JP2014087220A - Power-supplying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power-supplying device that allows reducing the influence of increase in the power supply capacity of a low-frequency power supply due to an inductance used for preventing intrusion of high-frequency power having a high frequency into a circuit for a low frequency in a synthesis circuit by two frequencies.SOLUTION: A power-supplying device 1 includes a low-frequency power supply 2, a saturable reactor 3 connected to the low-frequency power supply 2, a high-frequency power supply 4 having a higher frequency than the low-frequency power supply, and a capacitor 5 connected to the high-frequency power supply 4. One end of the saturable reactor 3 is connected to one end of the low-frequency power supply 2, and the other end of the saturable reactor 3 is connected to one end of a load 7. One end of the capacitor 5 is connected to one end of the high-frequency power supply 4, and the other end of the capacitor 5 is connected to the other end of the load 7. Output power from the low-frequency power supply 2 and output power from the high-frequency power supply 4 are supplied to the load 7.

Description

  The present invention relates to a power supply device. More specifically, the present invention relates to a power supply apparatus that combines powers having two different frequencies and supplies the power to a load, for example, a power supply apparatus that supplies power to a load such as a resistance welder.

As an example of a power supply device, a spot welding device is used to weld stacked steel plates. FIG. 11 is a cross-sectional view schematically showing spot welding between the steel plates 50. As shown in FIG. 11, in spot welding between steel plates 50, the overlapping portion between the steel plates 50 is sandwiched between a pair of electrodes 52, and a predetermined force is applied to the electrodes 52 in the direction of the arrows to press the steel plates 50 together. .
Next, a large current of kA order is applied to the electrode 52 while maintaining the pressurized state, and the crimped portion between the steel plates 50 is instantaneously melted by Joule heat to form a molten lump called a nugget 54 having a predetermined diameter. (For example, refer nonpatent literature 1).

  Patent Document 1 discloses a metal material welding apparatus that forms a nugget on a work that is a metal material with power from a spot welding power source, and further heats the work with power from a high-frequency power source.

FIG. 12 is an equivalent circuit diagram for explaining a combined circuit using two frequencies of a low-frequency power source 62 and a high-frequency power source 64 in the welding apparatus 60 disclosed in Patent Document 1.
As shown in FIG. 12, the two-frequency synthesis circuit includes a low-frequency power source 62, a high-frequency power source 63, a coil 64, a capacitor 65, and a load 66 to which the low-frequency power source 62 and the high-frequency power source 64 are applied. It is configured. One end of the low frequency power supply 62 is connected to one end of the coil 64, and the other end of the coil 64 is connected to one end of the load 66. The other end of the low frequency power supply 62 is connected to the other end of the load 66. One end of the high frequency power supply 63 is connected to one end of the coil 64. The other end of the high frequency power supply 63 is connected to the other end of the load 66 through a capacitor 65. The coil 64 is also called a reactor.

  As shown in FIG. 12, the high-frequency current is expressed by the following equation (1).

Here, I ₀ is a high frequency current, I ₁ is the high-frequency current, I ₂ flowing within the low-frequency power source 62 side of the I ₀ is the high frequency current flowing through the inner load 66 of I _0. That is, the high frequency current I ₀ is the sum of I ₂ flowing to the load 66 side and I ₁ flowing to the low frequency power source 62 side. I ₁ is a meaningless current for the load 66 side and a harmful current for the low frequency power supply.

  As shown in FIG. 12, the low frequency current is expressed by the following equation (2).

Here, I ₃ is low frequency current, I ₄ is a low-frequency current flowing through the inner high frequency power source 63 side of the I _3, I ₅ is a low-frequency current flowing in the inner load 66 of I _3.

When synthesizing the low frequency power source 62 and the high frequency power source 63, generally, an inductance, that is, a coil 64 is inserted to synthesize both power sources of the low frequency power source 62 and the high frequency power source 63. The purpose of this inductance is to prevent high frequency current from the high frequency power supply 63 from flowing into the low frequency power supply 62. For example, when the frequency of the low frequency power supply is f _L , the inductance, that is, the impedance (X _L ) of the inductive reactance L is expressed by the following equation (3).

The difference in frequency between the low-frequency power source 62 and the high-frequency power source 63 with this impedance (X _L ) becomes the impedance difference, and this impedance changes linearly.

JP 2010-82665 A

Edited by the Japan Welding Society, “Welding and Joining Handbook”, Maruzen Co., Ltd., September 30, 1990, pp. 392-398

In the combined circuit of the low-frequency power source 62 and the high-frequency power source 63, the coil 64 is directly connected to the low-frequency power source 62, so that I ₃ that is a low-frequency current is also affected. In other words, prevent insertion into the low-frequency power source 62 of the high-frequency current by inserting a coil 64, to easily flow a low frequency current to the load 66 affects the I ₃ is the current from the low-frequency power source 62. As a result, it is necessary to increase the voltage of the low frequency power supply 62 by the inductance formed by the connected coil 64 to flow the same current, that is, to increase the power supply capacity of the low frequency power supply 62.

  In view of the above-mentioned problems, the present invention has the advantage that the power capacity of a low-frequency power source is increased by an inductance used to prevent high-frequency power having a high frequency from entering a low-frequency circuit in a two-frequency synthesis circuit. It is an object of the present invention to provide a power supply device that can reduce the influence.

  In order to achieve the above object, a power supply apparatus according to the present invention includes a low-frequency power source, a saturable reactor connected to the low-frequency power source, a high-frequency power source, and a capacitor connected to the high-frequency power source, and a saturable reactor. Is connected to one end of the low frequency power supply, the other end of the saturable reactor is connected to one end of the load, one end of the capacitor is connected to one end of the high frequency power supply, and the other end of the capacitor is connected to the other end of the load. The output power from the low frequency power supply and the output power from the high frequency power supply are supplied to the load.

In the above configuration, preferably, an electrode is provided between the power supply device and the load, and welding is performed by a low-frequency power source applied to the electrode.
The saturable reactor is preferably a saturable reactor with a control winding.
The power supply device preferably further includes another low-frequency power source or a high-frequency power source.

  According to the power supply device of the present invention, by connecting a saturable reactor in series with a low frequency power supply, compared to a conventional synthesis circuit of a low frequency power supply and a high frequency power supply using a coil, to a low frequency power supply. Can be reduced to almost zero.

It is a circuit diagram which shows the structure of the electric power supply apparatus which concerns on embodiment of this invention. It is a perspective view which shows the structure of a saturable reactor. It is a figure which shows the change of the inductance value with respect to the electric current value of the saturable reactor of FIG. It is a circuit diagram which shows the structure of the modification of the electric power supply apparatus by this invention. It is a perspective view which shows the structure of a saturable reactor with a control winding. It is a figure which shows the control current dependence of the impedance of the saturable reactor with a control winding. It is a time chart for demonstrating operation | movement of a bias current control part. It is a figure which shows typically the structure of the modification of the electric power supply apparatus which concerns on embodiment of this invention. It is an electrical circuit diagram of the welding apparatus shown in FIG. It is sectional drawing which shows typically the electric current distribution which arises in a steel plate when electric power is simultaneously applied to two superposed steel plates from a low frequency power supply and a high frequency power supply. It is sectional drawing which shows the spot welding of steel plates typically. In the welding apparatus disclosed by patent document 1, it is an equivalent circuit diagram explaining the synthetic | combination circuit by two frequencies of a low frequency power supply and a high frequency power supply.

Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 is a circuit diagram showing a configuration of a power supply device 1 according to the first embodiment.
In FIG. 1, the power supply device 1 includes a low frequency power source 2, a saturable reactor 3 connected in series to the low frequency power source 2, a high frequency power source 4, and a capacitor 5 connected to the high frequency power source 4. Configured. A load 7 is connected to the output terminal 6 of the power supply device 1. One end of the saturable reactor 3 is connected to one end of the low frequency power supply 2, and the other end of the saturable reactor 3 is connected to one end of the load 7. One end of the capacitor 5 is connected to one end of the high frequency power supply 4, and the other end of the capacitor 5 is connected to the other end of the load 7. The other end of the load 7 may be grounded.
Note that the frequencies of the low-frequency power source 2 and the high-frequency power source 4 are referred to as a first frequency (denoted as f _L ) and a second frequency (denoted as f _H ), respectively. The second frequency f _H is a frequency higher than the first frequency f _L.

  As the low-frequency power source 2, a commercial power source of 50 Hz or 60 Hz, an oscillator including a so-called inverter, or the like can be used. Similarly, an oscillator composed of an inverter can be used as the high frequency power source 4.

  FIG. 2 is a perspective view showing the configuration of the saturable reactor 3. As shown in FIG. 2, the saturable reactor 3 includes a magnetic core 3a and a winding 3b. The magnetic core 3a is made of a magnetic material, and a core made of an iron core or ferrite is used. As shown in FIG. 2, the saturable reactor 3 is composed of a winding 3b obtained by winding a copper wire with a predetermined number of insulation coatings around a magnetic core 3a made of, for example, ferrite. The inductance value of the saturable reactor 3 varies depending on the number of turns of the winding 3b.

  As a ferrite core used as the magnetic core 3a, a core material such as PE22T manufactured by TDK can be used. The core material has an inner diameter of 50 mm, an outer diameter of 80 mm, and a height of about 20 mm.

  FIG. 3 is a diagram illustrating a change in inductance value with respect to the current value of the saturable reactor 3 in FIG. 2. As shown in FIG. 3, the inductance value of the saturable reactor 3 is a large value in the low current region and a very small value in the large current value region. In other words, the saturable reactor 3 may be saturated by a large low-frequency current flowing through the saturable reactor 3 connected in series to the low-frequency power source 2 so that the inductance value is reduced. In this case, the voltage drop of the saturable reactor 3 due to the flow of the low frequency current is eliminated, that is, it becomes very small.

  For this reason, the voltage of the low frequency power supply 2 is almost applied to the load 7. As a result, the voltage of the low frequency power supply 2 does not need to be increased because the voltage drop caused by the inductance is eliminated when the conventional inductance is used without using the saturable reactor 3.

One end of the capacitor 5 is connected to the other end of the high frequency power supply 4, and the other end of the capacitor 5 is connected to the other end of the load 7. That is, the other end of the capacitor 5 is grounded and connected to a so-called ground. The capacitive reactance X _C by the capacitor 5 is given by the following equation (4).

The capacitive reactance X _C has a large value at a low frequency (f _L ). For this reason, current leakage from the low frequency power supply 2 to the high frequency power supply 4 is prevented by the large capacitive reactance X _C of the capacitor 5 at the low frequency (f _L ). That is, the capacitor 5 serves as a low frequency current blocking capacitor.

Of the impedance when the low-frequency power source 2 is viewed from the high-frequency power source 4, the capacitive reactance X _C (X _C = 1 / (2πf _H C) of high frequency (f _H ), where f _H is the high-frequency power source 4 Is a small value at high frequencies.

On the other hand, in the high frequency, the inductive reactance X _L due to the inductance (L) of the saturable reactor 3 is given by the following equation (5).

Here, f _H is the frequency of the high frequency power supply 4.
X _L given by the equation (5) is a large value at the frequency (f _H ) of the high-frequency power source 4. Therefore, current leakage to the low-frequency power source 2 of high-frequency power source 4 is blocked by the large inductive reactance X _L of the saturable reactor 3 at high frequencies (f _H). That is, the saturable reactor 3 serves as a high-frequency current blocking inductance.

  In the power supply device 1, the capacitor 5 acts as a current blocking capacitor from the low frequency power supply 2 to the high frequency power supply 4, and the saturable reactor 3 is a current blocking inductance from the high frequency power supply 4 to the low frequency power supply 2, that is, a choke coil. The action of.

  Since the saturable reactor 3 is used in the power supply device 1 in FIG. 1, the impedance changes linearly in the unsaturated portion as shown in FIG. 2, but the impedance becomes almost zero in the saturated region. For this reason, the saturable reactor 3 saturated with a low-frequency large current can substantially eliminate an inductance voltage drop due to the low-frequency current, and an increase in the power supply capacity of the low-frequency power source 2 can be eliminated. That is, in the power supply device 1, the current from the low-frequency power source is changed by changing the high-frequency inflow inductance (coil) used in the conventional synthesis circuit of the low-frequency power source and the high-frequency power source to the saturable reactor 3. The impact on can be reduced. Thereby, the influence of the saturable reactor 3 on the low frequency power supply can be reduced to almost zero.

(Modification of power supply device)
4 is a circuit diagram showing a configuration of a modified example of the power supply device 20, FIG. 5 is a perspective view showing a configuration of a saturable reactor 23 with a control winding, and FIG. 6 shows a configuration with a control winding. It is a figure which shows the control current dependence of the impedance of the saturation reactor.
The power supply device 20 shown in FIG. 4 is different from the power supply device 1 in FIG. 1 in that the saturable reactor 3 connected to the low-frequency power source 2 is replaced with a saturable reactor 23 with a control winding, The bias current control unit 25 is supplied to the control winding 23c. The other configuration is the same as that of the power supply device 1 of FIG.

  As shown in FIG. 5, the saturable reactor 23 with a control winding further has a control winding 23c to which a direct current is applied to the saturable reactor 3 shown in FIG. That is, the saturable reactor 23 with the control winding is composed of the magnetic core 23a, the AC side winding 23b connected to the low frequency power source 2, and the control winding 23c to which a DC current is applied.

  In the saturable reactor 23 with a control winding shown in FIG. 6, when a DC control current (also referred to as a bias current) is passed through the control winding 23c, the magnetic core 23a is excited by a DC magnetic field, and the control current is increased. Since the core is likely to be magnetically saturated, the AC impedance of the AC side winding 23b to which the low frequency power supply 2 is applied rapidly decreases. When the DC magnetic field applied to the magnetic core 23a increases as the bias current increases and the magnetic core 23a is saturated, the AC impedance of the saturable reactor 23 with control winding becomes extremely small.

  The control current flowing through the saturable reactor 23 with the control winding is controlled by the bias current control unit 25. The bias current control unit 25 may be controlled so that the bias current with which the AC impedance of the saturable reactor 23 with the control winding is minimized flows only when the low frequency power supply 2 is applied to the load 7. When the high frequency power supply 4 is applied to the load 7, the bias current of the saturable reactor 23 with the control winding may be reduced so that the AC impedance is increased.

  Since the power supply device 20 uses the saturable reactor 23 with the control winding, as shown in FIG. 6, the voltage drop of the inductance due to the low frequency current can be more significantly reduced by controlling the bias current. it can.

FIG. 7 is a time chart for explaining the operation of the bias current control unit 25. In FIG. 7, the horizontal axis represents time, and the vertical axis represents the current waveform applied from the bias current control unit 25 to the control winding 23 c of the saturable reactor 23 with control winding and the current waveform flowing through the load 7. The load 7 shows a current waveform to which the high frequency power supply 4 is applied after the low frequency power supply 2 is applied.
As shown in FIG. 7, a bias current is applied to the control winding 23c simultaneously with the low-frequency current flowing through the load 7. The saturable reactor 23 with the control winding is oversaturated during the time when the bias current is passed, so that the impedance of the saturable reactor 23 with the control winding can be made very small and the voltage drop can be eliminated. Thereby, according to the power supply device 20 shown in FIG. 4, the voltage of the low-frequency power source 2 is almost applied to the load 7 without causing a voltage drop due to the low-frequency current more efficiently than the power supply device 1 of FIG. 1. In addition, it is possible to prevent current from flowing from the high frequency power source 4.

Next, a modified example of the power supply device according to the first embodiment of the present invention will be described. In this modification, a spot welder will be described as an example of the load 7 of the power supply device 1.
FIG. 8 is a diagram schematically showing an example of the configuration of the welding apparatus 40 using the power supply apparatus 1 according to the embodiment of the present invention, and FIG. 9 is an electric circuit diagram of the welding apparatus 40 shown in FIG. is there.
As shown in FIG. 8, the welding apparatus 40 includes the power supply apparatus 1 and further includes an electrode unit 10 and an energization control unit 8 that performs output control of the low-frequency power source 2 and the high-frequency power source 4. . The electrode unit 10 includes an electrode arm 12, an electrode support unit 13 having one end connected to the upper part 12A and the lower part 12B of the electrode arm 12, and a pair of electrodes 14 respectively connected to the other end of each electrode support unit 13. And is composed of.

The low frequency power source 2 is connected to the electrode 12 through the saturable reactor 3. The high frequency power source 4 is connected to the electrode 12 via the capacitor 5. The power supply device 1 may have a configuration of the power supply device 20 using the saturable reactor 23 with a control winding. In the case of the power supply device 20, the saturable reactor 3 may be a saturable reactor 23 with a control winding, and a bias current control unit 25 may be added.
Although not shown, the welding apparatus 40 includes a fixed base that supports the electrode arm 12, a drive mechanism that drives the electrode arm 12, a pressing mechanism (not shown) that pushes one electrode 14 out of the electrode support portion 13, and the like. Is further provided. The pressing mechanism is used to press the metal material 19 to be a welded member, which will be described later, with the electrodes 14 and 14.

  The pair of electrodes 14 and 14 are opposed to each other with a gap, and two steel plates are inserted as the metal material 19 into the gap. The electrode 14 is made of copper, for example. The shape of the surface of the electrode 14 in contact with the steel plate 19 is a circle or an ellipse, and is a cylinder or a rod. The two steel plates 19 sandwiched between the pair of electrodes 14 correspond to the load 7 of the power supply device 1 shown in FIG.

  As shown in FIG. 9, the electric circuit of the welding device 40 includes the power supply device 1 and the electrode unit 10 surrounded by a dotted line. The low frequency power source 2 is a welding power source, for example, a commercial power source 22 having an output frequency of 50 Hz or 60 Hz, a low frequency power source control unit 24 connected to one end of the commercial power source 22, and the other end of the commercial power source 22. And a welding transformer 26 connected to the output terminal of the low-frequency power supply control unit 24. Both ends of the secondary winding 26A of the welding transformer 26 are connected to the left end of the upper portion 12A and the left end of the lower portion 12B of the electrode arm 12, respectively. The low frequency power supply control unit 24 includes a power control semiconductor element such as a thyristor, a gate drive circuit, and the like, and performs energization control from the commercial power supply 22 to the electrode 14.

  A bypass capacitor 27 is connected in parallel with the secondary winding 26 </ b> A of the welding transformer 26. The bypass capacitor 27 has a low capacitive impedance with respect to the frequency of the high frequency power supply 4. For this reason, the voltage in which the high frequency voltage from the high frequency power source 4 is applied to the secondary winding 16A can be minimized, and the high frequency induced voltage to the primary side of the welding transformer 26 can be lowered.

  The high-frequency power source 4 includes an oscillator 28 and a matching transformer 30 connected to the output terminal of the oscillator 28. One end of the matching transformer 30 is connected to the upper part 12 </ b> A of the electrode arm 12. The other end of the matching transformer 30 is connected to the lower part 12 </ b> B of the electrode arm 12 via the capacitor 5. The capacitor 5 can also serve as a matching capacitor for a series resonance circuit described later. The capacitance value of the capacitor 5 depends on the oscillation frequency of the oscillator 28 and the stray inductance 32 of the electrode arm 12. The oscillator 28 includes an inverter using various transistors, and controls the energization power of the high-frequency power source 4 to the electrode 14.

  The series resonance circuit may be configured by the matching capacitor 5 and the stray inductance 32 generated in the electrode arm 12.

  In the welding apparatus 40, the capacitor 5 acts as a current blocking capacitor from the low frequency power source 2 to the high frequency power source 4. The saturable reactor 3 acts as a current blocking inductance from the high frequency power source 4 to the low frequency power source 2, that is, a choke coil. Furthermore, since the saturable reactor 3 is saturated at a large current at a low frequency and its inductance becomes very small, the voltage drop of the inductance due to the low frequency current can be almost eliminated, and the power capacity of the low frequency power source 2 can be reduced. The increase can be eliminated.

(Current distribution in the steel sheet)
FIG. 10 is a cross-sectional view schematically showing a current distribution generated in the steel plate 19 when power is simultaneously applied from the low frequency power source 2 and the high frequency power source 4 to the two stacked steel plates 19.
In FIG. 10, the solid line indicates the high-frequency current 36 from the high-frequency power source 4, and the dotted line indicates the low-frequency current 38 from the low-frequency power source 2. The electrode 4 is made of copper, has a diameter of 6 mm, and the frequency of the low-frequency power source 2 is 50 Hz. The thickness of one steel plate 19 is 2 mm, and the frequency of the high-frequency power source 4 is 25 kHz. The low frequency current 38 flows through the entire inside of the electrodes 14 and 14, and the steel plate 19 is energized with a cross-sectional area width of approximately the nugget diameter.
Here, the whole nugget corresponds to a circular interior 19 </ b> A obtained by projecting the axial cross section of the electrode 14 onto the steel plate 19.

  Since the heating time of the steel plate 19 by the high-frequency power source 4 can be controlled by the energization control unit 8, partial temperature increase can be performed only at the spot welded portion of the steel plate 19 or the like to be spot welded, and the power consumption required for heating is reduced. be able to.

  The power supply devices 1 and 20 and the welding device 40 described above may further include another low-frequency power source or a high-frequency power source. When a low frequency power supply is added, the saturable reactor 3 may be connected in series with the low frequency power supply to be added. When a high frequency power supply is added, the capacitor 5 may be connected in series with the added high frequency power supply.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Absent. The inductance value of the saturable reactor 3 in the above-described embodiment can be appropriately designed according to the frequency and output power of the low frequency power supply 2.

DESCRIPTION OF SYMBOLS 1, 20: Electric power supply apparatus 2: Low frequency power supply 3: Saturable reactor 3a, 23a: Magnetic core 3b, 23b: Winding 4: High frequency power supply 5: Capacitor 6: Output terminal 7: Load 8: Current supply control part 10: Electrode part 12: Electrode arm 12A: Upper part 12B: Lower part 13: Electrode support part 14: Electrode 19: Metal material 22: Commercial power supply 23: Saturable reactor 23c with control winding: Control winding 24: Low frequency power supply control part 25 : Bias current controller 26: Welding transformer 26A: Secondary winding 27: Bypass capacitor 28: Oscillator 30: Matching transformer 32: Floating inductance 36: High frequency current 38: Low frequency current 40: Welding device

Claims (4)

A low frequency power supply,
A saturable reactor connected to the low frequency power source;
A high frequency power supply,
A capacitor connected to the high-frequency power source;
With
One end of the saturable reactor is connected to one end of the low frequency power source, the other end of the saturable reactor is connected to one end of a load,
One end of the capacitor is connected to one end of a high frequency power supply, the other end of the capacitor is connected to the other end of the load,
A power supply device that supplies output power from the low-frequency power source and output power from the high-frequency power source to the load.   The power supply device according to claim 1, wherein an electrode is provided between the power supply device and the load, and welding is performed by a low-frequency power source applied to the electrode.   The power supply apparatus according to claim 1, wherein the saturable reactor is a saturable reactor with a control winding.   The power supply apparatus according to claim 1, wherein the power supply apparatus further includes another low-frequency power source or a high-frequency power source.

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