Device for balancing unsteady single-phase load, the flash butt machine

 

(57) Abstract:

The invention relates to the field of welding. The technical result - ensuring the uniformity of distribution of currents in three-phase mains. The device contains a reactive power compensator and symmetrise device, forming n identical modules, the reactive elements are connected through a thyristor contactor to the load and to free the phase diagram of Steinmetz. The device includes a sensor level of welding current having n outputs and connected to a current transformer in the primary circuit of the welding transformer, the shaper pulses, synchronized with the phases of the network feeding the inductive elements of the modules, the output of which is connected to the input of the phase delay of the pulses. The device also contains conditioners pulses, synchronized with the phases of the network feeding the capacitive elements of the modules and connected in parallel to the respective thyristor contactors, control unit mentioned modules, consisting of n identical channels. Each channel contains three synchronous trigger whose output is connected to the control unit thyristor contactors corresponding module, and the United enforce, United clock inputs of one of the triggers of each channel is connected to the output of the phase delay of the pulses, and the clock inputs of the other two triggers, each channel connected to the outputs of the respective pulse shapers, synchronized with the phases of the network feeding the capacitive elements of the corresponding module. 2 Il.

The present invention relates to the field of welding, and more specifically to a device for balancing unsteady single-phase load, the flash butt machine.

The level of technology.

A device for balancing single-phase non-stationary load, consisting of two 3-phase thyristor rectifiers connected in opposite parallel and working on a common load, the primary winding of the welding transformer (Low pin machine non-profit partnership-25-42 for butt welding by continuous fusion boiler tubes, "Welding production", 1990, N 2, S. 22-24, N. In.Hem, E. P. Krivonos, A. A. Danko and others). One of the rectifiers generates positive and the second negative half-wave of the output voltage of the low frequency. However, when using low frequency significantly increase the size and Masi number of phases as balancing devices have not found wide industrial application.

A known machine for flash butt welding, working on direct current. In these machines the function of balancing devices perform three-phase welding transformers or one three-phase transformer, the secondary windings of which are connected to the rectifier (see, for example, "Canadian Welder and Fabricator" - 1989, 80, No. 9, S. 15, 17-19, Butt welding with three-phase DC power).

The disadvantages of the known device consists in a substantial voltage drop across the diodes (up to 30% of the nominal circuit voltage of the welding circuit), as well as in the higher harmonics caused by the rectification circuit. They come in 3-phase system and distort the shape of the voltage curve. In addition, the complicated design of the secondary circuit of the welding machine.

A device for balancing single-phase load (see, for example, patent GDR N 213796, MKI H 02 J 3/26, 1983), containing a regulating transformer, connected to two phases of the mains, as between its outlet and the third phase included balancing capacitor. A disadvantage of the known device is that it does not provide compensation of the reactive power of the welding machine. In addition, the capacitance of the capacitor and the position of the tap of the transformer should Er, during flash butt welding process, to obtain a balanced load 3 phase when using the known device is not possible.

It is also known a device for balancing single-phase load (see, for example, patent Germany N 3927437, 1989, H 02 J 3/26, B 23 K 11/24), taken as a prototype. The device contains one module of the reactive elements, consisting of a reactive power compensator, is in parallel with the primary winding of the welding transformer, and a balancing device consisting of a serially connected capacitor and inductor, common point which is connected to the free phase, and the other two to the phases of the load. The device also contains a measure of the welding current and voltage, are included in the primary circuit of the welding transformer, the outputs of which are connected with the control unit, in which the measurement of active and reactive power and determination of the parameters necessary for compensation and balancing of single-phase loads.

This device provides uniform distribution of current on the three phases of the mains supply at a constant load parameters. However, during flash butt welding reflow resistance IAS the government should change the power compensating and balancing elements. Practically implement continuous adjustment of inductance in a wide range is very difficult, and capacity - impossible. Therefore, the use of the known device during flash butt welding does not give the desired effect.

Another disadvantage of the known device is that it does not solved the problem of switching the reactive elements of the large capacity, which can be an emergency, when the current in the supply network is many times greater than the load current.

The essence of the invention.

The basis of the invention is to create a device for the balancing of single-phase non-stationary load, the flash butt machine, ensure uniform distribution of currents in 3-phase mains through the automatic connection of the reactive elements necessary power.

The problem is solved in that the device for balancing single-phase load, containing the current transformer included in the primary circuit of the welding transformer, reactive power compensator, is in parallel with the primary winding of the welding transformer, and symmetrise device consisting of a capacitor and inductor,obreteniyu, consists of n identical modules, capacitors and inductors which are connected to the above mentioned phases through thyristor contactors, the device additionally introduced gauge welding current having n outputs and connected to a current transformer; shaper pulses, synchronized with the phases of the network feeding the choke modules, the output of which is connected to the input of the phase delay of the pulses; the pulse shapers, synchronized with the phases of the network, power supply capacitors, modules, and connected in parallel to the respective thyristor contactors; a control unit mentioned modules, consisting of n identical channels, each of which contains three synchronous trigger, the outputs are connected to the control unit thyristor contactors corresponding module, and the integrated information inputs of triggers, each channel connected to the corresponding sensor output level of the welding current, United clock inputs of one of the triggers of each channel is connected to the output of the phase delay of the pulses, and the clock inputs of the other two triggers, each channel connected to the outputs of the respective pulse shapers, synchronized the business side of the device for balancing, and the control unit mentioned modules allows you to automatically change the device settings when the load changes, thus achieving a uniform distribution of the currents on the three phases of the mains and excluded emergency when switching reactive elements of great power.

List of figures.

The invention is further illustrated by the example of execution with reference to the accompanying drawings, in which:

Fig. 1 depicts a block diagram of the device for balancing unsteady single-phase load, the flash butt machine according to the invention;

Fig. 2 is graphs illustrating the effectiveness of the balancing of single-phase non-stationary load when the device contains one (a) two (b) three (C) module of the reactive elements.

Information confirming the possibility of carrying out the invention.

Device for balancing unsteady single-phase load, the flash butt welding machine according to the invention, contains a current transformer 1 (Fig. 1) included in the primary circuit of the welding transformer 2. The output of the current transformer 1 is connected to the sensor input level Nestor reactive power 4, consisting of n identical blocks 5 (5n) connected in parallel. Each block contains a capacitor battery 6 connected to the phases of the load And, through thyristor contactor 7. In parallel with the thyristor contactor 7 is connected to the pulse shaper 8, synchronized with the phases of the network And C

Sammarinese device 9 consists of n identical blocks condenser batteries 10 (10n), connected in parallel, and n identical blocks chokes 11 (11n) connected also in parallel with each other. Each capacitive unit 10 (10n) contains a battery of capacitors 12, connected to the phase load and free phase through the thyristor contactor 13. In parallel, the latter is connected to the pulse shaper 14, synchronized with the phases of the network B, C. Each inductive unit 11 (11n) contains a throttle 15, connected to the phase of the load and to the free phase through the thyristor contactor 16. These same phases (a, C), feeding inductive blocks 11 (11n) connected shaper synchronized pulses 17, the output of which is connected to the input of the phase delay 18 mentioned pulses. Capacitive blocks of 5, 10 and inductive unit 11 form one module of the reactive elements of the device according to the invention.

The control unit is n, 21n, 22n) to control respectively the reactive power compensator 5(5n), the capacitor Bank 10 (10n) and the inductor 11 (11n) a single module. In turn, each sub 20 (21, 22) consists of a synchronous trigger 23(24, 25), the output of which is connected to the control unit 26 (27, 28) corresponding thyristor contactor named module. United informational inputs synchronous triggers 23, 24, 25 of the first channel connected to the first sensor output level of the welding current 3. The consolidated data inputs synchronous triggers other channels are connected similarly. United clock inputs of flip subunits 22, 22n is connected to the output of the phase delay of the pulses 18. The clock inputs of the triggers 20, 21 connected to the output of the shaper synchronized pulses 8, 14, respectively. Similarly connected to the clock inputs of flip subunits 20n, 21n to the shapers of synchronized pulses in blocks 5n and 10n, respectively.

Thyristor contactors 7, 13, 16 represent two of the power thyristor connected in opposite parallel. Their purpose switching power reactive elements of the modules of the device. Since the contactors 7, 13, 16 are in the "on-off", Rivately synchronized pulses 8, 14, 17 are converters sinusoidal voltage of the respective phases in the sequence of short pulses, which are formed at the transition points of the sine wave crosses zero. In the delay unit 18, the input pulses are shifted in phase by 90 electrical degrees relative to phase a With feeding an inductive load. Sensor 3 levels of welding current includes measuring node and n Comparators having different job level of the welding current. On the respective outputs of the sensor 3 receive signals of logical "1" when the welding current exceeds a specified value.

The proposed device for balancing single-phase non-stationary load works in the following way. Reactive power, which must be compensated, as well as the active power required for the load balancing, proprofessional load current. Therefore, the settings of the device according to the invention vary depending on the magnitude of the welding current.

In the initial state, when no welding current, all outputs of the sensor 3 levels of welding current signal is a logical "0". The same signal at the output of all synchronous triggers prohibits the inclusion of the thyristor contactors welding circuit will not exceed the value of the idle current of the welding transformer. When reaching the threshold of the first comparator sensor 3 at its first output a signal of logic "1" which is supplied for informational inputs synchronous triggers 23, 24 and 25 of the first channel control unit 19 preparing the inclusion of the reactive elements of the first module. In the time of arrival of the next synchronizing pulse from the driver 8 to the clock input of the trigger 23 of the latter switches and its output a signal of logic "1" to allow the control unit 26 to the firing of the thyristor contactor 7. When connected to the network, the capacitor Bank 6 of the first unit 5 reactive power compensator 4.

In the time of arrival of the next synchronizing pulse from the shaper 14 to the clock input of the trigger 24 of the last switch at its output a signal of logic "1" to allow the control unit 27 on the firing of the thyristor contactor 13. When connected to the network, the capacitor Bank 12 of the first block 10 balancing device 9. With the arrival of the next synchronizing pulse from the delay unit 18 to the clock input of the trigger 25 last switches and its output a signal of logic "1" resolution unit 28 on unlocking tiristor the way, when the level of the welding current, which triggers the first comparator sensor 3, all the reactive elements of the first module of the device for balancing is connected to 3-phase network.

With increasing load the welding current reaches the threshold of the second comparator sensor 3. The second output is a logical signal "1" and connect to a 3-phase circuit of the second module of the device for balancing similarly connected to the first module, as described above.

Depending on the range of variation of welding current and discrete tasks in sensor 3 levels of welding current at the same time works a certain number of modules of the reactive elements, i.e., the balancing of single-phase non-stationary load automatically. This prevents the occurrence of accidents on the network when switched reactive elements high power, since the capacitive blocks compensator of reactive power and balancing devices are connected to the phases of the network at the moment of transition sine wave voltage through zero on the corresponding capacitor battery, and blocks the choke is shifted in phase by 90 electrical degrees. Prietula all outputs of the sensor 3 level of welding current signal is a logical "0" to return the device for balancing in the original off state.

The discrete nature of the control parameters of the device for balancing at variable load provides full compensation for n certain values of welding current. At other values of current is incomplete balancing single-phase load. However, the use of the proposed device in comparison with the prototype has a significant effect.

Indeed, the single-phase load can be represented as the sum of direct and inverse symmetrical component current. If the load connected to the phases A and B (see Fig. 1), the current in phase a IA= I, and in phase current IB= -I, where I is the load current. The task of balancing loads in 3-phase three-wire system with symmetrical supply voltage is reduced to compensate for the backward component of the current IA2the greatest value of which corresponds to the value If the load distribution in the range of 0<I maxuniformly, the resistance of the reactive elements of XLand XCeach module can be chosen from the condition of equality of the load current of one module balancing devices:

From the graphs shown in Fig. 2, it is seen that when n=1 (prototype) maximum nesbalansirovannoe device, having three modules of the reactive elements, reducing by half the maximum unbalanced part of the reverse component of the load current in comparison with the prototype and 4 times compared to single-phase load. With increasing number of modules of the reactive elements is achieved better balancing of single-phase variable load.

The proposed device can be used for flash butt machines for welding continuous and pulsed fusion, as well as the pre-heat resistance.

Device for balancing unsteady single-phase load, the flash butt machine that contains the current transformer included in the primary circuit of the welding transformer, reactive power compensator, is in parallel with the primary winding of the welding transformer, and symmetrise device consisting of a capacitor and inductor, one of the conclusions of which is connected with a free mains phase, and the latter findings - phase network load, characterized in that symmetrise the device consists of n identical modules, capacitors and inductors which are connected to the above mentioned phases through thyristor contactors, with the transformer current, shaper pulses, synchronized with the phases of the network feeding the choke modules, the output of which is connected to the input of the phase delay of the pulse shapers pulses, synchronized with the phases of the network, the supply capacitor modules and connected in parallel to the respective thyristor contactors, power management modules, consisting of n identical channels, each of which contains three synchronous trigger whose output is connected to the control unit thyristor contactors corresponding module, and the integrated information inputs of triggers, each channel connected to the corresponding sensor output level of the welding current, United clock inputs of one of the triggers of each channel is connected to the output of the phase delay of the pulses, and the clock inputs of the other two triggers, each channel connected to the outputs of the respective pulse shapers, synchronized with the phases of the network feeding the capacitors of the corresponding module.

 

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