Multiphase conversion device for induction heating

FIELD: electricity.

SUBSTANCE: proposed invention relates to conversion equipment and may be used in installations for induction heating and melting of metal. Main circuit of multiphase double-frequency conversion device comprises source of DC voltage, the first and second filter throttles, and also three circuits, every of which is formed by controlled valve, serially with which one of load-inductor windings is connected, being shunted by capacitor, at the same time the first output of DC voltage source is connected with the first output of the first filter throttle, the second output of which is connected to three first outputs of three controlled valves, at the same time the second outputs of three windings of load inductor shunted by capacitors are connected to each other and joined to the first output of the second filter throttle, the second output of which is connected to the second pole of DC voltage source, at the same time load-inductor is made of three windings, two of which are connected accordingly serially, and all three controlled valves are connected directly relative to polarity of DC voltage source. Each winding of load inductor with shunting capacitor is tuned for high frequency of double-frequency field of loading circuit. Parallel to each winding of load inductor there is a serial circuit connected made of capacitance and inductance, own frequency of which is equal to lower frequency of double frequency field of loading circuit. High-frequency and low-frequency multiphase components of electromagnetic field in loading circuit are formed by means of special logic for control of controlled valves, when each controlled valve is repeatedly connected and disconnected and forms packs of phase-shifted high-frequency pulses.

EFFECT: provision of simultaneous generation of high frequency and low frequency multiphase electromagnetic fields.

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The present invention relates to Converter equipment and can be used for induction heating and melting of metal.

Known devices used for various purposes, parallel type, when the load and commutating capacitor connected in parallel, and serial type, when the load and commutating capacitor connected in series (C1, ciganko I.M. and other Basics converters. Educational. Handbook for the specialty "Industrial electronics". - M.: Higher school, 1974). These converters are analogues of the present invention.

It is also known that during induction heating and melting of metal with increasing mass of the metal increases the power Converter units and reduces their output frequency (L.2, Thyristor converters high frequency electrotechnological installations. Ehimekpi and others - 2nd ed. revised and enlarged extra - L.: Energoatomizdat (Leningrad. office, 1983), while in the range 500÷1000 Hz is most often used parallel inverter, as the most cost-effective at these frequencies, the remaining devices in this frequency range have an increased weight and dimensions. Therefore, as the prototype is set to the most commonly used pavement parallel to invert the p current (Annex 1, L.2. p.16, 2.1).

It is known that the intensity of the induction heating increases with increasing frequency electromagnetic fields (L, Shamov A.M., Badikov VA Design and operation of high-frequency installations. Ed. 2nd, supplementary and Rev. L: engineering (Leningrad. branch), 1974, 280). It is also known that in the single-frequency electromagnetic field to the molten metal in the load-coil under the action of electromagnetic forces moving in the lower part of the inductor near the walls from the bottom up, and about the axis of the coil from top to bottom, in the upper portion of the inductor metal around the walls of the inductor moves down the axis of the inductor from the bottom up, i.e. creates two circuit. As a result of this movement is the stirring of the liquid metal, which improves its quality. However, when two contours circulation mixing of the metal is not effective. To improve the efficiency of electromagnetic stirring is necessary multiphase low-frequency electromagnetic field, and to improve the efficiency of induction heating requires high-frequency electromagnetic field (L). In L.4 it is proposed to use two generators - one for intensive high-frequency induction heating, and the second low-frequency three-phase - to intense electromagnetic stirring (L.4. Weinberg A.M. Induction survive the global furnace. - M.: Energy, 1967). However, this increases the installed capacity of the heating equipment and requires for electrotechnical process of switching in power circuits.

Thus, analogues and prototype have the disadvantage, which is that they cannot generate high-frequency electromagnetic field at a time and multi-phase low-frequency electromagnetic field, or recommend the use of two generators, i.e. they do not achieve the stated technical result consists in the simultaneous generation of high-frequency and low-frequency multiphase electromagnetic fields and simplification.

The present invention solves the problem of creating multi-phase dual Converter device for induction heating, the implementation of which allows to achieve the stated technical result consists in the possibility of the simultaneous generation of high-frequency and low-frequency multiphase electromagnetic fields and simplification.

The essence of the invention lies in the fact that the device containing the constant voltage source, two filter inductor, a controlled valve and the load-inductor shunted by a capacitor, with the first pole of the DC voltage is connected to the first output of the first filter inductor, the second output of which is connected to the first output of the controlled valve, the second terminal of which is connected to the first conclusions of the load inductor and a capacitor, the latter findings are interconnected, and the load-inductor made of three windings along the length of the inductor, but also introduced two similar circuits, each consisting of a controlled valve and consistently connected with it by winding the load inductor shunted by a capacitor, all three circuits are connected in parallel to each other and connected between the second output of the first filter inductor and the first output of the second filter inductor, the second output of the second filter inductor is connected to the second pole of the DC voltage source, and all three managed valve included in the forward direction relative to the polarity of the DC voltage source.

The claimed technical result is the simultaneous generation of high-frequency and low-frequency multiphase electromagnetic fields and simplification is achieved as follows. Three controllable valves supplying power to the three windings of the load inductor, allows using the proposed control algorithm is controlled by valves, which are described below, get in the windings of the load inductor currents with high attotney and low frequency components, this low-frequency component generates currents in the three windings of the load-inductor multi-phase system without additional generators.

Thus, the claimed multi-phase dual Converter device supports the achievement of the claimed technical result is the simultaneous generation of high-frequency and multi-phase low-frequency electromagnetic fields and simplification.

In some cases, to enhance multi-phase low-frequency component of the current windings of the load inductor, i.e., for amplification of electromagnetic stirring of liquid metal, it is advisable to connect a serial circuit consisting of inductance and capacity in parallel each of the three windings of the load inductor, while the frequency of this additional circuit is equal to the frequency, the low-frequency component of the current windings of the load inductor.

Thus, in the proposed multi-phase dual Converter devices is achieved by the claimed technical result is simultaneously generated high-frequency and low-frequency multiphase electromagnetic fields and simplification.

Figure 1 and 2 shows variants of Converter devices.

The inverter device shown in figure 1, contains the source of the permanent voltage, the first 1 and second 2 filter chokes, the first 3, the second 6 and third 9 controlled valves, the first 4, the second 7 and third winding 10 of the load inductor, and the first 5, second 8 and third 11 capacitors, with the first pole of the constant voltage source connected to the first output of the first filter inductor 1, the second terminal of which is connected with the first findings of the first 3, the second 6 and third 9 controllable valves, while the second output of the first 3 controlled valve connected with the first conclusions of the first winding 4 load inductor and the first capacitor 5 the second output of the second 6 controlled valve connected with the first conclusions of the second winding 7 of the load inductor and the second capacitor 8, and the second output of the third 9 controlled valve connected with the first conclusions of the third winding 10 of the load inductor and the third capacitor 11, while the second set of conclusions of the first 4, the second 7 and third windings 10 load inductor, and the second the findings of the first 5, second 8 and 11 third capacitors are connected together and connected to the first output of the second 2 filter inductor, the second terminal of which is connected to the second pole of the DC voltage source, while the first 4 and the second winding 7 of the load inductor have a common output and enabled sequentially according to each other, and managed valves 3, 6 and 9 included the forward direction relative to the polarity of the DC voltage source.

Conversion device operates as follows. In the steady state through the first 1 and second 2 filter chokes DC current is flowing. When the vehicle is unlocked first controlled valve 3 constant current flows on a path

when the capacitor 5 is charged to a voltage shown in Fig 1 by the signs "+", "-". Then unlocked the third controlled valve 9 and a constant current flows on a path

in the circuit 3-9-11-5-3 to the first controlled valve 3 is applied a negative voltage, which ensures the locking of the first controlled valve 3, and the current through it stops, while the third capacitor 11 is charged to a voltage, shown in figure 1 the signs "+", "-", and the first capacitor recharges in 5 loop 5 - 4 - 5 to the voltage shown in figure 1 marks"(-)", (+)". Once this is unlocked first controlled valve 3, and the third controlled valve 9 is locked, then unlocked the third controlled valve 9, and so several times. Then again unlocked the first controlled valve 3, but then unlocked the second controlled valve 6 and the constant current flows through the circuit 7

in the circuit 3-6-8-5-3 to the first controlled valve 3 is applied Autry is atelinae voltage, which ensures the locking of the first controlled valve 3, and the current through it stops, the second capacitor 8 is charged to a voltage, the polarity of which is shown in figure 1 the signs "+", "-", and the first capacitor 5 recharges in the circuit 5-4-5 to a voltage, the polarity of which is shown in figure 1 marks"(-)", "(+)". Then again unlocked the first controlled valve 3, and so several times. After this first controlled valve 3 terminates, and the second controlled valve 6 starts to operate alternately with the third controllable valve 9. After a few positives of the second controlled valve 6 terminates, and the third controlled valve 9 works alternately with the first controllable valve 3. All processes are repeated and are similar to those described. The number of high frequency pulses in a packet, the packet duration and the pause is determined by the ratio of the frequencies of low-frequency and high-frequency components of the load current and the same in each winding of the load inductor. The frequency FP of the high-frequency component of the current of each winding of the load inductor is determined by the time course of the pulse constant current through one winding and provides efficient heating of the metal, and the frequency Fn of the low-frequency component of the current in each winding of the load inductor is determined by the formula/p>

where n is the number of high frequency pulses in each period of the low frequency, which provides an electromagnetic stirring of metal, with each low-frequency period consists of bundles of high-frequency pulses t_stumpsdetermining a low-frequency pulse, and a pack of high-frequency pulses t_dupdefining the low-frequency break the current in each winding of the load inductor, the optimal ratio is

since in this case the most effective forms of multiphase low-frequency electromagnetic field, which provides the transformation of two circulating flows of liquid metal in the upper and lower parts of the inductor in one the circulation flow along the length of the inductor. The number n can be 3, 6, 9, etc. So, for n=9 sequence of operation controlled valves will be next: 3,9-3,9-3,9-3,6-3,6-3,6-6,9-6,9-6,9-3,9-3,9-3,9 etc. where 3,9 means alternately unlocked valves 3 and 9; 3,6 means alternately unlocked the valves 3 and 6; 6,9 means alternately unlocked valves 6 and 9.

In conclusion, it should be noted that to ensure the work is considered converting device it should have a starter, which would provide a steady DC current through the filter shall be the fir 1 and 2, which for simplicity is not shown in figure 1.

The inverter device shown in figure 2, in addition to the elements shown in figure 1, contains the first 12, second 14 and third 16 chokes, and the fourth 13, 15 fifth and sixth capacitors 17, with the first conclusions of the first 4, the second 7 and third windings 10 load capacitor connected to the first conclusions, respectively, of the first 12, second 14 and third 16 chokes, the second set of conclusions which are connected with the first pins respectively fourth 13, 15 fifth and sixth capacitors 17, the latter findings are connected to the second conclusions accordingly, the first 4, 7 and the second third windings 10 of the load inductor. The natural frequency of the sequential circuits formed above the inductors and capacitors, respectively 12, 13, 14, 15, 16, 17, is selected equal to the frequency Fn of low-frequency electromagnetic fields.

Conversion device operates as follows.

The algorithm of the first 3, the second 6 and 9 fourth controllable valves remains the same as described above for the device shown in figure 1. This algorithm, as shown above, provides for the formation of low-frequency electromagnetic field, which causes the serial resonance in series resonant circuits 12, 13; 14, 15, 16, 17, while formally resonant current flows through the circuits: the first con is ur the second circuitthe third circuit

In fact, the capacitors 5, 8 and 11 are selected from the conditions of forming the high-frequency pulses, i.e. they are relatively small. Therefore, resistance

relatively high and low-frequency resonance current actually flows through the circuits: the first circuit 13-12-4-13; a second circuit 15-14-7-15; the third circuit 17-16-10-17, i.e. load windings of the first inductor 4, the second 7 and third 10, and therefore, this low-frequency resonant current increases low frequency polyphase electromagnetic field and electromagnetic force for the electromagnetic stirring of liquid metal in the load inductor, which increases single-circuit circulation of this liquid metal and improves its quality.

In conclusion, it should be added that the Converter device must have a starting device, and controllable valves may be shunted by protective damping circuits consisting of resistors, diodes, capacitors, varistors.

1. Multiphase Converter dual-frequency device for induction heating, containing the constant voltage source, the first and second filter inductors, the first controlled valve, the first winding of the load inductor and the first capacitor, when atoms the first pole of the DC voltage source is connected to the first output of the first filter inductor, the second output of which is connected to the first output of the first controlled valve, the second terminal of which is connected to interconnected the first conclusions of the first winding load inductor and the first capacitor, while the second set of conclusions of the first winding load inductor and the first capacitor are connected, characterized in that it further introduced the second and third controllable valves, the second and third capacitors, and the load is an inductor made of three windings along the length of the inductor to the first output of the first controlled valve connected together by the first conclusions of the second and third controllable valves, while the second the output of the second controlled valve connected to the interconnected first conclusions of the second winding of the load inductor and the second capacitor, the second terminal of the third controlled valve connected to the interconnected first conclusions of the third winding of the load inductor and the third capacitor, while the second findings of the second winding of the load inductor and the second capacitor, and a third winding of the load inductor and a third capacitor connected to the second pins of the first winding load inductor and the first capacitor and connected to the first output of the second filter inductor, a second output which is outinen with the second pole of the DC voltage source, while the first and the second winding of the load inductor have a common output and enabled sequentially according to each other, and managed valves included in the forward direction relative to the polarity of the DC voltage source.

2. Multiphase Converter dual-frequency device according to claim 1, characterized in that it further introduced the first, second and third inductors, as well as the fourth, fifth and sixth capacitors, with the first findings of the first, second and third windings of the load inductor connected to the first conclusions respectively first, second and third inductors, the second set of conclusions which are connected with the first pins respectively the fourth, fifth and sixth capacitors, the latter findings are connected to the second conclusions respectively first, second and third windings of the load inductor.