JPH06570U - Consumable electrode type DC arc welding machine - Google Patents

Abstract

(57) [Abstract] [Purpose] A desired constant voltage output is supplied to the welding load by accurate constant voltage control without adding a winding to the output transformer. An output detector 22 that detects the secondary winding output of the output transformer 11, a converter 23 that rectifies the output of the detector 22 to form a DC voltage detection signal, a voltage detection signal and an output voltage An error amplifier 19 that outputs an error signal with respect to the reference signal for setting as a constant voltage control signal of the inverter 4 is provided, and the secondary winding output is directly detected to perform constant voltage control.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a consumable electrode type DC arc welding machine that supplies constant voltage DC to a welding load.

[0002]

[Prior art]

Conventionally, consumable electrode type DC arc welding such as CO ₂ welding, MAG welding, and MIG welding supplies a constant voltage DC to the welding load of the electrode and the base metal from the welding machine and short-circuits the electrode to the base metal. After being separated from the base metal and transferred to the arc, short circuit and arc are repeated. When the energy input to the welding load becomes excessive when a short circuit occurs, spatter increases, so this type of consumable electrode type DC arc welder is equipped with a large capacity DC reactor for smoothing at its output. This prevents a sharp increase in welding current and suppresses spatter generation.

That is, the conventional consumable electrode type DC arc welding machine is configured as shown in FIG. 2 for three-phase, and the three-phase AC power source of the power supply terminals 1a to 1c is rectified by the input rectifier 2 of the diode bridge configuration. Then, the output of the rectifier 2 is smoothed by the capacitor 3 and supplied to the inverter 4.

The inverter 4 includes input capacitors 5 and 6, a pair of semiconductor switching elements 7 and 8 such as a transistor, a MOS FET, and an IGBT, and a protection diode 9 provided in parallel with both the elements 7 and 8. It is configured as a half-bridge circuit by 10 and performs high frequency switching drive to convert direct current to high frequency alternating current. Then, the high frequency AC output of the inverter 4 is supplied to the primary winding 11 a of the output transformer 11, and the output of the tapped secondary winding 11 b (secondary winding output) of the transformer 11 is output to the output rectifier 12. Supplied.

The rectifier 12 is a full-wave rectifier of diodes 12a and 12b and rectifies the output of the secondary winding. Further, the output of the rectifier 12 is smoothed by the DC reactor 13, and the DC output formed by this smoothing is supplied to the consumable electrode 14 and the welding load 16 of the base material 15.

Further, in order to loop control the output to a constant voltage, the voltage of the direct current output on the output side of the DC reactor 13 is detected by the voltage detector 17, and the detection signal of this detector 17 and the output voltage setting device 18 The error amplifier 19 performs error amplification on the reference signal for setting the output voltage, and the error signal of both signals is formed as the constant voltage control signal of the inverter 4. Then, this control signal is supplied to the inverter drive circuit 20, and the drive circuit 20 controls the driving of the switching elements 7 and 8 of the inverter 4 to make the output voltage a constant voltage.

However, in this type of DC arc welding machine, the electrode 14 is short-circuited once to the base material 15 and then transferred to the arc to perform welding. Therefore, during this period, the voltage of the welding load 16 (load voltage) becomes large. fluctuate. In the case of FIG. 2, since the voltage on the output side of the reactor 13 is detected and the constant voltage control is performed, a very large fluctuation occurs in the detection signal of the voltage detector 17 due to the arc start, and this fluctuation is constant voltage control. However, there is a disadvantage that the control cannot be stabilized.

Therefore, a welding machine having the configuration shown in FIG. 3 has been devised. 3, the same reference numerals as those in FIG. 2 indicate the same or corresponding ones, and the difference from FIG. 2 is that the voltage detector 17 is omitted, and instead, the output transformer 11 is provided with a tertiary winding 11c. In addition, a converter 21 for rectifying the output (induced voltage) of the winding 11c and supplying it to the error amplifier 19 as a voltage detection signal is provided.

Then, a large fluctuation of the DC output due to the load voltage fluctuation is absorbed by the reactor 11, and the fluctuation of the output of the secondary winding 11b and the tertiary winding 11c of the output transformer 11 is prevented. Therefore, if the voltage (primary winding voltage) of the primary winding 11a of the output transformer 11 changes in a rectangular wave as shown in FIG. The induced voltage of 11c (third winding voltage) is not affected by the load voltage fluctuation due to the arc start and becomes the same rectangular wave voltage as the primary winding voltage.

Then, the induced voltage of the tertiary winding 11c is rectified by the converter 21 to form a DC voltage detection signal, and this detection signal is replaced with the error amplifier 19 instead of the detection signal of the voltage detector 17 of FIG. Is supplied to. Therefore, in the case of FIG. 3, the disturbance of the constant voltage control accompanying the arc start is suppressed, and the control stability is improved. It should be noted that, instead of adding the tertiary winding 11c to the output transformer 11, a transformer dedicated to detection may be provided separately from the output transformer 11, but in this case, the number of transformers increases and the welding machine is large. It becomes heavy.

[0011]

[Problems to be solved by the device]

 In the case of the conventional machine shown in FIG. 3, the output voltage (secondary winding voltage) of the secondary winding 11b of the output transformer 11 shown in FIG. 3 has an on-duty period Ton when the welding load 16 is short-circuited and the arc is repeated. Becomes shorter than that of the primary winding voltage and the tertiary winding voltage. That is, in the no-load state, no current flows in the welding load 16 and the secondary winding voltage has the same waveform as the primary winding voltage and the tertiary winding voltage.

However, during welding in which the welding load 16 is short-circuited and the arc is repeated, the current flowing through the diodes 12a and 12b of the output rectifier 12 is changed due to, for example, the rectangular change of the primary winding voltage shown in FIG. (Secondary winding current) changes as shown in (b) and (c) of the same figure. Then, as is apparent from FIGS. 4B and 4C, the secondary winding current flows based on the wiring inductance, the leakage inductance of the output transformer 11, the switching time of the diodes 12a and 12b, and the like. First, a transitional commutation overlap angle time Tu occurs.

Therefore, as shown in (d) and (e) of FIG. 4, the actual secondary winding voltage is such that the on-duty period Ton is less than the on-duty period Tin of the primary winding voltage and the tertiary winding voltage. The time Tu becomes shorter. In FIG. 4, PV is the primary voltage of the inverter 4, SV is the secondary voltage of the inverter 4, and Io is the output current.

Tu represents commutation overlap time, Ton represents an on-duty period, and Td represents an off-duty period. Further, (d) and (e) of FIG. 4 show the voltage between one end of the secondary winding 11b and the intermediate tap and between the other end and the intermediate tap.

The voltage waveforms of the secondary winding 11b and the tertiary winding 11c are different, and the on-duty period of the tertiary winding voltage becomes longer than that of the secondary winding voltage, and the tertiary winding voltage However, even if the output voltage is controlled to be constant based on the tertiary winding voltage, the constant voltage cannot be accurately controlled to a desired magnitude. Therefore, there is a problem that the control accuracy cannot be improved and a desired constant voltage output cannot be obtained to perform high quality stable welding.

Moreover, since the tertiary winding 11c is added to the output transformer 11, the output transformer 11 becomes large and heavy, and there is a problem that the welding machine cannot be made smaller and lighter. An object of the present invention is to obtain a desired constant voltage output without adding a winding to the output transformer.

[0017]

[Means for Solving the Problems]

 In order to achieve the above object, in the consumable electrode type DC arc welding machine of the present invention, an output detector for detecting the secondary winding output of the output transformer and a DC voltage by rectifying the output of this detector. A converter that forms a detection signal and an error amplifier that outputs an error signal between the voltage detection signal and the reference signal for setting the output voltage as a constant voltage control signal for the inverter are provided.

[0018]

[Action]

 In the case of the welding machine of the present invention configured as described above, the output detector detects the output of the secondary winding of the output transformer, and the drive of the inverter is controlled by the detection result to rectify the output of the secondary winding. , The smoothed DC output is controlled by constant voltage. At this time, since the load on the load side is absorbed by the DC reactor, the output of the secondary winding does not include the effect on the load side.

Further, since the secondary winding output itself is detected, it is not necessary to add a tertiary winding to the output transformer as in the conventional machine, and there is no deviation between the detected waveform and the output waveform. Therefore, the output voltage can be accurately controlled to a desired magnitude with a configuration that is smaller and lighter than in the past.

[0020]

【Example】

 One embodiment will be described with reference to FIG. In FIG. 1, the same reference numerals as those in FIGS. 2 and 3 denote the same or corresponding ones, and 22 denotes an output detector having a transformer configuration, and both ends of the primary winding 22a are the secondary windings of the output transformer 11. It is connected to both ends of 11b. Reference numeral 23 is a converter connected to the secondary winding 22b of the output detector 22, rectifies the output of the secondary winding 22b to form a DC voltage detection signal, and supplies this signal to the error amplifier 19. .

The output transformer 11 has only the primary winding 11a and the secondary winding 11b, and the tertiary winding 11c in FIG. 3 is omitted. Further, the voltage detector 17 of FIG. 2 and the converter 21 of FIG. 3 are not provided.

A constant voltage control loop is formed by the output transformer 11, the output detector 22, the converter 23, the error amplifier 19, the drive circuit 20, and the inverter 4, and the detector 22 is the secondary winding 11 b of the output transformer 11. The high-frequency AC voltage (secondary winding voltage) is detected. Further, the detection output of the detector 22 is rectified by the converter 23, a DC voltage detection signal corresponding to the DC output is formed, and this signal is supplied to the error amplifier 19.

Then, the error amplifier 19 amplifies the error between the voltage detection signal of the converter 23 and the reference signal of the setter 18, and supplies the error signal of both signals to the drive circuit 20 as a constant voltage control signal of the inverter 4. To do. In this case, since the DC reactor 13 absorbs the change in the current component caused by the voltage fluctuation on the load side, the secondary winding voltage of the output transformer 11 is short-circuited even when the welding load 16 is short-circuited and the arc is repeated. Not affected by load side fluctuations (load voltage fluctuations).

Since the detector 22 directly detects the secondary winding voltage of the output transformer 11, the magnitude of the DC output can be accurately detected even during welding. Therefore, the output transformer 11 is provided with the primary winding 11a and the secondary winding 11b, so that the DC output voltage can be accurately controlled to a desired voltage based on the reference signal by a small and lightweight structure, and high quality can be achieved. Stable welding can be performed.

[0025]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects. The output detector 22 detects the secondary winding output of the output transformer 11, and the detection result controls the drive of the inverter 4 to rectify and smooth the secondary winding output to perform a constant voltage control. Because the load side fluctuation is absorbed by the DC reactor 13, the secondary winding output does not include the effect of the load side fluctuation, and the secondary winding output itself is detected. Since it is not necessary to add a third winding to the output transformer 11 and there is no deviation between the detected waveform and the output waveform, the output voltage can be accurately controlled to the desired magnitude with a smaller and lighter configuration than before. In addition, high quality stable welding can be performed.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of a consumable electrode type DC arc welding machine of the present invention.

FIG. 2 is a connection diagram of an example of a conventional welding machine.

FIG. 3 is a connection diagram of another example of a conventional welding machine.

4A to 4D are waveform diagrams for explaining the operation of FIG.

[Explanation of symbols]

 4 Inverter 11 Output transformer 13 DC reactor 16 Welding load 19 Error amplifier 22 Output detector 23 Converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenzo Dangami 2-14-3 Awaji, Higashiyodogawa-ku, Osaka City Sansha Denki Seisakusho Co., Ltd. (72) Masayo Aoyama 2-3-14 Awaji, Higashiyodogawa-ku, Osaka Stock company Sansha Denki Seisakusho

Claims (1)

[Scope of utility model registration request] 1. A consumable electrode for supplying a high frequency AC output of an inverter driven by a constant voltage control loop to an output transformer, rectifying a secondary winding output of the transformer, smoothing it by a DC reactor, and supplying it to a welding load. Type DC arc welding machine, an output detector for detecting the secondary winding output, a converter for rectifying the output of the detector to form a DC voltage detection signal, the voltage detection signal and the output voltage setting Consumable electrode type DC arc welding machine having an error amplifier for outputting an error signal with respect to a reference signal for use as a constant voltage control signal of the inverter.