Induction reactor with electrically separable coil system
Patent Information
- Application Number
- JP2026506022
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-07-31
- Filing Date
- 2024-03-15
- Publication Date
- 2026-09-01
Smart Images
Figure 2026529567000001_ABST
Abstract
Description
Technical Field
[0001] Cross-Reference to Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 529,782, filed on July 31, 2023, the entire content of which is incorporated herein by reference.
[0002] The present invention relates to an electric induction furnace, and more particularly, to an induction furnace having an active coil and a passive coil that are selectively electrically connected by a detachable external jumper cable, a selector switch or the like, wherein the active coil and the passive coil are easily replaceable and can be electrically insulated for independent operation.
Background Art
[0003] Electric induction furnaces are used for heating and melting metals and other conductive materials. As shown in FIGS. 1(a) and 1(b), an induction furnace 10 utilizes an induction coil L1 powered by an AC power supply 14 having an AC-DC rectifier section 14a, a DC-AC inverter section 14b, and a tuning capacitor section 14c. The alternating current flowing through the induction coil L1 generates a magnetic field that is applied to a conductive charge disposed inside the coil of the furnace. Eddy currents induced by the magnetic field can be used for heating, melting, and superheating the charge. The magnetic coupling between the induction coil L1 and the charge is similar to a magnetic transformer coupling in which the induction coil L1 represents a primary winding and the conductive charge represents a short-circuited secondary winding, respectively.
[0004] Prior art discloses induction reactor systems for improving the efficiency of induction coils by utilizing a combination of an active induction coil connected to an AC power supply 14 and a passive induction coil connected to an LC tank circuit 16 and magnetically coupled to the active induction coil. As shown in Figures 1(c) and 1(e), the active and passive induction coils can be configured by electrically connecting either the upper coil L1 or the lower coil L2 to the AC power supply 14 or the LC tank circuit 16, respectively. U.S. Patent No. 6,542,535 (hereinafter referred to as the '535 patent), incorporated by reference in its entirety, discloses an active / passive coil system that improves the efficiency of an induction reactor system by using a passive coil to reflect the resistance of the LC tank circuit 16 to the active induction coil. The '535 patent further discloses a pair of different coils, or a single coil having an active and a passive part.
[0005] As shown in Figures 1(c) to 1(f), the active and passive coils of such induction furnace systems are typically electrically connected by internal and permanent copper brazing 18 between adjacent turns of the active and passive coils. For example, if the upper coil L1 represents the active coil and the lower coil L2 represents the passive coil, the lowest turn of the upper coil L1 is brazed to the highest turn of the lower coil L2. This electrical connection eliminates the potential difference between the two coils, which could degrade the insulation and shorten the effective operation and service life of the induction coil system. Furthermore, in active / passive coil systems, the electrical connection between the two coils allows the passive coil to be operably connected to an optional ground leakage detection (GLD) system incorporated into the active coil via an AC power supply. The GLD system performs fault monitoring and notifies the operator of short circuits from the load to the coil due to wear of the refractory lining or metal intrusion. In this way, any short circuits occurring in the passive coil or in the passive coil section are detected by the GLD system, allowing for appropriate shutdown and maintenance work to be carried out.
[0006] The permanent electrical connection between the active and passive coils can result in operational difficulties, such as a short circuit affecting only one coil causing the induction furnace to shut down until the short circuit is resolved, thus reducing the overall furnace throughput. Typically, when a fault is detected, diagnostics must be performed to troubleshoot and identify the cause of the fault, during which time the furnace must be shut down. After the cause of the fault is determined, repairs such as re-applying the refractory lining must be carried out, which involves delays due to the arrangement of maintenance personnel. Until the cause of the fault is determined and repairs are completed, the furnace remains inoperable under any circumstances. Furthermore, the furnace's service life may lead to additional operational difficulties due to fault monitoring and the permanent electrical connection between the active and passive coils. For example, when a new refractory lining is applied, excess moisture in the lining can cause a high GLD value in the initial weeks after application, potentially delaying or hindering furnace operation until the lining is completely dry.
[0007] Furthermore, typical active and passive induction coil systems have limited flexibility because the two coils cannot be switched between active and passive states once the associated furnace is filled with molten metal. For example, the upper coil L1 remains the active coil and the lower coil L2 remains the passive coil (or vice versa) throughout the operation of the coil system. Which coil is preferred to function as the active or passive coil may change throughout the furnace operation process, depending on the desired stirring or heating characteristics at various points in the operation. For example, connecting the lower coil L2 to the AC power supply 14 to make it the active coil has the advantage of allowing the lower coil L2 to be operated early with minimal material charging during the initial charging of the furnace without the risk of damaging the upper furnace structure. If the upper coil L1 is the active coil, power cannot be supplied until the liquid level of the conductive material reaches the upper coil, and it can only be operated at a limited power level until the upper coil is completely filled, otherwise the shunt may overheat and damage other furnace structures. However, since the electrical connections to the coil and the condenser bank also carry cooling water to the coil, attempting to replace the power supply and condenser bank between the coil or coil section while the furnace contains molten metal may cause the coil and surrounding structures to overheat and be damaged.
[0008] Furthermore, when handling molten metal, the accumulation of impurities or dross can cause significant problems in the operation of related induction heating applications, such as coating pots. During operation, impurities can accumulate and adhere to the bottom or sides of the pot, colliding with the feed material rollers or other immersion equipment in the molten metal, potentially causing defects in the feed material, the coating applied to the feed material, or both. Removing the dross at this stage requires considerable effort and may keep the coating pot offline for extended periods. Generally, stirring the molten metal can reduce the rate of dross accumulation, and high-intensity stirring can prevent dross sedimentation. However, simply adjusting the input power and frequency of only a portion of the segmented coil structure, such as the active section in prior art active / passive coil systems, does not easily optimize the stirring pattern. In particular, when the active section of an induction coil system is located in the upper coil, the stirring intensity is localized in the upper part of the furnace volume, while relatively low-intensity stirring is localized in the lower part. Dross accumulation can be reduced by adjusting the stirring intensity in both the upper and lower parts of the furnace volume throughout the entire operating process. [Overview of the project] [Problems that the invention aims to solve]
[0009] Therefore, there is a need for electric induction furnaces equipped with active and passive coils that can be electrically isolated for independent operation, and even for electric induction furnaces equipped with active and passive coils that can be selectively switched between active and passive states. [Means for solving the problem]
[0010] In one embodiment, the present invention relates to an apparatus for heating and melting a conductive material in an induction furnace system comprising an induction coil assembly defining an active coil or active coil section connected to a suitable alternating current (AC) power supply and a passive coil or passive coil section connected to one or more capacitors to form an LC tank circuit, wherein the active coil or active coil section and the passive coil or passive coil section are electrically connected via a detachable jumper cable located outside the induction coil, and the active coil or active coil section and the passive coil or passive coil section can be electrically isolated by removing the detachable jumper cable.
[0011] In another embodiment, the present invention provides a method for electrically isolating the upper coil or upper coil section and the lower coil or lower coil section of an induction coil assembly by removing an external jumper cable that electrically connects the upper coil or upper coil section and the lower coil or lower coil section of the induction coil assembly, and connecting an appropriate alternating current (AC) power supply to either the upper coil or upper coil section or the lower coil or lower coil section to operate the coil or coil section independently.
[0012] In another embodiment, the present invention is a method for reconfiguring the connection of an appropriate power supply and capacitor bank from the upper coil or upper coil section to the lower coil or lower coil section so that the upper coil or upper coil section and the lower coil or lower coil section can be selectively swapped between an active state and a passive state during the operation of an induction reactor.
[0013] Other aspects of the present invention described herein and in the appended claims are described herein. [Brief explanation of the drawing]
[0014] The drawings shown below, which are a brief summary, are provided for illustrative purposes only and do not limit the invention as described herein. [Figure 1(a)]Figure 1(a) shows a schematic plan view of a conventional induction reactor system. [Figure 1(b)] Figure 1(b) shows a simplified circuit diagram of the induction reactor system shown in Figure 1(a). [Figure 1(c)] Figure 1(c) shows a schematic plan view of an induction reactor system equipped with an advanced efficiency-improved coil system in which the upper coil is connected to an AC power source. [Figure 1(d)] Figure 1(d) shows a simplified circuit diagram of the induction reactor system shown in Figure 1(c). [Figure 1(e)] Figure 1(e) shows a schematic plan view of an induction reactor system having an advanced efficiency-improved coil system in which the lower coil is connected to an AC power source. [Figure 1(f)] Figure 1(f) shows a simplified circuit diagram of the induction reactor system shown in Figure 1(e). [Figure 2(a)] Figure 2(a) shows a schematic plan view of an example of an induction furnace equipped with the electrically separable coil system of the present invention, in which the upper coil is connected to the active circuit. [Figure 2(b)] Figure 2(b) shows a simplified circuit diagram of an induction reactor equipped with the electrically separable coil system shown in Figure 2(a). [Figure 2(c)] Figure 2(c) shows a schematic plan view of another example of an induction reactor featuring the electrically isolated coil system of Figure 2(a) utilizing a variable frequency resonant power supply and an adjustable capacitor bank. [Figure 2(d)] Figure 2(d) shows a simplified circuit diagram of an induction reactor equipped with the electrically separable coil system shown in Figure 2(c). [Figure 2(e)] Figure 2(e) shows a schematic plan view of another example of an induction reactor equipped with the electrically separable coil system of Figure 2(a) using a pulse-width modulated power supply and a software control system. [Figure 2(f)] Figure 2(f) shows a simplified circuit diagram of an induction reactor equipped with the electrically separable coil system shown in Figure 2(e). [Figure 3(a)] Figure 3(a) shows a schematic plan view of an example of an induction furnace equipped with the electrically separable coil system of the present invention, in which the lower coil is connected to the active circuit. [Figure 3(b)] Fig. 3(b) shows a simplified circuit diagram of an induction furnace provided with the electrically separable coil system of Fig. 3(a). [Figure 3(c)] Fig. 3(c) shows a schematic plan view of another example of an induction furnace provided with the electrically separable coil system of Fig. 3(a) using a variable frequency resonant power supply and an adjustable capacitor bank. [Figure 3(d)] Fig. 3(d) shows a simplified circuit diagram of an induction furnace provided with the electrically separable coil system of Fig. 3(c). [Figure 3(e)] Fig. 3(e) shows a schematic plan view of another example of an induction furnace provided with the electrically separable coil system of Fig. 3(a) using a pulse width modulation power supply and a software control system. [Figure 3(f)] Fig. 3(f) shows a simplified circuit diagram of an induction furnace provided with the electrically separable coil system of Fig. 3(e). [Figure 4(a)] Fig. 4(a) shows a schematic plan view of an example of an induction furnace provided with the electrically separable coil system of Fig. 2(c) having selector switches for alternately connecting each of an upper coil and a lower coil to an active circuit and a passive circuit, respectively. [Figure 4(b)] Fig. 4(b) shows an induction furnace provided with the electrically separable coil system of Fig. 4(a) in which the selector switch connects the upper coil to the active circuit and the lower coil to the passive circuit. [Figure 4(c)] Fig. 4(c) shows an induction furnace provided with the electrically separable coil system of Fig. 4(a) in which the selector switch connects the lower coil to the active circuit and the upper coil to the passive circuit. [Figure 5(a)] Fig. 5(a) shows a cross-sectional view of an example of an induction furnace provided with the electrically separable coil system of Fig. 4(a) in which a selector switch connects the lower coil to the active circuit, and the upper coil and the lower coil are electrically separated for operation with only the lower coil. [Figure 5(b)]Figure 5(b) shows a cross-sectional view of an example induction reactor with the electrically separable coil system of Figure 4(a), in which a selector switch connects the upper coil to the active circuit and the upper and lower coils are electrically isolated for operation of the upper coil only. [Figure 6(a)] Figure 6(a) shows a schematic plan view of a typical water-cooling system for an induction reactor equipped with an electrically separable coil system. [Figure 6(b)] Figure 6(b) shows a schematic plan view of an independent water-cooling system with an independent water source in an example of an induction reactor equipped with an electrically separable coil system. [Figure 6(c)] Figure 6(c) shows a schematic plan view of an independent water cooling system using a shared water source and multi-port valve in an example of an induction reactor with an electrically separable coil system. [Figure 7(a)] Figure 7(a) shows a cross-sectional view of a typical induction stirring pattern of the conventional induction reactor system shown in Figure 1(a), illustrating a state where dross accumulation at the bottom of the furnace is interfering with operation. [Figure 7(b)] Figure 7(b) shows a cross-sectional view of the improved stirring pattern achieved by the electrically separable coil system of the present invention, illustrating the reduction in dross accumulation. [Figure 7(c)] Figure 7(c) shows a cross-sectional view of another improved stirring pattern achieved by the electrically separable coil system of the present invention, illustrating the reduction in dross accumulation. [Figure 8(a)] Figure 8(a) shows a cross-sectional view of the induction reactor system, illustrating the filling lines corresponding to the optimal active circuit connections of the upper and lower coils, respectively, to prevent damage to the reactor system. [Figure 8(b)] Figure 8(b) shows a cross-sectional view of the induction reactor system shown in Figure 8(a) in a partially filled state where the upper coil is coupled to the lower coil and some components of the reactor system are overheated. [Figure 8(c)] Figure 8(c) shows a cross-sectional view of the induction reactor system in Figure 8(a) in a partially filled state, where the upper coil is cut and electrically isolated from the lower coil. [Figure 8(d)]Figure 8(d) shows a cross-sectional view of the induction reactor system shown in Figure 8(a) in a filled state, with the upper coil connected to the active circuit and the lower coil connected to the passive circuit. [Figure 8(e)] Figure 8(e) shows a cross-sectional view of the induction reactor system in Figure 8(a) in a filled state where the lower coil is cut and electrically isolated from the upper coil. [Modes for carrying out the invention]
[0015] Referring to the drawings, the same reference numerals indicate the same elements, and Figures 2(a) to 2(f) show examples of induction reactor systems utilizing an electrically separable coil system according to the present invention.
[0016] For explanatory purposes, the following disclosure describes the present invention in relation to induction heating of coating pot systems. However, it should be understood by those skilled in the art that the present invention is not necessarily limited to induction coating pot systems, and other induction furnace heating applications are also within the scope of this disclosure.
[0017] The induction furnace system 20 includes a furnace volume 21 into which a conductive material (charge or load) is introduced, where the conductive material is induction heated, melted, and superheated via induction coils positioned around the furnace volume. In an exemplary embodiment, the induction furnace system 20 includes a coating pot having a feeding mechanism for immersing a supply material into a molten charge to be coated. The coating pot further includes one or more rollers immersed in the molten charge, which guide the supply material.
[0018] In the illustrated embodiment, the induction coil comprises a split coil configuration that defines either an independent upper coil L1 and lower coil L2 sharing a common load, or a single coil defining the upper and lower coil sections. In alternative embodiments, induction coil configurations including more than two induction coils or coil sections are envisioned. As shown in Figures 2(a), 2(c), and 2(e), the upper coil L1 or upper coil section is connected at its terminal end to a suitable AC power supply 24 to define the active coil, and the lower coil L2 or lower coil section is connected to one or more parallel capacitors C2 to form a parallel LC tank circuit that defines the passive coil. In the illustrated embodiments of Figures 2(a) and 2(c), the AC power supply 24 comprises an AC / DC rectifier or filter section 27, a DC / AC inverter section 28, and a tuning capacitor section 29. The magnetic field generated by the current flow in the upper coil L1 generates a flux magnetic field that magnetically couples with the lower coil L2, inducing a current in the lower coil L2. As shown in Figure 2(c), one or more parallel capacitors C2 may further include an adjustable capacitor bank 25 comprising one or more auxiliary capacitors C2(a) in parallel, selectively connected via one or more intermediate switches S1, detachable bus links, cables, etc. In this way, the capacitance of the LC tank circuit can be easily adjusted to control resonance within the LC tank circuit. Although one auxiliary parallel capacitor C2(a) is shown in the illustrated embodiment of Figure 2(c), it should be noted that a capacitor bank 25 having any number of capacitors, where each capacitor can be selectively isolated from the LC tank circuit by one or more intermediate switches S1, is also within the scope of this disclosure.
[0019] Conversely, as shown in Figures 3(a) to 3(f), the lower coil L2 or lower coil section is connected at its terminal end to a suitable AC power supply 24 to define an active coil, while the upper coil L1 or upper coil section is connected to one or more capacitors C2 to define a parallel LC tank circuit and define a passive coil. Similarly, the magnetic field generated by the current flow in the lower coil L2 generates a flux magnetic field that magnetically couples with the upper coil L1, thereby inducing a current in the upper coil L1. The terminal connections between each of the AC power supply 24 and one or more capacitors C2 and each coil are identical and interchangeable, and the terminal connections can be easily switched between the upper coil L1 and the lower coil L2 as needed. In this way, the upper coil L1 and the lower coil L2 can alternately function as passive and active coils throughout the operation of the induction furnace system 20 to maximize the operating efficiency throughout the entire heating process, as further details are described elsewhere in this specification.
[0020] In the illustrated embodiment, an externally detachable jumper cable 26 electrically connects the upper coil L1 and the lower coil L2, preventing a potential difference between the upper coil L1 and the lower coil L2, thereby extending the service life and operation of the coils. The jumper cable 26, or other suitable detachable connection means between the upper coil L1 and the lower coil L2, may further include one or more passive filters, such as chokes. In the illustrated embodiment, the jumper cable 26 is operably connected to the lowest turn of the upper coil L1 and the highest turn of the lower coil L2. The jumper cable 26 may be detachable from each coil at both ends, thereby allowing the jumper cable 26 to be completely removed from the induction reactor system, or it may be detachable at only one end, thereby defining an electrical discontinuity at either the lowest turn of the upper coil L1 or the highest turn of the lower coil L2. In embodiments of induction coil systems having more than two induction coils, the jumper cable 26 is detachably fixed between each adjacent coil. Furthermore, the jumper cable 26 operably connects the passive coil to a GLD system located within the AC power supply 24 connected to the active coil. In this way, a ground fault in the passive coil is detected via the electrical connection between the active and passive coils. Alternatively, in some embodiments, separate GLD systems are associated with each of the upper coil L1 and lower coil L2, making it easier to identify which of the upper coil L1 or lower coil L2 has experienced a fault. In such embodiments, a capacitor is electrically connected between the upper coil L1 and the lower coil L2 to prevent a DC current from the GLD system of one coil from detecting a fault in the other coil. Because the jumper cable 26 is external, it is easily accessible so that the upper coil L1 can be electrically isolated from the lower coil L2 if a fault is detected. After removal, the upper coil L1 and the lower coil L2 are separated by an air gap, allowing for independent operation with the adjacent coil offline.For example, if a ground fault is detected in the active coil section, the AC power supply 24 can be disconnected from the active coil section and reconnected to the old passive coil section in order to continue operation while scheduling maintenance procedures, by disconnecting the jumper cable 26 to electrically isolate the active coil from the passive coil. One or more capacitors C2 must also be disconnected to further prevent mutual inductance with loads in adjacent unused coils. In this specification, “cable” includes a detachable flexible or rigid structure to which one or more inductive coils can be electrically connected, and the jumper cable 26 may include any of copper wire, plates, etc., of an appropriate size depending on the power, current, and voltage of a particular AC power supply. Alternatively, as described elsewhere in this specification, the jumper cable 26 may be replaced with or further included a switch or other selective electrical connection in order to reduce the requirement of manual operation of the system. In such embodiments, the switch can be actuated to disconnect the upper coil L1 from the lower coil L2.
[0021] The AC power supply 24 may include, but is not limited to, a variety of power supply topologies, including a voltage-fed converter in a full-bridge or half-bridge configuration with a series resonant tank capacitor, a current-fed converter with a series or parallel resonant tank capacitor, and a converter utilizing pulse width modulation (PWM) 30 as shown in Figures 2(e) and 3(e). Each of these power supply topologies comprises a rectifier and filter section 27 and a tuning capacitor section 29. In embodiments employing the PWM power supply 30, the output frequency can be changed, as details are described elsewhere in this specification, so that the desired efficiency and stirring characteristics are maintained even when the output power changes. The control system 32 is operably connected to the PWM power supply 30 and implements software configured to adjust the output frequency over multiple power levels without changing the capacitance of the passive coil (LC tank circuit) to maintain the desired efficiency and stirring characteristics. Voltage sensing means V1 and V2 are provided to sense the instantaneous voltage of the lower coil L2 and the upper coil L1, respectively, and the sensed voltages are transmitted to the control system 32. Similarly, current sensing means I1 and I2 are provided to detect the instantaneous current flowing through the lower coil L2 and the upper coil L1, respectively, and the detected current is transmitted to the control system 32. In this way, the software-controlled PWM power supply 30 facilitates adjustment of the power distribution and phase shift between the upper coil L1 and the lower coil L2, and consequently the stirring pattern and speed, independently of the output power, by changing the output frequency without changing the circuit.
[0022] The connections to the upper and lower coil terminals of the AC power supply 24 and the capacitor bank 25 are identical and interchangeable, allowing the upper coil L1 and lower coil L2 to be easily switched between active and passive states. In some embodiments, as shown in Figures 4(a) to 4(c), a selector switch of appropriate rating can operably connect each of the capacitor bank 25 and the AC power supply 24 to either the upper coil L1 or the lower coil L2, thereby allowing the AC power supply 24 and the capacitor bank 25 to be swapped between the upper coil L1 and the lower coil L2 without manual disconnection and reconnection from the coil terminals. In the illustrated embodiments, the AC power supply 24 is selectively connected to each of the upper coil L1 and the lower coil L2 via a switch S2 (power switch). When the switch S2 is in the first position, as shown in Figure 4(b), the switch S2 connects the AC power supply 24 to the upper coil L1, and when the switch S2 is in the second position, as shown in Figure 4(c), the switch S2 connects the AC power supply 24 to the lower coil L2. Similarly, the capacitor bank 25 is selectively connected to the upper coil L1 and the lower coil L2 via switch S3 (tank circuit switch). When switch S3 is in the first position, as shown in Figure 4(b), switch S3 connects the capacitor bank 25 to the lower coil L2. When switch S3 is in the second position, as shown in Figure 4(c), switch S3 connects the capacitor bank 25 to the upper coil L1. Each of switches S2 and S3 can also be selectively placed in a neutral third position, as shown in Figure 4(a), which disconnects the AC power supply 24 and the capacitor bank 25 from both the upper coil L1 and the lower coil L2. In such embodiments, when water-cooled conductors are used to connect to either coil, the use of a selector switch eliminates the need for separate water-cooling circuits that would otherwise be necessary to facilitate switching between the AC power supply 24 and the capacitor bank 25, as detailed elsewhere in this specification. Alternatively, a similar effect can be achieved by bolt connections within a junction box without incorporating a selector switch.Furthermore, in the illustrated embodiment, the switch S4 (insulated switch) selectively electrically connects the upper coil L1 and the lower coil L2, instead of using an externally detachable jumper cable.
[0023] If a ground fault occurs in either the upper coil L1 or the upper coil section, or the lower coil L2 or the lower coil section, the GLD system, which is operably connected to each of the active and passive coils via a detachable jumper cable 26 in relation to the AC power supply 24, will normally cut off the power supply to the coils and warn the operator of the possibility of a short circuit to the coil system from metal intrusion into the refractory lining or other loads. The jumper cable 26 is then removed to locate the fault, or the switch is opened to isolate the upper coil L1 from the lower coil L2. Once a fault is identified in one of the two coils or one coil section of a single coil system, the AC power supply 24 is connected to the coil terminals of the remaining coil or coil section to continue operating the furnace system using the single coil or coil section. In this way, the furnace can continue operating at reduced efficiency until repairs can be arranged and carried out, improving the overall system availability. Furthermore, since the AC power supply 24 is directly connected to the remaining operable coil or coil section, GLD protection is maintained in that remaining coil or coil section. For example, as shown in Figure 5(a), even if a ground fault is detected in the upper coil L1 or the upper coil section, the AC power supply 24 is connected to the lower coil L2 or the lower coil section in order to continue operating the lower coil L2. Similarly, as shown in Figure 5(b), even if a ground fault is detected in the lower coil L2 or the lower coil section, the AC power supply 24 is connected to the upper coil L1 or the upper coil section in order to continue operating the upper coil L1.
[0024] As shown in Figure 6(b), the induction reactor system includes separate cooling circuits that define the conductor cooling circuit and the coil cooling circuit. Thus, when the water-cooled conductor 60 is disconnected from the associated coil terminal 62 to switch the coil state between active and passive states, the induction coil maintains a consistent flow of water cooling through the coil to mitigate damage to the coil and insulation due to exposure to high temperatures of the load or charge, thereby facilitating changes in the coil state during operation of the induction reactor. This differs from the typical shared cooling system shown in Figure 6(a). In a typical induction reactor system, as shown in Figure 6(a), the water-cooled conductor 60 electrically connects the induction coil terminal 62 to the AC power supply 24 and capacitor C2, and the water-cooled conductor 60 receives cooling water from the water source 61. The water-cooled conductor 60 further supplies cooling water inside the upper and lower induction coils L1 and L2, which form the shared conductor and coil water-cooling circuit.
[0025] In contrast, the independent cooling circuit of the present invention, as shown in Figure 6(b), includes a shut-off valve 68 positioned between the primary water source 61 and the water-cooled conductor 60, which can continuously flow through the upper and lower induction coils L1 and L2 and shut off the fluid flow to the water-cooled conductor 60. In the embodiment shown in Figure 6(b), coil terminals 62 adjacent to the AC power supply 24 or capacitor bank C2 are provided with conductor inlets 65, and coil terminals 62 adjacent to the upper coil L1 and lower coil L2 are provided with conductor outlets 66, with water cooling being supplied through the water-cooled conductor from the conductor inlets 65 to the conductor outlets 66. Furthermore, one or more barriers 64 are present at each coil terminal 62 to prevent water from the conductor cooling circuit from flowing into the AC power supply 24, capacitor bank C2, and the upper coil L1 and lower coil L2, respectively. On the coil terminal 62 opposite the barrier 64, individual coil inlets 67 are provided so that water is supplied to each coil independently of the water flowing through the water-cooled conductor 60. In one embodiment, the water-cooled conductor 60 and the induction coil cooling circuit are connected to separate water sources (primary water source 61 and auxiliary water source 63) so that they can be shut off independently, as shown in Figure 6(b). In another embodiment, the water-cooled conductor 60 and the induction coil share a common water source 61 and are provided with a multi-port valve 69 that allows fluid to flow simultaneously to both the water-cooled conductor 60 and the induction coil in a first position, and to flow fluid only to the induction coil in a second position, as shown in Figure 6(c). In an alternative embodiment, where operationally appropriate, bolt connections in a junction box can be used to electrically connect each upper coil L1 and lower coil L2 to the AC power supply 24 and capacitor bank C2, respectively, in order to eliminate the need for a separate water-cooling circuit, instead of the water-cooled conductor 60.
[0026] During operation of the furnace system, dross 70 can be generated and accumulate, potentially reducing the operating life of the furnace system. For example, in the coating pot applications shown in Figures 7(a) and 7(b), dross accumulation along the bottom 72 and sides 74 of the furnace volume may interfere with the operation of the rollers or other feeding mechanisms or the operation of the material being coated. Alternatively, the particle size of the dross 70 may increase over time, significantly affecting the quality of the coating applied to the material. If the operation of the rollers is affected, it may be necessary to stop the furnace, discharge the furnace, and manually remove the dross 70, which is a time-consuming and laborious process. In this way, by changing the stirring characteristics during operation, the rate of dross 70 generation or accumulation can be reduced by selectively increasing the stirring intensity in the relevant parts of the furnace. For example, by maintaining a high relative stirring rate, the dross 70 particles can be kept suspended in the molten material while further reducing the particle growth of the dross 70. Furthermore, as described elsewhere in this specification, continuously or pulsatingly changing the stirring pattern (molten flow pattern) 76 during operation promotes the constant movement of dross 70 particles and more uniform mixing of the molten material. This suppresses the occurrence of dead zones, as shown in Figure 7(c), where there is little or no flow and dross 70 particles can settle and accumulate. The formation, growth, and accumulation of dross 70 particles are a function of residence time in the bath and bath temperature, among other things, and by maximizing the stirring rate, the generation and growth of dross 70 can be prevented at a stage where the particles are small enough not to cause measurable defects in the coating or feed material.
[0027] When the magnetic field generated by the induction coil interacts with the conductive material, a stirring pattern 76 is created within the molten material, aiding in heat distribution and homogenization of the molten material. The stirring pattern 76 can be affected by various parameters, such as the power distribution between the active and passive coil arrangements. For example, changing the output frequency of the AC power supply, changing the power level, changing the total capacitance C2 connected to the passive coil, switching the active coil from the upper coil L1 to the lower coil L2 or vice versa, operating with a single active coil, or changing the furnace volume or coil shape, or any combination thereof, will affect the generated stirring pattern.
[0028] Furthermore, unidirectional stirring can be achieved by introducing a phase offset between the active and passive coil currents, as disclosed in U.S. Patent No. 7,457,344 ('344 patent) and U.S. Patent No. 9,370,049 ('049 patent), which are entirely incorporated into the present invention by reference. The appropriate phase offset varies depending on the coil shape, load shape, and system symmetry. Alternatively, as described above, using a PWM power supply can offer significant substantial advantages because the output frequency is independent of the output power and can be modified to affect the stirring intensity and pattern over the entire operating range of the furnace system. For example, software associated with the control system 32 of the PWM power supply can adjust power distribution, phase shift, and consequently the stirring pattern 76 and speed by changing the output frequency independently of the output power without changing circuit capacitances such as the capacitance across the passive coils. Continuously varying the stirring pattern 76 can avoid dead zones with little or no flow and achieve a more uniform bath temperature, chemical composition, and dross 70 distribution.
[0029] Alternatively, when using an arbitrary resonant power supply, the power distribution between the active and passive coils can be changed by altering the parallel capacitance of the passive coils, thereby adjusting the stirring pattern 76 and speed. Similarly, by changing the parallel capacitance of the passive coils to adjust the operating frequency, a phase shift can be introduced between the upper and lower coil currents, thereby altering the stirring pattern 76 and speed. The parallel capacitance of the passive coils can be adjusted by activating the intermediate switch in the capacitor bank, as described above. For example, while keeping the total output power from the AC power supply constant, changing the number of parallel capacitors connected to the passive coils has various effects on the stirring pattern 76 and speed. As the parallel capacitance increases, the power of the passive coils increases and the operating frequency decreases. Furthermore, the current phase shift between the two coils increases with the parallel capacitance, generating a stirring pattern with substantially two or four distinct zones. Desired melting conditions are achieved when the average velocity of the molten material is maximized and the dead zone is minimized. The stirring pattern 76 and power distribution can also be changed via switches. Finally, to electrically isolate the active coil from the passive coil, the jumper cable can be removed, or in the embodiment using the selector switch described above, the switch can be activated. In addition, to prevent mutual inductance between the two coils, the parallel capacitance of the passive coil circuit must be disconnected by removing the cable, disconnecting the bus link, or activating the switch in the capacitor bank. In this way, the stirring pattern 76 is completely derived from the active coil and can be further adjusted as described above.
[0030] Furthermore, the active and passive coil configurations may become more or less desirable throughout the typical service life and operation of the induction furnace system. For example, as the amount of molten material in the furnace volume increases, it becomes more efficient to operate the upper and lower coils in different configurations, such as active, passive, or disconnected and electrically isolated from each other. In the illustrated embodiment of Figure 8(a), the upper coil L1 and lower coil L2 are connected to a parallel capacitor and an AC power supply, respectively. The furnace volume in Figure 8(a) is divided into various filling levels relative to the total furnace height H and thus the maximum filling level 82. In the illustrated embodiment, the minimum filling level 80 for operating the coil system is shown at approximately one-third of the furnace height H, i.e., at the centerline of the induction coil system (midpoint between the upper coil L1 and the lower coil L2). In some such embodiments, the minimum filling level 80 can range from 25% to 40% of the furnace volume, but significant advantages in power supply to the load have been observed at approximately 35% of the furnace volume compared to similar operating conditions when the furnace is full. Furthermore, operating the furnace with the upper coil L1 in the active circuit when the conductive charge or load material is below the threshold filling level 84, indicated at approximately 1 / 2H (midpoint of furnace volume), may adversely affect the lifespan of some furnace components, including the shunt and coil support. As shown in Figure 8(b), when there is no sufficient load to couple, such as when the top of the furnace volume is empty, the upper ends of the coil support and shunt may overheat.
[0031] For example, as shown in Figure 8(c), during the initial operating phase of the furnace, such as when initially charging a metal or other conductive material to be heated into the furnace, energy can be more efficiently transferred to the conductive charge or load material when the lower coil L2 is connected to the active circuit and the upper coil L1 is disconnected from the parallel capacitor C2 and electrically isolated from the upper coil L1. When the liquid level of the molten material in the furnace volume rises above the minimum filling level 80, the upper coil L1 can be electrically connected, but when operating below the maximum filling level, the power to the upper coil L1 must be limited to reduce the risk of damage to the equipment. For example, to prevent overheating of the upper components of the furnace, when the conductive material is between the minimum filling level 80 and the maximum filling level 82, the upper coil L1 must be operated with reduced power as a function of the filling rate of the furnace volume. Thus, operating the furnace system with the lower coil L2 as the active circuit and the upper coil L1 disconnected during the initial stages of operation is desirable to increase efficiency and reduce the load on the equipment. When the amount of charge or load reaches the maximum filling level 82, the upper coil L1 can be switched to an active circuit and the lower coil L2 to a passive circuit, as shown in Figure 8(d), or they can be completely disconnected, as shown in Figure 8(e), and vice versa, as necessary to achieve the desired stirring characteristics described above. In embodiments using more than two induction coils or coil sections, as the furnace volume is filled, the induction coils closest to the current filling level can be sequentially switched to an active circuit. For example, when the current filling level exceeds the height of the next induction coil, the previous induction coil switches to a passive circuit, and the next induction coil switches to an active circuit.
[0032] Other active and passive coil arrangements are also disclosed within the scope of the invention, including arrangements involving two or more independent induction coils. For example, multiple active and / or passive coil circuits may be used in various configurations having one or more overlapping coils and / or one or more non-overlapping coils.
[0033] The drawings show one type of power supply for use with the electrically separable coil system of the present invention, but other power supply topologies can also be used to take advantage of the benefits of the coil system in the induction reactor system of the present invention.
[0034] Examples of the present invention include references to specific electrical components. Those skilled in the art can implement the present invention by substituting components, not necessarily of the same type, but which produce the desired conditions of the present invention or achieve the desired results of the present invention. For example, a single component may be represented by multiple components, or vice versa.
[0035] Throughout this specification, references such as “an example or embodiment,” “a certain example or embodiment,” “one or more examples or embodiments,” or “different examples or embodiments” mean, for example, that certain features may be included in the practice of the invention. In this specification, various features may be grouped together in a single example, embodiment, drawing, or description therein to simplify the disclosure and aid in understanding various inventive aspects.
[0036] The present invention has been described in terms of preferred examples and embodiments. Except as expressly stated, equivalents, substitutions, and modifications are also possible and are within the scope of the invention. Those skilled in the art who have benefited from the teachings herein can make modifications without departing from the scope of the invention.
Claims
1. An induction reactor system comprising an electrically separable coil system, Furnace volume and, An induction coil system for induction heating and melting a conductive material placed in the furnace volume, wherein the induction coil system is At least one active induction circuit, An active induction coil having two or more active coil terminals surrounds a portion of the furnace volume, A power supply having an input configured to be connected to an external power supply for the induction reactor system, and a primary ground fault detection system configured to detect ground faults in at least one active induction circuit, The at least one active induction circuit comprises, wherein the AC output of the power supply is operably connected to two or more active coil terminals via one or more water-cooled conductors for each active coil terminal, At least one passive inductive circuit, A passive induction coil having two or more passive coil terminals surrounds a portion of the subsequent section of the aforementioned furnace volume, One or more parallel capacitors operably connected to the two or more passive coil terminals that define the L-C tank circuit, The at least one active induction circuit is positioned relative to the at least one passive induction circuit such that it magnetically couples with the passive induction coil when an alternating current flows through the active induction coil, A separable electrical connection that electrically couples the at least one active induction circuit and the at least one passive induction circuit when they are connected, and electrically insulates the at least one active induction circuit from the at least one passive induction circuit when they are disconnected, An induction reactor system equipped with the following features.
2. The induction furnace system according to claim 1, wherein the separable electrical connection comprises an externally located jumper cable detachably mounted between the active induction coil and the passive induction coil.
3. The induction furnace system according to claim 2, wherein the externally arranged jumper cable is selectively disconnected from either the active induction coil or the passive induction coil.
4. The induction reactor system according to claim 1, wherein the separable electrical connection further comprises at least one passive filter.
5. The induction reactor system according to claim 1, further comprising an auxiliary ground fault detection system operably connected to at least one passive induction circuit.
6. The induction furnace system according to claim 5, further comprising an intermediate filter capacitor disposed between the at least one active induction circuit and the at least one passive induction circuit, wherein the intermediate filter capacitor is configured to prevent a DC current from the primary ground fault detection system from being passed to the at least one passive induction circuit.
7. The induction furnace system according to claim 1, wherein the separable electrical connection comprises an isolation switch configured to selectively connect the at least one active induction circuit and the at least one passive induction circuit in a first position, and to selectively electrically isolate the at least one active induction circuit and the at least one passive induction circuit in a second position.
8. It further includes an independent water cooling circuit, and the independent water cooling circuit is A primary water cooling circuit having a primary water source, which supplies cooling water through one or more water-cooled conductors between the conductor inlet and conductor outlet of each of the water-cooled conductors, A shut-off valve is provided at each of the conductor inlet and conductor outlet, and is configured to stop the flow of cooling water through the primary water cooling circuit when closed. A secondary water cooling circuit having an auxiliary water source, which supplies cooling water through the active induction coil and the passive induction coil between the coil inlet and coil outlet located at each active coil terminal and each passive coil terminal, The system comprises a partition wall between each active coil terminal and each passive coil terminal between the conductor outlet and the coil inlet, The induction furnace system according to claim 1, wherein the partition wall prevents cooling water from the primary water cooling circuit from flowing into the active induction coil and the passive induction coil.
9. The water cooling circuit further includes a bypass circuit, and the water cooling circuit is A primary water source operably connected to a conductor inlet and a conductor outlet via one or more multiport valves, wherein at least one of the one or more multiport valves is operably connected to the coil inlet of each active coil terminal and each passive coil terminal of the primary water source, The one or more multi-port valves are configured to supply cooling water from the primary water source through the one or more water-cooling conductors at a first position, and to bypass the one or more water-cooling conductors at a second position. The induction furnace system according to claim 1, wherein when one or more multi-port valves are in the first position and the second position, cooling water from the primary water source is supplied to each coil inlet.
10. The induction furnace system according to claim 1, wherein each terminal connector of the one or more water-cooled conductors is identical and interchangeable, and the power supply and the one or more parallel capacitors can be swapped between the active induction coil and the passive induction coil, each defining a new active induction circuit and a new passive induction circuit.
11. The induction furnace system according to claim 1, wherein the one or more parallel capacitors are interconnected by an intermediate switch defining a capacitor bank, and the total capacitance of the one or more parallel capacitors is adjustable via the operation of the intermediate switch.
12. An induction reactor system comprising an electrically separable coil system, Furnace volume and, An induction coil system for induction heating and melting a conductive material placed in the furnace volume, wherein the induction coil system is At least one active induction circuit, An active induction coil having two or more active coil terminals surrounds a portion of the furnace volume, A power supply having an input configured to connect to an external power supply for the induction reactor system, and having an output frequency adjustable over a range of output power, The system comprises at least one active induction circuit, wherein the AC output of the power supply is connected to each active coil terminal of the active induction coil, At least one passive inductive circuit, A passive induction coil having two or more passive coil terminals surrounding a sequential portion of the furnace volume, One or more parallel capacitors connected to each passive coil terminal that defines the L-C tank circuit, The at least one passive induction circuit is positioned relative to the at least one active induction circuit such that the active induction coil is magnetically coupled to the passive induction coil when an alternating current flows through the active induction coil, An insulating switch disposed between the at least one active induction circuit and the at least one passive induction circuit, wherein in the closed position the at least one active induction circuit is electrically coupled to the at least one passive induction circuit, and in the open position the at least one active induction circuit is electrically isolated from the at least one passive induction circuit, The control system comprises the at least one active induction circuit, the at least one passive induction circuit, and the isolation switch, Equipped with, The control system is further configured to receive feedback from one or more voltage sensors and one or more current sensors associated with each of the at least one active induction circuit and the at least one passive induction circuit, and to modulate the output frequency of the power supply over a range of output power to dynamically change the stirring pattern within the furnace volume. An induction furnace system wherein the control system selectively operates the isolation switch between the closed position and the open position to electrically isolate at least one active induction coil from at least one passive induction coil.
13. One or more power switches that selectively connect the AC output of the power supply to the active induction coil in a first position and selectively connect the AC output of the power supply to the passive induction coil in a second position, One or more tank circuit switches that selectively connect one or more parallel capacitors to the passive induction coil in a first position, and selectively connect one or more parallel capacitors to the active induction coil in a second position, Furthermore, The induction furnace system according to claim 12, wherein the control system is configured to operate the power switch and the tank circuit switch between a first position and a second position in order to selectively connect the power supply and the one or more parallel capacitors to an alternative induction coil.
14. The induction reactor system according to claim 12, wherein the one or more parallel capacitors are interconnected by one or more intermediate switches that define a capacitor bank, and the control system is configured to selectively operate each of the one or more intermediate switches to adjust the effective capacitance of the capacitor bank.
15. The induction furnace system according to claim 12, wherein the control system is further configured to dynamically adjust the output frequency of the power supply to maintain a desired stirring pattern within the furnace volume over a range of power levels.
16. The induction furnace system according to claim 12, wherein the control system is configured to modulate the output frequency to maintain the average velocity of the molten material in the conductive material at a maximum value.
17. The induction furnace system according to claim 13, wherein the one or more power switches and the one or more tank circuit switches are further selectively movable in a third position, and when the one or more power switches and the one or more tank circuit switches are in the third position, the power supply and the one or more parallel capacitors are electrically isolated from the active induction coil and the passive induction coil.
18. A method for electrically isolating one or more induction coils in an induction reactor system having at least one ground fault detection system, in order to operate one or more unaffected induction coils independently when a ground fault is detected in one or more induction coils, A step of surrounding the furnace volume with one or more induction coils, wherein each coil terminal of at least one induction coil is operably connected to an AC output of a power supply, and each coil terminal of at least one remaining induction coil is operably connected to one or more parallel capacitors defining an L-C tank circuit, The steps include detecting the presence of a ground fault to one or more induction coils of the induction reactor system via the at least one ground fault detection system, A step of disconnecting a separable electrical connection between one or more induction coils, wherein the separable electrical connection is selected from the group consisting of an externally detachable jumper cable and an isolation switch that is selectively movable between a first closed position and a second open position. The steps include disconnecting one or more parallel capacitors from the coil terminals of at least one remaining induction coil, The steps include connecting the AC output of the power supply to the coil terminals of one or more unaffected induction coils, A method that includes this.
19. A step of providing a water cooling system having independent cooling water paths, wherein a first cooling water path is defined along a water cooling connection that operably connects an AC output to the coil terminals of one or more induction coils and connects one or more parallel capacitors to the coil terminals of at least one remaining induction coil, and a second cooling water path is defined along the interior of one or more induction coils. A step of closing one or more valves of the first coolant path before disconnecting any of the associated coil terminals from the water cooling connector, wherein the closing of the one or more valves prevents coolant from flowing through the water cooling connection, while maintaining the flow of coolant along the second coolant path, The method according to claim 18, further comprising:
20. A method for switching between an active and a passive state of induction coils surrounding the furnace volume of an induction furnace system while a molten charge is placed within the furnace volume, The steps include: defining an active induction circuit by supplying alternating current from the AC output of a power source to one or more induction coils surrounding the furnace volume; A step of electrically connecting one or more parallel capacitors to one or more remaining inductive coils that are not connected to the AC output, wherein the one or more remaining inductive coils are positioned relative to the one or more inductive coils so as to be magnetically coupled to the one or more inductive coils of the active inductive circuit, thereby defining a passive inductive circuit. Steps include electrically connecting adjacent inductor coils of one or more inductor coils via a separable connection, wherein the separable connection is configured to electrically insulate each of the adjacent inductor coils when it is disconnected from at least one of the adjacent inductor coils, The step of initiating the exchange between the active induction circuit and the passive induction circuit, The steps include: separating the separable connection from the adjacent induction coil; The steps include disconnecting the one or more remaining induction coils from the one or more parallel capacitors, The steps include disconnecting one or more induction coils from the AC output, The steps of connecting one or more induction coils to one or more parallel capacitors, The steps include connecting the one or more remaining induction coils to the AC output, The steps include electrically connecting the adjacent induction coils via the separable connection, A method that includes this.
21. The steps include first connecting the lowest induction coil of one or more induction coils to the active induction circuit, The steps include determining the current filling level of the furnace volume, Each time the current filling level exceeds one or more threshold filling levels, a step is to initiate the exchange between the active induction circuit and the passive induction circuit, wherein each threshold filling level is related to parameters of the induction reactor system selected from the group consisting of the total furnace volume height and the effective height of the subsequent induction coil among the one or more induction coils. The method according to claim 20, further comprising: