FIELD OF INVENTION
This invention relates to an improved three phase inverter for heavy-duty industrial application.
BACKGROUND OF THE INVENTION
A conventional three-phase inverter known in the art aims to transform DC power to three-phase AC power to drive a load. The three-phase AC inverter consists of a plurality of insulated gate bipolar transistors (IGBT's) connected in parallel. The gates of the I GET are controlled by PWM control signals, the upper and lower arm control signals corresponding respectively to R, S and T phases.
Parallel coupling is accomplished and controlled by coupling two or more sets of IGBTs of the same make & model number. Only one gate control signal is required to drive atleast two IGBT's that are coupled in parallel at the same time.
The inverter described above is having some technical problems, such as current distribution, malfunctioning, low efficiency and capacity, which can be detailed as follows.
Because the static and dynamic characteristics of IGBTs are not always the same, controlling with direct parallel operation results in different current flowing through two or more IGBTs while turning on in a static condition or switching dynamically. As a result, current distribution in the IGBTs is not equal. In serious conditions, the IGBTs could overheat and burn out.
As the transistors use the same set of control signal to pass through gate control circuits and drive the IGBTs, if one IGBT is opened or the actuation circuit is abnormal (such as signal interruption), in terms of the parallel structure, as long as one IGBT is turned on normally, the overall output actuation is not affected. The actual load current waveform is also the same as the normal signal. Hence malfunctioning of the IGBT cannot be detected, and protection of the IGBT is difficult. Isolation of the malfunction is also not easy. Moreover, when one IGBT malfunctions, excessive current could flow through another IGBT. When the malfunction is not detectable, the other IGBT could burn out. Reliability is thus lacking.
The power loss of the general inverter can be classified as conduction loss and switching loss (including turn-on losses and turn-off loss). In general, a higher switching frequency of the IGBT has a more desirable output waveform, but the power loss is also greater, and the overall efficiency is lower. For an inverter of a greater capacity, to maintain a high switching frequency to achieve a desired waveform output is difficult.

In term of capacity, the safety current of the IGBT must be reduced as the switching frequency increases. Moreover, the dividing current is not equal when the IGBTs are coupled in parallel. Hence the total safety current has to be reduced.
Pulse width modulator (PWM) inverters are used in three phase bridges, H-bridges, and half-bridge configurations. The bus capacitors, typically electrolytic, consist of two or more capacitors connected in series or parallel that is fed from a rectifier or actively switched front end section.
In order to reduce the aforementioned problems, attempts have been made for an improved dispensing system. Some of the inverters described in U. S. patent No. 6404655, U. S. patent No. 7199622, U. S. patent No. 7091690 and U. S. patent No. 5552977 are incorporated herein as prior art systems. However, the prior art systems have general short-comings and do not adequately address the aforementioned problems.
What is needed is a means of efficiently operating power inverters, especially for non-linear, high harmonic content, and/or unbalanced loads. This design must also be cost effective to manufacture and implement, and allow for easy incorporation into current designs.
Some of the available inverters do not have monitoring 85 controlling software interface. The problem faced by using these inverters is that when the battery goes low it shuts down the system connected to it abruptly. This results in the loss of data & system failure.
Some of inverters which claim to have monitoring & controlling software
have the following drawbacks-fa) Nonavailabiltiy of real time monitoring & controlling software interface. They do not provide instantaneous values of the various parameters of the system and cannot do power audit. The product up-gradation is also not possible by these softwares.
(b) In the systems where remote monitoring and controlling was possible, an additional card or hardware (SNMP and other like that) was to be connected to the inverter system. This increases the hardware as well as cost of the system.
OBJECT OF THE INVENTION
The primary object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application which is very efficient, cost effective and three phase power inverter for use in heavy duty application varying the connected load having high inrush current drawing

needs or other very cost sensitive applications. Three phase power generation is through dual DSP's (digital signal processor) using PWM with space-vector modulation technique. The entire inverter function is controlled by the dual DSP's being used in the system.
Further object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application, comprising a rectifier section connected to a three-phase 4wire source for generating the DC source for charging the battery bank connected thereto.
Another object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application, for generating a balanced regulated AC output, comprising a AC-DC converter, an inverter section for generating the regulated AC output from the DC source, a DSP control section connected to the inverter section for pulse width modulating the inverter, wherein the control section has a voltage loop and a current loop for each phase of the AC output, and in which the control section has a means of processing.
Still further object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application comprising IGBTs to provide AC wherein the regulated AC output is three-phase.
Further object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application comprising dual digital signal processor's (DSP) in the control section.
Still another object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application having a driver section to drive the inverter IGBTs wherein driver is controlled by DSP.
Yet another object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application further comprising a three-phase filter connected to the regulated AC source.
Further object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application supplying DC power supply to different sections and drivers.
Yet another further object of the present invention is to propose an improved three phase inverter for heavy-duty industrial application having the connectivity through GSM modem. Using this user can monitor & control the product from a remote location through his mobile phone. This feature is very useful at those remote locations where the user does not have computer and wants to check the status of the inverter.
SUMMARY OF THE INVENTION
The present invention provides an improved three phase power inverter and control method to facilitate high quality and low output total harmonic

distortion operation of three phase power inverters, particularly when applied to non-linear, high harmonic content, and/or unbalanced loads, common in modern power distribution systems, both commercial and industrial. Although insulated gate bipolar transistor (IGBT) power switches are the preferred embodiment in high voltage inverter applications, other power switches used in the lower voltage applications for example FET's are also within the scope of the invention.
The control printed circuit board (PCB) of the present invention having a digital signal processor (DSP) based digital PWM with space vector modulated AC voltage and/or current regulator, with independent phase voltage and current control loops. Independent voltage loops control the line to neutral voltage of each phase output. In one embodiment, voltage feedback is provided by three individual resistances and integrator capacitors to boost DC gain and thereby enhance DC offset voltage rejection. Independent current loops control the output phase currents. Current feedback is also provided by resistors and filter capacitor circuits for optimum system tuning. Both the voltage and current loops have digitally selected proportional and integral terms, and the feedback circuits have analog phase lead. Thus, precise closed loop transient performance is accomplished.
Due to DSP controller, the present invention helps in prolonged life of battery bank as well as providing longer backup for inverter.
The present invention also has additional generator start facility by giving command to generator through DSP to optimize the use of generator available.
The present invention diagnoses the problem in the inverter for example the status of the battery, battery life, overload, short circuit etc.
According to the invention, the unbalanced dividing current resulting from different IGBT characteristics may be resolved and the abnormal signal of one power transistor or gate driver may be detected easily through the current waveform.
According to the principle and aspect of the invention, the switching loss of the power transistor may be reduced, the overall efficiency may be increased, the failure rate of the inverter may be reduced and the total reliability may be increased.
According to the principle and aspect of the invention, the parallel capacity may be increased and the cost of the elements may reduce.
The present invention also provides real time management using internet for an inverter connected to computer. As the same DSP, that is used to control the inverter is communicating with the computer based software, the real time parameters are transferred to the computer. This is through the

dedicated communication protocol that is implemented inside the DSP and also in the monitoring software. The DSP technology provides faster and precise control of inverter system for effective and safe mechanism. Through the DSP the product up-gradation is also possible as the commands are directly sent to the DSP. This web based facility is without any additional hardware thus reducing the hardware and also the cost of the system. The inverter control section is connected to the computer via any serial port communication cable or the USB cable or RJ45 cable. The inverter installed anywhere in the world can be centrally monitored and controlled by the user. The present invention also provides facility to monitor & control the inverter via mobile.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings indicating exemplary embodiments of the present invention and wherein:
FIG. 1 shows a block diagram of the three phase inverter of the invention;
FIG. 2 shows the circuit diagram of mains input feedback transformer;
FIG. 3 shows the circuit diagram of three phase charger;
FIG. 4 shows the circuit diagram of SCR section;
FIG. 6 shows the circuit diagram of the DSP control -Master;
FIG. 7 shows the circuit diagram of the DSP control-Slave;
FIG. 8 shows the circuit diagram of driver card
FIG. 9 shows the circuit diagram of inverter IGBT section;
FIG. 10 shows the circuit diagram of the DC/DC converter circuit;
FIG. 11 shows the circuit diagram of switching circuit;
FIG. 12 shows the circuit diagram of the LCD interface with DSP;
FIG. 13 shows the circuit diagram of front display (bar graph);
FIG. 14 shows the circuit diagram of front display (indicator);
FIG. 15 shows circuit diagram of RS-232 interface with DSP;
FIG. 16 shows the circuit diagram of RS-232 cable connection;
FIG. 17 shows a pictorial diagram of power management system controlled
by web monitoring software using computer system;
FIG. 18 shows a pictorial diagram of power management system controlled
by web monitoring software using mobile;
FIG. 19 shows the flow of the software program pertaining to the operation of
the invention for monitoring purpose of the system;
FIG.20 shows the flow of the software program pertaining to the operation of
the invention for controlling the various parameters of the system;
FIG 21 shows the pictorial diagram of inverter with GSM connectivity

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
Reference may be made to fig. 1 indicating a block diagrammatic overview of one of the three phase power inverter and control method, for use in AC distributed power systems, typically in pulse width modulation (PWM) with space-vector technique, inverter power generation and/or conditioning applications.
The three phase inverter of the present invention is designed through dual DSPs using PWM with space vector modulation technique and with IGBT as power devices. These are three Phase input & three Phase output inverters. These are designed for heavy-duty industrial application eg. Air conditioners, Lifts / escalator, welding machine, heavy machinery, motor loads etc.
The three phase power inverter and control method is illustrated as a system showing a power source, such as a three-phase configured AC source that connects to the charger section. The charger provides isolation from the AC line through input transformer, as well as being a regulating source by sensing current of the SCR section. SCRs are true rectifiers and thus they only allow current through them in one direction. SCR-SCR modules are used to charge the battery from the mains power available. The charging is being controlled by the charger card which has settings for battery charging voltage & charging current. Heavy-duty charger with charging current ranging from 20A - 200A is provided to charge the batteries. The charger will be sensing the battery voltage and have current limiting capabilities. The rectified AC then passes through the battery bank. The SMPS power supply cards takes battery voltage as input & provides isolated +5V & + 15V supplies, which are used by DSP cards 85 IGBT driver cards to drive the inverter IGBTs. IGBTs provide faster speeds, better drive and output characteristics than power BJTs and offer higher current densities than equivalent high-powered MOSFETs.
Inverter module includes multiple of IGBTs and capacitors depending on the capacity of the system. This type of circuit provides enhanced inrush current withstand capability. Module can double the modulation frequency of the inverter, reduce the switching loss and improve the system efficiency with minimum noise, leading to improvement in performance of the sysem and reduction in its cost. The inverter module IGBTs receive the DC power and provide regulated AC power at the power output. Control of the circuit is achieved by controlling the IGBTs with pulse width modulated (PWM) signals generated by the inverter DSP controller, via the isolated gate driver circuits.

IGBT driver cards provide protection & increases current capability of PWM signals. The IGBT driver cards receive input signals from inverter control circuit (DSP) and provide output drive signals to inverter module IGBT. The two complementary PWM signals generated by the DSP cannot be high simultaneously thus this is controlled by the logic gates. IGBT driver card provides isolation between DSP side and IGBT side with the help of opto-couplers. If there is any short circuit or voltage drop in the IGBT side and VCE becomes greater than the specified value then the driver takes protection by isolating the DSP side and IGBT side. Since DSP does not have the sufficient current to drive the inverter thus IGBT driver card increases the current capability of DSP.
The dual DSPs are carrying out the entire inverter function. One processor may be referred to as a DSP slave, or simply a slave, and the other may be referred to as a DSP master, or simply a master. The master is configured to monitor data regarding status parameters of the inverter and to implement control commands to control operation of the inverter. The slave is configured to relay information between the communication port and the master processor. The DSP control card senses the input voltage, output voltage, output current and battery voltage and gets ambient temperature feedbacks. It generates three phase PWM with Space vector Modulation. Dual DSPs used in these products communicate with each other & exchange information. The output PWM signal is transmitted to the output inverter power switches via gate driver circuits.
The dual DSP control card also connects to any serial communication port (say RS232) to monitor the inverter status on local or remote location. This card also provides data to be displayed on the LCD. The processor is configured to perform its various functions by reading and executing computer-readable, computer-executable software instructions stored in the memory. The master can further receive commands/instructions from the computer via the network and the slave and control portions of the inverter to implement the commands.
Potential free contacts are provided with intelligent DSP control for generator start, battery low protection, on mains/ on battery status.
The isolation transformer is used to increase or decrease the voltage of the AC power from the inverter power module IGBT and to provide isolation between a load and the inverter. The isolation transformer is typically system dependant, the capacity of which is typically dependent on inverter output power specifications. The isolation transformer separates the input neutral & output neutral. Thus, any disturbances or fault in input does not affect the output. It also blocks the noise in neutral and provides galvanic isolation.

The transformer output is filtered and is then available as a balanced, regulated three phase, 4 wire AC power output.
Current feedback as well as voltage feedback is taken from the transformer output. The three phase current feedback is connected directly to the inverter DSP for A/ D conversion. The three phase voltage feedback signals are connected to the DSP via resistor divider and filter capacitor signal conditioning circuits.
After conversion, the voltage feedback terms are summed with the voltage set point commands, resulting in voltage error signals. The voltage error signals are multiplied by the voltage proportional and integral terms. The resulting output is compared to the current limit term, clamped if required and then sent to the current loop.
Current feedback is taken from the inverter output phase current sensors, scaled and filtered, and the resulting current feedback signals, are fed to the DSP A/D converters.
There are numerous variables (such as PWM filter circuit, DC link voltage, desired output impedance and PWM carrier frequency) that will impact feedback compensation, and gain selections. However, there are certain guidelines that provide a general method of approximation for selecting critical components and gain terms for a variety of PWM inverter applications.
The other basic constituents of the inverter are three phase front panel mimic display card, front panel load & battery bar graph card, contactors & relay, current transformers, power transformers, blower and temperature sensor.
Current transformers are used to measure the input & output currents & control the inverter function depending on the currents. It provides signal to the DSP card to cater to overload conditions.
The output generated by these inverter are pure sine wave with regulated voltage & frequency i.e. voltage regulation within 1% & frequency regulation within 0.1%. Even at 100% unbalanced load the output voltage regulation is within 2%.
These inverters have very high inrush bearing capability as compared to generators e.g. 200% for 5 Sec & 300% for 2 sec. These inverters can be run at 100% load continuously whereas generators are to be run at 80% load only. Hence, for the same load requirement a smaller capacity of inverter is required than a generator.
Blower operation is the novel feature of the invention as it operates only when it requires. It is controlled using a temperature sensor mounted on the heat sink. It operates only when the temperature of heat sink reaches 55 deg C & switches off when temperature comes down to 45 deg C. Hence the life of Blower is enhanced 85 also there is power saving. The blower is so located that it takes fresh cold air from bottom & flushes the air through the heat sink. Hence, it results in cooling to the maximum possible in the shortest possible time.
The present invention also have a front panel display consisting of for example 20x4 lines LCD, mimic diagram to indicate the status of input mains, output phase and bypass mode. It also displays the loads on the 3 phases using a bar graph with overload indications too. Further, it displays the battery level using bar graph, battery voltage; short-circuit condition, output low/high condition.
The present invention also provides real time web based remote monitoring as well as multiple user local monitoring for inverter with the help of Power Management Software using internet as shown in the fig 17 85 18.
Power Management Software includes:
1. Web based monitoring Application.
2. Local Monitoring Application.
With the help of web based monitoring software, the inverter installed anywhere in the world can be centrally monitored and controlled by the user. It supports all operating systems such as Windows version 85 various Linux, Solaris versions. A licensed copy of the software is installed and run on the computer connected to the power system via any communication cable (say RS-232/ USB/ RJ-45) through which it starts receiving data. The unique and fully validated software solution allows various parameters of the systems to check and the system can be upgraded, including load and status of each system. The novel feature of the software is that it does not require any additional hardware like SNMP card for web monitoring. Even local monitoring is done by using TCP/ IP. Use of computer instead of SNMP provides two way communication and product up-gradation possibility which was not possible by using SNMP hardware as seen in the existing monitoring software. The Power Management Software not only controls the start/shutdown of the inverter but also provides control for various parameters in inverter and system up-gradation. The software is very useful for unmanned locations or mission critical application where power backup systems are installed and where their assured availability is essential and mission critical. Some of the examples are ATMs, Telecom towers; Satellite based systems, online process control equipments, fully networked chain of retail stores, chain of multiplexes, their supply chain systems. Such inherent flexibility lends itself for condition based operational utilization of power backup systems thus adding considerable value and enhancing the maintainability and assured availability of systems.

Local power monitoring software requires a serial connection between a computer & the system via serial port communication cable. Inverter control section is connected to the computer via any communication cable (say RS232) as shown in fig 17 & 18.
The web monitoring software facilitates checking of various parameters in the form of digital and graphical representation. Data logging of these parameters can be ensured at defined time intervals say every 10 or 15 seconds. The flow chart in fig 19 & 20 presents the functioning of the software for monitoring and controlling the system.
Chief components of the Power Management Software
The Power Management Software comprises of the following two components
(A) Local Server application
(B) Local Client Application
(A) Local Server application performs communication with the inverter, its shutdown as well as that of local clients, emailing and broadcasting of inverter events
Interpreting Main Panel
The main panel display provides node information and information on the status of the power, inverter battery system, system operations, and communications. The display automatically detects the configuration of the inverter and adjusts itself accordingly.
The main panel is a graphical representation of the operational status of the system. Input and output voltage, input and output frequencies are shown with the help of analog meters. Battery voltage and load % along with output current, output power and inverter capacity are indicated with the help of bar graphs.
It provides detailed information regarding the present power situation and controls features such as orderly system shutdown and configuring alerts. It also provides system shutdown time, review of the power event and battery management logs to handle other tasks.
Following are the utilities provided by the software and local server can configure the system accordingly
1. Data view
Data view uses bar graphs and text to show the power situation. The display is divided into sections as follows:
Output

Output information shows the actual output load on the inverter. The output section includes the following:
• Status: Condition of the inverter battery
• % Load: Percentage of the inverter's calculated full load in use
including overload conditions
• Volts: Output voltage for the load including over voltage and under
voltage conditions
• Hz: Output frequency for the load including high and low frequency
conditions
Input
The input section is a green, yellow and red bar on a row below the output
section showing the utility power source voltage and limits. The colors on
the display indicate whether the power is within acceptable limits. If the
voltage reading is in the green range it shows that the inverter is operating
on the utility power. Yellow or red range indicates that the work is to be
saved.
2. Battery Status and Load
Battery Status information provides description of the status of the battery. Load feature gives the present load on inverter.
3. Secure Access
The Software provides secure access for a valid user to make changes in the Power Management Software Application.
4. Email Notification
User can configure Power Management software to send an email message to upto 4 people when an event occurs.
5. Data Log
Data Log provides the log of inverter parameters input and output voltage, input and output frequency, power, inverter status, output current, battery capacity, load and capacity at specified time interval.
6. Inverter Settings
Power Management Software provides the way to set some inverter settings like
• Output voltage/ output frequency as per requirement.
• Battery low/ battery high protection can be changed.
• Buzzer can be Disabled/ Enabled.

• Change High/ Low cut level.
• Inverter Shutdown/ Restart.
7. Broadcasting Messages
User can configure Power Management Software to broadcast a notification message when an event occurs in the following way-
8. Customize Alerts
It can be used to change the text of an alert message or to change the response that system makes to alert.
9. Delay Times
User can change the delay time for message for e.g. 10, 20, 30, 40, 50 or 60 sec.
10. Client Connection
This option disables/ enables Client-Server communication.
11. Update User Information
Under this option user can update his/her personal information like name, company name, address, phone number etc.
12. Priority based Settings
Attached equipments to the inverter may be given two levels of priority, namely Low and High. Time entered against this setting defines the time for low priority equipment to shutdown. The value for high priority equipment is double of this time.
13. Inverter Scheduler Settings
Weekly shutdown schedule' can be used to shut down all or segments of the inverter load at a certain time each day. Periods when the system is scheduled to be ON are shown in orange. Periods when the system is scheduled to be off are shown in white.
14. Server Shutdown Settings
It sets the interval between the time the Power Management Application software begins to shut down of the Windows environment and the power from the inverter shuts off.

15. View Data Logged File
User can view the Logged file at any time. Data which is logged as:
• Date
• Time
• Input and Output Voltage
• Input and Output Frequency
• Output Current
• Output Power
• Load percentage
• Total Units
• Ambient Temperature
• Capacity
• Battery Voltage
• Status
16. Connected Users List
Server lists the client's status, whether they are online or offline, client's name, priority and their IP addresses. Connected users show the number of clients online.
17. View Graphs
User can view 3 kinds of graphs
• Input & output voltage
• Input & output frequency
• Output power
This utility provides the following features-
• Auto and Manual saving of graph
• Plotting of input and output voltage, input and output frequency,
output power
• Maximum and minimum value over a period of time
• Plotting of data from files
• Start and End Time at which user had actually started/ ended the
plotting in graph
• Printing of the graph
(B) Local client application registers and communicates with the local server.
Interpreting Main Panel
The main panel display provides node information and information on the status of the power, inverter battery system, system operations, and communications.

The main panel is a graphical representation of the operational status of the system. Input and output voltage, input and output frequency is shown with the help of analog meters. Battery voltage and load % are indicated with the help of bar graphs, besides output current, output power and inverter capacity.
It provides detailed information regarding the present power situation. It also provides system shutdown time, review of the power event and battery management logs.
Following are the utilities provided by the software and the local client can configure the system accordingly.
1. Data view
Data view uses bar graphs and text to show the power situation. The display is divided into sections as follows:
Output
Output information shows the actual output load on the inverter. The
Output section includes the following:
• Status: Condition of the inverter battery
• % Load: Percentage of the inverter's calculated full load in use
including overload conditions
• Volts: Output voltage for the load including over voltage and under
voltage conditions
• Hz: Output frequency for the load including high and low frequency
conditions
Input
The input section is a green, yellow and red bar on a row below the output section showing the utility power source voltage and limits. The colors on the display indicate whether the power is within acceptable limits. If the voltage reading is in the green range it shows that the inverter is operating on the utility power. Yellow or red range indicates that the work is to be saved.
2. Battery Status and Load
Battery status information provides description of the status of the battery. Load feature gives the present load on inverter.
3. Update Server IP
Client has the permission to change the Server IP address. Connection gets closed as soon as user would change Server IP.
4. Update Priority

Client has, by default, priority 'Low'. Client can change his priority. Clients are allowed to change their priority from 'Low' to 'High' and vice versa.
5. Update User Name and Password
Client can change his user name and password.
Now if the user has to monitor/ control the inverter system remotely he has to go through web monitoring. The web monitoring application includes -
1. Power Management Software reads data from the DSP of inverter
through RS-232/ RJ45/ USB port.
2. Similarly live data of 'N' number of inverter data are available on
Server in every 3 to 10 seconds.
3. A valid user has to login on a specific website which will display list of
all inverters.
4. "Details" link displays the live status and parameters of the product.
5. One can view the data log of product, date & time wise accordingly.
6. One can also view the summary of the product since installed. The
summary contains blackouts, brownouts, number of units drawn by
load through inverter, review of grid power in terms of fluctuations
and number of outages etc.
7. Blackouts contains each and every moment when mains are not
present.
8. Brownout contains duration of inverter mode when there is low
voltage.
9. Other details can be viewed like:
• Input Voltage duration:
1. < 180V
2. > 180V & < = 200V
3. > 200V & < = 230V
-25-
4. > 230V & < = 250V
5. > 250V & < = 270V
6. > 270V
• Input Frequency duration:
1. < = 49.8 Hz
2. < = 49.5 Hz
3. < = 48 Hz
4. > = 50.2 Hz
5. > = 50.5 Hz
• Output Power / Load duration:
1. < = 25%
2. 26% - 50%
3. 51% - 75%
4. 76% - 100%
5. > = 101%

• Duration of Status i.e. duration of on mains/ on
battery/ overload conditions etc.
10. Charts of input voltage vs time, input frequency vs time, output
voltage vs time, output frequency vs time, battery voltage vs time,
output power vs time, load vs time, blackouts vs date are available for
analysis.
11. One can send request code of particular product to retrieve live
status of product immediately.
12. Controlling can be done through web and mobile to-

• Set Output Voltage/ Output Frequency as per
requirement.
• Change Battery Low/ Battery High protection.
• Disable/ Enable buzzer.
• Change High/ Low cut level.
• Shutdown/ Restart the inverter.
13. Local computers can also be controlled/ scheduled shutdown by
using TCP/ IP.
In the present invention, the system also has the connectivity through GSM device (Fig.21). It provides connectivity of the inverter to the internet without a computer. Using this, the user can monitor & control the product from a remote location using his mobile phone. This feature is very useful at those remote locations where the user does not have a computer and wants to check the status of the inverter. Additional advantage of this facility is that it reduces the cost of the system and does not require additional telephone lines. The data is recorded locally by the monitoring system and relayed to the server via the GSM network. Using the password, user can retrieve his unit's data at any time with the help of any internet access anywhere in the world. Fig. 1 shows the connectivity of the GSM device with the inverter. GSM device is connected to the inverter via DSP through the RS232/ RJ45/ USB cable and through GPRS connectivity data is transmitted to the remote locations.
The inverter data is processed in a central database. User can access to the data records at any time using protected internet access. The important parameters of the inverter like input voltage, input frequency, output voltage, frequency, power, current of all three phases, battery voltage, battery level, number of power cuts & their duration can be monitored on the mobile phone. It is also possible to switch ON/ OFF the system from a remote location. Also the output voltage, battery low level and load can be changed from a remote location. Under various alarm conditions the system sends SMS to the predefined numbers so that corrective action can be

taken. This is a very useful feature which allows the remote monitoring & control of the product.
ADVANTAGEOUS FEATURES
1. The output generated by these inverters is pure sine wave with
regulated voltage & frequency with voltage regulation within 1% &
frequency regulation within 0.1%. Even at 100% unbalanced load, the
output voltage regulation is within 2%.
2. These inverters have very high inrush bearing capability as compared
to generators. E.g. 200% for 5 Sec & 300% for 2 sec. These inverters
can be run at 100% load continuously whereas generators are to be
run at 80% load only. Hence, for the same load requirement a smaller
capacity of inverter is required than a generator.
3. Potential free contacts with intelligent DSP control for generator start,
battery low protection, mains/ on battery status.
4. Monitoring and controlling of the system on internet 85 status can be
seen on mobile phone. System can also be controlled & set by the
mobile.
5. The system also has the connectivity through GSM modem to monitor
& control the product from a remote location using the mobile phone.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM
1. An improved three phase inverter for heavy-duty industrial application
comprising of an Inverter section controlled by DSP, charger section
which charges the batteries from mains, and change over section and
IGBT's being used as power devices for inverter function & isolation
transformer at the output.
2. An improved three phase inverter for heavy-duty industrial application
as claimed in claim 1 wherein the IGBT driver cards receive input
signals from the inverter control circuit (DSP) and provide output drive
signals to inverter IGBT Modules.
3. An improved three phase inverter for heavy-duty industrial application
as claimed in claim 2 wherein the DSP comprising of DSP slave and
DSP master connected to each other in which the master is configured
to monitor data regarding status parameters of the inverter and
implement control commands to control operation of the inverter and
the salve is configured to relay information between the
communication port and the master processor.
4. An improved three phase inverter for heavy-duty industrial application
as claimed in any of the preceding claims wherein the dual DSP
control card is connected to a serial communication port such as RS
232 so as to monitor the inverter status on local or remote location in
which the card also provides data to be displayed on LCD.
5. An improved three phase inverter for heavy-duty industrial application
as claimed in any of the preceding claims comprising of a blower
controlled by a temperature sensor mounted on heat sink.
6. An improved three phase inverter for heavy-duty industrial application
as claimed in claim 5 wherein the master DSP is connected to GSM
modem.
7. An improved three phase inverter for heavy-duty industrial application
as claimed in claim 6 wherein the same inverter can also be used in
Solar Application.
8. An improved three phase inverter for heavy-duty industrial application
substantially as herein described with reference to the accompanying
drawings.