Smelting power supply resonant capacitance adjusting system and control method thereof

Abstract

The invention relates to a smelting power supply resonant capacitor adjusting system and a control method thereof. A plurality of groups of vacuum contactors are connected in parallel on one side of a fixed resonant capacitor; a plurality of groups of switchable resonant capacitors are connected in series at one side of the vacuum contactor; one end of a secondary coil of the high-frequency transformer is connected with one end of the smelting coil through a water-cooled cable, the other end of the secondary coil of the high-frequency transformer is connected with a pin at one end of the fixed resonant capacitor, and a pin at the other end of the fixed resonant capacitor is connected with the other end of the smelting coil through a water-cooled cable; the main control system connects or disconnects the plurality of groups of switchable resonant capacitors by controlling the vacuum contactor, connects or disconnects the switchable resonant capacitors and the fixed resonant capacitors in parallel, and changes different optimal resonant capacitor capacities connected to the smelting coil in parallel. The vacuum melting power supply is supported, automatic calculation and rapid switching of the resonant capacitor capacity after the load melting coil is replaced are realized, and the production efficiency, the power utilization energy efficiency and the melting quality are improved.

Description

Technical Field

[0001] Embodiments of the present invention relate to a resonant capacitor regulation system and its control method in the technical field of vacuum precision casting furnaces, and particularly to a melting power supply resonant capacitor regulation system and its control method. Background Art

[0002] A vacuum precision casting furnace is a melting equipment used to inductively heat and remelt a pre-alloyed high-temperature master alloy material in a vacuum environment and pour it into a mold in a vacuum environment to make the required precision castings. During the production process, the melting coil of the corresponding specification needs to be replaced according to the weight of the alloy to be melted. In the existing vacuum melting power supplies, a fixed resonant capacitor configuration is mostly adopted. When the load melting coil is replaced with a different specification (such as changing from a 50 kg crucible to a 1000 kg crucible), the equivalent inductance varies greatly, resulting in the following problems:

[0003] 1) Inefficient manual intervention: Since the resonant capacitors required by the traditional vacuum melting power supply adopt a fixed connection method, the switching of the resonant capacitor capacity depends on manual calculation and manual switching. The adjustment takes more than 1 hour, the melting cycle is long, and the production efficiency is low.

[0004] 2) Mismatch of the resonant tank circuit: Since the resonant capacitors required by the traditional vacuum melting power supply adopt a fixed connection method, the optimal resonant capacitor capacity of the tank circuit cannot be automatically calculated and supplemented during the melting process according to the working state of the tank circuit, and the power consumption efficiency is low.

[0005] 3) Parameters cannot be saved: Since the resonant capacitor capacity required by the traditional vacuum melting power supply is obtained through manual calculation and there is no electronic storage system to support the storage of the optimal supplemented resonant capacitor capacity parameters, it is necessary to consult the manual historical record or recalculate when switching the resonant capacitor next time, which takes a lot of time and has low efficiency.

[0006] Based on the above disadvantages, it is necessary to provide a melting power supply resonant capacitor regulation system that supports the vacuum melting power supply to automatically calculate and quickly switch the resonant capacitor capacity after replacing the load melting coil (corresponding to crucibles with capacities of 50 kg - 1000 kg), and improve the production efficiency, power consumption efficiency, and melting quality: Summary of the Invention

[0007] The purpose of the embodiments of the present invention is to provide a melting power supply resonant capacitor regulation system that can automatically calculate and quickly switch the resonant capacitor capacity after replacing the melting coil, and improve the production efficiency, power consumption efficiency, and melting quality.

[0008] To achieve the above purpose, the first embodiment of the present invention designs a melting power supply resonant capacitor regulation system, including:

[0009] High-frequency transformer;

[0010] The primary - side power supply is connected to the primary - side power supply on one side of the high - frequency transformer;

[0011] Fixed resonant capacitors, and a plurality of the fixed resonant capacitors are connected in parallel at one end of the secondary coil of the high - frequency transformer;

[0012] Vacuum contactors, and a plurality of groups of vacuum contactors are connected in parallel on one side of the fixed resonant capacitors;

[0013] Switchable resonant capacitors, and a plurality of groups of the switchable resonant capacitors are connected in series on one side of the vacuum contactors;

[0014] The melting coil, the other end of the secondary coil of the high - frequency transformer is connected to one end of the melting coil through a water - cooled cable, one end of the secondary coil of the high - frequency transformer is connected to one end pin of the fixed resonant capacitor, and the other end pin of the fixed resonant capacitor is connected to the other end of the melting coil through the water - cooled cable;

[0015] The main control system, the main control system controls the vacuum contactors to connect or disconnect a plurality of groups of the switchable resonant capacitors, so that the switchable resonant capacitors are connected in parallel with or disconnected from the fixed resonant capacitors, and the capacity of different optimal resonant capacitors connected in series with the melting coil is changed.

[0016] Further, in the melting - power - supply resonant - capacitor regulation system of the present invention, the vacuum contactors and the switchable resonant capacitors form a switchable resonant - capacitor circuit.

[0017] Further, in the melting - power - supply resonant - capacitor regulation system of the present invention, the high - frequency transformer, the fixed resonant capacitors, the vacuum contactors, the switchable resonant capacitors, the water - cooled cable and the melting coil form an RLC series - resonant circuit.

[0018] Further, in the melting - power - supply resonant - capacitor regulation system of the present invention, the primary - side power supply further includes:

[0019] A rectifier, and one side of the rectifier is connected to a three - phase power supply;

[0020] A filter, and one side of the filter is connected to the other side of the rectifier;

[0021] An inverter, and one side of the inverter is connected to the other side of the filter; one end of the other side of the inverter is connected to one end of the primary side of the high - frequency transformer.

[0022] A current transformer, and one end of the other side of the inverter passes through the induction ring of the current transformer;

[0023] The primary capacitor of the high-frequency transformer, one end of the primary capacitor of the high-frequency transformer is connected to the other end of the other side of the inverter, and the other end of the primary capacitor of the high-frequency transformer is connected to the other end of the primary side of the high-frequency transformer;

[0024] The first voltage sensor, one end of the first voltage sensor is connected to one end of the primary side of the high-frequency transformer, and the other end of the first voltage sensor is connected to the other end of the primary side of the high-frequency transformer.

[0025] Furthermore, in the resonant capacitor regulation system of the melting power supply of the present invention, the output end of the inverter is respectively connected to a bus bar, and the primary capacitor of the high-frequency transformer is connected in series in one of the bus bars of the inverter output; the circuit composed of the rectifier, the filter, the inverter, and the primary capacitor of the high-frequency transformer rectifies, filters, and inversely converts the input three-phase industrial frequency alternating current into a single-phase alternating current with adjustable frequency and voltage, and supplies it to the RLC series resonant circuit.

[0026] Furthermore, in the resonant capacitor regulation system of the melting power supply of the present invention, the main control system further includes:

[0027] The main control board, the main control board is arranged in the main control system;

[0028] The power monitor, the power monitor is electrically connected to the main control board;

[0029] The PLC, the PLC is electrically connected to the main control board, and the main control board is electrically connected to the inverter;

[0030] The on-site operation console, a start power button and a stop power button are arranged on the on-site operation console; the start power button and the stop power button are respectively electrically connected to the PLC.

[0031] Furthermore, in the resonant capacitor regulation system of the melting power supply of the present invention, the voltage acquisition terminals of the second voltage sensor are respectively connected to the other ends of the two water-cooled cables, and the signal output terminal of the second voltage sensor is electrically connected to the main control board.

[0032] Furthermore, in the resonant capacitor regulation system of the melting power supply of the present invention, the voltage acquisition terminals of the first voltage sensor are respectively electrically connected to both ends of the primary side coil of the high-frequency transformer, and the signal output terminal of the first voltage sensor is electrically connected to the main control board;

[0033] The induction ring of the current transformer is sleeved on one of the bus bars of the inverter output, and the signal output terminal of the current transformer is electrically connected to the main control board;

[0034] The main control board is electrically connected to the vacuum contactor.

[0035] In the second embodiment of the present invention, a control method for the resonant capacitor adjustment system of the melting power supply is designed, including the following steps:

[0036] Step S1: Connect the melting coil to the output terminal of the melting power supply through a water-cooled cable, and add the maximum allowable amount of steel materials to be melted into the crucible corresponding to the melting coil, then enter Step S2;

[0037] Step S2: Conduct a routine inspection before starting the power supply. After completion, power on the power supply, then enter Step S3;

[0038] Step S3: Input the parameters of the current melting coil on the screen of the power supply monitor. The power supply monitor sends the input parameters to the main control board, then enter Step S4;

[0039] Enter Step S4: The main control board conducts self-inspection on the power supply. After the self-inspection is normal, the power supply is ready and enters the standby startup state, then enter Step S5;

[0040] Step S5: Press the power startup button on the on-site operation console. The PLC sends an inverter startup signal to the main control board to control the inverter to start working. The power supply operates at a low frequency, then enter Step S6;

[0041] Step S6: The main control board calculates the resonant frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors according to the voltage on the primary side of the high-frequency transformer detected by the first voltage sensor and the current on the primary side of the high-frequency transformer detected by the current transformer, then enter Step S7;

[0042] Step S7: Adjust the power supply to the full-power operation state on-site. The main control board calculates the operating frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors according to the voltage on the furnace side detected by the second voltage sensor, then enter Step S8;

[0043] Step S8: The main control board calculates the total inductance of the system according to the resonant frequency, operating frequency, voltage on the furnace side, and current capacitance capacity of the system series resonant circuit; the main control board reads the optimal operating frequency range parameters of the melting coil 13 stored and sets them as the target value, and then calculates the optimal capacitance capacity and capacitance quantity to be additionally invested with the upper limit of the voltage on the furnace side as the constraint condition, then enter Step S9;

[0044] Step S9: Confirm the optimal capacitance capacity and quantity to be additionally invested calculated by the system on the screen of the power supply monitor. The main control board saves the parameters to the current specification melting coil parameter table of the system and takes effect when the power supply starts and operates next time, then enter Step S10;

[0045] Step S10: Press the power stop button on site. The PLC sends an inverter stop signal to the main control board to control the inverter to stop working, and the power supply stops running, then enter Step S11;

[0046] Step S11: Press the reset button on the main control board on site. The main control board resets and performs a self - check on the power supply system. The main control board sends a corresponding channel closing signal of one or more switchable resonant capacitors that need to be supplemented to the vacuum contactor according to the currently set melting coil specifications; then enter Step S12;

[0047] Step S12: One or more of the corresponding vacuum contactors are energized to supplement the corresponding number of capacitors. The power supply is ready and enters the standby startup state, then enter Step S13;

[0048] Step S13: Press the power startup button on the on - site console. The PLC sends an inverter startup signal to the main control board to control the inverter to start working, and the power supply system operates with optimal parameters, that is, the current melting coil operates under vacuum at the best operating frequency and close to the highest allowable voltage of the induction coil.

[0049] Compared with the prior art, the embodiment of the present invention is characterized in that a primary - side power supply is connected to one side of the high - frequency transformer; several fixed resonant capacitors are connected in parallel at one end of the secondary coil of the high - frequency transformer; several groups of vacuum contactors are connected in parallel on one side of the fixed resonant capacitors; several groups of switchable resonant capacitors are connected in series on one side of the vacuum contactors; the other end of the secondary coil of the high - frequency transformer is connected to one end of the melting coil through a water - cooled cable, one end of the secondary coil of the high - frequency transformer is connected to one end pin of the fixed resonant capacitor, and the other end pin of the fixed resonant capacitor is connected to the other end of the melting coil through a water - cooled cable; the main control system controls the vacuum contactor to connect or disconnect several groups of switchable resonant capacitors, so that the switchable resonant capacitors are connected in parallel or disconnected from the fixed resonant capacitors, and the capacity of different optimal resonant capacitors connected in series with the melting coil is changed.

[0050] The resonant capacitor adjustment system of the melting power supply in the present invention supports the vacuum melting power supply to automatically calculate and quickly switch the capacity of the resonant capacitor after replacing the load melting coil (corresponding to crucibles with a capacity of 50 kg - 1000 kg), improving production efficiency, power consumption efficiency and melting quality, and having the following advantages:

[0051] 1) By controlling the on - off of the contacts of the corresponding vacuum contactor in the electrical system to automatically switch and adjust the required number of resonant capacitors, it avoids consuming a large amount of operation time due to manually switching the required resonant capacitors after changing the coil specifications, shortens the melting cycle, and improves production efficiency;

[0052] 2) The main control board configured for the vacuum melting power supply can automatically detect the power supply working parameters (including the primary side voltage of the high-frequency transformer, the primary side current of the high-frequency transformer, and the voltage on the furnace side), and automatically calculate the optimal resonant capacitor capacity of the RLC series resonant circuit based on the self-test parameters to improve the power efficiency;

[0053] 3) The main control board configured for the vacuum melting power supply can store the parameters of each specification of melting coil separately, which is convenient for direct call when replacing the melting coil, without the need for manual time-consuming review and input of historical parameter information, thus improving work efficiency;

[0054] Since the resonant capacitor adjustment system can automatically calculate and switch the optimal resonant capacitor capacity, the replaced smelting coil can operate under vacuum at the optimal frequency range of the corresponding furnace capacity and close to the maximum allowable voltage of the smelting coil, ensuring high-quality products are smelted with high energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic diagram of the main circuit of the resonant capacitor adjustment system of the present invention;

[0056] Figure 2 A schematic diagram of a control circuit of a resonant capacitor adjustment system of the present invention;

[0057] Figure 3 This is a working flow chart of the resonant capacitor adjustment system of the present invention.

[0058] In the figure: 1-rectifier, 2-filter, 3-inverter, 4-current transformer, 5, primary side capacitor of high-frequency transformer, 6-first voltage sensor, 7-high-frequency transformer, 8-fixed resonant capacitor, 9-vacuum contactor, 10-switchable resonant capacitor, 11-second voltage sensor, 12-water cooling cable, 13-smelting coil, 14-power supply monitor, 15-on-site operation table, 151-start power button, 152-stop power button, 16-PLC, 17-main control board, 20-primary side power supply, 40-main control system. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical scheme and advantages of the present invention clearer, the following will be described in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present invention, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed for protection in the claims of the present application can be implemented.

[0060] The first embodiment of the present invention relates to a smelting power supply resonant capacitor adjustment system, such as Figure 1 and Figure 2 As shown, including:

[0061] In the melting power supply resonant capacitor adjustment system of this embodiment, a high-frequency transformer 7 is provided; the high-frequency transformer 7 mainly functions to transform the voltage between the primary side and the secondary side.

[0062] One side of the high-frequency transformer 7 is connected to the primary side power supply 20; the primary side power supply 20 mainly provides a stable AC power supply after inversion.

[0063] Several fixed resonant capacitors 8 are connected in parallel at one end of the secondary coil of the high-frequency transformer 7; the high-frequency transformer 7, the fixed resonant capacitors 8, the vacuum contactor 9, the switchable resonant capacitors 10, the water-cooled cable 12, and the melting coil 13 together form an RLC series resonant circuit.

[0064] Several groups of vacuum contactors 9 are connected in parallel on one side of the fixed resonant capacitor 8;

[0065] Several groups of switchable resonant capacitors 10 are connected in series on one side of the vacuum contactor 9; the vacuum contactor 9 is used to switch the number of switchable resonant capacitors 10 connected to the circuit. By automatically controlling the on-off of the contacts of the vacuum contactor 9, the switchable resonant capacitors 10 can be connected in parallel with or disconnected from the fixed resonant capacitors 8, thereby changing the capacitance of the resonant capacitors in the RLC series resonant circuit.

[0066] The other end of the secondary coil of the high-frequency transformer 7 is connected to one end of the melting coil 13 through the water-cooled cable 12, one end of the secondary coil of the high-frequency transformer 7 is connected to one end pin of the fixed resonant capacitor 8, and the other end pin of the fixed resonant capacitor 8 is connected to the other end of the melting coil 13 through the water-cooled cable 12; the melting coil 13 functions for high-frequency melting.

[0067] The main control system 40 controls the vacuum contactor 9 to connect or disconnect several groups of switchable resonant capacitors 10, connects the switchable resonant capacitors 10 in parallel with or disconnects them from the fixed resonant capacitors 8, and changes the capacitance of different optimal resonant capacitors connected in series with the melting coil 13. The main control system 40 mainly functions to control the melting power supply resonant capacitor adjustment system in the present invention.

[0068] The melting power supply resonant capacitor adjustment system in this embodiment supports the automatic matching calculation and rapid switching of the resonant capacitor capacitance after the load melting coil is replaced (corresponding to crucibles with a capacity of 50 kg - 1000 kg) in the vacuum melting power supply. The specific technical advantages are as follows:

[0069] 1) The power supply resonant capacitor adjustment system can automatically switch the number of required switchable resonant capacitors 10 by controlling the on-off of the contacts of the corresponding vacuum contactor 9, avoiding the consumption of a large amount of operation time due to manually switching the required switchable resonant capacitors 10 after changing the specification of the melting coil 13, shortening the melting cycle, and improving production efficiency.

[0070] 2) The main control board 17 configured in the power supply resonant capacitor regulation system is respectively connected to the signal output terminals of the second voltage sensor 11, the current transformer 4, and the first voltage sensor 6, and can self-check the power supply operating parameters (the voltage on the furnace side, the primary side current of the high-frequency transformer, and the primary side voltage of the high-frequency transformer), and automatically calculate the optimal resonant capacitor capacity of the RLC series resonant circuit according to the parameters.

[0071] 3) The main control board 17 configured in the power supply resonant capacitor regulation system can separately store the parameters corresponding to each specification of the melting coil 13, which is convenient for direct calling when replacing the melting coil, without the need for manual time-consuming access and input of historical parameter information, improving work efficiency.

[0072] 4) The power supply resonant capacitor regulation system can automatically calculate and switch the optimal resonant capacitor capacity, enabling the replaced melting coil 13 to operate at the optimal frequency range corresponding to the furnace capacity and close to the highest allowable voltage of the melting coil 13 under vacuum, ensuring the melting of high-quality products with high energy efficiency.

[0073] To achieve the above technical effects, in the melting power supply resonant capacitor regulation system of this embodiment, as Figure 1 and Figure 2 shown, the vacuum contactor 9 and the switchable resonant capacitor 10 form a switchable resonant capacitor circuit.

[0074] To achieve the above technical effects, in the melting power supply resonant capacitor regulation system of this embodiment, as Figure 1 and Figure 2 shown, the high-frequency transformer 7, the fixed resonant capacitor 8, the vacuum contactor 9, the switchable resonant capacitor 10, the water-cooled cable 12, and the melting coil 13 form an RLC series resonant circuit.

[0075] To achieve the above technical effects, in the melting power supply resonant capacitor regulation system of this embodiment, as Figure 1 and Figure 2 shown, the primary side power supply 20 further includes:

[0076] One side of the rectifier 1 is connected to the three-phase power supply; the rectifier 1 mainly rectifies the three-phase AC power supply into direct current;

[0077] One side of the filter 2 is connected to the other side of the rectifier 1; the filter 2 mainly plays a filtering role.

[0078] One side of the inverter 3 is connected to the other side of the filter 2; the inverter 3 mainly plays a role in inverting direct current into alternating current.

[0079] One end of the other side of the inverter 3 is connected to one end of the primary side of the high-frequency transformer 7, and the other end of the other side of the inverter 3 is connected to one end of the primary-side capacitor 5 of the high-frequency transformer; the other end of the primary-side capacitor 5 of the high-frequency transformer is connected to the other end of the primary side of the high-frequency transformer 7.

[0080] The circuit composed of the rectifier 1, the filter 2, the inverter 3, and the primary-side capacitor 5 of the high-frequency transformer rectifies, filters, and inverses the externally input three-phase industrial-frequency alternating current into a single-phase alternating current with adjustable frequency and voltage for the RLC series resonance circuit to work.

[0081] To achieve the above technical effects, in the melting power supply resonance capacitor adjustment system of this embodiment, as Figure 1 and Figure 2 shown, the main control system 40 further includes:

[0082] The main control board 17 is set in the main control system 40; the control board 17 is electrically connected to the vacuum contactor 9, and the main control board 17 sends the switching signal of the switchable resonance capacitor 10 of the corresponding channel to the vacuum contactor 9 to automatically control the suction or release of the vacuum contactor 9, thereby switching the corresponding resonance capacitor into the RLC series resonance circuit.

[0083] The power supply monitor 14 is electrically connected to the main control board 17; the power supply monitor 14 mainly functions to input parameters and display.

[0084] The PLC 16 is electrically connected to the main control board 17, and the main control board 17 is electrically connected to the inverter 3; the PLC 16 plays a role in input and output control.

[0085] The on-site operation console 15 is provided with a start power button 151 and a stop power button 152; the start power button 151 and the stop power button 152 are respectively electrically connected to the PLC 16.

[0086] The voltage acquisition terminals of the second voltage sensor 11 are respectively connected to the other ends of the two water-cooled cables 12, and the signal output terminal of the second voltage sensor 11 is electrically connected to the main control board 17.

[0087] The induction loop of the current transformer 4 is sleeved on a busbar output by the inverter 3; the signal output terminal of the current transformer 4 is connected to the main control board 17 to transmit the primary-side current acquisition signal of the high-frequency transformer 7 to the main control board 17.

[0088] One end of the first voltage sensor 6 is connected to one end of the primary side of the high-frequency transformer 7, and the other end of the first voltage sensor 6 is connected to the other end of the primary side of the high-frequency transformer 7. The signal output terminal of the first voltage sensor 6 is connected to the main control board 17, and the first voltage sensor 6 transmits the primary-side voltage acquisition signal of the high-frequency transformer 7 to the main control board 17.

[0089] The main control board 17 automatically calculates the optimal resonant capacitance of the RLC series resonant circuit based on the detected voltage acquisition signal on the furnace side, the primary side current acquisition signal of the high-frequency transformer 7, and the primary side voltage acquisition signal of the high-frequency transformer 7.

[0090] In the present invention, a control method for a resonant capacitance regulation system of a melting power supply is also provided, as Figure 3 shown, including the following steps:

[0091] Step S1: Connect the melting coil 13 to the output terminal of the melting power supply through the water-cooled cable 12, and add the maximum allowable amount of steel materials to be melted into the crucible corresponding to the melting coil 13, and then enter Step S2;

[0092] Step S2: Conduct a routine inspection before starting the power supply. After completion, power on the power supply and enter Step S3;

[0093] Step S3: Input the parameters of the current melting coil 13 on the screen of the power supply monitor 14. The power supply monitor 14 sends the input parameters to the main control board 17, and then enter Step S4;

[0094] Enter Step S4: The main control board 17 conducts a self-check on the power supply. After the self-check is normal, the power supply is ready and enters the standby startup state, and then enter Step S5;

[0095] Step S5: Press the power startup button 151 on the on-site operation console 15. The PLC 16 sends an inverter startup signal to the main control board 17 to control the inverter 3 to start working. The power supply operates at a low frequency and enters Step S6;

[0096] Step S6: The main control board 17 calculates the resonant frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors 8 according to the primary side voltage of the high-frequency transformer detected by the first voltage sensor 6 and the primary side current of the high-frequency transformer detected by the current transformer 4, and then enter Step S7;

[0097] Step S7: Manually adjust the power supply to the full-power operation state. The main control board 17 calculates the operating frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors 8 according to the furnace side voltage detected by the second voltage sensor 11, and then enter Step S8;

[0098] Step S8: The main control board 17 calculates the total inductance of the system according to the resonant frequency, operating frequency, furnace side voltage, and current capacitance of the system series resonant circuit; the main control board 17 reads the optimal operating frequency range parameters of the melting coil 13 stored and sets them as the target value, and then calculates the optimal capacitance capacity and capacitance quantity to be additionally invested with the upper limit of the furnace side voltage as the constraint condition, and then enter Step S9;

[0099] Step S9: Confirm on the screen of the power monitor 14 the optimal additional capacitance capacity and quantity calculated by the system. The main control board 17 saves the parameters to the current specification melting coil parameter table of the system, which will take effect when the power supply starts running next time, and proceed to Step S10;

[0100] Step S10: Press the power stop button 152 on-site. The PLC 16 sends an inverter stop signal to the main control board 17 to control the inverter 3 to stop working, and the power supply stops running, and proceed to Step S11;

[0101] Step S11: Press the reset button on the main control board 17 on-site. The main control board 17 resets and self-checks the power supply system; the main control board 17 sends a closing signal for one or more corresponding channels of the switchable resonant capacitors 10 that need to be additionally invested according to the currently set melting coil specifications to the vacuum contactor 9, and proceed to Step S12;

[0102] Step S12: One or more of the corresponding vacuum contactors 9 are closed to additionally invest the corresponding quantity of capacitors; the power supply is ready and enters the standby start state, and proceed to Step S13;

[0103] Step S13: Press the power start button 151 on the on-site operation console 15. The PLC 16 sends an inverter start signal to the main control board 17 to control the inverter 3 to start working, and the power supply system operates with optimal parameters, that is, the current melting coil works at the best operating frequency and close to the highest allowable voltage of the induction coil under vacuum.

[0104] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention, and in practical applications, various changes can be made in form and details without departing from the spirit and scope of the present invention.

Claims

1. A resonant capacitor regulation system for a smelting power supply, characterized in that, Comprising: High-frequency transformer (7); Primary side power supply (20), connecting the primary side power supply (20) to one side of the high-frequency transformer (7); Fixed resonance capacitor (8), connecting several of the fixed resonance capacitors (8) in parallel to one end of the secondary coil of the high-frequency transformer (7); Vacuum contactor (9), connecting several groups of vacuum contactors (9) in parallel to one side of the fixed resonance capacitor (8); Switchable resonance capacitor (10), connecting several groups of the switchable resonance capacitors (10) in series to one side of the vacuum contactor (9); Melting coil (13), connecting the other end of the secondary coil of the high-frequency transformer (7) to one end of the melting coil (13) through a water-cooled cable (12), connecting one end of the secondary coil of the high-frequency transformer (7) to one end pin of the fixed resonance capacitor (8), and connecting the other end pin of the fixed resonance capacitor (8) to the other end of the melting coil (13) through the water-cooled cable (12); Main control system (40), the main control system (40) connects or disconnects several groups of the switchable resonance capacitors (10) by controlling the vacuum contactor (9), making the switchable resonance capacitors (10) in parallel with or disconnected from the fixed resonance capacitor (8), and changing the capacity of different optimal resonance capacitors connected in series with the melting coil (13).

2. The resonant capacitor regulation system of the smelting power supply according to claim 1, wherein The vacuum contactor (9) and the switchable resonance capacitor (10) form a switchable resonance capacitor circuit.

3. The resonant capacitor regulation system of the melting power supply according to claim 1, characterized in that The high-frequency transformer (7), the fixed resonance capacitor (8), the vacuum contactor (9), the switchable resonance capacitor (10), the water-cooled cable (12) and the melting coil (13) form an RLC series resonance circuit.

4. The resonant capacitor regulation system of the melting power supply according to claim 1, characterized in that The primary side power supply (20) further comprises: Rectifier (1), connecting one side of the rectifier (1) to a three-phase power supply; Filter (2), connecting one side of the filter (2) to the other side of the rectifier (1); Inverter (3), connecting one side of the inverter (3) to the other side of the filter (2); one end of the other side of the inverter (3) is connected to one end of the primary side of the high-frequency transformer (7). Current transformer (4), passing the induction loop of the current transformer (4) through one end of the other side of the inverter (3); High-frequency transformer primary side capacitor (5), connecting one end of the high-frequency transformer primary side capacitor (5) to the other end of the other side of the inverter (3), and connecting the other end of the high-frequency transformer primary side capacitor (5) to the other end of the primary side of the high-frequency transformer (7); First voltage sensor (6), connecting one end of the first voltage sensor (6) to one end of the primary side of the high-frequency transformer (7), and connecting the other end of the first voltage sensor (6) to the other end of the primary side of the high-frequency transformer (7).

5. The resonant capacitor regulation system of the melting power supply according to claim 4, wherein The output terminals of the inverter (3) are respectively connected to a busbar, and the primary side capacitor (5) of the high-frequency transformer is connected in series in one of the busbars of the inverter output; the circuit composed of the rectifier (1), the filter (2), the inverter (3), and the primary side capacitor (5) of the high-frequency transformer rectifies, filters, and inverses the input three-phase industrial frequency alternating current into a single-phase alternating current with adjustable frequency and voltage, and supplies it to the RLC series resonance circuit.

6. The resonant capacitor regulation system of the smelting power supply according to claim 1, characterized in that The main control system (40) further includes: A main control board (17), and the main control board (17) is arranged in the main control system (40); A power supply monitor (14), and the power supply monitor (14) is electrically connected to the main control board (17); A PLC (16), the PLC (16) is electrically connected to the main control board (17), and the main control board (17) is electrically connected to the inverter (3); A field operation console (15), and a power supply start button (151) and a power supply stop button (152) are arranged on the field operation console (15); the power supply start button (151) and the power supply stop button (152) are respectively electrically connected to the PLC (16).

7. The resonant capacitor regulation system of the melting power supply according to claim 5, wherein The voltage acquisition terminals of the second voltage sensor (11) are respectively connected to the other ends of the two water-cooled cables (12), and the signal output terminal of the second voltage sensor (11) is electrically connected to the main control board 17.

8. The resonant capacitor regulation system of the smelting power supply according to claim 4, wherein The voltage acquisition terminals of the first voltage sensor (6) are respectively electrically connected to both ends of the primary side coil of the high-frequency transformer (7), and the signal output terminal of the first voltage sensor (6) is electrically connected to the main control board (17); The induction ring of the current transformer (4) is sleeved on one of the busbars of the inverter output, and the signal output terminal of the current transformer (4) is electrically connected to the main control board (17); The main control board (17) is electrically connected to the vacuum contactor (9).

9. The control method of the resonant capacitor regulation system of the melting power supply according to any one of claims 1-8, characterized in that, It includes the following steps: Step S1: Connect the melting coil (13) to the output terminal of the melting power supply through the water-cooled cable (12), and add the maximum allowable amount of steel material to be melted into the crucible corresponding to the melting coil (13), and enter Step S2; Step S2: Conduct a routine inspection before starting the power supply. After completion, power on the power supply and enter Step S3; Step S3: Input the parameters of the current melting coil (13) on the screen of the power supply monitor (14), and the power supply monitor (14) sends the input parameters to the main control board (17), and enter Step S4; Enter Step S4: The main control board (17) conducts a self-inspection on the power supply. After the self-inspection is normal, the power supply is ready and enters the standby start state, and enter Step S5; Step S5: Press the power supply start button (151) on the field operation console (15), and the PLC (16) sends an inverter start signal to the main control board (17) to control the inverter (3) to start working, and the power supply operates at a low frequency, and enter Step S6; Step S6: The main control board (17) calculates the resonant frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors (8) according to the primary side voltage of the high-frequency transformer detected by the first voltage sensor (6) and the primary side current of the high-frequency transformer detected by the current transformer (4), and enters Step S7; Step S7: Adjust the power supply to the full-power operation state on-site. The main control board (17) calculates the furnace-side voltage detected by the second voltage sensor (11); calculates the operating frequency of the RLC series resonant circuit in the state of connecting four groups of fixed resonant capacitors (8), and enters Step S8; Step S8: The main control board (17) calculates the total inductance of the system according to the resonant frequency, operating frequency, furnace-side voltage, and current capacitance of the system series resonant circuit; the main control board (17) reads the optimal operating frequency range parameters of the melting coil 13 stored and sets them as the target value, and then calculates the optimal capacitance capacity and number of capacitors to be supplemented with the upper limit of the furnace-side voltage as the constraint condition, and enters Step S9; Step S9: Confirm the optimal capacitance capacity and number of capacitors to be supplemented calculated by the system on the screen of the power supply monitor (14). The main control board (17) saves the parameters to the current specification melting coil parameter table of the system and takes effect when the power supply starts to run next time, and enters Step S10; Step S10: Press the power stop button (152) on-site. The PLC (16) sends an inverter stop signal to the main control board (17) to control the inverter (3) to stop working, and the power supply stops running, and enters Step S11; Step S11: Press the reset button of the main control board (17) on-site. The main control board (17) resets and self-checks the power supply system; the main control board (17) sends a closing signal of one or more corresponding channels of the switchable resonant capacitor (10) to be supplemented according to the current set melting coil specification to the vacuum contactor (9), and enters Step S12; Step S12: One or more of the corresponding vacuum contactors (9) are energized to supplement the corresponding number of capacitors; the power supply is ready and enters the standby start state, and enters Step S13; Step S13: Press the power start button (151) on the on-site operation console (15). The PLC (16) sends an inverter start signal to the main control board (17) to control the inverter (3) to start working, and the power supply system operates with optimal parameters, that is, the current melting coil works at the best operating frequency and close to the highest allowable voltage of the induction coil under vacuum.

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