Induction heating and melting systems having improved induction coils
First Claim
1. In electric inductive heating apparatus an improved inductive coil comprising a rigid open ended sleeve-like coil unit that includes two or more co-axial, co-extensive helical coil windings embedded in a temperature resistant, reinforced resin, each of said coil windings comprising a plurality of helical turns of multi-strand insulated conductor, means for connecting said coil windings in parallel and current balancing means operative in response to current flow respective ones of said coil windings thereby automatically forcing said coil windings to maintain a selected predetermined share of current flow including during variations of load and/or frequency.
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Accused Products
Abstract
Improved electric induction heating apparatus wherein the coil has two or more windings of special low loss conductor with such windings electrically connected in parallel. The two or more windings can be wound simultaneously one on top of the other and/or disposed radially one outside of the other. The coil windings embedded in a rigid set resinous material thus providing a rigid cylindrical unit. At least one of the coil windings has the low loss conductor around a tube the latter providing a fluid flow path for circulatig cooling fluid therethrough by at least one of current balancing transformers, transposition of the windings, and appropriately choosing the number of turns of each coil layer. A split ring bus can be used at the ends of the coils to connect the windings in parallel and laminated steel yokes can be disposed about the coil. There is also disclosed an improved inductive coil assembly for electric inductive heating apparatus comprising a cylindrical winding embedded in a temperature resistant non-magnetic material such as glass fibre reinforced resin and a heat sink rigid unit removably disposed within such coil unit. The heat sink unit comprises conduit means embedded in a temperature resistant material and providing a fluid flow passage for circulating a cooling fluid therethrough. The heat sink is removably inserted in the inductive coil unit. The helical winding is wound from a liquid cooled low loss conductor.
71 Citations
46 Claims
- 1. In electric inductive heating apparatus an improved inductive coil comprising a rigid open ended sleeve-like coil unit that includes two or more co-axial, co-extensive helical coil windings embedded in a temperature resistant, reinforced resin, each of said coil windings comprising a plurality of helical turns of multi-strand insulated conductor, means for connecting said coil windings in parallel and current balancing means operative in response to current flow respective ones of said coil windings thereby automatically forcing said coil windings to maintain a selected predetermined share of current flow including during variations of load and/or frequency.
- 22. An improved electric induction heating apparatus coil comprising a tabular coil winding that has a plurality of helical turns of a liquid-cooled insulated conductor, said conductor including an inner cooling tube having predetermined heat transfer properties and predetermined eddy losses taking into account coil geometry, frequency and ampere turns for which the coil has been designed and an outer layer of high conductivity insulated strands disposed spirally about such tube, said strands having a diameter to provide selected eddy losses and of sufficient number to carry a predetermined current through said coil winding and a reinforced resin encapsulating said coil winding to form a strong, rigid and vibration free unit in the form of an open-ended cylinder.
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37. An induction apparatus comprising two or more cylindrical, closely coupled, multiple turn, co-axial co-extensive coil windings embedded in a rigid resinous material and providing a rigid open-ended generally cylindrical coil unit, means connecting said coil windings in parallel and current balancing means comprising transformers connected to said coil windings such as to provide feed back from one winding to another and thereby automatically forcing all windings to share a predetermined portion of the total current.
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38. In electrical induction heating apparatus an improved induction coil comprising a rigid open-ended generally cylindrical unit having at least one sleeve-like coil winding embedded in a rigid set resin material, said sleeve-like coil winding comprising a plurality of helical turns of conductor said conductor consisting of a plurality of insulated multi-strand cabled conductors spirally disposed about the outer surface of a tube.
- 39. In an electric induction heating apparatus, an induction coil assembly comprising a first rigid open-ended sleeve-like coil unit of at least two coil windings embedded in a glass fibre reinforced resin material, each said coil winding comprising multiple helical turns of conductor comprising a central cooling tube selected to have predetermined heat transfer properties and predetermined eddy losses at the coil geometry chosen and for the frequency and ampere turns for which the coil is designed and an outer layer of high conductivity insulated strands spirally disposed about said cooling tube, the diameter of said strands and the number being so chosen as to provide selected eddy current loss characteristics for a chosen design current and a rigid open-ended sleeve-like heat shield unit removably inserted in said coil unit, said heat shield unit comprising tubular passage means through a rigid heat resistant resinous material for circulating a cooling fluid therethrough.
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42. Improvements in induction heating apparatus comprising a rigid generally cylindrical induction coil unit having a helical coil winding of water-cooled conductor encapsulated in glass fibre reinforced resin to form a strong, rigid and vibration free unit;
- a helically wound heat-shield winding encapsulated in a glass fibre reinforced resin forming a second strong rigid sleeve like unit removably disposed within and concentric with said induction coil unit for facilitating replacement in case of damage, said water-cooled conductor, from which the induction coil is wound, comprising an inner cooling tube around which is spirally disposed an outer layer of high conductivity insulated strands which carry the main induction current of the heating coil, the material of the inner cooling tube having adequate heat transfer properties to remove the heat generated by the current through the outer layer while at the same time having an electrical resistivity which is sufficiently small that the eddy losses induced in the cooling tube will be very small compared to the losses in the main conducting portion of the water-cooled conductor, the diameter of the strands comprising the outer conducting layer providing selected eddy loss characteristics, which depend on the frequency and the field strength required in the coil while predetermined number of strands are provided to carry the current for which the induction coil is designed, said strands being transposed so that each will carry its proper share of the total current, said heat sink winding comprising a tube helically wound into the form of an open ended cylinder and embedded in a fibre reinforced resin.
- View Dependent Claims (43, 44, 45)
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46. The improvement as defined in calim 45 wherein said means connecting said windings in parallel comprises a split ring bus at one end of said coil windings.
Specification