Technical Field of the Invention
The present invention relates to compact and light weight on load tap changer arranged with a transformer to regulate a voltage.
Brief Summary of the Invention
The prime object of the invention is to provide an On Load Tap Changer (OLTC) used for transformers which is having simplified design with respect to Power Switch, Mechanical and Electrical Systems.
According to a first aspect of the present invention, the OLTC is adapted to be arranged with a transformer to regulate the voltage it comprises of a power switch assembly with unique design to avoid frequent servicing, an electro-mechanical assembly to change the tap position and a Mild Steel (MS) tank to provide mechanical protection for the said power switch and the electro-mechanical assembly.
In accordance with the first aspect of the present invention, wherein the OLTC is light in weight, compact and the same can be used for both oil cooled and dry type transformers up-to 33kV Class.
In accordance with the first aspect of the present invention, further the OLTC is secerned to use minimum wiring in the Power Switch, Mechanical and Electrical System which makes the Operations easier.
In accordance with the first aspect of the present invention, the OLTC is helpful in seamless operation of transformer used in various critical industrial segments, including but not limited to Power generation, Substations, Small, medium and large

scale manufacturing industries, Hospitals, R&D Centers and Educational Institutes etc.
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In accordance with the first aspect of the present invention, OLTC is qualified to maintain LV (load side) voltage constantly in-spite of variation in the input supply voltage within a selected bandwidth by energizing the required tap position provided in the transformer HV winding and maintains LV voltage automatically with the help of automatic voltage regulator (AVR).
In accordance with the first aspect of the present invention, the OLTC further comprises of a mechanical module that includes a Geneva, a CAM Assembly a Gear Mechanism; an electrical module that includes one or more of a Contactors, a Limit Switch, a Motor Protection Circuit Breaker, a Miniature Circuit Breaker, a Counter, a Toggle Switch and a Selector Switch, and a power switch module that includes Phase Board, Barrier Board, Moving Contact and a Resistor.
In accordance with the first aspect of the present invention, the OLTC comprises of a power switch assembly which connects number of brought out taps from the transformer HV winding by using a plurality of components including but not limited to at least one of a barrier board; a phase board with fixed contacts; a moving contact assembly with resistor; an end supporter; a rotating assembly; a phase board supporter; a common lead fixed contact; a resistor; and few copper lugs.
In accordance with the first aspect of the present invention, a power switch assembly is arranged to connect number of brought out taps from the transformer HV winding through a barrier board and the components that are used are applicable for both oil filled OLTC and dry type OLTC.
In accordance with the first aspect of the present invention, all the corners and sides of the power switch assembly are designed smoothly to avoid carbon deposits on the fixed taps, edges, etc. during the tap changing operation.

In accordance with the first aspect of the present invention, further the OLTC comprises an electro-mechanical assembly that detects difference in LV (Load Side) voltage value based on the signal contractor and then the electrical module either increases/decreases the tap position. To do these various components are included but not limited to an electrical module, a front plate assembly and a back plate assembly.
In accordance with the first aspect of the present invention, the electro-mechanical assembly is further arranged to drive the mechanical gear assembly by operating three phase induction motor based on the signal generated from the contractor and comprises mechanical gear assembly that has a Geneva mechanical locking component which is mechanically coupled with rotor shaft of phase board, with this movement the moving contact rotates and change in tap position occurs.
In accordance with the first aspect of the present invention, the OLTC further comprises an MS tank that provides mechanical protection for the Power Switch & Electro-Mechanical Assemblies. The components include but not limited to a mounting plate, an end mounting plate, an inspection cover and an electro-mechanical assembly mounting plate.
In accordance with the first aspect of the present invention, further the MS tank holds the insulating oil and avoids leakage as it is provided with minimum welding joints.
For purposes of summarizing embodiments of the invention, certain aspects, advantages, and improved features of the invention have been described herein. It is to be understood that not necessarily all such aspects, advantages, or improved features will be embodied in any embodiment of the invention.

Brief Description of the Drawings
Various objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, in conjunction with the accompanying drawings, wherein like reference numerals have been used to designate like elements, and wherein:
FIG. 1 illustrates a side view depicting a conventional On-Load Tap-Changer (OLTC) arranged with a transformer.
FIG. 2A and 2B illustrate a front perspective view and rear perspective view respectively depicting OLTC tank according to the present invention.
FIG. 3A, FIG. 3B and FIG. 3Cillustrate a front view, side view and top view respectively depicting the major components involved in OLTC tank assembly according to the present invention.
FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D illustrate a front view, side view, top view and isometric view respectively depicting the components involved in power switch assembly according to the present invention.
FIG. 5 illustrates an exploded view depicting the components of power switch assembly according to the present invention.
FIG. 6A, FIG. 6B, FIG. 6C and FIG. 6D and FIG. 6Eillustrate a front view, side view, top view and isometric views respectively depicting the components involved in an electro-mechanical assembly according to the present invention.
FIG. 7 illustrates a front view depicting a Geneva mechanical locking component according to the present invention.

FIG. 8 illustrates a front, side and top view depicting the components involved in MS tank according to the present invention.
Detailed Description of the Invention
Present invention relates to an On Load Tap Changer that is used along with transformers to regulate the voltage.
According to a first exemplary embodiment of the present invention, present invention provides an On-load tap changer having phase boards that are connected to the barrier board through a guiding mechanism which helps ease in operation & reduces assembly time. Further the fixed contacts along with connection to barrier board are molded in epoxy/FRP/Similar liquids & materials which withstand elevated temperature and fire damages.
In accordance with the first exemplary embodiment, the present invention provides On-load tap changer with a power switch that comprises Barrier Board, Phase Board with Rotating Shaft, Phase Board Supports and End Supports with bearings.
In accordance with the first exemplary embodiment, the present invention further provides On-load tap changer having the phase boards comprises of a continuous ring with one break which works as a coarse & fine contact.
In accordance with the first exemplary embodiment, the On-load tap changer disclosed in the present invention useful for Power and Distribution Transformers.
Referring to the drawings, FIG. 1 illustrates a conventional On-Load Tap-Changer (OLTC) arranged with a transformer. •
FIG. 2A and FIG. 2B illustrate a front perspective view 200a and rear perspective view 200b depicting OLTC tank assembly according to the present invention. The

On Load Tap-Changer (OLTC) helps to regulate the voltage, designed with a plurality of components such as power switch assembly 202a & 202b which is uniquely designed to avoid frequent servicing; an electro-mechanical assembly 204b to change the tap position and a Mild Steel (MS) tank 206c to provide mechanical protection for the power switch and the electro-mechanical assemblies.
A power switch assembly 202band 'the brought out taps from Transformer HV winding are connected through Barrier Board and based on the signal received from the contactor of Electro-Mechanical Assembly 204b, the 3 Phase induction motor operates and drives the mechanical gear assembly to change the taps accordingly. A Mild Steel (MS) tank 206b is surrounded over the power switch assembly 202b and electro-mechanical assembly 204b to provide protection. Also, the MS tank holds the insulating oil and provides an aesthetic look to the product.
FIG. 3A, FIG. 3B and FIG. 3C illustrate a front view, side view and top view respectively depicting the major components involved in OLTC tank assembly according to the present invention. Reference numeral 300 depicts the major components involved in OLTC tank 'assembly according to the present invention. The light weight and compact OLTC majorly comprises of a power switch assembly 302, electro-mechanical assembly 304 and a MS tank 306. Electro-Mechanical Assembly comprises a mechanical and electrical module within, a mechanical module includes Geneva, CAM Assembly and a Gear Mechanism; an electrical module includes one or more Contactors, a Limit Switch, a Motor Protection Circuit Breaker (MPCB), a Miniature Circuit Breaker (MCB), a Counter, a Toggle Switch and a Selector Switch and the power Switch module includes Phase Board, Barrier Board, Moving Contact and a Resistor.
The On Load Tap-Changer makes a new contact easily before breaking the old contact to avoid the arc. To avoid the circulating current produced by short circuit of tap turns a resistor is connected inside the circuit. To prevent heavy currents that are flowing through the resistor for an extended period, a spring mechanism is used for

quick operation. An electrical motor is incorporated to operate the spring mechanism. In-spite of this, an arc is inevitable, and this contaminates the oil. Hence, to prevent the transformer from oil contamination the OLTC is built in such a way that it separates the transformer tank by using a barrier board.
FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D illustrate a front view, side view, top view and isometric view respectively depicting the components involved in power switch assembly according to the present invention. The Power Switch Assembly and brought out taps from Transformer HV winding are connected through a barrier board and based on the signal received from contactor of Electro-Mechanical Assembly the 3 Phase induction motor operates and drives the mechanical gear assembly to change the tap position accordingly. To operate the power switch assembly a plurality of components is incorporated such as barrier board 402, at least three numbers of phase boards with fixed contacts 404, at least three numbers of moving contact assembly 406, plurality of end supporters 408, rotating assembly 410, phase board supporters 412, common lead fixed contact 414, resistor 416 and lugs 418, etc.
A barrier board 402 is a separator/partition that is arranged between transformers main tank and on load tap changer as shown in FIG. 1. This barrier board 402 avoids carbon that is formed in OLTC due to the internal operations from entering the transformer main tank. At least three numbers of phase boards with fixed contacts 404 are electrically connected with the transformer winding tap connections through barrier board 402 and movable contacts 406. A fixed contact embedded into the phase board 404 is a piece of electrically conductive material made of copper, when pair of contacts touch they pass electrical current with a certain contact resistance.
At least three numbers of moving contact assemblies 406 with resistors 416 are assembled in power switch assembly, each moving contact assembly 406 with resistor 416 is embedded in the' phase board. The resistor 416 helps in controlling/regulating the flow of electrical current during the transit of moving

contact in the circuit. Each moving contact assembly 406 is connected to a rotating shaft 410 to rotate up to 340° and also used to connect the fixed contacts of HV windings in the transformer. A plurality of rotating assemblies 410 are used to align and keep intact the three moving contact assemblies 406 and three phase boards 404 with a power switch end supporter 408. A plurality of end supporters 408 are used to hold the complete power switch module together in the same plane. A plurality of phase board supporters 412 are fixed to a phase board 404 to align and keep intact the three phase boards 404 with power switch end supporters 408. A common lead fixed contact 414 is also one of the components assembled in power switch assembly which helps in closing the circuit loop and provides the path while changing the tap. Finally, a plurality of copper lugs 418 are fixed in the assembly which allows to distribute the electric current without any hindrance between the barrier board 402 and phase board 404. Connecting Lugs 418 are integral part of phase board 404, so there is no chance of mismatch/error because all are externally connected, and no connections are visible. While assembling all the above mentioned components, no wires are visible either in phase board 404 or barrier board 402, all are internally packed and embedded in a mould.
Power switch assembly has many advantages such as, it can be used for Oil filled OLTC or Dry Type OLTC. All corners & sides of Power Switch Assembly are kept smooth to avoid carbon deposits on the fixed taps, edges, etc. during tap changing operation. Power Switch Assembly is compact, provided with minimum joints and very few fasteners are used. The Power Switch Assembly is uniquely designed and simple in construction and avoids the frequent service/ maintenance issues.
FIG. 5 illustrates an exploded view 500 depicting the components of power switch assembly according to the present invention. The power switch assembly helps in changing the tap position based on the signal from contractor of electro-mechanical assembly. Power Switch Assembly includes end supporters 508, phase board with fixed contacts 504, moving contact assembly 506 with resistors 516, phase board supporters 512, rotating assembly 510 and barrier board 502.

A plurality of end supporters 508 are connected at both the ends of the power switch assembly to hold the complete switch module together in the same plane. At least three numbers of phase board with fixed contacts 504 are placed adjacent to both end supporters 508 to electrically connect the transformer winding tap connectors through barrier board 502 and movable contacts 506. Each phase board with fixed contact 504 has a movable contact assembly 506 with a resistor 516 to control/ regulate the flow of electrical current during the transit of moving contact in the circuit.
A plurality of phase board supporters 512 are fixed to the phase board 504 to align and keep intact the three phase boards 504 with Power Switch end supporters 508. Plurality of rotating shafts are arranged inside the moving contact assembly 506 to rotate 340° and used to connect the fixed contacts of HV winding in the transformer. The rotating shaft assembly also helps in aligning and keeping intact the moving contact assembly 506 and three phase boards 504 with Power Switch end supporters 508. Finally, a barrier board 502 has a specially designed step that acts as a barrier and overcomes the creep-age or flash over issue. A barrier board 502 is a separator/partition that is fixed between transformer main tank & On Load Tap Changer. By placing it avoids carbon formed in OLTC entering transformer main tank as shown in FIG. 1.
FIG. 6A, FIG. 6B, FIG. 6C and FIG. 6D and FIG. 6E illustrate a front view, side view, top view and isometric views respectively depicting the components involved in an electro-mechanical assembly according to the present invention. Reference numeral 600 depicts the components involved in an electro-mechanical assembly according to the present invention. An Electro-mechanical assembly is compact and light in weight; components used in this can be assembled quickly and easily. The electro-mechanical assembly includes a plurality of components like electrical module, front plate assembly and back plate assembly.

A motor protection circuit breaker (MPCB), this is used to control and protect the electrical panel and the other devices from overflow of electrical power. MCB ensures safety and quality of the energy provided. An electrical counter, this keeps track on the tap changer operations that occur periodically. A toggle switch, when the actuator of the toggle is moved, the armature in the switch moves the moveable contact into a position or either helps in energizing/de-energizing the circuit. A thermostat, is a device that automatically regulates the temperature and reduces the gap between the desired and measured temperatures. A relay, switches low voltage through its contacts, a phase sequence relay, for phase monitoring and sequence controlling. A cable connector, is a part of a cable that plugs into port or interface to connect one device with another device.
A component front plate assembly of an electro-mechanical assembly includes a plurality of internal components such as crank shaft front bearing house 601, is a pedestal used to provide support for rotation of crank shaft (front portion) with the help of compatible bearings & various accessories. Geneva Front Bearing Housing 602, is a pedestal used to provide support for rotation of Geneva shaft (front portion) with the help of compatible bearings & various accessories. A drive gear 604 is to alter the speed, torque and direction of rotating shafts. A drive gear bearing housing 606, is a pedestal used to provide support for rotation of drive gear shaft with the help of compatible bearings & various accessories.
Tap Position Indicator (TPI) Board 608, indicates the current tap position and a stepping wheel 610, consist the tap numbers. The tap number in a tap position indicator 608 is indicated through ON and OFF of forward and reverse contacts, so this helps in reminding the customer about the remaining service time. A Three Phase Induction Motor with Pulley 611, is a constant speed & variable frequency drive application. A Drive Pulley 612, designed to support movement and change of direction of a pulley and a Link Belt 614 connects the 3 Phase Induction Motor & pulley.

A component back plate assembly of an electro-mechanical assembly includes a plurality of internal components such as Spring Set 615, to control the speed of the 3 phase induction motor, Crank Shaft Back Bearing Housing 616, is a pedestal used to provide support for rotation of crank shaft (back portion) with the help of compatible bearings & various accessories, Geneva Back Bearing Housing 618, is a pedestal used to provide support for rotation of Geneva shaft (back portion) with the help of compatible bearings & various accessories, a Spring Carrier with Bearing Housing 620, is a pedestal used to provide support for rotation of spring carrier with the help of compatible bearings & various accessories.
A Crank 622, is a mechanical part able to perform a conversion between reciprocating motion and rotational motion, a Crank Shaft 624 which aligns the CAM Assembly, Main Gear, Crank, Roller Assembly & Spring Carrier. A CAM Assembly 626 is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion. The crank 622 and cam 626 are designed in such a way that they minimize the OLTC operation noise. A Main Gear 628 is a rotating machine part having cut teeth or cogs, which mesh with another toothed part to transmit torque. A Geneva 630 is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. Geneva Mechanical lock 730 prevents tap changing from 1st tap to 17th tap position & 17th tap to 1st tap position as shown in FIG. 7.
An electro-mechanical assembly is having major advantages such as it can be detached easily from Power Switch by delinking the mechanical couple of Rotor Shaft without disturbing the Power Switch, the electrical connections are all in one plate and can be removed in few minutes which is extreme advantage during maintenance. RTCC to OLTC connections are provided through male & female socket which saves time during transformer erection and allows function of OLTC seamlessly for 1 million operations.

FIG. 7 illustrates a front view 700 depicting a Geneva mechanical locking component according to the present invention. The Geneva mechanical locking 730 is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. Geneva Mechanical lock is provided which prevents changing of tap from 1st tap to 17th tap position and 17th tap to 1st tap position.
The Mechanical Gear Assembly consists of a Main Gear, a CAM Assembly, a spring set and a Geneva as shown in FIG. 6. By the operation of the Mechanical Gear Assembly, the Geneva being integral part of the mechanism rotates. The Geneva's shaft end is mechanically coupled with Rotor Shaft of Phase Board with this movement even moving coil rotates and the change in tap position occurs.
FIG. 8 illustrates a front, side and top view 800 depicting the components involved in mild steel (MS) tank according to the present invention. The MS tank manufactured is unique in design. The MS tank includes a plurality of components like Mounting Plate 802, End Mounting Plate 804, Inspection Cover 806 and Electro-Mechanical Assembly Mounting Plate 808. MS tank provides mechanical protection for the Power Switch & Electro-Mechanical Assemblies. It also holds the insulating oil, has minimum welding joints and is designed in such a way that it provides an aesthetic look to the product.
MS tank is compact in size, utilizes less oil and overall lead time of product reduces drastically. The designed MS tank is easy to transport & a cost saving component for customer as more number of units can be shipped per vehicle.
From a reading of the description aboVe of the preferred embodiment of the present invention, modifications and variations thereto may occur to those skilled in the art. Therefore, the scope of the present invention is to be limited only by the claims of this invention.

5. Claims I/We Claim:
1. TheSturdy Volt On-Load Tap-Changer (OLTC) adapted to be arranged with
a transformer to regulate a voltage, comprises:
a power switch assembly with unique design to avoid frequent
servicing;
an electro-mechanical assembly to change the tap position;
a mild steel (MS) tank to provide mechanical protection for the said
power switch and the electro-mechanical assembly; and
wherein, the OLTC can be used with both oil cooled and dry type
transformers.
2. The OLTC according to claim 1, secerned to use minimum wiring in a Power Switch, Mechanical and Electrical System which makes the Operations easier.
3. The OLTC according to claim 1, distinguished and helps in seamless operation of transformer used in various critical industrial segments, include but not limited to:
Power generation;
Substations;
Small, medium and large scale manufacturing industries;
Hospitals;
R&D Centers;
Educational Institutes; etc.
4. The OLTC according to claim 1, qualified to maintain LV (load side) voltage
constantly in-spite of variation in input supply voltage with in a selected
bandwidth by energizing the required tap position provided in the
transformer HV winding.

5. The OLTC according to claim 1, maintains LV voltage automatically with the help of automatic voltage regulator (AVR).
6. The OLTC according to claim 1, comprises:
a mechanical module includes Geneva, CAM Assembly and a Gear
Mechanism;
the electrical module includes one or more of a Contactor, a Limit
Switch, a Motor protection circuit breaker, a Miniature Circuit
Breaker, a Counter, a Toggle Switch and a Selector Switch; and
the power Switch module includes at least one Phase Board, Barrier
Board, Moving Contact and a Resistor.
7. The OLTC according to claim 1, tagged to comprise a power switch
assembly that connects number of brought out taps from the transformer HV
winding by using a plurality of components include but not limited to:
at least one of a barrier board; a phase board with fixed contacts; a moving contact assembly with resistor; an end supporter; a rotating assembly; a phase board supporter; a common lead fixed contact; a resistor; and few copper lugs.
8. The power switch assemblyaccording to claim 7, differentiated to connect number of brought out taps from the transformer HV winding through a barrier board.
9. The power switch assembly according to claim 7, wherein components used are applicable for both oil filled OLTC or dry type OLTC.
10. The power switch assembly according to claim 7, wherein all the corners and sides are smooth that avoids carbon deposits on the fixed taps, edges, etc. during tap changing operation.

11. The OLTC according to claim 1, marked to comprise an electro-mechanical
assembly that detects difference in LV (Load Side) voltage value based on
the signal contractor and the electrical module either increases/decreases the
tap position, wherein the components include:
an electrical module;
a front plate assembly; and
a back plate assembly.
12. The electro-mechanical assembly according to claim 11, qualified to drive the mechanical gear assembly by operating three phase induction motor based on the signal generated from the contractor.
13. The electro-mechanical assembly according to claim 11, distinguished to comprise mechanical gear assembly that has Geneva mechanical locking component which is mechanically coupled with rotor shaft of phase board, with this movement the moving contact rotates and change in tap position occurs.
14. The OLTC according to claim 1, differentiated to comprise a MS tank that provides mechanical protection for the Power Switch and Electro-Mechanical Assemblies, wherein the components include:
a mounting plate;
an end mounting plate;
an inspection cover; and
an electro-mechanical assembly mounting plate.
15. The MS tank according to claim 14, wherein the MS tank holds the
insulating oil and avoids leakage by having minimum welding joints.