FORM - 2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RUEES, 2003
PROVISIONAL SPECIFICATION
(See section 10 and Rule 13)
FIELD OF POWER SUPPLY

APLAB LIMITED
an Indian Company of Aplab House, A5 Wagle Industrial Estate, Thane 400 604,
Maharashtra, India,
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION


Field of the Invention:
The invention relates to the field of power supply.
Particularly, the invention relates to the field of Uninterruptible Power Supply.
Background of the Invention:
An Uminterruptible Power Supply (UPS) is a cfevice which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source, typically through its battery, when utility power is not available. There are two distinct types of UPS: off-line and line-interactive (also called on-line).
An off-line UPS remains idle until a power failure occurs, and then switches from utility power to its own power source, almost instantaneously. An on¬line UPS continuously powers the protected load from its reserves (usually lead-acid batteries), while simultaneously replenishing the reserves from the AC power.
The on-line type of UPS, in addition to providing protection against complete failure of the utility supply, provides protection against all common power problems, and for this reason it is also known as a power conditioner and a line conditioner.
In on-line type of UPS, normally load is always fed by an inverter through a static switch. Under unstable conditions, the switch switches over from the inverter to a regulator, typically to an AC regulator, when the inverter is
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inadequately charged or unable to sustain the load. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. Voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element. This forms a negative feedback servo control loop. If the output voltage is too low, the regulation element is commanded to produce a higher voltage. For some regulators if the output voltage is too high, the regulation element is commanded to produce a lower voltage; however, many just stop sourcing current and depend on the current draw of whatever it is driving to pull the voltage back down. In this way, the output voltage is held roughly constant.
The AC regulator acts as the bypass circuitry. The load is transferred from inverter to the bypass circuitry in case of excessive short term overloads. The load is re-transferred from bypass circuitry to inverter after a pre¬defined delay, typically of 10 seconds to 30 seconds based on the nature of the load; if overload persists, then load is again transferred to inverter. A maximum pre-detennined number of attempts are made to transfer load back to the inverter of the UPS system. If overload still persists, then load remains connected to the bypass circuitry. In the event of bypass circuitry failure, load will drop even if inverter is working, and even if the battery of the LIPS system has adequate capacity to feed the load. This unwanted transfer and re-transfer creates system transients and instability.
Typically, an inverter houses a transformer, the primary and/or secondaiy windings of which have external connections called taps. Multiple taps may be provided to allow selection of the input vs. output voltage ratio. The taps
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may be connected to an automatic on-load tap changer for voltage regulation of distribution circuits. Regulators generally operate by selecting the appropriate tap on a transformer with multiple taps. If the output voltage is too low, the tap changer switches connections to produce a higher voltage. If the output voltage is too high, the tap changer switches connections to produce a lower voltage. The controls provide a dead band wherein the controller will not act, preventing the controller from constantly hunting (constantly adjusting the voltage) to reach the desired target voltage. The use of a static switch makes the UPS system susceptible to hunting or oscillations, wherein, Oscillation is the repetitive variation, typically in time, of some measure about a central value, i.e. about a stable value to sustain the load.
Sudden changes in voltages, typically whilst 'hunting' to assume a stable voltage for sustenance of the load leads to occurrence of transients. Circuit damage as well as damage to sensitive loads may occur because of presence of transients.
It is hence necessary that the occurrence of hunting, oscillations, and transients be eliminated to provide a robust, more sensitive UPS system
Objective of the Invention:
An objective of this invention is to rid the device of hunting problems, oscillations, or transient currents.
Another object of this invention is to provide a UPS system with a robust switching system.
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Summary of the Invention:
According to this invention, there is provided in an Uninterruptible Power Supply system, an automatic switching means for switching the output from a first operating configuration to a second operating configuration, wherein first operating configuration involves connection of load to an inverter and second operating configuration involves connection of load to a voltage regulator. The automatic switching means may be a digital circuit or an analog circuit or a combination of both. In accordance with an embodiment of this invention, there is provided a sensing means wherein, the instantaneous load current is sensed and load is transferred to bypass circuitry as soon as it exceeds a pre-defined value. The load is feci by the bypass circuitry for a minimum preset period even if load falls below the pre-defined value, (e.g. equal to or above 80% of full load current). The load is re-transferred to the inverter only if load is below the pre-defined value (e.g. below 80% of full load current) and remains in this condition (i.e. deriving voltage from inverter) for a pre-defined amount of time (e.g. 10 seconds). This ensures that the load is not transferred bach to the bypass circuitry within a short period of time. Hence, multiple transfers and re-transfers are completely eliminated. The output, thus, remains stable without any transients. The system is ready to handle another overload without tripping the inverter.
The teclinical advance of the system in accordance with this invention ensures that short term overloads, typically occurring due to starting of motor, switching of SMPS Power Supply, lamps and the like electrical apparatus which draw heavy inrush current at the instance of switching ON
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become redundant. The inverter overload rating of the UPS system can be substantially reduced if the bypass circuitry supply availability is fairly good.
Brief Description of the Accompanying Drawings:
The invention will now be described in relation to the accompanying drawings, in which:
Figure i mustrates the cwirehing system of existing knowledge connecting an input AC current via the inverter of a UPS system and a bypass circuitry to a load; and
Figure 2 illustrates the switching system with the envisaged technical advance connecting the inverter of the UPS system and the bypass circuitry to a load.
Detailed Description of the Accompanying Drawings:
Figure l illustrates the switching system of existing knowledge connecting an input AC current via the inverter of a UPS system and a bypass circuitry to a load.
In on-line type of UPS, normally load (L) is always fed by an inverter (I) preceded in-line by a charge (C) [charged through an AC Input (AC I/P)] through a static change over switch (S). Under unstable conditions, the switch switches over from the inverter (I) powered by a battery (B) to a regulator, typically to an AC regulator (AC RGR), when the inverter (I) is inadequately charged or unable to sustain the load (L). A voltage regulator (AC RGR) is an electrical regulator designed to automatically maintain a constant voltage level. Voltage regulators (AC RGR) operate by comparing
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the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element. This forms a negative feedback servo control loop. ]f the output voltage is too low, the regulation element is commanded to produce a higher voltage. For some regulators if the.output voltage is too high, the regulation element is commanded to produce a lower voltage; however, many just stop sourcing current and depend on the current draw of whatever it is driving to pull the voltage back down. In this way, the output voltage is held roughly constant.
The AC Regulator (AC RGR) acts as the bypass circuitry (BP). The load (L) is transferred from the inverter (I) to the bypass circuitry (BP) in case of excessive short term overloads. The load (k) is re-transferred from bypass circuitry (BP) to inverter (I) after a pre-defined delay, typically of 10 seconds to 30 seconds based on the nature of the load (k); if overload persists, then load (k) is again transferred to the battery (B) based inverter (I). A maximum pre-determined number of attempts are made to transfer load (k) back to the battery (B) based inverter (I) of the UPS system. If overload still persists, then load (k) remains connected to the bypass circuitry (BP). In the event of bypass circuitry (BP) failure, load (k) will drop even if inverter (I) is working, and even if the battery (B) of the UPS system has adequate capacity to feed the load (k). This unwanted transfer and re-transfer creates system transients and instability.
Figure 2 illustrates the switching system (ST/SW CTRL & DRV CKT, SI, S2) with the envisaged technical advance connecting the inverter (I) of the UPS system and the bypass circuitry (BP) to a load (L).
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According to this invention, there is provided in an Uninterruptible Power Supply system an automatic cwitching means (ST/SW CTRL & DRV CKT) for switching the output from a first operating configuration to a second operating configuration, wherein first operating configuration involves connection of load to an inverter (I) and second operating configuration involves connection of load to a voltage regulator (AC RGR). The automatic switching means (ST/SW CTRL & DRV CKT) may be a digital circuit or an analog circuit or a combination of both.
In accordance with an embodiment of this invention, there is provided a monitoring means wherein, the instantaneous load current is monitored and the load (L) is transferred to bypass circuitry (BP) via switch (S2) as soon as it exceeds the pre-defined value. The load (L) is fed by the bypass circuitry (BP) for a minimum preset period even if load (L) falls below a pre-defined value, (e.g. equal to or above 80% of full load current). The load (L) is re-transferred to the inverter (I) via switch (SI) only if load (L) is below the pre-defined value (e.g. below 80% of full load current) and remains in this condition [i.e. deriving voltage from inverter (I)] for a pre-defined amount of time (e.g. 10 seconds). This ensures that the load (L) is not transferred back to the bypass circuitry (BP) within a short period of time. Hence, multiple transfers and re-transfers are completely eliminated. The output, thus, remains stable without any transients. The system is ready to handle another overload without tripping the inverter (I).
Thus, the inverter (I) overload rating of the UPS system can be substantially reduced if the bypass circuitry (BP) supply availability is fairly good.
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While considerable emphasis has been placed herein on the components and component parts of the preferred ernbodirnenis, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
Dated this 22nd day of May, 2008

(Mohan Dewan) OfR. K. Dewan&Co. Applicant's Patent Attorney.
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