Claims:1. A system for electrically operated mechanism of a motorized changeover switch disconnector, wherein said system comprising:
a switch configured to connect either a first source or a second source to an electrical load or disconnect said load,
a motor driven mechanism having a motor driven by a motor control circuit module, wherein said mechanism adapted to drive a shaft to either a first position or a second position or a OFF position of said switch based on an input, wherein said first position connecting said switch to said first source and said second position connecting said switch to said second source;
a controller unit coupled to said motor driven mechanism for energizing said motor, wherein said controller unit configured to perform measuring of input phase voltage, scanning of said received input data corresponding to said switch position, controlling shaft position of said switch, and generation of gate pulses for driving said motor control circuit module according to said received input for a normal or a braking operation, wherein said controller unit adapted to determine if said received input is equal to a current shaft position to avoid selected simultaneous inputs;
a voltage sensing module coupled to said controller unit and adapted to sense power supply and thereby enable said controller unit to energize said motor for said normal operation if said power supply is within a pre-defined voltage range.

2. The system as claimed in claim 1, wherein said controller unit adapted to receive said inputs corresponding to said first position or second position or OFF position of said switch from an input command circuit module.

3. The system as claimed in claim 1, wherein said controller unit is supplied with power by means of a power supply circuit module and said voltage sensing module adapted to continuously sense power supply in said power supply circuit module is within said pre-defined voltage range.

4. The system as claimed in claim 1, wherein said controller unit adapted to turn OFF said motor operation by disabling receive of said inputs if said power supply is more or less than said pre-defined voltage range.

5. The system as claimed in claim 4, wherein during motor operation, said controller unit adapted to trigger one or more fault indicator means indicating fault condition if required position is not reached within the given time.

6. The system as claimed in claim 1, comprises an integral plugging mechanism to restrict rotation of said motor when desired position is obtained, to avoid over travel of said shaft of switch.

7. A method of operating the system for an electrically operated mechanism of changeover switch disconnector as claimed in claims 1-6, wherein said method comprising:
receiving, by means of an input command circuit module, input data corresponding to a first or second or OFF position of a switch, and thereby transmitting said input data to a controller unit;
determining, by means of a voltage sensing module, whether power supply to said controller unit is within a predefined voltage range, wherein said voltage sensing module enable said controller unit to energize a motor driving circuit module if said voltage is within a predefined voltage range, else turn OFF said motor operation;
determining, by means of said controller unit, if said input data is equal to a current shaft position of said switch, wherein said controller unit adapted to store, by means of a storing module, said input data if said input data corresponds to a new position of said switch;
energizing, by means of said controller unit, motor control circuit module for driving a motor driver to rotate said shaft means corresponding to said new position of said switch.
, Description:TECHNICAL FIELD OF THE PRESENT INVENTION

[001] The present subject matter described herein, in general, relates to changeover switch disconnectors, and more particularly relates to a control circuit module for an electrically operated mechanism (EOM) of changeover switch disconnector.

BACKGROUND OF THE PRESENT INVENTION

[002] Electrical distribution systems employ a variety of devices for controlling and managing the distribution of electrical power, including changeover switch disconnectors (COSD). Changeover switch disconnector is also called open transition transfer switch. Changeover switch disconnector is generally used at the incoming side of load and it has three stable positions called mains, generator and OFF as shown in figure 1. Depending on the availability of power supply, load will be connected to either mains or generator and during maintenance it will be in OFF position.

[003] Changeover switch disconnectors are employed in a wide variety of residential and commercial structures to allow an electrical load therein to be supplied with power from an alternate power source in the event of instability and/or loss of power from a main power source.

[004] Here the user has to change the position of the Changeover switch disconnector manually using handle. Due to changing system requirements, there is a need of some electrically operated mechanism (EOM) to perform the same operation. EOM is an accessory of changeover switch disconnector. It is basically a motor driven mechanism, based on the input command it will change the position of the changeover switch disconnector. A power transfer from a “normal” power source to an alternate “emergency” power source is initiated by the electronic controller energizing the motor operated mechanism. The motor operated mechanism is energized until the switching mechanism is moved to a desired position and the control contacts cut off power to the motor. Accordingly, a need remains for quickly, inexpensively and reliably converting an operating manual COSD into motorized COSD without a significant power outage.

[005] Reference is made to US20050116670A1 which discloses a method to using micro controller and electro mechanical relays. Dependable operation of the switch actuators is critical to the operation of the Changeover switch disconnectors. Replacement of these actuators, which typically comprise a motor, always requires disconnection of the line voltage for safety reasons.

[006] However, the drawbacks of the above mentioned US ‘670A1 is as follows:
• Motor actuators are energized without sensing the available voltage, which will cause damage to the motor and control circuit.
• During under voltage condition, the electromagnetic relays will malfunction and will cause damage to motor and control circuit.
• During over voltage condition electromagnetic relays and motor will get damaged.
• Prolonged energization of the motor with unstable supply voltages may result in permanent damage to the motor and require replacement and disconnection of the EOM from the COSD. This necessitates disconnection of the power sources and an interruption in power to the load.

[007] Reference is further made to US20060145642 which discloses a motor drive control device which uses mechanical switches configured in an H-bridge shape and can protect the mechanical switches being damaged from over voltages. The motor drive control device includes: two relay switching units which are coupled to both sides of a motor and each of which is formed in an H-bridge shape and is connected to an output terminal of a bridge circuit; a switching unit which controls a voltage source applied to the relay switching units; and an inverter controller which first controls any one of the relay switching units and then controls the switching unit so that the motor starts to operate, and first controls the switching unit and then controls the one of the relay switching units so that the motor comes to a halt.

[008] However, the above mentioned US ‘642 provides controlled voltage to the electromagnetic relay circuit and motor circuit, but during the under voltage condition, the electromagnetic relays will malfunction and will cause damage to motor and control circuit.

[009] Accordingly, there is a need for an improved motor operator arrangement that overcomes these drawbacks of the prior art. In addition there is a need of electrical braking to provide controlled deceleration of a motor-driven device to avoid over travel problems in the COSD which will cause twisting of shaft and hence mechanical damage.

SUMMARY OF THE INVENTION

[0010] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0011] An object of the present invention is to provide quick, inexpensive and reliable solution for converting an operating manual COSD into motorized COSD without a significant power outage.

[0012] Another object of the present invention is to provide a system with a control circuit module to measure input phase voltage, scanning of input commands, shaft position of COSD and Binary coded decimal (BCD) switch, generation of gate pulses to motor driver circuit for normal and braking operation of the load.

[0013] Yet another object of the present invention is to provide a control circuit module with an integral plugging mechanism to stop the rotation of DC motor when the desired mechanism position has been obtained to avoid over travel problems in the COSD which will cause twisting of shaft and hence mechanical damage.

[0014] Still another object of the present invention is to provide a control circuit module with inbuilt command interlocking to avoid simultaneous command.

[0015] Accordingly to one aspect, the present invention provides a system for electrically operated mechanism of a motorized changeover switch disconnector, wherein said system comprising:
a switch configured to connect either a first source or a second source to an electrical load or disconnect said load,
a motor driven mechanism having a motor driven by a motor control circuit module, wherein said mechanism adapted to drive a shaft to either a first position or a second position or a OFF position of said switch based on an input, wherein said first position connecting said switch to said first source and said second position connecting said switch to said second source;
a controller unit coupled to said motor driven mechanism for energizing said motor, wherein said controller unit configured to perform measuring of input phase voltage, scanning of said received input data corresponding to said switch position, controlling shaft position of said switch, and generation of gate pulses for driving said motor control circuit module according to said received input for a normal or a braking operation, wherein said controller unit adapted to determine if said received input is equal to a current shaft position to avoid selected simultaneous inputs;
a voltage sensing module coupled to said controller unit and adapted to sense power supply and thereby enable said controller unit to energize said motor for said normal operation if said power supply is within a pre-defined voltage range.

[0016] In another aspect of the present invention, there is provided a method of operating the system for an electrically operated mechanism of changeover switch disconnector, wherein said method comprising:
receiving, by means of an input command circuit module, input data corresponding to a first or second or OFF position of a switch, and thereby transmitting said input data to a controller unit;
determining, by means of a voltage sensing module, whether power supply to said controller unit is within a predefined voltage range, wherein said voltage sensing module enable said controller unit to energize a motor driving circuit module if said voltage is within a predefined voltage range, else turn OFF said motor operation;
determining, by means of said controller unit, if said input data is equal to a current shaft position of said switch, wherein said controller unit adapted to store, by means of a storing module, said input data if said input data corresponds to a new position of said switch;
energizing, by means of said controller unit, motor control circuit module for driving a motor driver to rotate said shaft means corresponding to said new position of said switch.

[0017] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0018] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0019] Figure 1 illustrates the block diagram of a typical system for an electrically operated mechanism (EOM) of changeover switch disconnector.

[0020] Figure 2 illustrates the block diagram of the proposed system, according to one embodiment of the present invention.

[0021] Figure 3 illustrates the schematic diagram of the motor actuating control circuit, according to one embodiment of the present invention.

[0022] Figure 4(a-g) illustrates the flowchart representation of the method implemented in the control circuit module, according to one embodiment of the present invention.

[0023] Figure 5 illustrates the timing circuit of enabling solid state switches, according to one embodiment of the present invention.

[0024] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0025] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0026] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0027] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0028] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0029] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0030] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0031] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0032] Changeover switch disconnector is generally used at the incoming side of load and it has three stable positions called mains, generator (auxiliary) and OFF as shown in Fig.1. Depending on the availability of power supply, load will be connected to either mains or generator and during maintenance it will be in OFF position. The motorized changeover switch disconnector having a switch configured to connect one of two sources to a load or disconnect the load, a mechanical drive, an actuator, microcontroller and a solid state switches. The mechanical drive is configured to drive the switch to either first position, or second position or to OFF position. The first position connecting the switch to the first source, and the second position connecting the switch to the second source. The actuator is in mechanical communication with the mechanical drive to cause the mechanical drive to move on command. An auxiliary switches are connected mechanically to respective positions of COSD for status indication purpose

[0033] In one implementation, as shown in figure 2, the block diagram of the operating system consists of bridge rectifier, regulated power supply, controller unit (i.e., the microcontroller section), input commands circuit module, voltage detection circuit, position sensing section and Motor driving circuit module. In the present invention a low end and low cost microcontroller is used as a controller unit which is configured for taking decisions and perform operations as per input signals. This controller unit (as shown in figure 2) is responsible to measure input phase voltage, scanning of input commands, shaft position of COSD and BCD switch, generation of gate pulses to motor driver circuit module for normal and braking operation of the motor. The Controller unit can be configured for measuring phase voltage using inbuilt analog to digital (ADC) module and store value in a volatile memory. When voltage is within range then normal system operation of the motor takes place based on input command and when voltage is out of range then input commands will be disabled and a fault indication may be given to an indicator means.

[0034] In one implementation, referring to figure 3, wherein energization of the motor can be accomplished by a signal from the controller unit which is provided to the motor actuator solid state switches Q1 to Q4. To bring COSD to mains position from OFF or generator position, motor driven will be enable to rotate in forward direction. Similarly to bring COSD to generator position from OFF or mains position, motor will be enabled to rotate in a reverse direction. When the power supply connected to the motorization module is within the pre-defined voltage range (i.e., 60% to 115%), and then only input commands will be accepted by the input commands circuit module. LED indication as an exemplary indicator means, may be triggered when the power supply connected to the motorization module is out of pre-defined voltage range.

[0035] In the implementation, the controller unit is configured take actions according to the input commands given. In real time world there are chances of simultaneous input commands to the system due to improper implementation in PLCs. This problem can be avoided if the system is designed to ignore simultaneous commands, but this cannot be done, because in emergency situation OFF command should have priority. So system should ignore only selected simultaneous commands. The system of the present invention is configured to accept a new command before the switch has reached the position of the previous command if previous command vanishes. During transfer towards source-I position if source-I command persists, source-II command can’t be executed and vice-versa, whereas OFF command can be executed. During transfer towards OFF position if OFF command persists, neither source-I command nor source-II command can be executed. System can be used for either continuous or momentary (>50ms) input commands.

[0036] In one implementation, Figure 4 represents a flow chart of the method implemented in the controller unit. As shown in Figure 4 (a), at 206 input scan task will be started. This task will get scheduled at preferably every 100 m sec by means of a scheduler. At 207 state of user input switch status and shaft position status will be scanned by and input data will get stored in a local memory, based on the scanned data a determination is made at 208, to check if any user input switch is pressed then a message flag will be raised and scanned data is stored in a shared memory. When motor control task will get schedule, it will take decision based on stored data.

[0037] In one implementation, as shown in Figure 4 (b), at 221 motor control task will be started. This task will get schedule at preferably every 1ms. Availability of normal power will be checked at 222 using a voltage sensing circuit module described above. If normal power is not sensed, the routine branches at 227 to turn OFF motor operation and restart task timer to reschedule task after preferably 1ms. If normal power is sensed, a check will be made at 223 for command from input scan task as described above. If command has not arrived routine will branch at 237, if command has arrived at 224 a check will be made for previous command and current command, if no difference found it means either user has pressed button for long time or same button pressed again. At 231, current position of shaft will be identified and compared with received input command to ensure proper operation of system. If current position of shaft and new command are equal it means system need not to perform any operation and routine will branches to 226, if shaft position is not at desired position then new command will be stored in shared memory. At 224 if new command found, shared memory get updated and routine will branch to 226.

[0038] In one implementation, as shown in Figure 4 (c), at 227 based on the new command stored in shared memory routine will branch to 228 if new command is for switch to mains, 229 for switch to OFF and 230 for switch to Auxiliary position. When switch to mains command arrived subroutine will branch to 228 as described in Figure 4 (d). At 232 a determination will be made for the input command and current position of shaft, if both are same, at 235 driver operation will get stopped and routine will branch at 237. At 233 a determination will be made to check current state of motor driver, if driver is busy in rotating the shaft of COSD towards auxiliary supply at 236 driver stop COSD shaft rotation and after a delay of preferably 50ms it start rotation of COSD shaft towards mains supply. If driver is not busy at 233, at 234 driver will rotate COSD shaft toward mains supply.

[0039] In one implementation, when switch to OFF command arrives, subroutine will branch to 229 as described in Figure 4(e). At 238 a determination will be made for command and current position, if both are same at 243 driver operation stopped and routine will branch to 237. At 239 a determination will be made to check current position of shaft of COSD, if position is mains position, a determination will be made at 240 to check current state of motor driver, if driver is busy to rotate shaft towards mains supply, at 241 driver operation stops and after preferably 50ms motor driver rotate the shaft towards auxiliary supply. If driver state is ideal then at 242 driver start rotation of shaft towards auxiliary supply without applying any reverse delay. At 239 if position of shaft is not at mains supply a determination will be made at 244 to check shaft position at auxiliary supply if found correct and driver is ideal at 245, at 247 driver will start rotation of shaft towards mains supply. If driver is busy at 246, then after preferably 50ms sec the motor driver will rotate shaft of COSD towards mains. If at 244 position of shaft is not at auxiliary supply routine will branch to 237.

[0040] In one implementation, when switch to Auxiliary input command arrives, subroutine will branch to 230 as shown in Figure 4(f). At 248 a determination will be made for command and current position, if both are same at 249 driver operation will be stopped and routine will branch at 237. At 250 a determination will be made to check state of driver, if driver is in busy in rotating the shaft of COSD towards mains supply at 252 driver stop COSD shaft rotation and after delay of preferably 50ms it start rotation of COSD shaft towards auxiliary supply. If driver is not busy at 250, at 252 driver will rotate COSD shaft towards auxiliary supply.

[0041] In one implementation, input command execution routine is described in Figure 4(g). Based on input command cases as shown in Figure 4(c) and corresponding validation of commands, command execution takes place. At 253 status of command execution will be checked and if no command execution takes place then it resets the timer and starts again the periodic timer. When command execution takes place at 253 then it checks whether the required position is reached or not at 254, if not then it checks whether operation time out of preferably 2 sec will be elapsed or not at 256. If 2 sec time is elapsed then at 257 steady LED indication is given to indicate some fault in the system otherwise it keep checking the position until time elapses.

[0042] In one implementation, if it reaches the required position at 254 then it stops the motor rotation and starts the plugging operation with pre and post delay of preferably 50ms at 255. An electrical braking feature has been added in motor control systems to provide controlled deceleration of a motor-driven device, to avoid over travel problems in the COSD which will cause twisting of shaft and hence mechanical damage. Here electrical braking can be accomplished by energizing a motor in the direction opposite the current direction of rotation. Here an integral plugging mechanism is included to stop the rotation of the DC motor when the desired mechanism position has been obtained. To avoid shoot through fault in H-bridge circuit, incorporated preferably a 50ms dead time pre and post plugging operation. The forward commands will enable Q1and Q3 solid state switches in the H-bridge, while reverse command will enable Q2 and Q4 solid state switches in the H-bridge as shown in Figure 5. The present invention, uses of micro controller based circuit, which will ameliorate the aforementioned problems.

[0043] Some of the non-limiting advantages of the present invention are as follows:
• The present invention solves the problems of the prior art and also provides additional benefits for “fail-safe” circuit operation.
• In the present invention, an integral plugging mechanism is included to stop the rotation of the DC motor when the desired mechanism position has been obtained to avoid over travel problems in the COSD to prevent twisting of shaft and hence preventing mechanical damage.
• The present provides a simple control circuit with easy factory adjustable plugging time to match with different sizes of COSD and mechanical tolerances.
• During motor operation, the controller unit adapted to trigger fault indicator means indicating fault condition if required position is not reached within the given time.
• The present invention provides a control circuit module with inbuilt command interlocking to avoid simultaneous commands.
• In the present invention an inbuilt OFF command priority overrides the Main/Gen commands.
• This control circuit based system for electrically operated mechanism of a motorized changeover switch disconnector is a simple and less costly solution.
• By removing the electromagnetic relays, the present invention reduces downtime for preventative maintenance as compared to motorized COSDs employing electromagnetic relays.
• Reduced mechanical wear and reduced contact erosion from electrical arcing can be realized.
• Fault indication for Under/Over voltage indication.
• A more compact motorized COSD systems.
• Ease of assembly and maintenance.

[0044] Although a system and method for electrically operated mechanism of a motorized changeover switch disconnector has been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the system and method for electrically operated mechanism of a motorized changeover switch disconnector.