Single-phase welding rectifier

 

(57) Abstract:

Usage: electric arc welding with consumable electrode. Single-phase rectifier with electronic current control ensures high stability of the process when welding at low currents (15-90) that can be welded thin sheet structures (0.8 to 1.5 mm) made of carbon and alloyed steels electrodes with a diameter of 2.6-3,25 mm When welding metal large thickness increases weld quality due to the increased dynamic effects of the arc on the weld pool, increasing the depth of molding and improving the crystallization of the metal. Easy excitation and high arc stability, negligible loss of metal spatter and high energy performance, wide range of smooth regulation of current and convenience to ensure the successful application of the rectifier in a domestic environment, for plumbing work in small enterprises, in repair workshops. Single phase rectifier contains a transformer, thyristor rectifier with a control unit and recharge, phase shifting device, two threshold devices, and symmetric thyristor with a control unit and line sudais electrode short circuit arc gap.

Known single-phase welding rectifier containing a transformer with two secondary windings larger and smaller voltage, a smoothing choke, two diodes and four thyristor, the connection of which with the conclusions of the transformer and the output circuit provides the obtaining of two controlled rectifier bridges with a common diagonal, implementing the device in the welding modes, battery and starter engine start car [1]

The disadvantages of the known rectifier can be attributed to a large size, weight and value of the smoothing inductor, connected in series in the welding circuit. This additional inductance in the welding circuit limits the rate of rise of current at short circuit arc gap. In addition, the transfer of electrode metal is accompanied by an increased spatter, since the destruction of the jumpers occurs when a large current values.

The closest in technical essence to the invention is a welding rectifier [2] contains the transformer, full-wave thyristor rectifier, phase shifting device, the control unit thyristor rectifier, two threshold device and Mitel provides simultaneous power arc from malalbergo block recharge and thyristor rectifier, that increases the arc stability and allows to exclude from the circuit of the thyristor rectifier smoothing choke. This improves weight and dimensions of the rectifier. The proposed algorithm works rectifier provides for limiting the current in the welding circuit in case of short circuit the interelectrode gap by prohibiting the inclusion of a rectifier that prevents "freezing" of the electrode to the product when the initial excitation of the arc.

The disadvantage of this straightener is the dependence of the fracture behavior of jumpers from the duration of the short circuit. In particular, if a short circuit begins and ends in one half-cycle when the thyristors, due to the inability to turn them off until the end of the half gap jumper will occur when the current value of the short circuit current of the thyristor rectifier, the value of which can be achieved amplitude value, which leads to increased spraying of the metal electrode.

If the short circuit ends in one of the subsequent half-cycle, in accordance with the algorithm the current in the welding circuit is limited to the value defined miliamperes Blo is practical sustainability.

The aim of the invention is the expansion of technological capabilities of the rectifier by improving process stability and reduce splashing of the metal electrode.

This goal is achieved by the fact that in the known rectifier containing a transformer, full-wave thyristor rectifier, phase shifting device, the control unit thyristor rectifier, two threshold device and the power feeding entered symmetric thyristor connected to the input of the thyristor rectifier in parallel to the main secondary winding of the transformer, the control unit symmetrical thyristor and the delay line, the input of which is connected to the output of the first threshold device, and the output from the deny control unit symmetrical thyristor and the control unit thyristors of the rectifier, thus enabling inputs of the control unit symmetrical thyristor and the control unit thyristors connected to the output of the second threshold device, and the inputs of the first and second threshold devices connected to the arc gap.

In Fig. 1 presents a functional diagram of the welding rectifier, Fig. 2 timing diagram of the welding current and voltage on Duhova the t transformer 1, parallel to the secondary winding 2 which is connected symmetric thyristor 3 and full-wave thyristor rectifier 4, and the additional secondary winding 5 connected to the power feed 6, the output of which is connected in parallel with the output of full-wave thyristor rectifier 4 and the arc gap 7. To arc the gap 7 is also connected to the inputs of the first 8 and second 9 threshold devices. In addition, the rectifier includes a control unit thyristors of the rectifier 10, the control unit symmetrical thyristor 11, prohibiting the inputs of which is connected through the delay line 12 to the output of the first threshold device 8, and enabling inputs to the output of the second threshold device 9. The output of the phase shifting device 13 is connected with the control input of the control unit thyristor rectifier 10, and the output from an additional secondary winding 5 of the transformer 1.

Welding rectifier operates as follows.

When applying to the input of the transformer 1, the voltage at the output of block recharge 6, and, therefore, the arc gap 7 appears open circuit voltage sufficient for the excitation of the arc (phase 1, Fig. 2). This voltage is fed to the inputs of threshold devices 8 and 9. In Oia idling, but most of the arc voltage and the threshold device 9 with the threshold voltage U02whose value is greater than the sum of the voltage drops on the jumper liquid metal and the radius of the electrode, but less than the voltage across the arc gap in the arc.

At the time of the initiation of the arc by zakolachivaniya electrode on the product of the voltage across the arc gap 7 is reduced to the magnitude of the voltage drop in the departure electrode (phase 2, Fig. 2). When it reaches a value less than the threshold U01a threshold device 8 generates a signal that triggers the delay line, which at the time3prohibits the operation of the control unit thyristors of the rectifier 10 and the control unit symmetrical thyristor 11. The main thyristors of the rectifier and the symmetric thyristor 3 are in non-conductive condition. The excitation of the arc at this point in time is only possible from malalbergo block recharge 6, which provides the minimum value of the short circuit current, therefore, primerzanie" electrode to the product at the moment of contact does not occur.

When the separation of the electrode from the workpiece excited maloamperny arc (phase 3, Fig. 2). Upon expiration of the duration of the ban, the delay line 3 removes blokirovki begins to flow the total current from the power feeding 6 thyristor rectifier 4 (phase 4, Fig. 2). The firing angle of the thyristors of the rectifier 4 is specified phase shifting device 13 for determining the effective value of the welding current.

The second threshold device 9 voltage arc gap 7 is continuously compared with the reference voltage U02. When the droplet formation of the metal electrode and its growth arc gap is reduced, the arc voltage decreases and when it reaches the value U02the second threshold device 9 outputs a signal from the beginning of the short circuit (phase 5, Fig. 2). This signal regardless of the phase shifting device 13 includes thyristors of the rectifier 4, providing an accelerated transition to a drop of the metal electrode. At the final stage short circuit (phase 6, Fig. 2) the voltage across the arc gap 7 starts to rise and when it reaches the value U02the second threshold device 9 outputs a signal to activate symmetric thyristor 3. However, depending on the current half-cycle unlocked one of the symmetric thyristor shunt the input of the rectifier 4. The thyristors of the rectifier 4 is transferred in a non-conductive state, causing an abrupt decrease in current magnitude equal to a current of short circuit power feed 6. The gap p is nania half-cycle symmetric thyristor switches to a nonconducting state, and the thyristors of the rectifier 4 is included in the time specified phase shifting device 13 (phase 8, Fig. 2), and the process continues.

The tests of the inventive welding rectifier showed that the introduction of additional elements and blocks (symmetric thyristor, the control unit symmetrical thyristor and delay lines) provides the expansion of technological capabilities of the rectifier by increasing technological stability of the welding process and reduce splashing of the metal electrode.

Single-phase welding rectifier primarily for arc welding with coated electrodes, containing a transformer with multiple secondary windings, a full-wave thyristor rectifier, the power feeding phase shift unit, the control unit thyristor rectifier and two threshold device, characterized in that it introduced the symmetric thyristor connected to the input of the thyristor rectifier in parallel to the main secondary winding of the transformer, the control unit symmetrical thyristor and the delay line, the input of which is connected to the output of the first threshold device, and the output from the deny control unit si is s symmetric thyristor and the control unit thyristor rectifier connected to the output of the second threshold device, the output control unit symmetrical thyristor is connected to a control electrode of the symmetric thyristor, an additional winding of the transformer is connected to the input unit of recharge and phase shifting devices, the output of which is connected to the input of the control unit thyristor rectifier, the inputs of the first and second threshold devices connected to the outputs of the thyristor rectifier and power feed connected in parallel with each other.

 

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