Claims:1. An electrically operated mechanism , said mechanism comprising:
at least one switching unit provided between at least one mains source and at least one generator source, wherein said switching unit having at least three stable position comprising:
first position,
second position, and
OFF position,
Wherein, in said first position the switching unit is adapted to establish connection of at least one load with said mains source, in said second position the switching unit is adapted to establish connection of said load with said generator source;
at least one mechanical drive, actuated to drive said switching unit to said first position or said second position or said OFF position;
at least one load actuator means, mechanically communicating with said mechanical drive to enable said mechanical drive to move, wherein said load actuator means is adapted to receive an output command from at least one control circuit module to actuate plurality of solid state switches;
said control circuit module comprises: an arrangement of logical circuit module; and a plugging mechanism;
wherein, said control circuit module adapted to receive continuous or momentary input commands corresponding to each of mains source command or generator source command or OFF command from potential free contacts, and thereby generate said output command to connect/disconnect said mains source or said generator source to said load according to said first position or said second position of said switching unit, wherein said control circuit module adapted to:
transfer switching of said switching unit to said first position from said OFF or second position and/or to said second position from said OFF or first position, by energizing said load in a direction opposite to the current direction of rotation.
2. The mechanism as claimed in claim 1, wherein said logical circuit module comprising:
an arrangement of plurality of logic gates selected from AND gate, OR gate, NOR gate and/or EX-NOR gate;
plurality of Tri-state active low buffers; and
D-flip flops.

3. The mechanism as claimed in claim 1, wherein said control circuit module adapted to receive input voltage from a voltage comparator provided within a pre-defined voltage range, preferably 65% to 110% of rated input supply voltage.

4. The mechanism as claimed in claims 2-3, wherein said control circuit module adapted to receive said continuous input command corresponding to said main source command or said generator source command, if said input voltage is within a pre-defined voltage range and Ex-NOR gate output is low.

5. The mechanism as claimed in claim 2, wherein control circuit module adapted to receive said momentary input command using a latching mechanism achieved by said D-flip flop.

6. The mechanism as claimed in claims 1, wherein said output command from said control circuit module to said solid state switches corresponds to a forward command and a reverse command.

7. The mechanism as claimed in claims 6, wherein said control circuit module adapted to:
transfer switching of said switching unit from said OFF or second position to said first position, by enabling said rotation of said load in forward direction using said forward command; and
switching said switching unit to said second position from said OFF or first position, by enabling said rotation of said load in a reverse direction using said reverse command.
8. The mechanism as claimed in claims 1, further comprising: at least two limit switches adapted to provide feedback to said control circuit module to cut-off supply to said load when desired position is reached by disabling said load actuator solid state switches energizing said load.

9. The mechanism as claimed in claim 1, wherein said plugging mechanism adapted to restrict said rotation of said load when a desired position of said switching unit is obtained by generating one or more plugging command at a plugging duration.

10. The mechanism as claimed in claim 1 comprising an electrical braking mechanism to provide controlled deceleration of said mechanism, by energizing said load in the direction opposite the current direction of rotation.
, Description:TECHNICAL FIELD

[001] The present invention described herein, in general, relates to electrical operated mechanism, and more particularly, to control circuit module for controlling the operation of an electrically operated mechanism (EOM).

BACKGROUND

[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. 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. Typically, an operator has to change the position of the Changeover switch disconnector manually using handle. Due to changing system requirements, there is a need of an electrically operated mechanism (EOM) to perform the same operation.

[004] EOM is an accessory of changeover switch disconnector. It is basically a motor driven mechanism, which is adapted to change the position of the changeover switch disconnector based on the input command. 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] The prior art US20050116670A1 discloses a method to achieve above goals, but there are chances for the controller to damage the electric operator or actuators which provide the mechanical motion to effect the transfer from normal to emergency power or vice versa. 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. In prior art devices, motor actuators are energized without sensing the available voltage, which will cause damage to the motor and control circuit. For example, during under voltage condition, the electromagnetic relays will malfunction and will cause damage to motor and control circuit. Similarly 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.

[006] The Prior art US20060145642 solved the above problem by providing controlled voltage to the electromagnetic relay circuit and motor circuit, but during the under voltage condition the problem as described under the prior art US20050116670A1 persisted.

[007] Accordingly, there is a need to provide a motor operator arrangement that overcomes the 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

[008] 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.

[009] An object of the present invention is to provide a motor control arrangement that overcomes the drawbacks of the prior art mentioned above.

[0010] Another object of the present invention is to provide an electrical braking mechanism to provide controlled deceleration of the motor-driven device to avoid over travel problems in the COSD which will cause twisting of shaft and hence mechanical damage.

[0011] Accordingly to one aspect, the present invention provides an electrically operated mechanism , said mechanism comprising:
at least one switching unit provided between at least one mains source and at least one generator source, wherein said switching unit having at least three stable position comprising:
first position,
second position, and
OFF position,
Wherein, in said first position the switching unit is adapted to establish connection of at least one load with said mains source, in said second position the switching unit is adapted to establish connection of said load with said generator source;
at least one mechanical drive, actuated to drive said switching unit to said first position or said second position or said OFF position;
at least one load actuator means, mechanically communicating with said mechanical drive to enable said mechanical drive to move, wherein said load actuator means is adapted to receive an output command from at least one control circuit module to actuate plurality of solid state switches;
said control circuit module comprises: an arrangement of logical circuit module; and a plugging mechanism;
wherein, said control circuit module adapted to receive continuous or momentary input commands corresponding to each of mains source command or generator source command or OFF command from potential free contacts, and thereby generate said output command to connect/disconnect said mains source or said generator source to said load according to said first position or said second position of said switching unit, wherein said control circuit module adapted to:
transfer switching of said switching unit to said first position from said OFF or second position and/or to said second position from said OFF or first position, by energizing said load in a direction opposite to the current direction of rotation.

[0012] 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

[0013] 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:

[0014] Figure 1 illustrates the changeover switch disconnector and its three stable position according to one embodiment of the present invention.
[0015] Figure 2 illustrates a block diagram representation of various components of the motor drive control device according one embodiment of the present invention.
[0016] Figure 3 illustrates motor actuator solid state switches Q1 to Q4 receiving input from the controller unit according to one embodiment of the present invention
[0017] Figure 4 illustrates a voltage comparator circuit module for detecting input voltage, according one embodiment of the present invention.
[0018] Figure 5 illustrates a schematic of input commands for the control circuit module in the mechanism of the present invention.
[0019] Figure 6 illustrates hardware configuration of the control circuit module, according to one embodiment of the present invention.
[0020] Figure 7 illustrates limit switches according to one embodiment of the present invention.
[0021] Figure 8(a) illustrates trailing edge circuit module for plugging mechanism and figure 8(b) illustrates plugging command, according to one embodiment of the present invention.
[0022] Figure 9 illustrates a timing circuit diagram for enabling solid state switches.

[0023] 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

[0024] 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.

[0025] Accordingly, those of ordinary skilled 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.

[0026] 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.

[0027] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] It is also to be understood that the term “module” is used in the specification to indicate an apparatus, unit, component and the like. The term “means” when used in the specification is taken to specify the mode by which desired result is achieved.

[0032] In one embodiment, the present invention provides a control circuit module in an electrically operated mechanism in a Changeover switch disconnector (COSD). The COSD is also called an 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 Figure1. The electrically operated mechanism can be a motor-drive control system.

[0033] In one embodiment, 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 switching unit configured to connect one of two sources to a load or disconnect the load, a mechanical drive, an actuator, 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 will be 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.

[0034] The present invention may include some of the following advantages: reduced downtime for preventative maintenance as compared to motorized COSDs employing electromagnetic relays; by removing the electromagnetic relays, reduced mechanical wear and reduced contact erosion from electrical arcing can be realized; sensing of input supply voltage; plugging mechanism; a more compact motorized COSD systems; a less costly systems; ease of assembly; ease of maintenance. The advantages of using universal motor in dc mode like reduced core losses, copper losses and noise has been utilized when powered from single phase ac source.

[0035] In one embodiment, the operating method is represented in a block diagram as shown in Figure 2. The motor-drive control device particularly consists of bridge rectifier, regulated power supply, level translator, MOSFET driver circuit, logic control section, voltage detection circuit(voltage comparator), and H bridge circuit.

[0036] In one embodiment, referring to figure 3, energization of the motor can be accomplished by a signal command from a controller unit which is provided to the motor actuator solid state switches Q1 to Q4. When the power supply connected to the motorization module is within the pre-defined voltage range (65% to 110%), then only input commands will be accepted by the control circuit. This voltage detection is achieved using window comparator circuit as shown in figure 4.

[0037] In one embodiment, the input commands to the control circuit module will be given only from potential free contacts as shown in Figure 5. The control circuit module will be enabled to perform according to the input commands given in the table1 as shown below:

Table 1

[0038] In real time world, there are chances of simultaneous input commands to the system due to improper programming in a programmable logic circuit (PLC). 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. It should accept a new command before the switch has reached the position of the previous command if previous command vanishes. As shown in table, it is to be understood that 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.

[0039] In one embodiment, figure 6 represents a hardware configuration of the analog control circuit module and the control elements associated therewith which is suitable for implementing the present invention. The control circuit comprises logic gates which includes AND, OR, NOR, and EX-NOR, Tri-state active low buffers, and D flip-flops. The output of window comparator will enable (V_En) the control circuit only when the input voltage is within the pre-defined voltage range (65% to 110% of rated input supply voltage). When applied voltage is within the range and EX-NOR gate output is low then only mains or Generator command will be accepted otherwise it will ignore the command. Here, EX-NOR gate can be used for checking the simultaneous command of mains and Generator. For accepting momentary command there should be some latch mechanism and this is achieved using D Flip-flop. To accept new command during transfer period if previous command vanishes and also when required position is reached, there should be some reset mechanism and this is achieved using NOR gate. The output of NOR gate is connected to reset input of D flip-flop.

[0040] In one embodiment, as shown in figure 7, the limit switches (10 and 11) sense the position of a cam (12) which is coupled to a shaft of the COSD mechanism. Limit switch (10) can be responsible for mains position and limit switch (11) can be responsible for generator position. These limit switches can be used as feedback for the control circuit module to cut-off the supply to motor by disabling load actuator solid state switches Q1 to Q4 when desired switch position is reached according to the input command.

[0041] In one embodiment, in order to switch the COSD to mains position from OFF or generator position, load such as motor will be enabled to rotate in forward direction. Hence OR gate used for bringing the forward command when COSD is in OFF or generator position; similarly to bring COSD to generator position from OFF or mains position, motor will be rotated in a reverse direction.

[0042] In one embodiment, to avoid shoot through fault in H-bridge circuit, incorporated 20ms dead time between forward and reverse operation of the load using dead time circuit. 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 9.

[0043] In one embodiment, 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 is accomplished by energizing a motor in the direction opposite the current direction of rotation.

[0044] In one embodiment, there is an integral plugging mechanism which is included to stop the rotation of a load such as a DC motor when the desired mechanism position has been obtained. This is achieved using trailing edge circuit module as shown in Figure 8(a). Using this circuit module, at the end of every operation a pugging command as shown in Figure 8(b) will get generated and the plugging duration is adjusted according to potentiometers R1 and R2.

[0045] Some of the advantages of the present invention, are as follows:
• Reduced downtime for preventative maintenance as compared to motorized COSDs employing electromagnetic relays
• By removing the electromagnetic relays, reduced mechanical wear and reduced contact erosion from electrical arcing
• Simple analog based control circuit; a less costly solution
• 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 which will cause twisting of shaft and hence mechanical damage.
• Easy factory adjustable plugging time to match with different sizes of COSD
• The advantages of using universal motor in dc mode like reduced core losses, copper losses and noise are utilized when powered from single phase ac source

[0046] Although a control circuit module for electrically operated mechanism have 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 control circuit module for electrically operated mechanism.