Title of Invention

AN EXTERNALLY MOUNTED ONLOAD TAPCHANGER FOR THREE PHASE TRANSFORMER

Abstract The present invention relates to a compact upto 33 KV externally mounted 500 amps current carrying capacity onload tapchanger for three phase transformer. More particularly it relates to high speed resistor type onload tapchanger for a three-phase transformer having a rating upto 33 Kv and current upto 500 amps, comprising: • Selector switch for transferring current from one tap to the next; the said selector switch consisting of three phase boards; each phase board mounted with required number of fixed contacts upto maximum 17 numbers; moulded selector switch arm consisting of main moving contact assembly and resistor moving contact assembly; the whole selector switch built as a rigid unit, and the moulded selector switch arms rotated by a common drive shaft; • Six epoxy moulded brackets are used for mounting the selector switch on the base of the container of the tapchanger; eight epoxy moulded spacer rods are used for positioning the phase boards assembly with respect to each other in the said selector switch; • Six transition resistor assemblies are used during a tapchange, the said assembly being connected between the main moving contact and the resistor moving contact of each moulded selector switch arm assembly; • One driving mechanism to provide a drive to operate the tapchanger; the said mechanism consisting of an electric motor operating a gear train through clutch assembly to charge springs of the energy accumulator in the mechanism to rotate the moulded selector switch arm assembly by discharging during a tapchange, either in the clockwise or anticlockwise direction to raise or lower the tap numbers as desired; • Control unit consisting of thermal overload relay for motor protection, local /remote switch to enable operation of tapchanger locally or from a remote location; directional sequence switch to hold the supply during tapchange and to • provide correct sequence to motor and limit switch to stop the tapchanger at extreme ends both lower and upper; • Auxiliary transformer used to provide supply to the control unit;
Full Text FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
PATENT RULES, 2003
PROVISIONAL/COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
Compact upto 33 KV externally mounted 500 Amps current carrying
capacity onload tapchanger for transformer
2. APPLICANT(S)
(a) Name: CTR Manufacturing Industries Ltd
(b) Nationality: Indian Company
(c) Address: Nagar Road,
POONA 411014, MAHARASHTRA, INDIA
3. PREAMABLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (SECTION 10 AND RULE 13)
COMPACT UPTO 33 KV EXTERNALLY MOUNTED 500 Amps CURRENT CARRYING CAPACITY ONLOAD TAPCHANGER FOR TRANSFORMER
CTR MANUFACTURING INDUSTRIES LTD; AN INDIAN COMPANY, NAGAR ROAD, PUNE 411014, MAHARASHTRA, INDIA.
The following specification particularly describes the nature of the invention and the manner in which it is to be performed.

Compact upto 33 KV externally mounted 500 Amps current carrying capacity Onload tapchanger for transformer
Field of invention:
The present invention relates to an externally mounted compact onload tapchanger upto 33 KV with 500 amp current carrying capacity. More particularly it relates to a high-speed resistor type onload tapchanger used for three phase power transformers.
Prior art:
Electrical power generated from a power plant has to be stepped down or stepped up for use. Electrical power means a combination of supply voltage and load current. Electrical power is most efficiently transmitted to locations at high voltage achieved through transformers. Sometimes the voltage needs to be closely regulated to meet certain conditions of certain end uses such as electronic equipment used in medical electronics, process engineering etc. Conversion of supply voltage to another voltage with precise regulation can be done in a transformer only by using associated equipment called tapchanger. If this stepping up or stepping down of the supply voltage is done without disconnecting the load, the tapchanger is known as an onload tapchanger.
A tapchanger is a device fitted to transformer for regulation of the output voltage within a desired bandwidth level. This is achieved by altering the active number of turns in winding of the transformer. The principle of an onload tapchanger is that the load current cannot be interrupted during tapchange and no section of the transformer winding may be directly short-circuited during tapchange.
One of the main requirements of any electrical system is that the voltage available to the user must remain within closely defined limits, irrespective of changes in the end load or incoming supply variation of the system.
In industries such as chemical, plating plants, arc furnaces, etc, transformers with high current rating are used and it is most


advantageous that transformer fitted with high current onload tapchanger be used to provide regulated voltage of the desired level to avoid failure of the end use equipment.
Currently available high current rating onload tapchangers are mounted inside the transformer and known as intank onload tapchangers. This type of construction has following disadvantages:
i. Inspection of tapchanger contacts is difficult.
ii. Time taken for maintenance is much longer, since tapchanger has
to be attended from within the transformer after lowering the
level of transformer oil thereby exposing the transformer oil
and the windings to atmospheric moisture,
iii. Maintenance requires the transformer to be taken out of
service.
iv. Exorbitant cost of intank model.
Hence there is a need of designing an onload tapchanger which will overcome all the above-mentioned drawbacks.
Object of invention:
The main object of the present invention is, to provide an onload externally mounted out of tank three phase tapchanger operating upto 33 Kv with 500 amp current, which will obviate all the drawbacks of the presently available onload intank tapchanger as discussed in the prior art.
Another object of the invention is, to provide an onload tapchanger for low voltage and higher current rated three phase transformers typically for transformers of 11 Kv and 22 Kv and current rating of 500 amps.
Yet another object of the present invention is, to provide an onload tapchanger, which is fitted externally to the power transformer tank for ease of replacement, since outside the transformer tank.
Yet another object of the present invention is to provide an onload tapchanger, offering easy maintenance, since outside the


transformer tank.
Yet another object of the present invention is to provide an onload tapchanger, at a significantly lower cost compared to other models presently available.
Yet another object of the present invention is, to provide an onload tapchnager, providing easy access for inspection, since outside the transformer tank.
Yet another object of the present invention is to provide onload tapchanger, of simple design with less moving parts thereby enhancing reliability.
Yet another object of the present invention is to provide onload tapchanger, with less oil quantity to reduce initial and subsequent cost of oil required.
Statement of the Invention:
Accordingly, present invention of upto 33 Kv externally mounted 500 amp current carrying capacity onload tapchanger comprises:
Selector switch for transferring current from one tap to the next; the said selector switch consisting of three phase boards; each phase board mounted with required number of fixed contacts upto maximum 17 numbers; moulded selector switch arm consisting of main moving contact assembly and resister moving contact assembly; the whole selector switch built as a rigid unit, and the moulded selector switch arms rotated by a common drive shaft.
Six epoxy-moulded brackets are used for mounting the selector switch on the base of the container of the tapchanger; eight epoxy moulded spacer rods are used for positioning the phase board assemblies with respect to each other in the said selector switch.
Six transition resistor assemblies are used during a tapchange, the
said assembly being connected between the main moving contact and
the resistor moving contact of each moulded selector switch arm
assembly.
One driving mechanism to provide a drive to operate the tapchanger; the said mechanism consisting of an electric motor operating a gear


train through clutch assembly to charge springs of the energy accumulator in the mechanism to rotate the moulded selector switch arm assembly by discharging during a tapchange, either in the clockwise or anticlockwise direction to raise or lower the tapnumbers as desired.
Control unit consisting of thermal overload relay for motor protection, local /remote switch to enable operation of tapchanger locally or from a remote location; directional sequence switch to hold the supply during tapchange and to provide correct sequence to motor and limit switch to stop the tapchanger at extreme ends both lower and upper.
Auxiliary transformer used to provide supply to the control unit.
In this onload tapchanger switching contacts are made of copper/tungsten alloy; transition resistors consist of Chromium, Aluminium and Iron alloy resistance wire wound on a moulded insulating former.
Brief description of the drawings:
Figure 1: Shows overall view of selector switch assembly to
present invention.
Figure 2: Shows detailed constructional diagram of each phase board
assembly of the selector switch according to present
invention.
Figure 3: Shows the driving mechanism used for operating tapchanger
according to present invention.
Figure 4: Shows detailed enlarged view of fixed contacts and arcing
tips.
Figure 5: Shows detailed view of the contact spindle assembly of
the main moving contact assembly and resistor moving
contact assembly.
Figure 6(a) to 6(e): Shows the diagram view of the process of the
onload tapchanging according to present invention.


Detailed description of the invention:
The above objects, with other features and advantages of invention will become apparent from the following description read in conjunction with the accompanying drawings.
Tapchanger can be connected to the primary or secondary windings of a transformer depending on:
• Current rating
• Insulation levels
• Type of winding
• Position of the tapchanger in the winding
• Step voltage and circulating current
• Dimentions
• Cost
Meanings of the reference numerals used in the drawings are as follow:
A. Selector switch
B. Contact spindle assembly
C. Drive Mechanism
1. Phase Board Assembly
2. Epoxy Spacers
3. Epoxy Moulded Bracket
4. Container
5. Selector Shaft
6. Epoxy cast resin Arm
7. Fixed Contact
8. Arcing Tip
9. Bakelite Phase Board
10. Brass Mounting Block


11. Main Moving Contact Assembly
12. Resistor Moving Contact Assembly
13. Collector Ring
14. Transition Resistor Assembly
15. Energy Accumulator
16. Gear Wheel
17. Lost Motion Cam
18. Cam
19. Crank
20. Spring Piston
21. Selector Wheel
22. Mechanical Stop
23. Slipping Clutch
24. Hand Drive Mechanism
25. Three phase motor
26. Over ride clutch
27. Sliding dog carrier
28. Locking arm
29. Lost motion shaft
30. Drive pin
31. Tap selector arm
Now we will discuss the invention with reference to Fig. 1 to 6 in the accompanying drawings. Fig. 1 is the overall view of selector switch assembly according to present invention.
The selector switch (A) consists of three phase board assembly (1), which holds together by epoxy moulded spacers (2) . Epoxy moulded bracket (3) are provided to attach the selector switch to the base of the container (4) . These three phase board assemblies are used as three phases of the tap changer. The selector shaft (5) is of


steel and it carries six epoxy cast resin arms (6).
As shown in figure 2, each phase board assembly consists of seventeen-fixed contacts (7) of copper with both ends having arcing tips (8) of copper tungsten material. Each contact fastened to bakelite board (9) to form the circle of thirty-four fixed contact on both sides of board. These fixed contacts are mounted on a block of brass called as brass mounting blocks (10). Epoxy cast resin arms (6) fixed on main shaft on both sides of phase board. Each arm has two contact assemblies arranged sides by side. It is known as main moving contact assembly (11) and resistor contact assembly (12). Main moving contact assembly (11) and resistor contact assembly consists of two contact spindles of a pair on opposite sides of the arm with spring loaded towards each other, so that they are self aligning in action. Hence, there is no resultant side thrust on the selector arms in the direction of the shaft axis.Main moving contact pair engages between the copper parts of the fixed contact and the copper collector ring (13). Resistor moving contact pair engages between the copper part of same fixed contact and one side of the transition resistor assembly (14) . The other side of transition resistor assembly (14) connected to the original pair of the main moving contact. To withstand contact erosion due to arcing, there is copper tungsten material roller on each of the two pairs of moving roller contacts. The epoxy cast resin maintains the insulation between the contacts assemblies. The transition resistors are short time rated, due to high-speed operation of tapchanger. Hence, for uninterrupted operation, independent auxiliary electrical supply is essential. In addition, the correct switching speed gives arc extinction at first current zero to obtain minimum contact wear and minimum oil contamination. An energy accumulator (15) employed to meet these requirements.
Figure 3 shows the driving mechanism, which is used to operate the tapchanger. The gear train rotates the gear wheel (16) causes the lost motion cam (17) to engage with cam (18) . Continued rotation causes crank (19) rotation of the spring piston (20) to compress the spring when the spring is fully compressed. Crank (19) is at


top-dead-centre. ON passing top-dead-centre the spring energy is released and the lost motion assembly allows the crank (19) to drive on the selector wheel (21) mechanism.
A mechanical stop (22) is provided in the driving mechanism and is encountered if an attempt is made up tapchange beyond the range. During normal operation, there are ~Raise' and Lower' electrical limit switch, designed to avoid over-running into the mechanical stop. Mechanical stop (22) should only occur if the appropriate limit switches fail or when over winding the mechanism by hand. On attempting to proceed beyond limit, the slipping clutch (23) will become operative, thus avoiding damage to the mechanism drive. Selector wheel (21) coupled with main shaft (5) when mechanism starts rotating as per above procedure, selector wheel (21) rotates the selector arms which were mounted on main shaft (5) change its position from one tap to next adjacent tap and complement the tapchange operation. The mechanism drive contains the hand drive mechanism (24) . Manual operation can also be possible with the help of handle.
Now we will discuss how the tapchanging takes place without interrupting the load current. As shown in figure 6(a) to (e) , the operation of the tapchanger is of the Pennant cycle type. Figure 6(a) shows the main moving contact (iii) and resistor moving contact (iv) on the tap (i) in normal operating position. In sketch 6 (b) the resistor contact (iv) has left the fixed contact (i) but the load current is still carried by main contact, which is still on fixed contact (i) . Sketch 6 (c) shown the resistor contact now on fixed contact (ii), so that the resistor bridging between taps (i) and (ii) and is carrying circulating current. In Sketch 6 (d) the main contact has left fixed contact (i) and the load current is carried by the resistor moving contact (iv). Sketch 6(e) shows the both main moving contact (iii) and resister moving contact (iv) on fixed contact (ii). The load current is carried by main contact (iii) and tapchange is completed without interrupting the load current.
Present invention is based on asymmetrical Pennant cycle. This


method of performing a tapchange operation in which, in one direction of movement of the switch, the circulating current starts to flow before the through current is diverted from contacts, while the other direction of movement the through current diverted before the circulating current starts to flow.
Advantages of the present invention:
1. Onload tapchanger of the present invention is used for lower
voltage and higher current rated power transformers.
2. Due to high-speed operation, and arc extinction within specified time, produces low carbon during make and break of tapchanger contact, thereby improves life of oil.
3. Onload tapchanger according to present invention provides high performance with low operation cost and is long lasting.
Industrial Applicability:
After going through the above, the industrial applicability of an onload tapchanger of the present invention is apparent. It will find use in industries where the process is controlled by electronic circuitry especially where higher current rating transformers must be installed. It is also required to be used in applications where low voltage and high current required to be accurately controlled, such as arc furnace for melting steel, Railway traction for speed control etc.
The present invention is not limited to the above described embodiments, and various alterations, modifications, and/ or alternative applications of the invention may be possible, if desired, without departing from the scope and spirit of the invention which can be read from the claims and the entire specification. All these possible alterations, modifications and / or alternative applications of the invention are also intended to he within technical scope of the present invention.


We claim:
l. A compact, upto 33 KV, externally mounted 500 amps current carrying capacity, Onload tapchanger for three phase transformer comprising:
Selector switch for transferring current from one tap to the next;
the said selector switch consisting of three phase boards; each
phase board mounted with required number of fixed contacts upto
maximum 17 numbers; moulded selector switch arm consisting of main
moving contact assembly and resister moving contact assembly; the
whole selector switch built as a rigid unit, and the moulded
selector switch arms rotated by a common drive shaft;
Six epoxy moulded brackets are used for mounting the selector switch on the base of the container of the tapchanger; eight epoxy moulded spacer rods are used for positioning the phase boards assembly with respect to each other in the said selector switch;
Six transition resistor assemblies are used during a tapchange, the
said assembly being connected between the main moving contact and
the resistor moving contact of each moulded selector switch arm
assembly;
one driving mechanism to provide a drive to operate the tapchanger; the said mechanism consisting of an electric motor operating a gear train through clutch assembly to charge springs of the energy accumulator in the mechanism to rotate the moulded selector switch arm assembly by discharging during a tapchange, either in the clockwise or anticlockwise direction to raise or lower the tap numbers as desired;
Control unit consisting of thermal overload relay for motor protection, local /remote switch to enable operation of tapchanger locally or from a remote location; directional sequence switch to hold the supply during tapchange and to provide correct sequence to motor and limit switch to stop the tapchanger at extreme ends both lower and upper.
2. An onload tapchanger as claimed in claim 1, wherein switching contact are made of copper tungsten alloy of composition upto 60 percent tungsten and upto 40 percent copper.


3. An onload tapchanger as claimed in claim 1, wherein the transition resistors are made from resistance wire wound on an insulated former.
4. An onload tapchanger as claimed in claim 1, wherein the selector switch consists of six sets of main moving contacts and six sets of resistor moving contacts.
5. An onload tapchanger as claimed in claim 1 to 4 externally fitted on a three-phase transformer having rating upto 33KV with upto 500 amps current carrying capacity.
6. An onload tapchanger substantially as herein before with
reference to the accompanying drawings.


ABSTRACT
The present invention relates to a compact upto 33 KV externally mounted 500 amps current carrying capacity onload tapchanger for three phase transformer. More particularly it relates to high speed resistor type onload tapchanger for a three-phase transformer having a rating upto 33 Kv and current upto 500 amps, comprising:
• Selector switch for transferring current from one tap to the next; the said selector switch consisting of three phase boards; each phase board mounted with required number of fixed contacts upto maximum 17 numbers; moulded selector switch arm consisting of main moving contact assembly and resistor moving contact assembly; the whole selector switch built as a rigid unit, and the moulded selector switch arms rotated by a common drive shaft;
• Six epoxy moulded brackets are used for mounting the selector switch on the base of the container of the tapchanger; eight epoxy moulded spacer rods are used for positioning the phase boards assembly with respect to each other in the said selector switch;
• Six transition resistor assemblies are used during a tapchange, the said assembly being connected between the main moving contact and the resistor moving contact of each moulded selector switch arm assembly;
• One driving mechanism to provide a drive to operate the tapchanger; the said mechanism consisting of an electric motor operating a gear train through clutch assembly to charge springs of the energy accumulator in the mechanism to rotate the moulded selector switch arm assembly by discharging during a tapchange, either in the clockwise or anticlockwise direction to raise or lower the tap numbers as desired;
• Control unit consisting of thermal overload relay for motor protection, local /remote switch to enable operation of tapchanger locally or from a remote location; directional sequence switch to hold the supply during tapchange and to


• provide correct sequence to motor and limit switch to stop the tapchanger at extreme ends both lower and upper;
• Auxiliary transformer used to provide supply to the control unit;


Documents:

1739-mum-2007-abstract(11-9-2007).pdf

1739-mum-2007-abstract(18-3-2011).tif

1739-MUM-2007-ABSTRACT(21-3-2011).pdf

1739-MUM-2007-ABSTRACT(25-2-2011).pdf

1739-MUM-2007-ABSTRACT(9-2-2011).pdf

1739-mum-2007-abstract(granted)-(21-3-2011).pdf

1739-mum-2007-abstract.doc

1739-mum-2007-abstract.pdf

1739-mum-2007-cancelled pages(21-3-2011).pdf

1739-mum-2007-claims(11-9-2007).pdf

1739-mum-2007-claims(amended)-(18-3-2011).tif

1739-MUM-2007-CLAIMS(AMENDED)-(21-3-2011).pdf

1739-MUM-2007-CLAIMS(AMENDED)-(25-2-2011).pdf

1739-MUM-2007-CLAIMS(AMENDED)-(9-2-2011).pdf

1739-mum-2007-claims(granted)-(21-3-2011).pdf

1739-mum-2007-claims.doc

1739-mum-2007-claims.pdf

1739-MUM-2007-CORRESPONDENCE(11-9-2012).pdf

1739-mum-2007-correspondence(17-3-2011).pdf

1739-MUM-2007-CORRESPONDENCE(21-3-2011).pdf

1739-mum-2007-correspondence(ipo)-(21-3-2011).pdf

1739-mum-2007-description (complete).pdf

1739-mum-2007-description(complete)-(11-9-2007).pdf

1739-mum-2007-description(granted)-(21-3-2011).pdf

1739-mum-2007-drawing(11-9-2007).pdf

1739-MUM-2007-DRAWING(25-2-2011).pdf

1739-MUM-2007-DRAWING(9-2-2011).pdf

1739-mum-2007-drawing(granted)-(21-3-2011).pdf

1739-mum-2007-drawings.pdf

1739-mum-2007-form 1(11-9-2007).pdf

1739-MUM-2007-FORM 1(9-2-2011).pdf

1739-mum-2007-form 13(1)-(9-2-2011).pdf

1739-MUM-2007-FORM 13(11-9-2012).pdf

1739-mum-2007-form 13(9-2-2011).pdf

1739-mum-2007-form 2(complete)-(11-9-2007).pdf

1739-mum-2007-form 2(granted)-(21-3-2011).pdf

1739-mum-2007-form 2(title page)-(18-3-2011).tif

1739-MUM-2007-FORM 2(TITLE PAGE)-(21-3-2011).pdf

1739-MUM-2007-FORM 2(TITLE PAGE)-(25-2-2011).pdf

1739-MUM-2007-FORM 2(TITLE PAGE)-(9-2-2011).pdf

1739-mum-2007-form 2(title page)-(complete)-(11-9-2007).pdf

1739-mum-2007-form 2(title page)-(granted)-(21-3-2011).pdf

1739-MUM-2007-FORM 26(25-2-2011).pdf

1739-MUM-2007-FORM 26(9-2-2011).pdf

1739-mum-2007-form 3(11-9-2007).pdf

1739-MUM-2007-FORM 3(9-2-2011).pdf

1739-MUM-2007-FORM 5(9-2-2011).pdf

1739-mum-2007-form-1.pdf

1739-mum-2007-form-18.pdf

1739-mum-2007-form-2.doc

1739-mum-2007-form-2.pdf

1739-mum-2007-form-3.pdf

1739-mum-2007-form-9.pdf

1739-mum-2007-marked copy(18-3-2011).pdf

1739-mum-2007-marked copy(18-3-2011).tif

1739-MUM-2007-MARKED COPY(21-3-2011).pdf

1739-MUM-2007-MARKED COPY(25-2-2011).pdf

1739-mum-2007-other document(18-3-2011).tif

1739-MUM-2007-REPLY TO EXAMINATION REPORT(25-2-2011).pdf

1739-MUM-2007-REPLY TO EXAMINATION REPORT(9-2-2011).pdf

1739-MUM-2007-REPLY TO HEARING(18-3-2011).pdf

1739-mum-2007-specification(amended)-(18-3-2011).tif

1739-MUM-2007-SPECIFICATION(AMENDED)-(21-3-2011).pdf

1739-MUM-2007-SPECIFICATION(AMENDED)-(25-2-2011).pdf

1739-MUM-2007-SPECIFICATION(AMENDED)-(9-2-2011).pdf

abstract1.jpg


Patent Number 246905
Indian Patent Application Number 1739/MUM/2007
PG Journal Number 12/2011
Publication Date 25-Mar-2011
Grant Date 21-Mar-2011
Date of Filing 11-Sep-2007
Name of Patentee CTR MANUFACTURING INDUSTRIES LTD.
Applicant Address NAGAR ROAD, POONA-411014,
Inventors:
# Inventor's Name Inventor's Address
1 JEEVAN VASANT UTGIKAR CTR MANUFACTURING INDUSTRIES LTD., NAGAR ROAD, POONA 411014
PCT International Classification Number H01F29/00,H02J3/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA