JPS6240111B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a power transistor connected in series between a rectifier circuit and an arc load, not as a switch element, but as a variable resistance (analog) element. The present invention relates to a welding transistor DC power source that controls voltage and welding current.

[Prior art and problems to be solved by the invention] Normally, the output of a rectifier circuit of a DC output circuit is controlled by a transistor circuit composed of one or more transistors (hereinafter simply referred to as transistors). Accordingly, transistor-controlled DC power supplies that obtain a predetermined output voltage are increasingly being used. However, while these DC power supplies have the feature of being able to perform highly accurate control over a high frequency range, the voltage difference between the output voltage of the rectifier circuit and the arc voltage becomes the burden voltage of the transistors that make up the transistor circuit, so the arc When the voltage is set to a low voltage, the burden voltage of the transistor increases. For example, a normal arc welding machine requires a variable range of output voltage from 10V to 50V, but if you want to obtain this from a conventional DC output circuit with a fixed output voltage, you will need a transistor circuit. Considering the saturation voltage drop (that is, the voltage drop of the transistor in a saturated state when the transistor is completely conductive) and the ripple contained in the output of the rectifier circuit, use an output voltage of about 55V to 60V as a DC output circuit. It is necessary to use it. However, when obtaining an arc voltage of 50V using such a DC output circuit, the transistor only has to bear a voltage of about 5V to 10V, but when trying to obtain an arc voltage of 15V, the voltage is 40V to 45V.
It becomes necessary to bear the same voltage. Therefore,
For example, if the output current is 500A, more than 20KW of power loss will occur inside the transistor.
As a result, fairly large capacity transistors are required. Furthermore, an increase in power loss within the transistor causes a decrease in efficiency, and also causes various problems such as the need to use a large cooling mechanism.

[Means for Solving the Problems] A first embodiment of the present invention sets the output voltage of a DC output circuit that can variably adjust the output voltage to a voltage that slightly exceeds the arc voltage determined depending on the workpiece. Manually set this output voltage to a feedback controlled transistor circuit to generate the reference signal Er.
It is an object of the present invention to provide a transistor DC power source for welding which solves the above problems by lowering the arc voltage to an appropriate arc voltage set by the method.

Further, in the second embodiment of the present invention, the output voltage of a DC output circuit that can variably adjust the output voltage is automatically adjusted to a voltage slightly exceeding the appropriate arc voltage in conjunction with the setting of the reference signal Er corresponding to the appropriate arc voltage. The reference signal Er
It is an object of the present invention to provide a transistor DC power source for welding which is capable of lowering the arc voltage to an appropriate arc voltage set by.

In the present invention described above, the reason why the transistor circuit is controlled by feedback of the output voltage is as follows. The variable DC output circuit used in the present invention can set the output voltage in advance before the welding arc occurs, but it is possible to set the output voltage in advance before the welding arc occurs. , the output voltage changes. Therefore, first, the output voltage of the variable DC output circuit is preset to a voltage that slightly exceeds the arc voltage depending on the object to be welded. Next, a difference signal (Er - Ev) between the reference signal Er corresponding to the appropriate arc voltage and the feedback signal Ev corresponding to the arc voltage Ea that is about to change due to fluctuations in the output voltage of the variable DC output circuit is supplied to the transistor circuit. do. The transistor circuit uses this difference signal as input to control the voltage drop in the transistor circuit, and uses the arc voltage as a reference signal.
It is controlled to a constant value determined by Er.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 1 is a welding electrode, 2 is a workpiece, and 3 is a control signal Es (to be described later) that is input to change the collector-emitter resistance of a transistor. This is a transistor circuit that adjusts the voltage supplied between the devices 2 and 2. 4 is an arc voltage feedback circuit that inputs the arc voltage Ea and outputs a signal Ev corresponding to the arc voltage (for example, a signal proportional to the arc voltage); 5 is an arc voltage feedback circuit that outputs a signal Ev corresponding to the arc voltage (for example, a signal proportional to the arc voltage); This is a comparison circuit for a transistor circuit which inputs a reference signal Er of a reference signal generation circuit 20 for setting an arc voltage in advance in accordance with the above, and outputs a control signal Es consisting of a difference signal of Er-Ev to a transistor circuit 3. Note that the variable DC output circuit 10 includes a sliding transformer 11 and a rectifier 12.

In the above device, as shown in FIG. 5a, when the arc voltage is used at a relatively high value Ea, the output voltage of the variable DC output circuit 10 is set to a voltage Eo slightly exceeding the arc voltage Ea, for example. , the sliding tap of the sliding transformer 11 is set manually or by motor operation. During arc generation, the arc voltage feedback circuit 4 inputs the arc voltage Ea and outputs a signal Ev corresponding to the arc voltage (for example, a voltage proportional to the arc voltage). The transistor circuit comparison circuit 5 compares the output signal Ev of the feedback circuit 4 with a reference signal Er for setting an appropriate arc voltage.
A control signal Es consisting of a difference signal between Er and Ev is output to the transistor circuit 3. The transistor circuit 3 is
It is controlled by this control signal Es, inputs the output voltage Eo of the variable DC output circuit 10, and outputs an appropriate arc voltage Ea. The voltage drop Et across the controlled transistor in this case is Eo−Ea.

Next, as shown in Figure 5b, when using the arc voltage at a relatively low value Ea', the output voltage of the variable DC output circuit is also lowered to reduce the arc voltage at this time.
Set the voltage Eo' to slightly exceed Ea'. In this case, the voltage drop Et′ inside the transistor is Eo′−Ea′, and it can be set to a low value close to the voltage drop Et inside the transistor when the arc voltage is set high, so the arc voltage is set to a low value. Even in this case, the loss of the transistor does not increase.

To give an example here, when welding is performed with arc voltage Ea of 50V, Eo is set to, for example, 60V with a predetermined load current flowing. In this case, the voltage drop Et in the transistor circuit 3 is 10V. Next, the arc voltage is Ea′ = 15V
When welding at a lower Eo′, for example,
Set to 20V. In this case, transistor circuit 3
The voltage drop Et' at is 5V. In the conventional circuit,
Even when the arc voltage is set to Ea′ = 15V, Eo′ is
Since the voltage was 60V, the voltage drop in the transistor circuit becomes 45V, increasing the loss, but in the present invention,
As described above, this voltage drop can be reduced to about 5V, so losses can be significantly reduced.

Note that the output voltage Eo of the variable DC output circuit 10
is the voltage p corresponding to the peak value of the arc voltage Ea
and the signal Etmi corresponding to the saturation voltage of the transistor of transistor circuit 3, Eo≧Ep+
It is best to set it as small as possible within the range that satisfies the Etmin conditions. In this case, since it is troublesome to reset the voltage Eo for various arc voltages, Eo may be set to a larger value within a certain range without increasing the loss of the transistor.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which the same components as in FIG. 1 are given the same reference numerals. In the figure, 6 is a current detection circuit, 7 is a current feedback circuit, and by adjusting the output signal Ei and the output signal Ev of the voltage feedback circuit 4, the output voltage and output current of the transistor circuit 3 are adjusted. It is now possible to change relationships, ie external characteristics. 13 is a transformer with a tap; 14 is a switch such as an electromagnetic contactor or thyristor connected to each tap of the transformer 13; 15 is a switch switching control circuit; and the switch switching control circuit 15 is a reference signal for setting arc voltage.
A switch 14 connected to a tap that causes the variable DC output circuit 10 to output a voltage slightly higher than the arc voltage in response to Er is closed.

In this embodiment, if the reference voltage Er is selected to provide an appropriate arc voltage depending on the object to be welded, the output voltage of the variable DC output circuit 10 can be adjusted to prevent the loss in the transistor from increasing. Set.

FIG. 3 is a block diagram showing a third embodiment of the present invention, in which the same components as in FIG. 2 are given the same reference numerals. In the figure, 20 is a reference signal generation circuit that outputs a reference signal Er for setting the pulsed arc voltage, 8 is a peak value detection circuit that detects the peak value Ep of the reference signal Er corresponding to the peak value of the pulsed arc voltage, and 9 and 9' is a comparison circuit for the variable DC output circuit, and this comparison circuit 9 receives the sum of the peak signal Ep detected by the peak value detection circuit 8 and the signal Etmin corresponding to at least the saturation voltage of the transistor. Furthermore, the output signal of the comparison circuit 9 and a signal corresponding to the output voltage Eo of the variable DC output circuit 10 are input to the comparison circuit 9'. 16
is a normal welding transformer, 17 is a thyristor constituting a controllable semiconductor rectifier circuit, and 18 is a variable DC output circuit 10 whose output voltage Eo is adjusted by inputting the output signal of the variable DC output circuit comparison circuit 9'. Eo
This is a phase control circuit that controls the thyristor 17 to a value that satisfies ≧Ep+Etmin. Reference numeral 21 denotes a transistor saturation voltage signal generation circuit that generates a saturation voltage signal Etmin corresponding to the saturation voltage of the transistors constituting the transistor circuit.

Next, using the apparatus shown in FIG. 3, for example, as shown in FIG. 6, a pulse arc voltage of a first peak value Eb is applied for a time t1, and then reduced to a second peak value Eb'. The operation when the pulsed arc voltage is applied for a time t2 or when these are applied repeatedly will be explained. When the reference signal generation circuit 20 for arc voltage setting generates a pulse signal corresponding to the pulsed arc voltage of the peak value Eb, the peak value detection circuit 8 generates the peak signal Ep of the reference signal Er.
Detect. This peak signal Ep, a signal voltage Etmin corresponding to the transistor saturation voltage, and a signal corresponding to the output voltage Eo of the variable DC output circuit 10 are passed through the comparator circuits 9 and 9' to a difference signal (Ep+
Etmin−Eo), and this difference signal is input to the thyristor phase control circuit 18, which further controls the phase of the thyristor 17 to adjust its output voltage to approximately Eo (≧Ep
+Etmin). After time t1 has elapsed,
From the reference signal generation circuit 20 for arc voltage setting,
When a pulse signal corresponding to the pulse arc voltage of the peak value Eb' is generated, the peak value detection circuit 8 for the reference signal Er detects a signal Ep' corresponding to the peak value of the reference signal. The peak signal Ep', the signal Etmin corresponding to the transistor saturation voltage, and the signal corresponding to the output voltage Eo' of the variable DC output circuit 10 are input to the thyristor phase control circuit 18 via the comparison circuits 9 and 9', and further By controlling the phase of the thyristor 17, its output voltage is approximately Eo′ (≧Ep′+
Etmin).

FIG. 4 shows a fourth embodiment of the present invention, in which the same components as in FIG. 3 are given the same reference numerals. In the figure, 8' is a pulse arc voltage peak value detection circuit, and this detection circuit is used for the reference signal Er for setting the pulse arc voltage in Figure 3.
Instead, the peak value Eb or Eb' of the actual arc voltage Ea is detected. The operation of the embodiment shown in FIG. 4 is substantially the same as that shown in FIG. 3, so a description thereof will be omitted.

In the apparatus shown in FIGS. 3 and 4 which output a pulsed arc voltage having the waveform shown in FIG. 6, the frequency response of the first control loop including the arc voltage feedback circuit 4 and the comparison circuit 5 for transistor circuit The speed is the pulse arc voltage Eb or
Although it is necessary to increase the speed according to the frequency of Eb', the output voltage Eo of the variable DC output circuit 10 or
Since the frequency of Eo' is low, the frequency response speed of the second control loop including the peak value detection circuit 8 or 8' of the reference signal Er or arc voltage Ea and the variable DC output circuits 9 and 9' can be slowed down. . Therefore, the first control loop requires a transistor with a fast frequency response speed, whereas the second control loop requires a transistor with a fast frequency response speed.
The control loop may have a slow frequency response speed, so it is possible to control the phase of a thyristor with low loss,
The output voltage of a variable DC output circuit can be adjusted by switching the taps of a transformer using a thyristor or electromagnetic contactor, or by moving the sliding taps of a sliding transformer using a motor, electromagnet, etc. Therefore, the loss of the transistor can be reduced.

Further, as the variable DC output circuit 10 of the present invention,
A regular DC arc welder can be used. Furthermore, a resistor may be inserted between the output terminal of the variable DC output circuit 10 and the electrode 1 or the workpiece 2 to bear part of the voltage drop within the transistor circuit.

In each of the above embodiments, the transistor circuit 3
is illustrated in such a way that the collector-emitter resistance of one transistor is controlled by the base current, but this transistor circuit only needs to be a circuit that can adjust the output voltage according to the control signal Es.
Various variations can be considered. For example, if it is necessary to increase the current capacity, a plurality of transistors can be used in appropriate combination.

[Effects of the Invention] As described above, according to the present invention, the output voltage can be variably adjusted in a transistor DC power source for arc welding that uses a transistor as an analog control element that can obtain an output waveform with high accuracy up to a high frequency range. The output voltage of the variable DC output circuit is set to a voltage that slightly exceeds the arc voltage determined depending on the workpiece, and this output voltage is supplied to a transistor circuit that is feedback controlled to control the output voltage of the variable DC output circuit. Since the differential voltage between the output voltage and the arc voltage is set to a low value and then lowered to the appropriate arc voltage set by the reference signal Er, the loss inside the transistor circuit can be significantly reduced. In addition, it is possible to improve efficiency, downsize the cooling mechanism, and increase output. It also has the advantage of being able to reduce the input KVA for the same output.

In particular, according to the second embodiment, since the output of the variable DC output circuit can also be set in conjunction with the setting of the arc voltage, there is an advantage that the loss in the transistor circuit can be further reduced.

[Brief explanation of the drawing]

1 to 4 are connection diagrams showing the configurations of different embodiments of the present invention, FIGS. 5a and 5b are explanatory diagrams explaining the operation of the variable DC output circuit, and FIG. FIG. 4 is an explanatory diagram illustrating the operation of the fourth embodiment. DESCRIPTION OF SYMBOLS 1... Electrode, 2... Work to be welded, 3... Transistor circuit, 4... Arc voltage feedback circuit, 5... Comparison circuit for transistor circuit, 6...
Current detection circuit, 7... Current feedback circuit,
8, 8'... Peak value detection circuit, 9, 9'... Comparison circuit for variable DC output circuit, 10... Variable DC output circuit.

Claims (1)

[Claims] 1. A variable DC output circuit that outputs a voltage that slightly exceeds the arc voltage set depending on the object to be welded, and a variable DC output circuit that adjusts the output of the variable DC output circuit according to a control signal, and the adjusted output is applied to the electrode and the object to be welded. an arc voltage feedback circuit that inputs the arc voltage and outputs a signal Ev corresponding to the arc voltage, and a reference signal that outputs a reference signal Er corresponding to the arc voltage depending on the workpiece to be welded. a generating circuit, and a comparison circuit that receives as input the signal Ev output from the arc voltage feedback circuit and the reference signal Er, obtains a difference signal (Er−Ev), and supplies the difference signal to the transistor circuit as a control signal Es. A transistor DC power supply for welding, characterized by comprising: