JP4764991B2 - Contact-type electric welding pipe welding power supply - Google Patents

Description

  The present invention relates to a contact type electric resistance welding pipe welding power source apparatus.

An electric sewing tube is manufactured by forming a metal plate into a tubular shape and welding its end with a high-frequency current, and is widely used in civil engineering, architecture, steel towers, columns, and other structures.
FIG. 4 shows a main circuit configuration diagram of a contact type electric welding pipe welding power source apparatus, and FIG. 5 shows an external view of the apparatus.
First, referring to FIG. 5, a method for manufacturing an electric resistance welded tube will be described. In FIG. 5, 4 is an inductive impedance, 5 is an electric welding pipe welding power source, 8 is a contact type electric welding pipe load, 10 is a contact tip, and 11 is a squeeze roll.

  As shown in FIG. 5, the band-shaped metal is moved in the direction indicated by the arrow while being bent into an open pipe. The welding of the contact portion between the ends is performed by supplying electric power of several tens to several hundred kW and several tens to several hundred kHz from the electric sewing tube welding power source 5 to bring the contact tip 10 into contact with the contact type electric welding tube load 8. Is done. The squeeze roll 11 plays the role of press-contacting the welded portion. Here, since the contact-type electric sewing tube load 8 is constantly moving at several meters / minute to several tens of meters / minute, the contact-type electric sewing tube load 8 fluctuates vertically and horizontally as viewed from the contact tip 10, and Repeated contact and release frequently.

Next, the main circuit configuration will be described with reference to FIG.
The power converter 1 is a voltage type inverter that is configured by using a semiconductor element such as a vacuum tube or recently a MOSFET (metal oxide field effect transistor) and operates as a voltage source. Supply 100 kHz power. A capacitor 3 is connected in parallel to the output via an inductive impedance 2 to form an electric resistance welding power source 5 as a whole.

Connected to the output of the ERW welding power source 5 is a contact type ERW pipe load 8 composed of an inductive impedance 6 and a resistance component 7. The switch 9 is not actually provided, and shows the contact / opening operation between the electric welding pipe welding power source 5 and the contact type electric welding pipe load 8 generated by the position change of the electric sewing pipe load 8 in an easy-to-understand manner. Generally, the resistance of the heating load is several tens to several hundreds mΩ, and a large current is required, so various resonance circuits are used.
One of them is a composite resonance circuit, for example, as shown in Non-Patent Document 1, and another using a current-type inverter as a voltage source (for example, see Patent Document 1).

  The resonant circuit of FIG. 4 is a parallel circuit of inductive impedance 2 (L2), inductive impedance 6 (L6), and capacitor 3 (C3). Here, the inductive impedances 2 and 6 include inductive impedance due to the wiring of the electric welding pipe welding power source 5 and the contact type electric welding pipe load 8 (not shown).

  FIG. 6 shows these relationships when the output voltage and current of the power converter 1 are Vo and Io and the load current is IL in FIG. Specifically, when L2 = 1 μH, L6 = 0.08 μH, and C3 = 2 μF, the resonance frequency fr = 1 / [2 × π × √ [(L2 × L6) / (L2 + L6) × C3]] = 413 kHz. Thus, when the power converter 1 is operated at a frequency in the vicinity thereof, the relationship between Io and IL is IL≈Io × (L2 / L6), indicating that an IL that is about 10 times Io can flow.

In FIG. 4, when the contact type ERW pipe load 8 is released, the resonance frequency fr = 1 / [2 × π × √ (L2 × C3)] = 113 kHz, and the operating frequency of the power converter 1 is also significantly low. Become.
Further, as shown in FIG. 5, when the contact-type electric sewing tube load 8 has a function of preheating before the welded portion, high frequency power is supplied from the preheating power source 12 to the preheating coil 13 and induction heating is performed. . As an example, there is one shown in Patent Document 2, for example.

Transformerless Inverters for Induction Heating Applications, E.I. J. et al. DEDE, PCIM INTER '98 JAPAN PROCEEDINGS, p227-231 JP 2000-218380 A Japanese Patent Laid-Open No. 11-285856

As described above, when the contact type ERW pipe load is released, the operation frequency of the power converter is significantly reduced, so that the control becomes unstable, and a transformer is connected to the output side of the power converter. In some cases, there is a problem of causing saturation of the transformer core. Further, when preheating, there is a problem that a separate preheating power source is required.
Therefore, an object of the present invention is to enable stable control of the electric sewing tube load and eliminate the need for a preheating power source.

In order to solve such a problem, in the present invention, a contact type electric welded pipe welding in which a capacitor and a contact type electric pipe load are connected in parallel via an inductive impedance connected in series to the power converter. In power supply,
By connecting another inductive impedance in parallel with the contact type electric resistance tube load and using this another inductive impedance as a preheating coil, it is possible to omit a power source for preheating .

  According to the present invention, the inductive impedance is connected in parallel with the contact type electric resistance tube load, so that even when the contact type electric resistance pipe load is opened, the operating frequency of the power converter is reduced. Stable control is possible because the load is reduced to about half of the load contact. Furthermore, since the newly added inductive impedance also serves as a preheating coil, the preheating power source can be omitted, and the equipment can be greatly reduced and downsized.

FIG. 1 is a main circuit configuration diagram of a contact type electric welding tube welding power source apparatus showing an embodiment of the present invention, and FIG. 2 is an external view of the apparatus.
The difference between FIG. 1 and FIG. 4 is that the inductive impedance 4 is connected in parallel to the contact type electric resistance tube load. The difference between FIG. 2 and FIG. 5 is that the inductive impedance 4 as a preheating coil is electrically connected. It is connected to the sewing tube welding power source 5 and a new preheating power source and preheating coil are omitted from FIG.

  The resonant circuit in the case of FIG. 1 is a parallel circuit of inductive impedance 2 (L2), inductive impedances 6 (L6) and 4 (L4), and a capacitor 3 (C3). Here, the inductive impedances 2, 4 and 6 also include inductive impedances due to the wiring of the electric welding pipe welding power source 5 and the contact type electric welding pipe load 8 (not shown).

  FIG. 3 shows the relationship between the output voltage and current of the power converter 1 and the load current. Specifically, when L2 = 1 μH, L4 = 0.4 μH, L6 = 0.08 μH, and C3 = 2 μF, the resonance frequency fr = 1 / [2 × π × √ [(L2 × L4 × L6) / ( L2 × L4 + L2 × L6 + L4 × L6) × C3]] = 450 kHz. When the power converter 1 is operated at a frequency in the vicinity thereof, the relationship between Io and IL is IL≈Io × (L2 / L6), and Io is 10 It shows that about twice as much IL can flow.

  In FIG. 1, when the contact type ERW pipe load 8 is released, the resonance frequency fr = 1 / [2 × π × √ [(L2 × L4) / (L2 + L4) × C3]] = 210 kHz, and power conversion The operating frequency of the vessel 1 is not significantly lowered. That is, as apparent from a comparison between FIG. 3 and FIG. 6, the operating frequency of the power converter 1 when the electric sewing tube load 8 is opened is significantly lower in FIG. It turns out that it has not decreased so much.

The main circuit block diagram of the contact-type electric resistance welding pipe welding power supply which shows embodiment of this invention Device external view of FIG. FIG. 1 is an explanatory diagram of the operation. Main circuit configuration diagram of conventional contact-type ERW welding power supply Device external view of FIG. Operation explanatory diagram of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power converter, 2, 4, 6 ... Inductive impedance, 3 ... Capacitor, 5 ... Electric welding pipe welding power supply, 7 ... Resistance component, 8 ... Contact-type electric sewing tube load, 9 ... Switch, 10 ... Contact tip , 11 ... squeeze roll, 12 ... preheating power source, 13 ... preheating coil.

Claims (1)

In a contact type electric welding pipe welding power source device in which a capacitor and a contact type electric pipe load are connected in parallel via an inductive impedance connected in series to the power converter,
A contact type characterized in that another inductive impedance is connected in parallel with the contact type electric welded tube load, and the power source for preheating can be omitted by using this other inductive impedance as a preheating coil. ERW welding power supply.

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