SU1620239A1 - Starting device for welding transformer idle running limiter - Google Patents

Abstract

The invention relates to electric arc welding and can be used in devices for limiting the no-load voltage of welding transformers. The aim of the invention is to increase the sensitivity, speed and reliability as well as electrical safety and ease of use of the device. The device comprises a pulse voltage generator associated with the primary winding of the welding transformer, a measuring transformer and a switching element with a control circuit. In addition, a voltage pulse duration control unit, a counting pulse generator, the first pulse counter, the first coincidence circuit were introduced. The pulse duration control unit of the standby voltage contains a comparator, a second pulse counter, a second coincidence circuit, and a source of reference voltage. The capacitor and the switching element of the pulse voltage generator are connected in series with the primary winding of the welding transformer. When the open circuit, the power switching element is open and the secondary winding of the welding transformer contains impulse voltage. When the arc gap is closed, the control circuit gives a command to close the switching element, which allows to increase the electrical safety of welding operations. 3 з п. Ф-лы, 4 Il. yu (L

Description

The invention relates to electric arc welding, in particular, devices for limiting the no-load voltage of welding transformers.

The aim of the invention is to increase the sensitivity, speed and reliability of the device.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 is a block diagram of the device option; in fig. 3 - plots of signals acting in the device circuit; in fig. 4 is a block diagram of the idle limiter.

The device (Fig. 1) contains a generator of duty voltage pulses 1 associated with the primary winding of the welding transformer 2, a voltage transformer 3 whose primary winding is connected parallel to the primary winding of the welding transformer, and the secondary is connected to the first pulse control unit 4 of the duty pulse tension The second input of block 4 is connected to the output of the generator 5 counting pulses, and the output is connected to the reset input of the first counter 6 pulses, the counting input of which is connected to the output of the generator 5 counting pulses, and the output to the input of the first coincidence circuit 7, the output of which is the output of the device .

The generator 1 pulses of the duty voltage can be made similar to the prototype, i.e., a capacitor and a switching element in the form of a thyristor on

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go

with so

parallel to the primary winding of the welding transformer, and the capacitor is connected to the terminals of the network through a diode.

The generator 1 pulse voltage (Fig. 2) contains a capacitor 8 and a switching element 9 of two anti-parallel thyristors, connected consequently to the primary circuit of the welding transformer 2, and the thyristor phase control unit 10, the input of which is connected to the network terminals and the outputs are with thyristor control electrodes. The control unit 4 for the pulse voltage of the duty voltage contains a two half-period rectifier 11 connected by the input to the secondary winding of the voltage transformer 3, and the output to the first input of the voltage comparator 12, the second input of which is connected to the source 13 of the reference voltage and the output to the reset input of the second pulse counter 14, the counting input of which is connected to the generator output 5 of the counting pulses, and the output to the input of the second coincidence circuit 15, the output of which is connected to the reset input of the first pulse counter 6.

The purpose of the pulse duration control unit 4, the duty voltage is to measure the pulse duration, compare it with a predetermined value that determines the sensitivity threshold of the device, and issue a reset pulse to the first counter 6, which serves together with the first coincidence circuit 7 to control the presence of pulses at the output block 4.

The device works as follows.

When the power is turned on and the welding circuit is open, welding transformer 2 (Fig. 1) is supplied with pulses from the duty voltage from generator 1. The same pulses through the voltage transformer 3 are fed to the input of the watch voltage pulse control unit 4. If the duration of this pulse is greater than the predetermined value — the setting of the sensitivity of the device, then each pulse of the duty voltage corresponds to a reset pulse at the output of block 4, which enters the reset input of the first counter of 6 pulses, which is filled with counting pulses from the generator 5. At that, the number in the first the counter 6 is reset to zero, not reaching a predetermined value recorded in the first circuit 7, a match, and the trigger signal at the output of the latter is not generated.

When the welding circuit is closed for resistance less than the device sensitivity setting, for example less than 300 ohms, no reset pulses are generated at the output of unit 4. When the increasing number in the counter 6 reaches the value recorded

0

Q

5 g 0

five

0

In the first coincidence circuit 7, a trigger signal is produced at its output-voltage in the form of a voltage pulse.

If the pulse voltage generator 1 is half-wave, as in the prototype, in one of the half-periods the generator capacitor is charged from the network through the diode, and discharged through the switching element to the primary winding of the welding transformer 2 in the other. follow with the frequency of the mains supply, with the same frequency follow the reset pulses at the output of block 4. The number recorded in the first 7 matches must also be greater than the number of pulses produced by the generator 5 in one period of voltage mains, and the maximum delay possible incorporation of the welding transformer to full voltage, counting from the moment of closing the welding circuit is approximately equal to one period (average - one half, ie 10 ms at 50 Hz frequency..).

To reduce the on-delay, pulse voltage is generated with a double mains frequency, so that the maximum delay is reduced to half a period (10 ms) and the average to a quarter of a period (5 ms). This is achieved by using a two-half-cycle oscillator circuit 1. Condenser 8 (Fig. 2) recharges each half-voltage of the network through one of the thyristors of the switching element 9 and the primary winding of the welding transformer 2. The closing time of the switching element (the angle of delay of the thyristor unlocking) is determined node 10 phase control. The closure moment of the switching element (the angle of delay for unlocking the thyristor) of the phase control is determined by the node 10. By changing the angle of delay, it is possible to regulate the amplitude of the duty voltage pulse. The pulses of the duty voltage have a polarity corresponding to the polarity of the network voltage at the time of the formation of this pulse, therefore, in block 4, a two-wave rectifier 11 is inserted.

Operation of the device with a half-wave pulse voltage generator is illustrated by signal plots in FIG. 3. The impulses of the duty voltage on the secondary winding of the transformer 3 voltage have a pointed shape with a steep leading front and a close leading edge, and their amplitude practically does not depend on the duration. Decreasing the load resistance of the welding circuit decreases the length of the trailing edge of the pulse. The control parameter is the pulse duration measured at a predetermined level, for example, 30-70% of the amplitude value (1/3 of Fig. 3). These pulses are compared at the input of the voltage comparator 12 with the voltage of the block 13 of the reference voltage winding of the welding transformer 2, and there are pulses of the duty voltage. The pulses follow with a high porosity (the period following at industrial

wives When, the voltage of the 5 frequency is 10 ms, and the duration of the output of the comparator 12 of the pulse voltage at the level of 50% of the amplitude reduces the value of the logical 0, removing

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logical value

a reset signal from the second pulse counter 14, which begins to fill with pulses from the generator 5 counting pulses. When the number NU in the counter 14 reaches the number recorded in the second matching circuit 15, an i / i5 pulse is generated at its output, resetting the first counter 6 to zero. Ohm, the duration of the duty voltage pulse is reduced so much that the second pulse counter 14 is reset to zero before the number L reaches

depending on the load resistance, 0.05-0.4 ms in the prototype of the device). The signal at the input of the comparator .12 is a logical one. Which keeps the second counter 14 pulses in the reset state for most of the period while there are no pulses or the voltage on the secondary side of the voltage transformer L / C is less than the threshold value.

A small part of the period when (i.e., at the specified 0.05-0.4 ms) the output signal of the comparator 12 takes the value of logical 0, allowing the operation of the counter of 14 pulses. If the welding circuit of the jVis razor size, the C / 15 pulse does not form - 20, then the duty voltage of the duty voltage is relatively long (0.4 ms), the pulse counter 14 has time to count to the number L is (for which 0.27 ms is required) and the starting one no signal is generated. This causes the L / T trigger signal. The 25 pulses at the output of the first coincidence circuit and the first counter 6 will continue counting until the number A in it reaches the number NT recorded in the first coincidence circuit 7, which

The time t in FIG. 3 corresponds to the beginning of the last, before the welding circuit closes, the duty voltage pulse, and the torque / 2 to the formation of the last reset pulse; / h - endings are absent. The current in the primary circuit of the current transformer 18 is zero, at the outputs of the comparator 19 current and OR elements 21 - logical 0. The number in the counter 24 pulses is NUMBER,

the latter, before the welding circuit 30, recorded in the circuit 25, coincides, at the output circuit, of the impulse of the duty voltage. At time / 4, the welding circuit closes, moments / 5 and tf correspond to the beginning and end of the narrowed impulse of the duty voltage, and time t7 to the formation of the start signal.

The t / 3 pulses will be of opposite polarities, and the U pulses at the output of the full-wave rectifier 11 will be unipolar, following with a double network frequency. The NT number recorded in the first matching circuit 7 may in this case be twice as low, which doubles the device’s speed.

As an example in FIG. 4 is a block diagram of the idle limiter.

dah elements are NOT 23 and AND 22 is a logical 0, unlocking pulses to the thyristors of the power switch 16 is not applied. When the welding circuit is closed for a resistance of less than 300 ohms, the pulse duration decreases (less than 0.27 ms) and the second counter 14 is reset to zero, not having time to count to number A, 5, which allows the formation of a start signal (all numerical data to the prototype). At the output of the first coincidence circuit 7, a trigger signal appears in the form of a pulse, which, through the OR element 21, resets the counter 25 impchls to. In this case, a logic signal 0 appears at the outputs of the matching circuit 25,

40

welding transformer with use-45 output element HE 23 - logical

he proposed device. In addition to the start-and-output element And 22 - counting

device (elements 1-15), limiting impulses filling counter 24. The logger contains a power switching 1 at the output of the element HE 23, a trace element 16 with a generator 17 unlocking the operation of the generator 17 unlocking impulses, a current transformer 18, on-pulses and power thyristors the switch in series with the element 16 of the slide element 16 is opened, connecting

primary circuit welding welding trans-welding transformer 2 to the network. Generator 2, current comparator 19, reference voltage source 20, logic elements OR 21, AND 22, NOT 23, pulse counter 24 and coincidence circuit 25.

The rator 1 of the duty voltage pulses is switched off in this case, since the circuit of the series-connected capacitor 8 and the switching element 9 is closed

- - - - ,, СJTJ - --- -.-. -. .-.

The idle stop is operated by a short-circuit commutating element as follows.

When an open circuit power switching element 16 is open and on the secondary 16.

During welding, the instantaneous value of the voltage on the secondary winding of the transformed winding of the welding transformer 2 contains impulses of duty voltage. The pulses follow with a high porosity (the period following at industrial

 frequency is 10 ms, and the pulse duration is 50% of the amplitude

depending on the load resistance, 0.05-0.4 ms in the prototype of the device). The signal at the input of the comparator .12 is a logical one. Which keeps the second counter 14 pulses in the reset state for most of the period while there are no pulses or the voltage on the secondary side of the voltage transformer L / C is less than the threshold value.

A small part of the period when (i.e., at the specified 0.05-0.4 ms) the output signal of the comparator 12 takes the value of logical 0, allowing the operation of the counter of 14 pulses. If the welding circuit razor pulses at the output of the first circuit, there are no matches. The current in the primary circuit of the current transformer 18 is zero, at the outputs of the comparator 19 current and OR elements 21 - logical 0. The number in the counter 24 pulses is NUMBER,

written in the circuit 25, the outputs of the elements NOT 23 and 22 are logical 0, and the enabling pulses to the thyristors of the power switch 16 are not supplied. When the welding circuit is shorted to resistance less than 300 ohms, the pulse duration decreases (less than 0.27 ms) and the second counter 14 is reset to zero, before it reaches the number A, 5, which allows the formation of a start signal (all numerical data refer to prototype). At the output of the first coincidence circuit 7, a trigger signal appears in the form of a pulse, which, through the OR element 21, resets the counter 25 impchls to. In this case, a logic signal 0 appears at the outputs of the matching circuit 25,

The rator 1 of the duty voltage pulses is switched off in this case, since the circuit of the series-connected capacitor 8 and the switching element 9 is closed

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short-circuited power element 16.

During welding, the instantaneous value of the voltage on the secondary winding of the current transformer 18 (load resistor in the diagram is not shown) each period exceeds the reference voltage of source 20 and at the outputs of the current comparator 19 and logic element OR 21 a Logic 1 signal appears, resetting the pulse counter 24 to zero. The number in the counter 24 does not have time to reach the value recorded in the circuit 25, and the output of the logical element NOT 23 shows an improvement in the ignition of the arc and an increase in the productivity of the welder. The device does not require connection to the welding circuit, since it is connected between the power supply clamps and the power cable of the welding transformer and can be installed in the power distribution cabinet at the point where the latter is connected. This improves the reliability of his work. Reliability and performance of the open switching element 16 in the open state.

Logic 1 allows the operation of the technology to increase also due to the 17 pulse npirator supporting the digital integrated circuit and logic circuit with low power consumption and heat generation. The change in environmental conditions has almost no effect. When the welding circuit is opened, the current Yayat on the technical characteristics the device — the primary winding of the current transformer 18 is reduced to the value of the no-load current of welding transformer 2; the voltage on the secondary winding of the current transformer becomes less the reference voltage of the source 20, the output of the computational measuring range, current rator 19 and logic element OR 21 is set to logical 0. Counter 24 is filled to the number recorded in the matching circuit 25, after which

reliability and reliability due to the digital presentation of information. The device is completely built on serial elements and does not require the use of a special current transformer with an extension. Moreover, the proposed device is universal and can be used with any type of welding transformer.

at the output of the logic elements HE 23 and 22, all that is necessary to do this is to set the logical 0 to zero. The generator 17 of the triggering pulses is turned off, and the power switching element 16 is opened, the idle limiter goes into standby mode

the amplitude of the duty voltage pulse and the threshold of the current comparator (depending on the no-load current of this type of welding transformer), as well as the sensitivity in the mode compared to the prototype using the circuit of the welding circuit for a calibrated resistance.

Claims (3)

Claims 1. Triggering device limiting the duration of the pulse of the duty voltage as a controlled parameter allows to ensure high sensitivity of the proposed triggering device, ensuring its reliable switching when the resistance of the welding circuit is 300 ohm -jg of the stroke of the welding transformer, and less, and the prohibition of switching on when the co-generator of the impulses is on duty above 500 ohms. The sensing voltage associated with the primary winding of the device, along with the significant Koy welding transformer, and the measured pulse amplitude of the duty voltage transformer transformer, the generator On the secondary winding of the welding pulses, it turns on the connecting transformer in series, improves the stabilized capacitor and the switching element of the arc ignition. High sensitivity with control circuit, different In order to increase sensitivity, speed and reliability, it is equipped with an immobilizer control unit that is easily controlled by changing the pulse voltage, the number generator recorded in the coincidence pulse matching circuit, the first pulse counter and the first matching circuit, the first input the control unit of the pulse voltage of the duty voltage is connected with the secondary winding of the measuring voltage, in particular, from voltage fluctuations of the transformer PI-50, made in the form of a transient network. Ator voltage primary winding Thus, the proposed device, which is connected in parallel to the primary, has an increased speed of the welding transformer winding, the second, since the maximum lag in the input of the unit is connected to the counting generator of the start signal with respect to the pulse output, the closing of the welding circuit is not pre-55 of the first pulse counter, the incremental pulse of the pulse period is de-energized, which is connected to the generator of the numerical surge voltage of 20 or pulses, and output - with the first 10 ms input. The performance of a matching circuit device whose output is connected The device also contributes to increased electrical safety, for example, when changing electrodes. Sensitivity setting (roughly), and the magnitude of the reference voltage at the input of the voltage comparator (smoothly). The sensitivity of the device is almost independent of the amplitude of the pulses and, It helps to improve the ignition of the arc and increase the productivity of the welder. The device does not require connection to the welding circuit, since it is connected between the power supply clamps and the power cable of the welding transformer and can be installed in the power distribution cabinet at the connection point of the latter. This improves the reliability of his work. The reliability and speed of the device is also enhanced by the use of integrated digital digital and logic chips with low power consumption and heat dissipation. Changes in environmental conditions have almost no effect on the technical characteristics of the device's measuring range. reliability and reliability due to the digital presentation of information. The device is completely built on serial elements and does not require the use of a special current transformer with an extension to the technical characteristics of the measuring device, In addition, the proposed device is universal and can be used with a welding transformer of any type. To do this, you only need to set the required amplitude of the duty voltage pulse and the threshold of the current comparator (depending on the no-load current of this type of welding transformer), as well as the sensitivity in the circuit of the welding circuit to a calibrated resistance. Claims 1. Triggering device of a short stroke of a welding transformer, holding a pulse generator on duty with starting input limiter idle. 2. The device according to claim 2, characterized in that the control unit for the pulse voltage of the duty voltage comprises a comparator, a second pulse counter, a second coincidence circuit and a source of reference voltage, the first input of the block being connected to the first input of the comparator, the second input of which is connected to the source of the reference voltage, the output of the comparator is connected to the reset input of the second pulse counter, the counting input of which is connected to the second input of the unit, and the output through the second matching circuit is with the output of the block. 3. The device according to claim 1, characterized in that the capacitor and the switching element of the pulse voltage generator are connected in series with the primary winding of the welding transformer, and the switch is made in the form of two anti-parallel connected thyristors with a phase control unit, and the duration control unit duty voltage pulse contains a full-wave rectifier connected between the first input of the unit and the first input of the comparator. Network Xaroia FIG. 7 FIG. one figs 7 Fy