FIELD OF INVENTION
The present invention relates generally to static bypass switch, and more particularly, to static bypass switch for providing redundant supply to the critical loads.
RELATED ART
Voltage transfer switches are commonly used to switch between a primary and one or more alternate power sources in the event of failure or instability of the primary source. Such transfer switches are commonly used in applications that require continuity of power, such as in hospitals and critical processes in both industrial and commercial settings. For example, in a power system having a primary voltage source and one alternate voltage source, first and second switches are associated with the primary and alternate voltage sources respectively. The switches are activated by a controller, such that upon failure of the primary source, the first switch is opened to remove the primary voltage source from a load and the second switch is subsequently closed to connect the alternate source to the load and hence maintaining power to the load.
The "static switches" used for this switching function typically employ silicon controlled rectifier (SCR) devices. The controller applies signals to the SCRs' gate terminals to gate them into conduction and to commutate them on the basis of the condition of the primary and alternate voltage sources. Generally, the second switch is turned on as soon as possible after the load is disconnected from the primary source in an attempt to minimize the voltage disruption at the load side.
Publication no WO2005078893 discloses devices and methods for voltage source transfer switching that reduces or eliminates transformer saturation due to DC flux built up during a transfer event. First and second voltage sources (primary and alternate) are connectable to a load via corresponding switches. A transformer is connected downstream of the switches. A controller operates the switches according to various transfer methods wherein a switching time is determined to minimize downstream saturation current. This patent does not provide any monitoring and remote control facility
US patent no 6879060 and publication no WO2005083864 discloses devices and methods for improved voltage source transfer switching. First and second voltage sources (primary and alternate) are connectable to a load via corresponding first and second switches. A controller operates the switches according to various transfer methods. The controller force commutates off the primary source switch by turning on the appropriate alternate source switch for a brief period of time. In this case, the alternate source switches are "pulsed" (rather than being turned on continuously), so that the switches will naturally commutate off at the next current zero cross. This patent does not provide any monitoring and remote control facility
US patent no 3,932,764 discloses a method and apparatus for transferring an electrical load to an inverter from a utility A.C. power source without causing transient changes in the voltage and current fed to the load when such transfer is effected. This patent does not provide any monitoring and remote control facility
US patent no 7,345,380 discloses a backup power supply system supplies power from a first ac power source in normal condition. Since the mechanical switch is continuously closed, and requires no switching operation, the backup power supply system can supply the backup power with a null transfer time. This patent does not provide any monitoring and remote control facility
Publication no CA2095371 describes Sasb/ aoss (stand-alone static bypass) (add-on static switch). It transfers power sources without affecting the load or the power sources.
US patent no 5,808,378 and 6,331,798 are control arrangement and method for a power electronic system configured as a high-speed source-transfer switching systems (HSSTSS). The HSSTSS includes a controller that samples the voltage waveforms of each of the first and second sources to detect when transfer between the sources is desirable. This patent does not provide any monitoring and remote control facility.
US patent no 7,332,833 provides a switching circuit for the master-slave feeding mode of the low voltage power supply. The switching circuit utilizes the active switches as the switching devices, so that it can increase the switching speed, decrease the voltage drop and loss. This patent deals with a two way power supply for master slave feeding mode of the low voltage power supply.
US patent no 5,182,464 discloses a high speed transfer switch for transferring a multiphase load among a number of multiphase A.C. power sources. If the initially selected source deviates from desired limits, the transfer switch transfers the load to an alternate source on a phase-by-phase basis. Antiparallel-connected SCRs are used to allow the load current in each phase to commutate to zero before the load is transferred to the alternate power source. This patent does not provide any monitoring and remote control facility
US patent no 6,560,128 is directed to a static transfer switch for reducing ferroresonance in a load. The switch consists a first switch for connecting and disconnecting a primary power source to and from the load and a second switch for connecting and disconnecting a secondary power source to and from the load. Each switch includes a snubber circuit connected across the respective switch. This patent does not provide any monitoring and remote control facility
US patent no 6,208,126 discloses a circuit for supplying a load from an AC voltage supply. The circuit includes a control circuit and a bidirectional switch coupled in series with the load. The bidirectional switch includes two one-way switches connected in antiparallel and the control circuit controls the bidirectional switch based on a relatively low DC voltage. This invention relates to switches for a load supplied by the AC voltage source using a low voltage control signal.
US patent no 7,064,458 discloses a method and system for transferring a load from a first AC voltage source to a second AC voltage source. A temporary voltage source is connected to the load and to the first voltage source via a resistor. This patent does not provide any monitoring and remote control facility.
US patent no 5,646,459 discloses an integrated maintenance bypass switch and method of operation thereof. The maintenance bypass switch includes a selector switch configured to function in alternate normal, standby bypass and maintenance bypass modes of operation. The patent relates to a maintenance bypass switch that provides single switch isolation of power in bypass mode.
US patent no 3,646,355 discloses a static switch is operated upon sensing a loss of a primary power supply providing a rapid temporary connection of a secondary power supply to a load. Slower acting power contactors are also energized and their operation provides a permanent connection of the secondary power supply to the load and means for disconnecting the path of secondary power through the static switch. This patent does not provide any monitoring and remote control facility
US patent no 6,292,379 discloses a modular uninterruptible power supply having multiple power modules installed therein. Each of the individual power modules contains an internal bypass circuit sized for its particular power module. Preferably internal bypass circuitry is sized to carry two per unit load. The system and method of the invention also includes internal control circuitry for each of the modular power modules that control transitions between the inverter and bypass modes of operation. This invention relates to fault bypass circuitry for power inverters and in more general uninterruptible power supply systems.
US patent no 5,153,802 relates to a static power switch comprising a circuit breaker function. In this case, the fault detection circuit measures the voltage at the terminals of the semi-conductor and supplies an opening signal when this voltage exceeds a preset threshold. This patent does not provide any monitoring and remote control facility
US patent no 4,763,220 discloses an electric switch device having between two input and output terminals. The static industrial switch device or circuit is capable of frequently both establishing and interrupting electronically the power supply of a load, whose impedance may vary accidently and of protecting this load and the line against the effects of current surges and short circuits. This patent does not provide any monitoring and remote control facility
US patent no 4,262,214 is a system for switching a load between two AC sources wherein no degree of synchronization there between is required and wherein the switching is accomplished with the use of two electro-mechanical relays each having a
three pole, double throw contact arrangement. This patent uses two electromechanical relays having three pole double throw arrangement.
US patent no 4,717,841 relates to a static power switch circuit having a power switch member having a bidirectional power switch. The system consists of at least one controlled semiconductor of the thyristor or triac type with power terminals connected to an AC source in series with a load and a circuit for controlling the power switch member. There is a three pole static contactor which may be associated with a DC output interface of a programmable controller. This patent does not provide any monitoring and remote control facility
US patent no 3,961,235 static switch controller synchronized with a passage to zero of the supply voltage and which is insensitive to spurious firing currents is disclosed. A static switch is controlled by a control circuit having output terminals and input terminals. An alternating rectified voltage is applied across the output terminals and a closing signal is applied across the input terminals. The control circuit comprises a thyristor and a blocking circuit which blocks the cathode of the thyristor when the rectified voltage exceeds a threshold value. This patent does not provide any monitoring and remote control facility
US patent no 6,137,191 discloses a control arrangement and method for source-transfer switching systems including a high-speed control arrangement and high-speed switches to control the transfer of a load from one source to another with minimal transfer delays. This patent does not provide any monitoring and remote control facility
US publication no 20060226706 discloses an apparatus and methods for coordinated static switch operations for load transfers in uninterruptible power supply systems. The controller circuit may be operative to transition the load from a first state wherein the load receives power from the first power source via the first static switch to a second state wherein the load receives power from the second power source while isolated from the first power source. The patent deals with apparatus and method for coordinated static switch operation for load transfer in uninterruptible supply.
US patent no 3,638,040 discloses a system employing power transistors for transferring a load between two dependent power sources at any phase angle and in less than 20 microseconds. The system is unique in that it is extremely fast acting while at the same time does not require power source synchronization and produces no circulating currents during the switching interval. This patent does not provide any monitoring and remote control facility.
US patent no 5,814,904 and 5,644,175 discloses methods and apparatuses for providing alternate current paths to a junction through different sets of gate controlled SCRs coupled to the junction. The method starts with the step of initiating a switch from an active set of SCRs to an inactive set by removing a gate signal from two parallel connected, opposite sense current carrying SCRs which in combination carry AC current in either direction.
This patent does not provide any monitoring and remote control facility.
US publication no 2005207082 discloses a static tie switch designed to provide the upmost in reliable power to critical equipment, such as communications and computing equipment. The switch uses solid state devices, wherever possible and preferable uses silicon controlled rectifiers (SCR's) to tie corresponding phases of multiple buses together.
This patent does not provide any monitoring and remote control facility.
US patent no 3,798,530 describes static switch circuit for switching off a failed inverter of a power supply circuit includes a pair of inverters, each driven by a DC input, and a load supplied by the inverters.
US patent no 4,174,495 discloses a force commutated static switch composed of inverse parallel connected thyristors. A bilateral commutation circuit is connected across the thyristors. This patent relates to forced commutation of inverse parallel connected thyristors.
US patent no 5,939,799 describes that a power is supplied to a load from either a first power source or a second power source. A transfer switch determines which of the power sources provides the power to the load. A switch control detects a loss in the power provided by a first power source and signals the transfer switch to switch to a second power source. This patent particularly relates to supplying power to a load during a switch from a first power source to a second power source
US patent no 7,352,082 devices and methods for voltage source transfer switching that reduces or eliminates transformer saturation due to DC flux built up during a transfer event. First and second voltage sources (primary and alternate) are connectable to a load via corresponding switches. A transformer is connected downstream of the switches. A controller operates the switches according to various transfer methods wherein a switching time is determined to minimize downstream saturation current.
Publication no 2002109411 discloses a power delivery system including a primary power bus for transferring power to the facility from on-site generators and a secondary power bus for transferring power to the facility from a utility. The system includes a static disconnect switch capable of quickly isolating the facility from the utility power grid and a controller for controlling the overall operation of the power delivery system.
US patent no 3,634,701 discloses a static transfer system includes a first switch for connecting a normally used AC source to a lead and a second switch for connecting a standby source to the lead. A sensor is connected to an AC sine wave reference source for comparing at every instant of time the normal AC sine wave signal to the reference source signal and feeding an error signal to a logic circuit at any instant in time when the normal source signal falls below the reference signal. The patent does not provide any communication and monitoring facility to the system.
Publication no JP53010043 discloses static load circuit switching device. Destruction due to secondary yielding is not existed and excellent efficiency is obtained, by connecting static electricity induction type thyristor between electric current source and load in seties and making this static electricity induction type thyristor to do ON-OFF by static switching device. The patent does not provide any communication and monitoring facility to the system.
Publication no EP534866 discloses low-loss static switch. A static switch comprising at least one bipolar transistor whose base is controlled through an amplifier by a control signal, a sensor, insulated-gate bipolar transistor connected in parallel with bipolar transistor and means for cutting the control of the base of the said bipolar transistor when the current crossing the switch is less than a predetermined value. The patent does not provide any communication and monitoring facility to the system.
US patent no 3,366,867 discloses static switch for controlling the application of power to a DC to AC inverter including a SCR normally in high impedance state and having its anode and cathode connected as power electrode between a source of direct current and voltage and a DC to AC inverter. The patent does not provide any communication and monitoring facility of the system
US patent no 3798530 describes static switch circuit. The static switch circuit is connected between the inverters and the load and comprises a pair of fault detectors, each having inputs connected to the output of a corresponding one of the inverters and outputs for detecting a fault occuring in the corresponding inverter. This patent relates to the provision of backup power and line protection for critical loads
US publications 20080180263, 20080179958, 20080179967 describes transfer switch having a transfer control provides electric power to a load. The transfer switch includes a power switching device provided with electric power from a first power source, such as a utility power source, and a second power source, such as a generator power source. The transfer control is structured to monitor the second power source, maintain a runtime count of the second power source, locate a piece of data concerning a maintenance procedure in a storage corresponding to a current value of the runtime count, and provide an indication of a need to perform the maintenance procedure. These patent deals with a automatic transfer switch for the systems having an ability to monitor the generator
power source and providing an indication of required maintenance. The patent uses electromechanical equipment to switch the power source.
Reference may be made to an article entitled "Static switch handles interrupted power" by Emerson Network Power, Electronics talk, January 2008. The article explains the four-pole Liebert Hiswitch2 ensures maximum supply availability through automatic switching without any overlapping of the input sources. The Liebert Hiswitch2 family of static switches has been expanded with a new four-pole version. It automatically switches the load to the secondary source in case of a critical event in the primary source it can also solve possible problems due to load current in the grounding connection, by cutting off and switching the neutral wire as well as switching the load between the two sources.
Further, reference may be made to an article entitled "Static transfer switch " by Liebert Corporation, US. The article talks about static transfer switch which utilizes solid-state switching devices close to the critical load. Thus it produces high levels of power availability and power system tolerance. The switch is suited for data processing, distributed computing, telecommunications equipment, and high-tech manufacturing applications.
Reference may be made to an article entitled "Digital energy™ STS - static transfer switch CE model: Static transfer switches single/three phase, 25-1000Amp" by GE consumer and industrial electrical distribution. The article talks about static transfer switches (STS) designed to transfer the supply between two independent live AC power sources. Unlike traditional automatic transfer switches (ATS), a static transfer switch provides a fast load transfer (typically 1/4 of a cycle), which ensures uninterrupted operation of sensitive electronic equipment.
Reference may be made to an article entitled "A detailed model for a thyristor-based static transfer switch" by MN Moschakis, ND Hatziargyriou, IEEE Transactions on Power Delivery, Vol. 18, No. 4, pp. 1442-1449, 2003. The article proposes an analytical model of STS and its performance is verified using the electromagnetic transients for DC (EMTDC) simulation package. Simulations using this model are performed in order to handle voltage sags based on real measurements on an actual industrial customer's supply voltage. Different phase angles and magnitudes of the two alternate source prefault voltages and different fault instances are considered.
Reference may be made to an article entitled "Static transfer switch MODEL C" by i -STS Manufacturing, Australia. The article explains that the model C three phase static transfer switch (STS) provides uninterrupted power to your critical equipment by automatically switching between two independent power sources upon detection of a problem.
Reference may be made to an article entitled "The power advantage: Static switch SSW 230 V-6 kVA, Static switch SSW230 V- 20 kVA " by Delta Energy Systems, Switzerland. The static switch SSW 230 V - 6 KVA is a microcontroller driven state of the art switch between the AC mains and the inverter to provide uninterruptible AC power. After an extremely quick detection of a mains fault, the static switch transfers the load almost without cut off to the redundant AC line. A communication and synchronization bus is responsible for the system performance and the Delta inverters are synchronized to the public AC mains.
Reference may be made to an article entitled "Static bypass switch: STS207 HV, In: 2 x 230VAC, Out: 230VAC (7MVA)" by Eltek Valere, Germany. The new static switch of the series STS207 is a compact electronic switch. The digital PLL guarantees minimized synchronization time of inverter and mains frequency. Due to the high synchronization speed the unit can also be used together with diesel gensets as bypass mains supply. The transfer time between the two inputs is less than 4ms. Therefore the use within an IT environment is possible. The STS monitors both incoming sources according to the voltage level, frequency and their synchronization.
Reference may be made to an article entitled "Determination of locations for static transfer switches using genetic algorithms and fuzzy multi-objective programming" by Ying-Yi Hong, Hong-Ming Hsieh and Saw-Yu Ho, International Journal of Electrical Power & Energy Systems Vol 29, Issue 6, Pages 480-487, July 2007. In this paper, the problem is formulated as a fuzzy multi-objective programming problem considering STS investment cost, sensitive bus voltage deviations and total voltage sags. Genetic Algorithms (GAs) using a vertex encoding/decoding are used to solve the problem. The vertex-based Prufer number is used in GAs for encoding/decoding the chromosomes (strings). The Prufer number ensures that the distribution system structure is radial in the iterations. The simulation results obtained from a 3 3-bus system are used to show the applicability of the proposed method.
Reference may be made to an article entitled "Static switches" by Schaefer, Inc., US. The article explains that the static switch has two inputs for load supply, a priority and anon-priority input, and synchronizes the frequency of one supply to the other. If the static switch detects deviation from tolerance through monitoring, it will transfer the load to the no priority input. When the supply of the priority input has returned to be within parameters of voltage and frequency, the static switch reverses this selection.
Reference may be made to an article entitled "Powerware static transfer switch (STS) " by Eaton. The article describes static transfer switches which are designed to enhance our line of advanced backup power management solutions, adding an increased level of power quality, flexibility, availability and reliability to create the best ups power protection infrastructure.
Reference may be made to an article entitled "APOTRANS static transfer switch" by Piller Power Systems, USA. The APOTRANS static transfer switch is suitable either as a retrofit to existing power distribution systems or for new systems. It supports critical loads by invisibly switching to an alternative power source should the preferred source become out of tolerance or fail completely.
Reference may be made to an article entitled "MGE static transfer switches" by American Power Corporation. The article explains that MGE static transfer switches (STS) supply power to a range of equipment from two independent and redundant sources. Static transfer switches automatically transfer power to a stable alternate source in less than 4ms under normal operating conditions. Even under extreme conditions, such as 180 degrees out of phase, the STS will have detection and transfer times that are up to 10 times faster than many other switches.
Reference may be made to an article entitled "Static transfer switch" by Rittal. The article explains that single-wired devices can be operated with a redundant power supply by using the STS (Static Transfer Switch). The STS has two in feeds which are automatically switched. The switching time is less than 5 ms. The operating panel on the enclosure front represents all central functions and messages of the Static Transfer Switch.
Reference may be made to an article entitled "Static switch eases load transfer" by S Ashland, Hearst Electronics Products. The article explains thata static switch transfers the AC load from the mains to an inverter output and vice versa. It monitors input over voltages, under voltages, the utility power & the inverter, as well as output short circuits and alarms and faults.
Reference may be made to an article entitled "Static transfer switch" by Vishal Sapru, 14 Oct 2003. The static transfer switch (STS) allows instantaneous transfer of power sources to the load.
Reference may be made to an article entitled "Performance evaluation ofthyristor based static transfer switch" by Mokhtari, H.; Dew an, S.B.; Iravani, M.R., Summer Meeting, IEEE, Vol 2, Page(s):961, 2001. The article proposes a fast thyristor based static transfer switch (STS) which employs fast voltage-detection and thyristor gating strategies to connect the customer to either of the two sources. Performance of the designed STS system is evaluated using the electro-magnetic transients for DC (EMTDC). Simulation results are verified by comparing them with experimental results.
Reference may be made to an article entitled "Static transfer switch " by Patara Pacific, Pulsar STS. The article explains that Pulsar STS handles the automatic or manual transfer of your loads between two independent sources that you designate as preferred or
alternate. In the event of a failure, transfer is automatic and instantaneous. Pulsar STS can be used as an automatic bypass for the UPS. Pulsar STS lets you service one of the sources without interrupting the flow of power to your applications.
Reference may be made to the thesis entitled "High speed silicon controlled rectifier, static transfer switch " H Mokhtari, Department of Electrical and Computer Engineering, University of Toronto, Toronto, Canada 1999. This thesis presents new fault/disturbance detection and thyristor-gating schemes for a Silicon controlled rectifier (SCR) static transfer switch (STS) to achieve fast load switching between two sources of AC power.
Reference may be made to an article entitled "Application of an intelligent static switch to the point of common coupling to satisfy IEEE 1547 compliance" by K David; V Harry T, Power Engineering Society General Meeting, pp 1-4, June 2007. This paper describes the application of an SCR-based static switch, located at the point of common coupling (PCC), in a designed microgrid, which incorporates a high level system control scheme to maintain compliance with IEEE Standard 1547. In this application distributed resource equipment, which may be considered non-compliant, has been uniquely applied beyond the static switch to increase reliability, power quality, plus provide back up and universal power supply capability to customer load.
Reference may be made to an article entitled "Digital static transfer switch" by F Tamjidi, 1998. This paper describes that many uninterruptible power supply (UPS) and building system configurations become a possibility-from independent and isolated systems with only DSTSs allowing transfer of loads between systems to isolated redundant systems, which have bypasses fed from a standby UPS.
Reference may be made to an article entitled "Development of a high-speed static switch for distributed energy and microgrid applications" by K, Ben; P Christopher; L Jonathan; J Vinod; D SM, Proceedings Power Conversion Conference - Nagoya, pp. 1418-1423, 2007. This paper details the development and testing of a high speed static switch for distributed energy and microgrid applications.
With all the above discussed restrictions or limitations, it is required to have a static bypass switch, which is used to provide redundant non interrupting power supply to critical loads. The switch monitors all the input sources connected at the input. In case the source supplying the load fails or goes out of the predefined stable values, it automatically transfers the load from that source to the other available source. Due to the fast transfer time, the output load is not disrupted.
OBJECT OF THE INVENTION
The primary object of invention is to provide a static bypass switch which can provide redundant power supply to the critical load connected at the output.
Another object of the invention is to provide a static bypass switch which can have a comprehensive communication for complete monitoring and control of the static bypass switch.
Yet another object of the present invention is to provide a static bypass switch having programmable priority of the connected input sources to the static switch.
Another object of the present invention is to provide a static bypass switch having comprehensive display of the system information to the user.
Yet another object of the present invention is to provide a switching circuit which is simple in construction, contains relatively few parts and is correspondingly dependable in operation.
Yet another object of the present invention is to provide information of the connected input sources and provide advance alarm in case of certain user programmable setting to detect in advance any critical condition of the input sources so as to provide very high reliability of power t o the load.
Still another object of the present invention is to provide a static bypass switch with low power requirements and which introduces no hazard to the operator or the environment in which the circuit is employed.
SUMMARY OF THE INVENTION
In order to overcome the mentioned problems and achieve the said objects, the present invention discloses static bypass switch used to provide redundant non interrupting power supply to critical loads. In such systems atleast two input sources are connected as the redundant input sources at the input of the static bypass switch and the load is supplied from the output of the static bypass switch. The static bypass switch monitors all the input sources connected at the input and if the source supplying the load fails or goes out of the predefined stable values, it automatically transfers the load from that source to the other available source. As the transfer time is very fast, the output load is not disrupted. The switch comprises of different sections such as the digital signal controller section, power supply section, sense signal conditioning unit, SCR power module section, communication section, user configuration setting, display section etc.
The digital signal controller is the heart of the system. It controls the complete operation of the static bypass switch. Atleast two input sources i.e. Sourcel and Source 2 are connected at input of the static bypass switch and the main controller monitors both the input sources. One of the sources is treated as the master source and supplies the load when both the input sources are within the specified range. In case the preferred source goes out of the specified operating region, the digital signal switches the load to the alternate input source.
In an embodiment of the present invention, the various parameters of the sources connected at the input can be voltage, frequency, phase difference etc
In another embodiment of the present invention, the alternate source can be indicated with any color to show that the alternate source is ready and acting as standby for the preferred source.
In another embodiment of the present invention, any display device can be used to display various system parameters, user messages and system information.
In still another embodiment of the present invention, the phase voltage, frequency, load percentage, current, phase, source priority, buzzer setting and transfer sensitivity can be displayed.
With the help of the software it is also possible to remotely monitor and control the system through the internet.
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 the Static Bypass switch Block Diagram
Fig 2 shows the Main screen for the Monitoring and controlling software
Fig 2(i) shows the Monitoring and controlling software
Fig 2(ii) shows the Monitoring and controlling software
Fig 2(iii) shows the Monitoring and controlling software
Fig 2(iv) shows the Monitoring and controlling software
Fig 2(v) shows the Monitoring and controlling software
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
While the invention is susceptible of various modifications and alternative constructions, a certain illustrated embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed. On the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention.
Fig 1 shows the block diagram of the static bypass switch. Static bypass switch provides redundant non interrupting power supply to critical loads. In such systems two or more input sources are connected as the redundant input sources at the input of the static bypass switch and the load is supplied from the output of the static bypass switch. The static bypass switch monitors all the input sources connected at the input. If the source supplying the load fails or goes out of the predefined stable values then it automatically transfers the load from that source to other available source, wherein the transfer time is very fast so the output load is not disrupted. The switch comprises of different sections such as digital signal controller section, power supply section, sense signal conditioning
unit, output load sensing section, SCR power module section, communication section, user configuration setting and display section.
The digital signal controller is the heart of the system, which controls the complete operation of the static bypass switch. Two input sources Source 1 and Source 2, are connected at input of the static bypass switch. The main controller monitors both the input sources. One of the sources is treated as the master source and supplies the load when both the input sources are within the specified range. In case the preferred source goes out of the specified operating region, the digital signal switches the load to the alternate input source.
Under normal conditions, the controller switches the first switch to connect the first source (primary source) to the load. In the event that the first source fails while the second source (alternate source) is available, the controller detects the condition and operates the switches to disconnect the first voltage source from the load. It subsequently connects the second voltage source, maintaining power to the load.
Power Supply section provides the redundant power supply to the static bypass switch so that the system is powered up even if only one phase is present at the input. The digital signal controller is the main controller of the system. The input sources are monitored by the main controller continuously. The voltages are sensed through isolated sensing transformer connected. The main controller senses the voltage, frequency and phase for the connected sources. The controller reads the various user configurations such as source priority, voltage window setting, frequency setting etc. Based on the settings, if that source is available and ok, the main controller connects the load to the preferred source otherwise it connects the load through the alternate source. The main controller senses any decrease or increase in the voltage and frequency beyond the settings configured and transfers the load to the alternate source if that is within limits. The SCR power module is controlled by the main controller. The controller triggers the appropriate SCR from the back to back connected SCR at zero crossing to control the power output from the input source. The display section is controlled by the main controller to display all the relevant information to the user. The communication and monitoring section provides the facility for connection of PC and other smart interfaces to extract all the information from the system and also configuration of system settings. The sense signal condition section takes the input from various input output signals and gives it to the main controller.
The main controller senses the output load connected through the current transformers connected at the output load sense section. It monitors the overload condition of the three phases connected load and provides the visual and audio alarms to indicate the overload condition. If the user does not reduce the load for the specified time limits, the system output is turned off and continuous alarm is given to indicate the overload condition. The system can be turned on only after resetting from the front switch after overload shutdown.
The main controller also monitors any short circuit condition that might take place at the system output. In case of short circuit, the main controller instantly turns the output off and gives indication of the short circuit with continuous alarm. The user is required to correct the short circuit condition and then reset the system to turn on the output again.
The main controller also controls the LCD for the display of various system parameters, user messages and system information. All the phase voltage, frequency, load percentage, current, phase etc are displayed. The system settings such as source priority, buzzer setting and transfer sensitivity are also shown on the display. These settings are modified form the front panel switches as well as through the monitoring and controlling software.
The static bypass switch provides communication channel for complete monitoring and control of the static bypass switch. The main controller also reads the user configuration settings from the dip switches for voltage and frequency window settings.
The static bypass switch is interfaced to the connected input sources through communication channel so as to collect the complete information of their state of operation. In case of the input sources being UPS, the static bypass switch communicates with the system to measure various system parameters. In case of critical conditions such as battery low condition for the UPS input source, the static bypass generates alarms to inform the user in advance about the condition of the connected input sources. Also if the input source in generator the static bypass switch monitors the generator operating conditions such as fuel level left etc to give advance warning to the user in case of critical condition during operation. The ability to monitor the state of the input sources provides high reliability output power to the load because the system generates alerts to the user in advance so that corrective action are taken.
Further reference may be made to Fig 2 showing the main screen of the monitoring and controlling software. The screen shows the availability of the sources connected at the input to the static bypass switch. It also shows the various parameters of the sources connected at the input such as but not limited to voltage, frequency, phase difference etc. In case of any parameter being out of specified range, it is indicated on the screen. The screen also shows the priority of the connected sources and which source is connected to the load and supplying to the load. The power flow is indicated by the arrows flowing from the source to the load. The load percentage connected at the output of the source is also displayed. The alternate source is indicated with yellow color to show that the alternate source is ready and acting as a standby for the preferred source.
Fig 2(i) shows a condition where one of the phases of the preferred three phase source if out of the specified range, the load is automatically transferred from the preferred source to the alternate source. The phase having parameters out of range is indicated with message such as "High/Low Voltage" or "High/Low Frequency" etc.
Fig 2(ii) Shows a condition when only one input source is connected to the static bypass switch. The source that is not connected is shown as "Not Available" in red color and the load is supplied from the alternate source connected to the system.
Further, Fig 2(iii) shows the various configuration settings that are available through the software. The user by opening the settings menu sets the priority of the connected sources. The buzzer is disabled to recover from a fault condition. The transfer time sensitivity is programmed as Normal, Medium and High by the user. The user also schedules the operation of the two sources connected so that both the input sources can be used alternately.
Fig 2(iv) shows the typical event log done by the software during the operation of the static bypass switch. The software monitors all the events such as change in settings, transfer between preferred and alternate source, any abnormality in the sources connected in terms of out of range voltage, out of range frequency, overload on any of the phases and short circuit condition etc. This event logging is very useful in analysis of the system performance during the operation.
Again, Fig 2(v) shows the alert message that is generated in case any critical condition occurs. The alerts are sent to the mobile phones to the specified numbers or emailed to the specified email addresses.
With the help of the software, it is also possible to remotely monitor and control the system through the internet. All the information related with the operation of the static switch are viewed over the internet or through GSM, GPRS modem etc. from a remote location. The various configuration settings for the operation are also handled from remote location.
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. A static bypass switch comprising of digital signal controller section with user configuration setting senses and momtors various parameters through sense signal conditioning unit and output load sensing section, which controls power switch modules and generates alerts and displays results via communication section and display section, and power supply section provides the redundant power supply to the static bypass switch so that the system is powered up even if only one phase is available at the input.
2. A static bypass switch as claimed in claim 1, wherein the switch monitors all the input sources connected at the input in which on the failure of the source supplying the load, the switch automatically transfers the load from that source to the other available source.
3. A static bypass switch as claimed in claim 1 or 2, wherein the switch has very fast transfer time so that the output load is not disrupted in which the controller triggers the appropriate power switch to control the power output from the input source.
4. A controller as claimed in any of the preceding claims, wherein the controller biases the first switch to connect the first source (primary source) to the load under normal conditions in which the controller detects the condition and operates the switches to disconnect the first voltage source from the load in case the first source fails while the second source (alternate source) is available.
5. A controller as claimed in any of the preceding claims, wherein the main controller monitors any short circuit condition that takes place at the system output in which during short circuit, the main controller instantly turns the output off and gives indication of the short circuit with continuous alarm.
6. A static bypass switch as claimed in any of the preceeding claims, wherein the controller controls the display device to display various system parameters, user messages and system information in which the switch displays the phase voltage, frequency, load percentage, current, phase, source priority, buzzer setting and transfer sensitivity.
7. A static bypass switch as claimed in any of the preceding claims, wherein the software monitors the events such as change in settings, transfer between preferred and alternate source, abnormality in the sources connected in terms of out of range voltage, out of range frequency, overload on any of the phases and short circuit condition etc in which the system settings are configured from the front panel switches and through the monitoring and controlling software.
8. A power supply section as claimed in any of the preceding claims, wherein the power supply section provides the redundant power supply to the static bypass switch so that the system is powered up even if only one phase is available at the input in which the event logs are done by the software during the operation of the static bypass switch.
9. A static bypass switch as claimed in any of the preceding claims, wherein the static bypass switch shows the alert message in which the alert messages are generated in case of any critical condition such as the input source in generator, the static bypass switch monitors the generator operating conditions such as fuel level and gives advance warning to the user in case of critical condition during operation..
10. A static bypass switch as claimed in any of the preceding claims, wherein the alert messages are sent to the mobile phones to the specified numbers or emailed to the specified email addresses in which the static bypass monitors the state of the connected input sources of the static bypass switch and generates advance alerts and warning for the user to take corrective action.
11. A static bypass switch substantially as herein described with reference to the accompanying drawings.