any of the preceding claims wherein said control panel compares the products output with the reference output and makes a decision if the product under test is performing correctly or not.
An automated testing system as claimed in any of the preceding claims wherein the user according to the product under test can program the testing process.
6. An automated testing system as claimed in any of the preceding claims wherein the said programmable logic controller directs the process through signals at the outputs in response to input signals at the inputs.
7. An automated testing system as claimed in any of the preceding claims wherein the said programmable logic control block is interfaced with the input modules for interfacing with input parameters and directing the output for controlling the testing operation.
8. An automated testing system as claimed in any of the preceding claims wherein the said programmable logic controller block is also interfaced with the various power meters to measure input and output power for system efficiency calculation as well as total harmonic distortion calculation.
9. An automated testing system as claimed in any of the preceding claims wherein the said programmable logic controller controls the servo controlled voltage source and the load block through input output modules for various test condition.
10. An automated testing system as claimed in any of the preceding claims wherein all the parameters comprises of the technical specifications of the said systems e.g. input voltage, frequency, fuse & charging current and inverter parameters like no load voltage & current, full load voltage & current, overload voltage and current, output frequency, protections like short circuit are displayed on connected device along with their tested status.
11. An automated testing system as claimed in any of the preceding claims wherein the test can be performed on different types of load such as resistive load, inductive load, rectifier load or any combination.
12. An automated testing system substantially as herein described with reference to the accompanying drawings.