A kind of digital electromagnetic induction heater
Technical field
The present invention relates to a kind of smelting equipment, relate in particular to a kind of digital electromagnetic induction heater.
Background technology
Induction heating is to utilize electromagnetic induction principle, power supply is toward coil input power frequency, intermediate frequency or high-frequency alternating current, coil produces alternating magnetic field, and workpiece is placed in this alternating magnetic field, and workpiece produces the induced current of same frequency, this induced current is inhomogeneous in the distribution of workpiece, strong on the surface, and very weak in inside, arrive heart section close to zero, utilize this kelvin effect, surface of the work is heated rapidly.Induction heating has been widely used in a plurality of fields such as the quenching of Industrial Metal piece surface, Metal Melting, bar be diathermanous.
Induction heater generally includes induction heating power and coil, and induction heating power provides the alternating current that needs frequency for coil.The coil major part is tubulose, and the alternating magnetic field that this tubular coil produces is larger in the inside and outside strength ratio of coil, and just smaller at the both ends of coil, therefore, usually the workpiece of needs heating is placed on inside or the outside of coil.
Usually adopt at home at present electrothermal tube heating, because the electrothermal tube heating is slow, firing equipment is just done very large very longly, the large and complex structure of floor space.Have in Japan and to adopt electromagnetic induction to come generator amature, stator heating for workpiece being placed on the inside of tubular coil, have been designed special-purpose manipulator, and coil need to do very greatly, whole device structure is very complicated, and cost is very high.
Summary of the invention
The technical problem to be solved in the present invention is: provide a kind of low in energy consumption, cost is low, power saving effect, has the digital electromagnetic induction heater that tracking velocity is fast, precision is high, adjustability is strong and catch bandwidth.
In order to overcome the defective that exists in the background technology, the technical solution adopted for the present invention to solve the technical problems is:
A kind of digital electromagnetic induction heater, comprise the three phase mains, mains switch, the contactor that are electrically connected successively, also comprise an induction power supply heating controller, the input of described induction power supply heating controller is connected with the output of described contactor, described induction power supply heating controller also is connected with the PLC controller with the PC host computer respectively, and the output of described induction power supply heating controller is connected with a load coil.
Described induction power supply heating controller comprise successively the full bridge inverter that is used for making inverter output alternation drive waveforms that links to each other, by described load coil and heating material consist of equivalent electric circuit series resonant circuit, be used for realizing following the tracks of the resonance frequency of described series resonant circuit the all-digital phase-locked loop circuit, be used for providing the IGBT drive circuit that drives signal to described full bridge inverter.
Described full bridge inverter is connected with described series resonant circuit by a current transformer, and the secondary end of described current transformer is connected with described all-digital phase-locked loop circuit.
Described alternation drive waveforms is square wave.
Described load coil is wrapped in the outer surface of insulating.
The outer surface of described insulating is provided be used to the wire casing of placing described load coil.
Described insulating is nano heat insulating material.
Described full bridge inverter comprises IGBT pipe, the 2nd IGBT pipe, the 3rd IGBT pipe, the 4th IGBT pipe, and the output of described IGBT drive circuit is connected with described IGBT pipe, the 2nd IGBT pipe, the 3rd IGBT pipe, the 4th IGBT pipe respectively.
Induction heater disclosed in this invention has the following advantages:
(1). the frequency-tracking scope is large, flexibility is good: when processing method and parameter change, only need by changing Software for Design to adapt to corresponding variation.
(2). dynamic response is higher, precision is high: signal processing system can satisfy required precision by the figure place of A/D conversion, the word length of processor and suitable algorithm.
(3). good reliability: the impact that treatment system is caused by the interference of ambient temperature, humidity, noise and electromagnetic field is less.
(4) but. large-scale integrated: along with the development of semiconductor integrated circuit technology, the integrated level of digital circuit can be done very highly, has the advantages such as volume is little, power consumption is little, good product consistency.
Description of drawings
Fig. 1 is the induction power supply heating controller structure principle chart among the present invention;
Fig. 2 is the digital electromagnetic induction heater structural representation among the present invention.
Embodiment
As shown in Figure 1 and Figure 2, a kind of digital electromagnetic induction heater, comprise the three phase mains, mains switch, the contactor that are electrically connected successively, also comprise an induction power supply heating controller, the input of described induction power supply heating controller is connected with the output of described contactor, described induction power supply heating controller also is connected with the PLC controller with the PC host computer respectively, and the output of described induction power supply heating controller is connected with a load coil.
Described induction power supply heating controller comprise successively the full bridge inverter 1 that is used for making inverter output alternation drive waveforms that links to each other, by described load coil and heating material consist of equivalent electric circuit series resonant circuit 2, be used for realizing following the tracks of the resonance frequency of described series resonant circuit all-digital phase-locked loop circuit 3, be used for providing the IGBT drive circuit 4 that drives signal to described full bridge inverter.
Described full bridge inverter is connected with described series resonant circuit by a current transformer, and the secondary end of described current transformer is connected with described all-digital phase-locked loop circuit.
Described alternation drive waveforms is square wave.
Described load coil is wrapped in the outer surface of insulating.
The outer surface of described insulating is provided be used to the wire casing of placing described load coil.
Described insulating is nano heat insulating material.
Described full bridge inverter comprises that an IGBT pipe Q1, the 2nd IGBT pipe Q2, the 3rd IGBT pipe Q3, the 4th IGBT manage Q4, and the output of described IGBT drive circuit is connected with described IGBT pipe, the 2nd IGBT pipe, the 3rd IGBT pipe, the 4th IGBT pipe respectively.
Described electromagnetic induction heating controller is realized by following principle:
Full bridge inverter, circuit by alternately turning on and off the IGBT pipe, make the drive waveforms of inverter output alternation by fixedly DC power supply VCC power supply, and this drive waveforms is square wave.
Series resonant circuit, this circuit are the equivalent electric circuits of load coil and heating material, and any material is put into heater coil its fixing resonance frequency, and this resonance frequency is exactly the frequency that digital control circuit is set when initial; After the material heating, the resonance frequency of load is changed, the difference of the frequency of voltage control signal and the resonance frequency of load be embodied in the screens of voltage control signal and loop current poor on, both frequencies but equate all the time. when the phase place of loop current is ahead of the phase place of voltage control signal, load is capacitive, and the frequency of voltage control signal is less than the resonance frequency of load; When the phase place of loop current lagged behind the phase place of voltage control signal, load was perception, and the frequency of voltage control signal is greater than the resonance frequency of load; And when the phase place of loop current equaled the phase place of voltage control signal, the frequency of voltage control signal equaled the resonance frequency of load, and at this moment, power supply most effective, drive waveforms are sinusoidal wave.
The all-digital phase-locked loop circuit, this main circuit will be realized the frequency-tracking function, and wherein current feedback signal is loop current, and this current feedback signal is by the high-frequency current converter, obtains after changing through light-coupled isolation, modulus again; The digital control circuit output voltage control signal, control signal is by a drive circuit FEEDBACK CONTROL series-resonant inverting circuit.
The grid VT4 of grid VT3, the 4th IGBT pipe Q4 of grid VT2, the 3rd IGBT pipe Q3 of grid VT1, the 2nd IGBT pipe Q2 of a IGBT in described full bridge inverter pipe Q1 is connected with output VT11, VT22, VT33, the VT44 of described IGBT drive circuit respectively, realizes by described IGBT drive circuit turning on and off through the grid control IGBT pipe of output, IGBT pipe.
Smelting furnace provided by the invention is when devoting oneself to work, powered by power supply VCC, by alternately turning on and off the IGBT pipe, make the drive waveforms of inverter output alternation, wherein IGBT pipe is managed one group with the 3rd IGBT, the 2nd IGBT pipe is managed one group with the 4th IGBT, as opens IGBT pipe and the 3rd IGBT pipe, will close the 2nd IGBT pipe and the 4th IGBT pipe; By the Current Mutual Inductance effect, and in conjunction with series resonant circuit, be the acting of load coil and heating material by the load inductance in the series resonant circuit, the feedback current signal is to the all-digital phase-locked loop circuit simultaneously, change through high-frequency current converter, light-coupled isolation, modulus again and realize frequency-tracking, finally by full-bridge IGBT drive circuit driven and turn on and off the IGBT pipe.
A kind of smelting furnace disclosed in this invention adopts converter technique, with electrical network 50-60HZ frequency translation to our required optimum frequency, then large electric current is by the speciality coil, the interior material of molten aluminium holding furnace crucible is carried out directly to aluminium induction cutting, and being converted to fast heat, the graphite crucible heating need not heat transfer process.Thoroughly solve traditional electric stove heat-transfer effect not good, the disadvantage that the heat efficiency is not high.This furnace heat efficiency utilance can reach more than 90%, and power saving effect is fairly obvious.
By above-mentioned description, the relevant staff can in the scope that does not depart from this invention technological thought, carry out various change and modification fully.The technical scope of this invention is not limited to the content on the specification, must determine its technical scope according to the claim scope.