CN213073154U - Automatic induction heating of impedance adjustment, melting variable frequency power supply system - Google Patents
Automatic induction heating of impedance adjustment, melting variable frequency power supply system Download PDFInfo
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- CN213073154U CN213073154U CN202021875395.7U CN202021875395U CN213073154U CN 213073154 U CN213073154 U CN 213073154U CN 202021875395 U CN202021875395 U CN 202021875395U CN 213073154 U CN213073154 U CN 213073154U
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Abstract
A frequency conversion power supply system for induction heating and melting with automatic impedance adjustment is characterized in that a frequency conversion power supply is connected with a frequency conversion power supply rectifying circuit, the frequency conversion power supply rectifying circuit is connected with a frequency conversion power supply inverter circuit, the frequency conversion power supply inverter circuit is controlled by a circuit capable of automatically adjusting impedance to operate, the other path of the frequency conversion power supply inverter circuit is connected with an induction coil, and the input end and the output end of the induction coil are connected with a capacitor bank; when the temperature of the metal material changes in the variable-frequency induction heating process, the impedance of the metal material changes, and the automatic impedance adjusting circuit adds an adjusting function to the variable-frequency power supply to adapt to the inherent impedance change characteristic in the heating process. The fixed proportional relation between the inverted variable frequency voltage and the rectified voltage is changed into an adjustable proportional relation, the change of load impedance is adapted by automatically adjusting the variable frequency voltage, and the efficiency of the equipment is generally improved by 20-30% through actual use. The method has the advantages of time saving, power saving, high efficiency and obvious improvement on the stability of the variable frequency power supply.
Description
Technical Field
The utility model belongs to the technical field of metal frequency conversion induction heating, a metal frequency conversion induction heating and melting are related to, concretely relates to induction heating, melting variable frequency power supply system with automatic impedance adjustment.
Background
At present, in the domestic and foreign variable frequency induction heating and melting equipment, in the working process, the factor which has a great influence on the working efficiency of the whole system is the impedance change of the metal material caused when the temperature of the metal material is changed in the heating process. When the impedance deviates from the rated impedance of the equipment, the variable frequency power supply is in a working state of low electric efficiency and low output power. The alternating current is changed into controllable direct current through a three-phase controllable bridge rectifier circuit, and then oscillated through an inversion silicon controlled rectifier and a load L, C (a furnace body induction coil and a compensation capacitor) to form single-phase alternating current on the load. The former stage of the inverter bridge is a three-phase controllable bridge rectifier circuit, the equivalent impedance of cold metal is far less than the rated impedance (about 0.3-0.5 omega), because the rated output power of the variable frequency power supply is limited, the variable frequency power supply enters a current load stop state, the rectified current of the variable frequency power supply working in the state reaches the rated output current and is forcibly cut off, the rectified voltage of equipment is forcibly and automatically reduced, and the rectified voltage is less than the rated voltage. The AC-DC conversion efficiency of the three-phase controllable bridge in the state is only about 0.5. With the temperature rise of the metal material, the equivalent impedance begins to increase and reaches the maximum value before reaching the required temperature, at the moment, the rectified voltage of the variable frequency power supply rises to reach the rated voltage, the rectified current is smaller than the rated current due to the increase of the load impedance, and the output power of the variable frequency power supply cannot reach the rated output power. The system impedance change caused by the temperature change of the heated metal material enables the rectified voltage and the rectified current to continuously fluctuate along with the feeding of cold materials into the furnace and the discharging of hot materials out of the furnace when the variable frequency power supply works, and the fluctuation change directly influences the working efficiency of the variable frequency power supply and the reliability of equipment.
Disclosure of Invention
In order to overcome the defects of the prior art, the utility model aims to provide an automatic induction heating and melting variable frequency power supply system with impedance adjustment, which improves the efficiency of a variable frequency power supply and increases the reliability of equipment.
In order to realize the purpose, the utility model discloses a technical scheme is:
the utility model provides an induction heating with automatic impedance adjustment, fused variable frequency power supply system, includes variable frequency power supply (1), and variable frequency power supply (1) is connected variable frequency power supply rectifier circuit (2), and variable frequency power supply rectifier circuit (2) are connected variable frequency power supply inverter circuit (3), and variable frequency power supply inverter circuit (3) receive the control signal of automatic impedance adjustment circuit (4), and induction coil (5) is connected to another way, and capacitor bank (6) are connected to the input and the output of induction coil (5).
And the capacitor bank (6) is set according to the actual working condition.
The automatic impedance adjusting circuit (4) is characterized in that the data acquisition module converts the output current and voltage signals of the variable frequency power supply into digital signals, and the digital signals are input into the PLC to control the direct current voltage output by the inverter circuit (3) of the variable frequency power supply.
The utility model has the advantages that:
in the application of frequency conversion heating of non-ferrous metal materials, metal materials with different electrical resistivity and magnetic permeability such as copper, aluminum, magnesium, titanium, gold and silver cannot be used universally because the system impedance is different during heating and the traditional frequency conversion induction heating furnace or melting furnace with different design parameters is used. The frequency conversion induction heating furnace or the melting furnace adopting the patent technology is one device, and can adapt to heating or melting of various non-ferrous metal materials through automatic impedance adjustment. The same metal material can effectively adjust the fluctuation of the output power and efficiency of the equipment caused by the impedance change of different temperatures of the material, so that the whole heating or melting process is in a high-efficiency and high-power state. The operation efficiency of the equipment is greatly improved, the energy is saved, the time is saved, and the operation reliability is improved. The automatic impedance adjustment is carried out in a full-automatic, real-time and stepless manner in the working process. When the impedance changes extremely, the equipment can still normally play the functions of intercepting and cutting pressure, so that the system can work stably.
In the field of variable-frequency heating or melting of ferrous metal materials, the fluctuation of the output power and efficiency of equipment caused by the huge change of material impedance of the materials above and below the Curie point can be effectively adjusted, so that the whole heating or melting process is in a high-efficiency high-power state.
The utility model discloses a two targets improve variable frequency power supply and trade-straight conversion efficiency and basically maintain the purpose that the output rating is unchangeable. The practical operation proves that the variable frequency power supply with the patent technology saves time, saves electricity, is efficient and simultaneously obviously improves the stability of the variable frequency power supply compared with the variable frequency power supply without the function in the work.
The utility model discloses at present having used in the metal material hot working trade, extrusion's metal material has been in order to be used for aviation, traffic, new energy automobile, a plurality of fields such as electric power after this patent product heating.
Drawings
FIG. 1 is a schematic circuit block diagram of the present invention;
fig. 2 is a schematic view of the present invention.
Wherein, 1 is a variable frequency power supply; 2 is a variable frequency power supply rectifying circuit; 3 is inverter circuit of frequency conversion power supply; 4 is an automatic impedance adjusting circuit; 5 is connecting induction coil; 6 is a capacitor bank; 7 is a metal material; a, B, C is three-phase input AC, us is input voltage, is input current, Ud is rectified voltage, Id is rectified current, Ua is variable frequency voltage, and Ia is variable frequency current.
Detailed Description
The present invention will be further described with reference to the accompanying drawings
As shown in fig. 1 and 2, the induction heating and melting variable frequency power supply system with automatic impedance adjustment comprises a variable frequency power supply (1), wherein the variable frequency power supply (1) is connected with a variable frequency power supply rectifying circuit (2), the variable frequency power supply rectifying circuit (2) is connected with a variable frequency power supply inverter circuit (3), the variable frequency power supply inverter circuit (3) receives a control signal of an automatic impedance adjustment circuit (4), the other path of the control signal is connected with an induction coil (5), and the input end and the output end of the induction coil (5) are connected with a capacitor bank (6).
And the capacitor bank (6) is set according to the actual working condition.
The automatic impedance adjusting circuit (4) is characterized in that the data acquisition module converts the output current and voltage signals of the variable frequency power supply into digital signals, and the digital signals are input into the PLC to control the direct current voltage output by the inverter circuit (3) of the variable frequency power supply.
The variable frequency power supply rectifying circuit (2), the variable frequency power supply inverter circuit (3) and the automatic impedance adjusting circuit (4) can be conventional circuits in the field.
A method of regulating an induction heated, melting variable frequency power supply with automatic impedance regulation, comprising the steps of:
1. the variable frequency power supply (1) inputs alternating current to the variable frequency power supply rectifying circuit (2), and the mathematical relation between the output voltage Ua and the direct current voltage Ud and the power factor C0S phi is as follows through the variable frequency power supply rectifying circuit (2):
Ua = 1.1 × Ud /cos∮（1）
wherein Ua is the output voltage of the variable frequency power supply; ud is the direct current voltage of the variable frequency power supply; cos phi is the power factor, phi is the power factor lead angle;
from the formula 1, the output voltage Ua of the variable frequency power supply, the direct current voltage Ud of the variable frequency power supply and cos phi have a fixed proportional relationship, under the condition that cos phi is not changed, when the system impedance changes due to the temperature change of the metal material, the direct current voltage Ud of the variable frequency power supply is changed to adapt to the change, and the equipment efficiency is greatly reduced when Ud changes;
2. the mathematical relation between the output power P of the variable frequency power supply, the output voltage Ua of the variable frequency power supply and the resonance L.C is as follows:
P = Ua2*rs*C /Ls （2）
wherein, P is the output power of the variable frequency power supply; ua is the output voltage of the variable frequency power supply; c is a resonance capacitance (capacitive reactance); ls is the resonant inductance (inductive reactance); rs is the distributed resistance of the resonance inductor;
when the output power P of the variable frequency power supply is at a low temperature of a metal material, the system inductive reactance Ls is small, so that the output power P is increased and exceeds the rated power, only Ud is reduced, the rated power is kept, the electrical efficiency of the equipment is greatly reduced, when the output power P of the variable frequency power supply is increased due to the temperature rise change of the metal material, the output power P cannot reach the rated power, and the heating efficiency of the equipment is greatly reduced;
3. the method comprises the steps that signals of output voltage Ua and output current Ia of a variable frequency power supply are taken, the signals are converted into digital signals through an analog quantity conversion module of an automatic impedance adjusting circuit (4), the digital signals are input into a PLC (programmable logic controller), a control signal for adjusting the sending time of an inversion pulse is given out after calculation, the power factor cos phi is adjusted so as to achieve the purpose of adjusting the proportion of Ua to Ud, Ia is reduced when the inductive reactance Ls is large, cos phi is reduced (phi is enlarged), the proportion of Ua is increased, Ud is unchanged, Ua is increased, Ia is large when the inductive reactance Ls is small, cos phi is enlarged (phi is reduced), the proportion of Ua is reduced, Ud is unchanged, and Ua is reduced;
therefore, when the temperature of the metal material changes to cause the system impedance change, Ua and Ia change along with the impedance, the automatic impedance adjusting device adjusts cos phi according to the change, so that Ua adapts to the impedance change, the direct-current voltage Ud is ensured to be unchanged, and the equipment is in a high-efficiency state;
when the temperature of the metal material is increased and the system inductive reactance Ls is increased, the output power P of the variable frequency power supply is stable in a certain range because the change of Ua balances the change of power P caused by the change of Ls due to the increase of Ua.
The principle of the utility model is that:
the fixed proportional relation between the inverted variable frequency voltage Ua and the rectified voltage Ud in the original variable frequency power supply is changed into the variable proportional relation through automatic impedance adjustment. The working condition of the variable frequency power supply is automatically detected, the proportion of the variable frequency voltage and the rectified voltage is continuously adjusted, the rectified voltage of the variable frequency power supply is kept at the rated voltage (the electrical efficiency is highest) as much as possible, the impedance change of the metal material is adapted by automatically adjusting the variable frequency voltage, and the adjusting range of the variable frequency voltage reaches about 150V under the condition that the rectified voltage is not changed. The adjusting range of the variable frequency voltage of about 150V can adapt to the impedance change of the metal material in the heating process. When the low-temperature impedance is small, the variable-frequency voltage Ua is reduced, the overload of the rectified current Id can be avoided under the condition that the rectified voltage Ud is not changed, and when the high-temperature impedance is increased, the variable-frequency voltage Ua is increased, so that the power output of the variable-frequency power supply is basically not changed.
The automatic impedance adjusting circuit comprises a power supply voltage-stabilized power supply, a PLC (programmable logic controller) or a pulse controller, and a data acquisition module, wherein the data acquisition module converts output current and voltage signals of a variable frequency power supply into digital signals, inputs the digital signals into the PLC, calculates the digital signals through the PLC, and then gives out control signals for adjusting the sending time of inversion pulses, and controls and adjusts an impedance angle phi so as to adjust a power factor cos phi, thereby achieving the purpose of adjusting the proportion of Ua and Ud.
Claims (3)
1. The utility model provides an induction heating of automatic impedance adjustment, melting variable frequency power supply system, includes variable frequency power supply (1), its characterized in that, variable frequency power supply (1) connect variable frequency power supply rectifier circuit (2), variable frequency power supply rectifier circuit (2) connect variable frequency power supply inverter circuit (3), variable frequency power supply inverter circuit (3) receive the control signal of automatic impedance adjustment circuit (4), induction coil (5) is connected to another way, and capacitor bank (6) are connected to the input and the output of induction coil (5).
2. An automatic impedance-adjusted induction heating, melting, variable frequency power supply system according to claim 1, characterized in that the capacitor bank (6) is set according to actual conditions.
3. The automatic impedance-adjusting induction heating melting variable-frequency power supply system according to claim 1, wherein the automatic impedance adjusting circuit (4) is characterized in that the data acquisition module converts the output current and voltage signals of the variable-frequency power supply into digital signals, and the digital signals are input into a PLC (programmable logic controller) to control the direct-current voltage output by the variable-frequency power supply inverter circuit (3).
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| CN202021875395.7U CN213073154U (en) | 2020-09-01 | 2020-09-01 | Automatic induction heating of impedance adjustment, melting variable frequency power supply system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111918434A (en) * | 2020-09-01 | 2020-11-10 | 西安威特电力电子设备研究所 | Induction heating and melting system with automatic impedance adjustment function and adjustment method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111918434A (en) * | 2020-09-01 | 2020-11-10 | 西安威特电力电子设备研究所 | Induction heating and melting system with automatic impedance adjustment function and adjustment method |
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