JPH0347741Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to an engine-driven plasma cutting power supply device that is portable and can be used outdoors where commercial power supply facilities are not available.

"Prior Art" In general, field work, such as the construction of buildings, highways, and bridges, requires not only welding work but also cutting work. Conventionally, outdoor cutting operations have relied on gas cutting using acetylene gas, cutting using arc gouging using an engine generator, and furthermore, mechanical cutting. In conventional outdoor cutting operations of this kind, the cut surface is rough and uneven, and it is necessary to finish the cut surface again using a grinder or the like. For this reason, conventionally,
During field work, only thick plates and thick-walled pipes were cut on-site. Other thin plates and thin-walled pipes are currently manufactured at factories equipped with power supply equipment.

However, in recent years, automation and labor saving have been attempted even in outdoor work, and with this, transformer-type air plasma cutting, which uses commercial power, has been adopted, which allows for clean cut surfaces and high-precision machining. The machine was brought to the work site, and the transformer-type air plasma cutting machine was operated using an engine-driven generator as a power source. However, such usage has caused the following problems. In other words, the power required for air plasma cutting needs to be within the shaded area _T2 shown in Figure 2 depending on the cutting conditions, and if you set the load current according to the cutting conditions, you can always use the set current. While maintaining the so-called constant current characteristic, it is necessary as a no-load voltage to generate a plasma arc.
Must be set to 180 volts or higher. Therefore, as shown by the characteristic curve _T1 in Fig. 2, after transforming the commercial power supply with constant voltage characteristics to the voltage A volt necessary for generating a plasma arc, at the point 51 on the characteristic curve _T1 and the set value, The engine-driven generator used as _a power source for a transformer-type plasma cutter uses a It is necessary to use a device whose external characteristics exhibit constant voltage characteristics in accordance with the operating characteristics of various devices including transformers, and for this reason, point 5 shown in FIG.
As a result of using a device that requires extra apparent power by the amount enclosed by 3, 51, 58, and 53, and outputs a higher voltage by the amount of transformer that transforms the commercial power supply,
A device with a capacity approximately twice as large as the operating power required for plasma cutting must be used, resulting in considerable waste of power supplied to the plasma cutting machine, and furthermore, a large engine-driven generator must be used. As a result, the price was high, and maintenance costs such as fuel were also extremely expensive.

``Problem to be solved by the invention'' The object of the invention is to provide an engine-driven plasma cutting power supply device that does not require extra apparent power, is small and lightweight, and has excellent portability for outdoor work. With the goal.

``Means to be solved by the invention'' In order to achieve the above object, the invention aims to determine the external characteristics of the output voltage versus output current of a DC power source that is the rectified output of an AC electric machine driven by an engine, which is necessary for plasma cutting. A power generation device exhibiting drooping characteristics connecting the cutting operating voltage that slightly exceeds the voltage value corresponding to the variable maximum current value of the plasma cutting current-voltage operating characteristics and the no-load voltage required for plasma cutting. a generator output circuit, an external output terminal is connected to the generator output circuit through a capacitor, a constant current control device, and a reactor, and a load current detector is connected to the constant current control device. The present invention is characterized by an engine-driven plasma cutting power supply device.

"Example" Below, an example of the engine-driven plasma cutting power supply device according to the present invention will be described based on the drawings. In FIG. 1, 11 is an engine, and 12 is an alternator driven by the engine. The generator 12 is one that rotates at high speed and outputs high frequency waves, thereby reducing the size and weight of the generator itself. Field winding of the generator 12
Fg is connected to a power source 28 via a flywheel diode D. A capacitor C ₁ is connected to the generator 12 via a rectifier 13 .
The circuit from the generator 12 to the rectifier 13 is the generator output circuit. The capacitor _C1 not only functions to smooth the output of the rectifier 13, but also to store power for supplying power to the torch, and also absorbs the fluctuating current caused by the operation of the switching transistor TR, which will be described later. This prevents the leakage from returning to the power supply side of the rectifier 13 or the like. Also, since the output of the generator is high frequency, capacitor _C1 is
It is possible to use a device with a smaller capacity than that of a commercial frequency device, and therefore a small device can be used. The + terminal of capacitor _C1 is connected to switching transistor TR. switching transistor
TR is connected to an external output terminal 16 via a load current detector 14 and a DC reactor 15. The load current detector 14 is connected to the base of the switching transistor TR via a constant current control circuit 30. The constant current control circuit 30 has a current setting device 31. The switching transistor TR, the constant current control circuit 30, and the current setter 31 form the constant current control device. The switching transistor TR is also connected to the pilot terminal 17 via a resistor _R1 . A reed switch that closes when a load current flows through the DC reactor 15.
SW ₄ is attached, and the reed switch SW ₄ is connected to the power supply 26.
and is inserted into the series circuit of relay Ry. The generator 12 is connected to the primary winding of the high frequency transformer _T1 via a contact ms which is closed in conjunction with a torch switch operated by an operator and a contact ry of a relay Ry. The primary winding of the high frequency coupling coil 18 is connected to the secondary winding of the high frequency transformer T ₁ through a spark discharge circuit including a capacitor C ₂ and a spark discharge gap 25 . The secondary winding of the high frequency coupling coil 18 is a capacitor.
It is inserted between one terminal of _C1 and the other external output terminal 19. The base material 23 to be cut is connected to the external output terminal 16, and the electrode 21 of the torch 20 is connected to the external output terminal 19. The pilot terminal 17 is also connected to the tip 22 of the torch 20. Air can be injected from the chip 22 for cooling and focusing the plasma.

As a condition for arc generation in the above plasma cutting, a no-load voltage of 180 volts or more is required.
Further, as a result of experiments, it has been found that ideal operating conditions for plasma cutting are suitable for characteristics near B volts, as shown by the power region _T2 in FIG. Regarding air plasma cutting, as a result of various experiments, the operating characteristics of air plasma cutting draw curves 56 and 57 peculiar to air plasma cutting as shown in FIG. 2, and when the no-load voltage is set to 180 volts or more,
The best cutting results were obtained under all cutting conditions. Therefore, the no-load voltage of the generator 12 is set to 180 volts or higher, which is necessary for air plasma cutting, and the operating voltage is set to a value equal to or slightly higher than the maximum voltage in the power range required for plasma cutting. It is best to set it to the operating voltage. This changes the external characteristics to these no-load voltages 5
3 and the operating voltage to exhibit a drooping characteristic curve _T3 . Further, a constant current control device performs control in order to provide a constant current characteristic that drops from point 58 to point 52 on this drooping characteristic curve _T3 shown in FIG.

Next, this control operation will be explained based on the circuit shown in FIG. First, start the engine 11 and set it to the rated speed, then connect the external output terminal 1.
The above-mentioned no-load voltage occurs between 6 and 19. Then, when the operator operates the torch switch, the contact ms is closed. At this time, since no load current is flowing through the DC reactor 15, the contact ry is in a closed state. As a result, from the generator 12, after passing through the rectifier 13 and the smoothing capacitor _C1 , the power is connected between the external output terminal 19 and the pilot terminal 17 via the switching transistor TR and the resistor _R1 .
That is, at the same time power is supplied between the electrode 21 and the chip 22 of the torch 20, the power is supplied to the generator 12.
From there, high frequency power is applied via the contacts ms and ry, the high frequency transformer T ₁ , the spark discharge circuit and the high frequency coupling coil 18, thereby generating a pilot arc between the electrode 21 and the chip 22,
This triggers a main plasma arc between the electrode 21 and the base material 23. Electrode 21 and base material 2
3, a load current flows through the DC reactor 15, so the reed switch _SW4 closes due to the electromagnetic force of the DC reactor 15, which opens the contact ry and disconnects the high frequency cup from the generator 12. Supply of high frequency power to the ring coil 18 is stopped. Hereinafter, the constant current control circuit 30
is the switching transistor TR so that the value of the load current detected by the load current detector 14, that is, the value of the current supplied between the electrode 21 and the base material 23, becomes a preset value. control the behavior of Therefore, the load current flows between the electrode 21 and the base material 23.
Even if the distance between the generator 12 and the engine 11 fluctuates, it is always kept at a constant value, and even if the rotational speed of the engine 11 is irregular and the output voltage of the generator 12 fluctuates, it can be kept at a constant value. In particular, the generator 12 driven by the engine 11 is prone to this type of output voltage fluctuation, but even with such output voltage fluctuations, the load current can be maintained at a constant value. A beautiful cut surface can be obtained. When it becomes necessary to change the load current depending on cutting conditions, the current setting device 31 can be used to freely set the load current. When the load current is changed using the current setting device 31, as shown in _FIG .
It exhibits the characteristic of falling directly below the set value according to 1,
For example, out of the range that can be set from 10 amperes to 50 amperes using the current setting device 31, from 50 amperes to 10 amperes.
When the setting is changed to ampere, an external characteristic passing through points 53-60-59 corresponding to the current to be cut is obtained.

FIG. 3 shows another embodiment in which when the constant current value is changed by the current setting device 31, a droop characteristic corresponding to the set current to be cut is obtained. It is equipped with a temperature setting device. The droop degree setting device changes the number of parallel circuits for each phase of the armature winding. That is, in each phase, the armature winding is divided into three bare windings 35a to 35c, and the same voltage and the same current are induced in each of the bare windings 35a to 35c. Plain winding wires 35a to 35c
are connected in parallel with each other, and open/close switches Sw ₁ and Sw ₂ are interposed between two of the bare windings 35b and 35c. And each open/close switch
If Sw ₁ and Sw ₂ are sequentially opened and closed, the unwound wires 35a~
Since the values of the induced voltages 35c are the same, only the current capacity of the output of the generator 12 increases or decreases. As a result, in the characteristic diagram shown in Fig. 4, the on/off switch
With the no-load voltage maintained at approximately the same value by Sw ₁ and Sw ₂ , the droop characteristic curve T 3 is calculated from the droop characteristic curve T ₃ .
The degree of droop is increased to 3 so that the droop characteristic curve _T5 is reached through _T4 .
Adjust in stages. Therefore, when changing the setting from a ampere to b ampere using the current setting device 31, the open/close switch Sw ₂ is opened and the bare winding 3
If 5c is separated from the other bare windings 35a and 35b,
The degree of droop in the output characteristics of the generator decreases, and the operating current b
A drooping characteristic curve T ₄ passes through 61 points slightly higher than the operating voltage corresponding to the ampere. Thereby, it is possible to obtain generator power supply characteristics commensurate with the cutting operation voltage vs. current characteristics to be cut. Furthermore, the operating current a
When changing the setting from ampere to c ampere,
Open the on/off switches Sw ₁ and Sw ₂ to allow the drooping characteristic of the generator output to drop to T ₅ .

"Effects of the Invention" As described above, the engine-driven plasma cutting power supply device according to the present invention is designed to obtain a drooping characteristic of the generator output that matches the working conditions of plasma cutting, and is suitable for use as a generator. , it is sufficient to supply the minimum operating power required for plasma cutting, and as a result, as the generator capacity is reduced, the engine capacity can also be significantly reduced, making it possible to achieve a reduction in size and weight. Also, since the no-load voltage is increased and the generator output is controlled by the constant current control device,
Double arcs do not occur even if the distance between the torch and the base material changes during cutting, allowing highly accurate plasma cutting.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of an engine-driven plasma cutting power supply device according to the present invention, and FIG.
The figure is a characteristic diagram showing the droop characteristics of the generator and the operating characteristics of plasma cutting, and FIG. 3 shows another embodiment, and is a circuit diagram showing the main parts of the configuration of the droop degree setting device.
FIG. 4 is a characteristic diagram showing the characteristics of each degree of droop in the droop degree setter of FIG. 3 and the operating characteristics of plasma cutting. 11...engine, 12...alternator, 13
... Rectifier, 14... Load current detector, 15...
...DC reactor, 18...High frequency coupling coil, 20...Torch, 21...Electrode, 22...
Chip, 23... Base material, 26, 28... Power supply, 3
0... Constant current control circuit, 31... Current setting device,
T ₃ to T ₅ ...Drooping characteristic curve, 35a to 35c...
Armature winding bare winding, Sw ₁ , Sw ₂ ... switch,
TR...Switching transistor.

Claims (1)

[Scope of utility model registration request] The external characteristics of the output voltage vs. output current of a DC power supply that rectifies the output of an alternating current generator driven by an engine corresponds to the maximum variable current value of the plasma cutting current-voltage operating characteristics required for plasma cutting. It has a generator output circuit that exhibits a drooping characteristic that connects the cutting operating voltage that slightly exceeds the voltage value and the no-load voltage required for plasma cutting,
An engine-driven plasma characterized in that an external output terminal is connected to the generator output circuit via a capacitor, a constant current control device, and a reactor, and a load current detector is connected to the constant current control circuit. Power supply for cutting.