Title of Invention

AN APPARATUS FOR CONTINUOUSLY ANNEALING AMORPHOUS ALLOY CORES WITH CLOSED MAGNETIC PATH

Abstract

1. An apparatus for continuously annealing amorphous metal alloy cores with closed magnetic path comprising a tunnel furnace (6) having a heating zone (B) and a cooling zone (D), said furnace being provided with a DC bus bar (5) passing herethrough and extending beyond the same on either side thereof; conveyor means (F) for conveying said amorphous metal alloy cores into the said furnace continuously, the centre portion of said cores encasing the DC bus bar (5); at least two pairs of electrical contact means (1, 1', 1, X; 3, 3', 4, 4'), on each end of said bus bar (5) connected to a DC power source (C) through sequence switching means (S1 S2, S3, S4,) having control means (F) for sequentially opening and closing said electrical contact means to ensure continuous current flow through said DC bus bar (5), loading means (A) for loading the cores to conveying means (7) at the feeding end and unloading means (E) for discharging the annealed amosphous metal alloy cores at the delivery end of the said tunnel furnace from the conveying means (7).

Full Text

An apparatus for continuously annealing amorphous alloy cores with closed magnetic path. This invention relates to an apparatus for continuously annealing amorphous alloy cores with closed magnetio path. In India about 23% of the generated electrical energy is lost during transmission and distribution and is very high when compared to the 8 to 10% energy losses in other countries. Efforts have been made to reduce these losses to oonserve the existing energy generation. Distribution transformer contribute to a considerable amount of energy losses as these losses are present even when the transformer is under no load conditions. This is particularly important in rural areas where load factor is very low. The use of amorphous alloy steel in the place of cold rolled grain oriented silicon steel, commercially known as CRGO, for transformer cores reduces no-load losses or core losses of transformers by approximately 75%. If all the existing distribution transformers of the Indian power system are replaced by amorphous core transformers, the annual saving in energy cost would be around Rs.337 cores or in other words generation capacity would be increased by at least 370 MW. Though replacement of the existing transformer cores is not practical, new distribution transformers with amorphous alloy core may be .-— — ""■'■»■ mi ■ f m installed resulting in substantial energy saving. The word "amorphous metal" used heroin means a metal lacking in symmetrical structure or form. Amorphous metals are a group of alloys with metallic properties, but without the crystalline lattice of conventional metals. They have no atomic order and are amorphous like frozen in-met or glass. Consequently they are known as metallio glasses. Transformers having amorphous magnetic metallic core are known in the art. The manufacturing processes of such transformers are different from conventional CRGO steel core transformers. (Amorphous magnetic materials are hard and can be obtained as very thin sheets. These materials require magnetic field while annealing and they become less ductile after such annealing. Core manufacturing with amorphous magnetic metal comprises the steps of (a) core winding (2) core cutting (3) " core forming and (d) magnetic field annealing. The annealing step optimises the core losses. Amorphous metal glasses do not posses any magentocrystalline anisotropy because of its random atomic architecture. However, magnetic anisotrophy (i.e. the measure of the use of magnetisation away from a given direction) can be induced in metallic glasses. Amorphous core matrial in a cast state has huge quenching stress resulting from the rapid cooling rate during its manufacture. These stresses lead to * distribution of stress induced magnetic anisotrophy resulting in a complex domain structure. Annealing of the core is done to relieve this quenching stress and also to induce a preferred axis of magnetostriction along the ribbon length. Annealing is carried out at temperatures which will preserve the glassy nature of the material. A magnetic field of sufficient strength approximately 10 oersted, is applied to magnetically saturate the material at the annealing temperature. Annealing is carried out in an inert atmosphere in a temperature range of 300°C - 500°C. The object; of this invention is to develop an apparatus for annealing amorphous material continuously without interruption where consistent and stable parameters are maintained. The apparatus consists of a tunnel furnace of the desired length through which inert gas, such as nitrogen, is made to flow under constant pressure. The tunnel furnace has a heating zone and a cooling zone. An endless conveyor passes through the furnace which feeds the cores into the furnace. A bus bar supplied with predetermined direct current necessary for magnetic annealing is provided within the tunnel furnace. The core to be annealed is conveyed to the furnace such that the bus bar passes through the centre portion of the core. A discharge means is provided on the conveyor at the end opposite to the loading section for collecting the annealed cores discharged from the furnace. Each end of the bus bar is provided with at least two pairs of electrical contacts which are capable of closing and opening on actuation. These electrical contacts are sequentially connected to a direct current power supply source through sequence switching means. The switching means are provided with control means for opening and closing the said electrical contacts and to maintain continuous supply of current through the bus bar. This sequential switching system is programmed to keep one set of electrical contacts on each side of the bus bar open, while keeping the other set of contacts on each side closed; thus allowing the bus bar to be connected with the power source during continuous loading and unloading operation. This enables continuous annealing under more or less constant conditions. The heating zone of the furnace is heated electrically and is preferably provided with thyristor control for regulating the temperature. Preferably cooling is carried out by circulating water around the cooling zone. The invention provides an apparatus for continuously annealing amorphous metal alloy cores with closed magnetic path comprising a tunnel furnace having a heating zone and a cooling zone, the said furnace being provided with a DC bus bar passing therethrough and extending beyond the same on either side thereof; conveyor means for conveying amorphous metal alloy cores into the said furnace continuously, the centre portion of the said cores encasing the DC bus bar, atleast two pairs of electrical contact means on each end of the said bus bar connected to a DC power source through sequence switching neans having control means for sequentially opening and closing the said electrical contact means to ensure continuous current flow through the said DC bus bar, loading means for loading the cores to the conveying means at the feeding end and unloading means for discharging the annealed amosphous metal alloy cores at the delivery end of the said tunnel furnace from the conveying means. This invention will now be illustrated with reference to the single figure in the accompanying drawings : Reference numeral 6 indicates the tubular furnace through which the DC bus bar 5 passes. Conveying means is indicated by numeral 7 while A and E represent the loading and unloading means respectively. Two sets of electrical contacts on each end of the tunnel furnace are shown by 1, 1', 2, 2'; 3, 3', 4, 4' respectively. Switches which sequentially connect the electrical contacts are S^, S2, S3 and S4 respectively. C indicates the direct current source. Reference letters B and D represent the heating zone and the cooling zones in the furnace. The tunnel furnace 6 preferably has means for circulating inert gas therethrough. During the operation the switch contacts 1, 1' and 3, 3' get deactivated by the control means (F) while the switch contacts 2, T and 4, 4* remain in contact with the bus bar and connected to the power supply. When some of the cores fed by the conveyor, passes through the open contacts (1, 1', 3, 3'), contacts (2, 2') and (4, 4') are closed and DC power supply is connected to the bus bar. In the next sequence contacts (2, 2') and (4, 41) are open for the cores to pass through and this time contacts (1, 1') and (3, 3') are closed maintaining the connection of the DC power supply to the bus bar. Continuous annealing operation is thus ensured as the bus bar passes through the core window and the temperature variations in different zones of the furnace of the furnace does not affect the magnetic field applied to the core. The system is preferably provided with a DC current trip which senses the line input current and means for automatic change over to standby pulse width modulation control power supply, which is connected in parallel in the event of power failure to save the batch under processing. Preferably coolant water flow failure indicating means may be provided for over temperature trips. The I>C power supply source is provided with a main switch and water conductivity inter-lock means to avoid scaling in the coolant water pipes. Provisions are also made for changing over to dimmerstat control in the event of thyrister block failure to save the batch under processing. This invention has been described herein above with respect to a specific embodiment. Obvious equivalents and modifications known to persons skilled in the art are within the scope and ambit of the description and the appended claims. WE CLAIM : 1. An apparatus for continuously annealing amorphous metal alloy cores with closed magnetic path comprising a tunnel furnace (6) having a heating zone (B) and a cooling zone (D), said furnace being provided with a DC bus bar (5) passing herethrough and extending beyond the same on either side thereof; conveyor means (F) for conveying said amorphous metal alloy cores into the said furnace continuously, the centre portion of said cores encasing the DC bus bar (5); at least two pairs of electrical contact means (1, 1', 1, X; 3, 3', 4, 4'), on each end of said bus bar (5) connected to a DC power source (C) through sequence switching means (S1 S2, S3, S4,) having control means (F) for sequentially opening and closing said electrical contact means to ensure continuous current flow through said DC bus bar (5), loading means (A) for loading the cores to conveying means (7) at the feeding end and unloading means (E) for discharging the annealed amosphous metal alloy cores at the delivery end of the said tunnel furnace from the conveying means (7). 2. The apparatus as claimed in claim 1, wherein the tunnel furnace (6) has circulating means for circulating inert gas therethrough. 3. The apparatus as claimed in claims 1 or 2, wherein the said tunnel furnace is provided with thyristor control means for regulating the temperature of the heating zone (B). 4. The apparatus as claimed in any one of the previous claims, wherein the cooling zone (D) of the tunnel furnace is provided with water circulating means for cooling. 5. The apparatus as claimed in claim 4, wherein coolant failure indicating means is provided to indicate failure of coolant water flow. 6. The apparatus as claimed in any one of the preceding claims, wherein the tunnel furnace is provided with an over temperature tripping means. 7. The apparatus as claimed in claim 6, wherein the said over temperature tripping means is a silicon controlled rectifier switching circuit. 8. The apparatus as claimed in any one of the previous claims, wherein DC current trip is provided for sensing power failure and switching over to alternate supply. 9. The apparatus as claimed in claim 8, wherein a pulse width modulation control power supply is provided as an alternate supply which is actuated in the event of a power failure. 10. The apparatus as claimed in any one of the previous claims, wherein a dimmerstat control means is provided for temperature control of the heating zone of the furnace. 11. An apparatus for continuously annealing amorphous metal alloy cores with closed magnetic path, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

0503-mas-1996 claims.pdf

0503-mas-1996 correspondence-others.pdf

0503-mas-1996 correspondence-po.pdf

0503-mas-1996 description (complete).pdf

0503-mas-1996 drawings.pdf

0503-mas-1996 form-1.pdf

0503-mas-1996 form-26.pdf

0503-mas-1996 form-29.pdf

0503-mas-1996 others.pdf

503-MAS-1996 CORRESPONDENCE OTHERS 04-02-2013.pdf