Electric induction furnace lining leakage current signal detection and calibration device

Abstract

The invention relates to an electric induction furnace lining leakage current signal detection and calibration device, which detects and calibrates electric induction furnace lining leakage current signals through a current test mode, a resistance test mode and a current calibration mode, and the three modes are switched through a change-over switch. The current test mode and the resistance test mode are both realized through a test power supply, and the current calibration mode is realized through a test line. The device indirectly judges the refractory material condition of the intermediate frequency furnace in an off-line current test mode, provides a reference for the health condition of the furnace lining refractory material of the induction furnace for a post, provides a technical means for preventing a furnace penetration accident and guaranteeing safe production, and also has a leakage current signal simulation function; when the furnace leakage alarm system is maintained, the working states of an external circuit and a control panel can be tested, the furnace leakage alarm current value is calibrated, and the online operation reliability of the system is improved.

Description

Technical Field

[0001] This patent application belongs to the technical field of on-site test instruments. More specifically, it relates to a device for detecting and calibrating the leakage current signal of the lining of an induction furnace. Background Art

[0002] In the special metal material production industry, melting equipment such as intermediate frequency furnaces and vacuum induction furnaces that utilize the principle of electromagnetic induction to melt metals are widely used. The above-mentioned melting equipment has a series of advantages such as fast melting speed, high efficiency, and energy saving. Since the heating principle of the induction furnace is to rely on electromagnetic induction to cause eddy currents in the furnace charge to generate heat and reach the melting purpose, the intermediate frequency furnace is composed of an induction coil and refractory materials wrapped outside. Due to the large current, hollow rectangular copper tubes must be used as the material for making the coil, and circulating water is passed through the copper tubes to dissipate heat for the coil. To prevent the refractory materials from being eroded and thinned by molten steel or cracked due to thermal shock during use, and to prevent molten steel from invading and burning through the coil, resulting in water leakage and explosion accidents, induction electric furnaces are generally equipped with a leakage furnace alarm system.

[0003] The leakage furnace alarm system consists of a stainless steel mesh buried in the refractory material of the furnace wall, a stainless steel probe electrode at the bottom of the furnace, lead wires, and signal detection, leakage current display, and alarm parts. When the induction electric furnace is used until the end of the furnace campaign, the refractory lining becomes thinner, or after intermittent production, the refractory materials get damp, the leakage current indicating instrument of the leakage furnace alarm system will display the leakage current value. At this time, it is very important to judge whether there is really steel penetration in the refractory materials or whether the leakage current is generated due to the decrease in insulation resistance caused by dampness. However, there are few maintenance and test means at present, and there is no special equipment. The traditional method is to stop the furnace and visually inspect whether there are cracks in the furnace lining refractory materials, or to produce under the condition of leakage current and observe the change of the leakage current. If it gradually decreases or disappears, it is judged to be damp. If the current persists or shows an increasing trend, it can be judged that there is a possibility of damage to the furnace lining refractory materials. For safety considerations, it is necessary to disassemble the furnace and replace the refractory materials when necessary.

[0004] However, this direct judgment method of stopping the furnace affects production operation, is difficult to judge, highly depends on maintenance personnel, and cannot achieve intelligent operation. It does not have the function of simulating leakage current signals, cannot improve the on-line operation reliability of the system, and does not meet the requirements of intelligent steelmaking. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a device for detecting and calibrating the leakage current signal of the lining of an induction furnace. This device can indirectly judge the condition of the refractory materials of the intermediate frequency furnace through off-line current testing, provide a reference for the health status of the refractory materials of the induction furnace lining for the post, provide a technical means for preventing furnace penetration accidents and ensuring safe production. At the same time, it also has the function of simulating leakage current signals, can test the working state of the external circuit and control board when maintaining the leakage furnace alarm system, calibrate the leakage furnace alarm current value, and improve the on-line operation reliability of the system.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows: An induction furnace lining leakage current signal detection and calibration device. The device steps down the AC 220V power supply through a transformer (BK-25 220V / 55V) to generate an AC 55V voltage, which is converted into a DC 48V voltage through a bridge rectifier circuit (MDQ-75A / 1200V) and electrolytic capacitor filtering and used as the test power supply. This device has 3 test modes, which are independently completed by three unit circuits respectively. In the resistance mode, the test power supply generates a voltage signal through a voltage-dividing resistor, and the voltage signal proportional to the current is measured by a voltmeter and can be converted into a resistance value for reading; the current test mode is completed by connecting a current-limiting resistor in series with an ammeter to the test power supply; the current calibration mode is connected to the leakage furnace alarm system by a 0-1KΩ precision multi-turn potentiometer in series with an ammeter, and the calibration is completed by adjusting the potentiometer until the ammeter shows the leakage furnace alarm current value.

[0007] Specifically: An induction furnace lining leakage current signal detection and calibration device detects and calibrates the induction furnace lining leakage current signal through a resistance test mode, a current test mode and a current calibration mode. The above three modes are switched through a changeover switch. The resistance test mode and the current test mode are both realized through the test power supply inside the device; the current calibration mode realizes by simulating the leakage resistance through the precision multi-turn potentiometer inside the device, and the leakage resistance is connected to the leakage furnace alarm system through a test wire. Among them, The resistance test mode includes a resistance test button connected to one pole of the test power supply, a voltage-dividing resistor connected to the resistance test button, and a voltmeter connected in parallel with the voltage-dividing resistor. The other end of the voltmeter is connected to the furnace bottom stainless steel probe. The voltmeter marks the scale dial with resistance values. The other pole of the test power supply is connected to the stainless steel mesh. The test voltage is applied to the furnace lining refractory material. The loop current generates a voltage division on the voltage-dividing resistor, and the equivalent resistance value of the furnace lining refractory material is read on the voltmeter scale dial marked with resistance values; The current test mode includes a current test button connected to one pole of the test power supply, a current-limiting resistor connected to the current test button, and an ammeter connected to the current-limiting resistor. The other end of the ammeter is connected to the furnace bottom stainless steel probe. The other pole of the test power supply is connected to the stainless steel mesh. There is an equivalent resistance of the furnace lining refractory material connected between the leads of the furnace bottom stainless steel probe and the stainless steel mesh. The test current forms a loop through the equivalent resistance of the furnace lining refractory material, and the leakage current value of the furnace lining refractory material is shown on the ammeter scale dial; The current calibration mode includes a precision multi-turn potentiometer. The precision multi-turn potentiometer is connected to an ammeter. The precision multi-turn potentiometer is connected to a terminal through a changeover switch to switch the circuit, and is connected to the input end of the leakage furnace alarm system through an external test wire.

[0008] Further, the test power supply includes a transformer connected to an AC power supply and a rectifier bridge connected to the transformer. The rectifier bridge is connected with a current test button and a resistance test button.

[0009] Further, the rectifier bridge has a specification of MDQ-75A / 1200V, and it converts the AC power supply into a DC 48V voltage as the test power supply.

[0010] Further, the lead-out terminals of the rectifier bridge are also connected to terminal blocks. The other ends of the ammeter and the voltmeter are both connected to the terminal blocks. The stainless-steel probe at the bottom of the furnace and the stainless-steel mesh are connected to the corresponding terminal blocks through leads.

[0011] Further, the voltage-dividing resistor has a specification of RX20-25W-1KΩ, and the voltmeter is a pointer-type voltmeter. Its scale is marked with resistance values, and its range is 0-1MΩ.

[0012] Further, the resistance value of the precision multi-turn potentiometer is 0-1KΩ.

[0013] Further, it also includes a chassis and a panel. The change-over switch, the current test button, the resistance test button, the potentiometer knob of the precision multi-turn potentiometer, and the terminal blocks are all installed on the panel.

[0014] Due to the adoption of the above technical solution, the beneficial effects achieved by the present invention are as follows: The present invention effectively solves various problems encountered in production and maintenance such as the lack of maintenance and test means, the difficulty in judging false alarms, and the lack of dedicated equipment for off-line testing in the leakage alarm system of induction furnaces, provides a guarantee for the safe production of induction furnaces, has a broad application prospect in industries that widely use induction furnaces such as special steel, non-ferrous metal smelting, and casting, and has excellent popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the schematic diagram of the leakage alarm system of the induction furnace; Figure 2 is the schematic diagram of the resistance test mode of the present invention; Figure 3 is the schematic diagram of the current test mode of the present invention; Figure 4 is the schematic diagram of the current calibration mode of the present invention; Figure 5 is the schematic diagram of the chassis panel of the device of the present invention; Figure 6 is the schematic diagram of the device principle of the present invention; Among them: furnace leakage alarm system 1, transformer 2, rectifier bridge 3, current limiting resistor 41, voltage dividing resistor 42, voltmeter 5, ammeter 61, precision multi-turn potentiometer 7, adjustment knob 8, terminal 9, current test button 10, resistance test button 11, test line 12, furnace bottom stainless steel probe 13, furnace lining refractory equivalent resistor 14, stainless steel mesh 15, refractory material 16, molten steel 17, conversion switch 18. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below with reference to the embodiments.

[0017] First, let me introduce the furnace leakage alarm system 1. The detection principle of the furnace leakage alarm system 1 is as follows: Figure 1 As shown, a stainless steel mesh 15 is embedded in the refractory material 16, and a crucible built by the refractory material 16 is filled with molten steel 17. A furnace bottom stainless steel probe 13 is embedded in the bottom of the crucible. The furnace bottom stainless steel probe 13 and the stainless steel mesh 15 are connected to the furnace leakage alarm system 1 through leads.

[0018] Next, an induction furnace lining leakage current signal detection and calibration device proposed by the present invention is introduced. The device detects and calibrates the induction furnace lining leakage current signal through a resistance test mode, a current test mode, and a current calibration mode. The above three modes are switched through a conversion switch 18. The resistance test mode and the current test mode are both realized by a test power supply inside the device; the current calibration mode simulates the leakage resistance through a precision multi-turn potentiometer 7 inside the device, and the leakage resistance is connected to the leakage furnace alarm system 1 through a test line 12 to realize, wherein: The resistance test mode includes a resistance test button 11 connected to one pole of the test power supply, a voltage divider resistor 42 connected to the resistance test button 11, and a voltmeter 5 connected in parallel with the voltage divider resistor 42. The other end of the voltmeter 5 is connected to a furnace bottom stainless steel probe 13, and the other pole of the test power supply is connected to a stainless steel mesh 15. The test voltage is applied to the furnace lining refractory material, and the loop current generates a voltage divider on the voltage divider resistor 42. The equivalent resistance value of the furnace lining refractory material is read on the dial of the voltmeter 5 marked with the resistance value.

[0019] The current test mode includes a current test button 10 connected to one pole of the test power supply, a current limiting resistor 41 connected to the current test button 10, and an ammeter 61 connected to the current limiting resistor 41. The other end of the ammeter 61 is connected to a furnace bottom stainless steel probe 13, and the other pole of the test power supply is connected to a stainless steel mesh 15. A furnace lining refractory equivalent resistor 14 is connected between the lead-out wires of the furnace bottom stainless steel probe 13 and the stainless steel mesh 15. The test current forms a loop through the furnace lining refractory equivalent resistor 14, and the furnace lining refractory leakage current value is displayed on the ammeter dial.

[0020] The current calibration mode includes a precision multi-turn potentiometer 7. One end of the precision multi-turn potentiometer 7 is connected to the terminal 9 through a changeover switch 18. The precision multi-turn potentiometer 7 is connected to an ammeter 61. The other end of the ammeter 61 is connected to another terminal 9 and is connected to the input end of the leakage furnace alarm system 1 through an external test wire 12.

[0021] Such as Figure 6 , the device steps down the AC 220V power supply through a transformer 2 (BK-25 220V / 55V) to generate an AC 55V voltage, which is converted into a DC 48V voltage through a rectifier bridge 3 (bridge rectifier circuit MDQ-75A / 1200V) and electrolytic capacitor filtering as the test power supply. The device has 3 test modes, which are respectively switched by three unit circuits through a changeover switch 18. The resistance mode generates a voltage signal by the test power supply through a voltage-dividing resistor 42, measures the voltage signal proportional to the current through a voltmeter 5, and can be converted into a resistance value for reading; the current test mode completes the test by the test power supply in series with a current-limiting resistor 41 and an ammeter 61; the current calibration mode connects a 0-1KΩ precision multi-turn potentiometer 7 in series with an ammeter 61 to the leakage furnace alarm system 1. Adjust the resistance value of the precision multi-turn potentiometer 7, and the ammeter 61 displays the leakage furnace alarm current value. Compare it with the current value displayed by the leakage furnace alarm system, adjust the current value to be consistent, and complete the calibration.

[0022] The test power supply includes a transformer 2 connected to the AC power supply, a rectifier bridge 3 connected to the transformer 2, and a current test button 10 and a resistance test button 11 are connected to the rectifier bridge 3.

[0023] The resistance test mode includes a resistance test button 11 connected to one pole of the test power supply, a voltage-dividing resistor 42 connected to the resistance test button 11, a voltmeter 5 connected in parallel with the voltage-dividing resistor 42, the other end of the voltmeter 5 is connected to the furnace bottom stainless steel probe 13, the other pole of the test power supply (that is, the lead-out end of the rectifier bridge 3) is connected to the stainless steel mesh 15, and a furnace lining refractory equivalent resistance 14 is connected between the furnace bottom stainless steel probe 13 and the stainless steel mesh 15.

[0024] The current test mode includes a current test button 10 connected to one pole of the test power supply, a current-limiting resistor 41 connected to the current test button 10, an ammeter 61 connected to the current-limiting resistor 41, the other end of the ammeter 61 is connected to the furnace bottom stainless steel probe 13, the other pole of the test power supply (that is, the lead-out end of the rectifier bridge 3) is connected to the stainless steel mesh 15, and a furnace lining refractory equivalent resistance 14 is connected between the furnace bottom stainless steel probe 13 and the stainless steel mesh 15.

[0025] The current calibration mode includes a precision multi-turn potentiometer 7. The precision multi-turn potentiometer 7 is connected to an ammeter 61. An adjustment knob 8 is provided on the precision multi-turn potentiometer 7 for adjusting the resistance value. The other end of the ammeter 61 and the other end of the precision multi-turn potentiometer 7 are connected to a test wire 12 through a changeover switch 18 via a terminal 9. The test wire 12 is connected to the input end of the leakage furnace alarm system 1.

[0026] For ease of use, it also includes a cabinet and a panel. The changeover switch 18, the current test button 10, the resistance test button 11, the potentiometer knob of the precision multi-turn potentiometer 7, and the terminal 9 are all installed on the panel. Figure 5 It is a schematic diagram of the cabinet panel of the device of the present invention.

[0027] The following will introduce the three modes one by one.

[0028] Resistance test mode: As Figure 2 , the positive pole of the test power supply is connected to the lead-out wire of the furnace lining refractory stainless steel mesh 15 through a voltage-dividing resistor 42 (RX20 - 25W - 1KΩ), and the negative pole is connected to the electrode of the furnace bottom stainless steel probe 13. Press the resistance test button 11. The 48V test voltage forms a loop through the stainless steel mesh 15 and the equivalent resistance 14 of the furnace lining refractory, flows through the electrode of the furnace bottom stainless steel probe 13 and returns to the negative pole of the power supply. This leakage current generates a voltage drop on the voltage-dividing resistor 42 (RX20 - 25W - 1KΩ). The pointer voltmeter 5 (6C2 - V 0 - 150V 1M - 0) connected in parallel with the voltage-dividing resistor 42 shows a reading. The voltmeter 5 marks the scale plate with resistance values, with a range of 0 - 1MΩ, and the reading is the resistance value within the range of 0 - 1MΩ. The condition of the furnace lining refractory is judged based on this resistance value.

[0029] Current test mode: As Figure 3 , the positive pole of the test power supply is connected to the lead-out wire of the furnace lining refractory stainless steel mesh 15 through a current-limiting resistor 41 and an ammeter 61, and the negative pole of the test power supply is connected to the electrode of the furnace bottom stainless steel probe 13. Press the current test button 10. The 48V test voltage forms a loop through the stainless steel mesh 15 and the equivalent resistance 14 of the furnace lining refractory, flows through the electrode of the furnace bottom stainless steel probe 13 and returns to the negative pole of the power supply. The loop current is displayed as a current value on the scale plate of the ammeter 61. This current value corresponds to the leakage current indication of the leakage furnace alarm system 1 and can be mutually verified.

[0030] Current calibration mode: As Figure 4, Before the test, disconnect the connection line between the leakage furnace alarm system 1 and the furnace body. Connect the test line 12 of this device to the input end of the leakage furnace alarm system 1. The 0-1KΩ precision multi-turn potentiometer 7 inside the device simulates the furnace lining leakage current resistance and is connected in series to the detection circuit of the leakage furnace alarm system 1. Adjust the precision multi-turn potentiometer 7 until the ammeter 61 shows the leakage furnace alarm current value. The leakage furnace alarm system 1 emits an audible and visual alarm signal. If there is a deviation between the current display and the set value, adjust the set current value of the leakage furnace alarm system 1 and test again until the two current values are equal to complete the calibration. Calibrate regularly to verify that the function of the leakage furnace alarm system 1 is normal and effective.

[0031] This leakage current detection device is used for off-line testing and maintenance of the leakage furnace detection and alarm system. Safety should be ensured during use, and the power supply of the induction furnace should be completely disconnected. The resistance test mode can be carried out in the control room or at the furnace body part to test the furnace lining resistance off-line, solve the data discreteness caused by using general test instruments such as megohmmeters and multimeters, and continuously improve the judgment accuracy by accumulating data during the use of this device; the current test mode can be carried out in the control room or at the furnace body part to test the furnace lining leakage current off-line as a means of comparing with the on-line leakage current; the current calibration mode is used in the control room for regularly calibrating the leakage current alarm value, verifying the effectiveness and accuracy of the system function, and can also be used to determine whether the fault occurs in the circuit or the leakage furnace detection and alarm system itself when troubleshooting.

Claims

1. An induction furnace lining leakage current signal detection and calibration device, characterized in that: The leakage current signal of the induction furnace lining is detected and calibrated through a resistance test mode, a current test mode, and a current calibration mode. The conversion between the above three modes is achieved through a changeover switch (18). The resistance test mode and the current test mode are both realized through the test power supply inside the device; the current calibration mode simulates the leakage resistance through a precision multi-turn potentiometer (7) inside the device, and the leakage resistance is connected to the leakage furnace alarm system (1) through a test wire (12). Among them, The resistance test mode includes a resistance test button (11) connected to one pole of the test power supply, a voltage-dividing resistor (42) connected to the resistance test button (11), and a voltmeter (5) connected in parallel with the voltage-dividing resistor (42). The other end of the voltmeter (5) is connected to the furnace bottom stainless steel probe (13). The voltmeter (5) marks the scale on the dial with resistance values. The other pole of the test power supply is connected to the stainless steel mesh (15). The test voltage is applied to the furnace lining refractory material. The loop current generates a voltage division on the voltage-dividing resistor (42), and the equivalent resistance value of the furnace lining refractory material is read on the scale of the voltmeter (5) marked with resistance values; The current test mode includes a current test button (10) connected to one pole of the test power supply, a current-limiting resistor (41) connected to the current test button (10), and an ammeter (61) connected to the current-limiting resistor (41). The other end of the ammeter (61) is connected to the furnace bottom stainless steel probe (13). The other pole of the test power supply is connected to the stainless steel mesh (15). An equivalent resistance (14) of the furnace lining refractory material is connected between the leads of the furnace bottom stainless steel probe (13) and the stainless steel mesh (15). The test current forms a loop through the equivalent resistance (14) of the furnace lining refractory material, and the leakage current value of the furnace lining refractory material is displayed on the scale of the ammeter; The current calibration mode includes a precision multi-turn potentiometer (7). The precision multi-turn potentiometer (7) is connected to the ammeter (61). The precision multi-turn potentiometer (7) is connected to the terminal block (9) through the switching circuit of the changeover switch (18), and is connected to the input end of the leakage furnace alarm system (1) through an external test wire (12).

2. The leakage current signal detection and calibration device for the lining of an induction furnace according to claim 1, wherein: The test power supply includes a transformer (2) connected to the AC power supply and a rectifier bridge (3) connected to the transformer (2). The rectifier bridge (3) is connected to the current test button (10) and the resistance test button (11).

3. The leakage current signal detection and calibration device for the lining of an induction furnace according to claim 2, wherein: The rectifier bridge (3) has a specification of MDQ-75A / 1200V, and it converts the AC power supply into a DC 48V voltage as the test power supply.

4. The leakage current signal detection and calibration device for the lining of an induction furnace according to claim 2, characterized in that: The lead-out end of the rectifier bridge (3) is also connected to the terminal block (9). The other end of the ammeter (61) and the other end of the voltmeter (5) are both connected to the terminal block (9). The furnace bottom stainless steel probe (13) and the stainless steel mesh (15) are connected to the corresponding terminal block (9) through leads.

5. The leakage current signal detection and calibration device for the lining of an induction furnace according to claim 1, characterized in that: The voltage-dividing resistor (42) has a specification of RX20-25W-1KΩ. The voltmeter (5) is a pointer-type voltmeter with a range of 0-1MΩ.

6. The leakage current signal detection and calibration device for the lining of an induction furnace according to claim 1, wherein: The resistance value of the precision multi-turn potentiometer (7) is 0-1KΩ.

7. An induction furnace lining leakage current signal detection and calibration device according to any one of claims 1 to 6, characterized in that: It also includes a machine case and a panel. The changeover switch (18), the current test button (10), the resistance test button (11), the potentiometer knob of the precision multi-turn potentiometer (7), and the terminal block (9) are all installed on the panel.

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