JPS62107867A - Inverter type dc welding power source device - Google Patents

Abstract

PURPOSE:To prevent the breakage of elements due to the overcurrent and to eliminate the output fluctuaton by stopping the motion when the current passing to the switching element of the inverter circuit exceeds the prescribed value and by re-opening the motion after a given time period. CONSTITUTION:The current to be flowed to each switching element 6a-6d of the inverter circuit 6 is detected by a current detector 11. The inverter motion is then stopped via driving control circuit 14 by detecting with an abnormal current detecting circuit 12 when the detecting current becomes abnormal and exceeds the fixed value. Then after a fixed short time period the inverter motion is re-opened by resetting the abnormal current detecting circuit 12 by a delay circuit 13. The breakage of the switching element can be prevented therefore even if an overcurrent is flowed to a main transformer 7 due to a DC magnetic deflection, etc. The fluctuation in the output can be prevented as well because of the motion being re-opened in short time after the motion stoppage.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an inverter-type M-flow welding power supply device, particularly a maintenance system that prevents damage to the switching elements of a full-bridge inverter due to excessive current and outputs stable power. Regarding the W circuit.

[Conventional technology]

Figure 4 shows a circuit diagram of a conventional inverter-type DC welding power supply, in which (1) is a welding start command contact that outputs a welding start command signal, (21 is a welding start command contact that receives the welding start command signal and controls the welding sequence). (3) is an inverter output command circuit that operates in response to the output signal of the sequence circuit (2), and (4) is an inverter output setting device that sets the pulse width output by the inverter output command circuit.

(5) is a DC power supply, and (6) is a full-bridge inverter circuit, which includes two switching elements (6a) and (6d) connected in series, and two switching elements (6bl) connected in series. , (Be) are connected in parallel, the connection point of the switching elements (6a), (Be) and the connection point of the switching elements (6b), (6dl are connected to the DC power supply (5), and the connection point of the switching element (6a), (Be) is connected to the DC power supply (5).
l, (connection point of 6dl and switching element (6b)
, (6c) is connected to the primary side of the main transformer (7). Further, one output terminal (A) of the inverter output command circuit (3) is connected to the switching element (Ba), (8b) connected to one diagonal line, and the switching element (Ba), (8b) connected to one diagonal line is connected to the switching element (Ba), (8b). .

The switching element (6c) and (+y) are connected between the inverter output command and the other output terminal (B) of ¥i'5 (31).
is connected.

(8) is a rectifier connected to the secondary side of the main transformer Pif71, and (9) is a DC reactor connected to the output side of the rectifier (8).

A conventional welding power supply device is configured as described above, and when the welding start command contact (1) is closed at the start of welding, the sequence circuit (2) is activated to supply shielding gas to the welding part (not shown), etc. necessary for welding. At the same time, it outputs an operation command to the inverter output command circuit (3). As a result, the inverter output command circuit (3) sends two types of output signals with different phases to the full bridge inverter circuit (
6) each switching element (6a), (6b),
(6c), (output to 6dl. At this time, one output signal is output from the output terminal (leopard) to the switching element (6a
), (6b), and the other output signal is sent to the output terminal (Bl
are input to switching elements (Be) and (ad).

This re-output signal is a pulse having a pulse width (T) set by the inverter output setting device (4). In this way, when each output signal enters each switching element, the switching element (6a), (6b) is switched on and switched off at the same time, and then switching elements (6c) and (6dl are switched on at the same time.

Switch off and repeat this sequence.

As a result, the DC output from the DC power supply (5) causes current to flow in one direction on the primary side of the main transformer through the switching elements (6a) and (6b), and then through the switching elements (6c) and (6+( ) through the main transformation! (7
Current flows in the other direction on the primary side of 1. By sequentially repeating these operations, an alternating current having positive polarity and negative polarity is input to the main transformer (7). Main transformer (7)
The secondary AC output is converted back to DC by a rectifier (8) and smoothed through a DC reactor (9) to supply power to a welding section (not shown).

Figure 5 shows each output terminal (
Person 1. This figure shows output No. 3 in (B) and the output signal of the full bridge inverter circuit (6), that is, the voltage tTf, e type of the input signal of the main transformer (7). In the figure, (T) indicates the pulse width time.

[Problem that the invention seeks to solve]

With the conventional inverter-type DC welding power supply device as shown above (
However, there is a problem in that an excessive current flows through the switching element due to DC bias of the main transformer (7), and if the current exceeds the rating of the switching element, the switching element is damaged.

This invention was made to solve the above-mentioned problems, and even if excessive current flows through the switching elements of the inverter due to DC bias in the main transformer, the switching elements will not be damaged ( The object of the present invention is to provide an inverter type DC welding power supply device that can supply stable electric power to a welding machine.

[Means for solving problems]

In the inverter type DC welding power supply device according to the present invention, when the abnormal current detection circuit detects that the current flowing through each switching element in the full bridge type inverter circuit detected by the current detector becomes abnormal, the drive control circuit The inverter operation is immediately stopped, and the inverter operation is restarted by a delay circuit after a certain short period of time after the inverter operation is stopped.

[Effect]

In this invention, the inverter operation is immediately stopped when an abnormal current flows through the switching element of the inverter circuit, thereby preventing damage to the switching element. Furthermore, after the inverter operation is stopped, the inverter operation is restarted in a short time, thereby preventing fluctuations in the M current output to the welding machine.

〔Example〕

FIG. 1 is a circuit block diagram showing one embodiment of the present invention, and in the figure, (1) to (9) are completely the same as the conventional device described above. (11) is a current detector connected in series between the output terminal of the full-bridge inverter circuit (6) and the input terminal of the main transformer (7), and (12) is the current detector (1
(13) is a delay circuit whose input terminal is connected to the output terminal of the abnormal current detection circuit (12) and whose output terminal is connected to the reset input terminal of the abnormal current detection circuit (12). , (14) is a drive division circuit that controls the drive of the inverter output command circuit (3), and is composed of a two-man logical product circuit, one input terminal is connected to the output terminal of the sequence circuit (2), and the other is connected to the output terminal of the sequence circuit (2). The output terminal of the abnormal current detection circuit (12) is connected to the input terminal of the inverter output command circuit (3).

In the inverter-type DC welding power supply device configured as described above, when the welding start command contact (1) is closed due to the start of welding, the welding start output signal from the sequence # (2+) is It is input as a signal of "1" to the input terminal.The output signal of the abnormal current detection circuit (12) is input to the other input terminal of this AND circuit (14), and this input signal is normally "1". Therefore, the AND circuit (14) immediately issues a welding start command to the inverter output command circuit (3).As a result, the inverter output command circuit (3); , each switching element (6a), (6bl,
(6c), (is emitted to 6dl. At this time, one output terminal (signal from the ladle is sent to the switching element (6a),
(Bb), and the signal from the other output terminal (B) is input to the switching elements (6cl, (6dl).

This 100 output signal is a zero pulse with a pulse width (n) set by the inverter output setting device (4).

In this way, when each output signal is input to each switching element, the switching elements (6al, (sb)) are simultaneously switched on and switched off, and then the switching elements (6c), (6d) are simultaneously switched on. - Switching off and then switching element (6a) again.

(6b) are simultaneously switched on and switched off, and this operation is repeated sequentially. As a result, current flows from the DC power supply (5) to the negative side of the main transformer (7) through the switching elements (6a) and (6bl), and then through the switching elements (6c) and (6d) to the main transformer. Flow current in the other direction on the negative side of (7). By repeating this operation in sequence, alternating current with positive polarity and negative polarity is input to the main transformer (7). Main transformer Vessel (7
) is converted back into DC by the rectifier (8), smoothed through the DC reactor (9), and supplies power to a welding machine (not shown). At this time, inverter elements (6a), (6b), (6c), (
It is generally known that if there is a difference in switching speed in 6d), the output of the full bridge inverter (6) will be a form in which the DC output is superimposed on the AC output, and the main transformer (7) will be biased by the DC current. There is. When the amount of DC bias magnetism is large, the excitation impedance of the main transformer (7) decreases, and the switching elements (8a), (6bl, (6e)
, (a large current flows through either of the main transformers (7) and Then the input current increases and this −
When the next input current exceeds a certain value lower than the preset maximum rating of the switching element Ts f&, the abnormal current detection circuit (12) changes its output signal from the "1" state to the "0" state. . As a result, the welding start command that had been issued to the inverter output command circuit (3) from the AND circuit (14), which has the output signal of the abnormal current detection circuit (12) as one input, is immediately stopped, and the inverter operation is immediately stopped. The switching element is stopped and the switching element is protected from damage due to overcurrent. Then, when the inverter stops operating, the input to the main transformer (7)? After a certain period of time after fd7fE decreases or becomes zero, the delay circuit (13)
A reset signal is issued to the abnormal current detection circuit (12), and the output of the abnormal current detection circuit (13) returns to the original "1".
” status.

As a result, the AND circuit (14) outputs the welding start command again, restarts the operation of the inverter, and obtains the output of the welding machine. While the operation of the inverter is stopped, electric power is supplied to the welding machine by electromagnetic energy stored in the DC reactor (9). Therefore, by shortening the period during which the inverter is stopped, it is possible to protect the switching elements from damage without causing defects in the welds.

In the above embodiment, the main transformer (7) is demagnetized to eliminate DC bias by stopping the operation of the inverter, but by forcibly demagnetizing the main transformer (7), the inverter is Can reduce downtime.

Figure 2 shows the drive control port* (20) and the AND circuit (]4)
Another embodiment is shown in which the polarity determination circuit (21) is configured.

In this embodiment, the output signal of the current detector (11) is input to the abnormal current detection circuit (I2) and is also input to the polarity discrimination circuit (21).
The output signal is input to an output order selection input terminal of an inverter output command circuit (31k) equipped with an output sequential selection circuit. Note that since the other configurations are the same as the embodiment shown in FIG. 1, some illustrations are omitted in FIG. 2.

The operation of the embodiment shown in FIG. 2 will be explained based on the current waveform diagram in FIG. 3. At the start of welding, the terminals (person) of the inverter output command circuit (3a),'
Output signals (I) and (ff) are output alternately from (B), making it possible to weld, but during welding, the input current ([) of the main transformer (7) changes due to DC bias, etc. When the current becomes excessive and exceeds the detection level (I,) set in advance in the abnormal current detection circuit (12), the inverter operation is stopped in the manner described in the explanation of the operation of the embodiment shown in FIG. At this time, the polarity discrimination circuit (21) discriminates and stores the polarity (positive polarity or negative polarity) of the excessive input current of the main transformer (7), and the inverter operation is restarted by the operation of the delay circuit (13). and the input current (III) of the main transformer (7) is at the time (t
2), a command is given to the inverter output command circuit (3a) in which the output order can be selected so that the current flows from the polarity opposite to that at the time of stop (negative polarity or positive polarity).

As a result, as the inverter resumes operation, the main transformer (7)
This has the effect of eliminating the DC bias magnetization of ) can increase the stability of the current value (I).

〔Effect of the invention〕

As explained above, this invention detects the current flowing through a switching element in an inverter circuit, and when this current value exceeds a constant current value that is lower than the maximum rated current value of the switching element, immediately stops the inverter operation, Since the operation of the inverter is automatically restarted after a certain period of time, it is possible to prevent damage to the switching elements even if DC bias magnetization occurs in the main transformer.

In addition, since inverter operation can be restarted in a short time, welding current can be passed using the electromagnetic energy of the DC reactor during the stoppage time, making it possible to stabilize the welding current and prevent the occurrence of defects in the welded part. It can be effective.

[Brief explanation of drawings]

Figure 1 is a circuit block diagram showing an embodiment of Party B's invention;
The figure is a partial circuit block diagram showing another embodiment of the present invention.
Fig. 3 is a current waveform diagram showing the operation of the embodiment shown in Fig. 2, Fig. 4 is a circuit block diagram showing a conventional inverter type DC welding power source, and Fig. 5 is a current waveform diagram showing the operation of the embodiment shown in Fig. 4. It is a current waveform diagram. (1); Welding start command contact, (2); Nukens circuit, (31, (3a); Inverter output command circuit, (4)
); Inno(-ta output setting device, (5); DC power supply, (
6); Full bridge inverter times, (6a) ~ (
6d) ; Sui soting element, (7); Main transformer,
(81; DC reactor, (11); Current detector, (12); Abnormal current detection circuit, (13);
Delay circuit, (14); AND circuit, (21); JEtj
Gender discrimination circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Patent Attorney Tadashi Sato Year 1 Figure 11 t: fL tumor 12; Abnormal electric current nine strokes = times 'l elephant 13; Sushou circuit 14: Hydraulic product times λ Figure 2 Figure 3

Claims (3)

[Claims] (1) In a DC welding power supply device equipped with a full-bridge inverter connected between a DC power source and a main transformer and operated by the output of an inverter output command circuit, detecting the current flowing through each switching element of the inverter. one or more current detectors; an abnormal current detection circuit that receives the output of the current detector to detect an abnormal current; and receives an abnormal current detection signal from the abnormal current detection circuit to drive the inverter output command circuit. An inverter-type DC welding power supply device comprising: a drive control circuit for controlling the abnormal current detection circuit; and a delay circuit for resetting the abnormal current detection circuit after a certain short period of time in response to an abnormal current detection signal from the abnormal current detection circuit. (2) The inverter type DC welding power supply device according to claim 1, wherein the drive control circuit comprises an AND circuit inputting the output signal of the abnormal current detection circuit and the welding start signal. (3) The drive control circuit consists of an AND circuit that inputs the output signal of the abnormal current detection circuit and the welding start signal, and a polarity determination circuit that receives the output of the current detector and determines and stores the polarity of the abnormal current. The inverter type DC welding power supply device according to claim 1, wherein the output command circuit includes an output order selection circuit.