KR960007157B1 - Ac arc welding machine - Google Patents

Abstract

In an AC arc welding machine having a first coil for arc generation and a second coil for voltage generation for prevention of electric shock provided to a second side of a main transformer; a silicon controlled rectifier (SCR) and a smooth reactor are serially connected to the first coil. The machine includes a load discriminator discriminating a load of an output terminal of the main transformer; and a switch for turning off a gate trigger signal to cut off the welding current flowing across the first coil when opening the output terminal of the main transformer and turning on the second coil to produce an electric shock preventive low voltage and a switching part cutting off the second coil and turning on the gate trigger signal in case of short-circuit of the output terminal, so as to produce an arc current. The load discriminator determines that it is unloaded if the load voltage rises to a predetermined value as a welding bar is spaced away from a material and the arc becomes long, and turns off the gate trigger signal of the SCR and produces an electric shock preventive low voltage.

Description

Flow arc welding machine

1 is a block diagram of an SCR type AC welding power supply apparatus according to the present invention.

2a and 2b is an appearance and configuration of the control bar for remote control of the output current.

* Explanation of symbols for main parts of the drawings

T: Main transformer S1: Arc generating coil

S2: lightning protection voltage coil 1: SCR

4: relay 8: operational amplification and constant current circuit

11: Variable resistance with motor 13: Start control circuit

14: trigger generation circuit 15: polarity discrimination circuit

17: load discrimination circuit 18: switching circuit

19: electric shock prevention circuit 22: output current adjustment bar

The present invention relates to an AC arc welder, and in more detail, by phase-controlling the secondary side current of the main transformer by an SCR element, it is possible to simplify the circuit configuration and device, improve the start sensitivity and the electric shock prevention performance, and weld current. The present invention relates to an AC arc welder with a new structure that can be easily controlled remotely.

Conventionally known AC arc welding machines are known as movable iron cores and tap-changing types, but they are generally mechanical or contact type for driving the movable iron cores by large motors or controlling secondary welding current by tap-changing. The mold has a problem that the device is large and heavy due to the driving motor, the wear of the contact part or the vibration of the moving part is severe, and dust, salt, or other foreign substances in the device may cause damage to the device or electric shock. In particular, welding in the low current region is not possible with the control method by the movable core. Also, as in the conventional AC arc welding machine, when the electric shock prevention circuit is configured on the primary side of the main transformer which is the high voltage and low current and controlled by the magnetic switch, the start sensitivity is only about 1.5Ω, which makes it difficult to start welding smoothly. It is abrasion and it is easy to malfunction.

On the other hand, conventionally, semiconductor devices such as SCR have been used to control the welding current, but these are merely movable iron cores for controlling the motor by driving a relay, not directly controlling the secondary output current.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-described problems of an AC arc welder such as a conventional movable iron core, and the phase control of the secondary side output current of the main transformer by SCR, which is a semiconductor, allows the device and circuit configuration to be simplified and welded. It is to provide a new structure of AC arc welder with greatly improved current safety and control characteristics.

In addition, the present invention, unlike the prior art by configuring the electric shock prevention circuit on the secondary side, the AC arc of the new structure in which the switching operation between the welding current and the electric shock prevention current is made safe and secure while greatly improving the start sensitivity at the start of welding. It is to provide a welding machine.

In addition, the present invention is equipped with an adjustment bar for remote control of the welding current of the present invention, and by controlling the trigger generation timing of the SCR by adjusting the motor-mounted variable resistance according to the direction of contact of the adjustment bar, a new operation that can remotely control the welding current with simple operation during operation. It is to provide an AC arc welder of structure.

According to one aspect of the invention, in the AC arc welding machine having a first coil (S1) for generating arc and a second coil (S2) for generating an electric shock prevention voltage on the secondary side of the main transformer (T), the first arc The load discrimination unit 17 which connects the SCR 1 and the smoothing reactor 2 to the coil S1 in series, and discriminates whether the output terminals u and v of the main transformer T are loaded, and the output terminal u. when the gate is open, the gate trigger signal of the SCR 1 is turned off to cut off the welding current flowing through the first coil S1, and the second coil S2 is turned on to output a low voltage for preventing electric shock. and a switching unit 18 which cuts off the second coil S2 at the time of (u, v) short circuit and turns on the gate trigger signal of the SCR 1 to output a predetermined arc current. 17, the arc length is increased as the electrode is separated from the base material, and if the load voltage rises to a predetermined value, An AC arc welder is provided which turns off the gate trigger signal of (1) and outputs a low voltage for electric shock prevention.

According to another feature of the invention, the welding machine, the secondary output end (u) of the mate (T) of the output current control adjustment bar 22 having a contactor 23 is formed at both ends and provided with a diode 24 therein and a polarity discrimination circuit 15 which detects a change in polarity according to the contact direction of v), and at the rear end of the polarity discrimination circuit 15, the rotation direction of the volume control motor of the control power supply 20 is reversely driven. An AC arc welder is provided, characterized in that the motor drive unit 16 is connected to control the gate trigger signal of the SCR 1 to remotely control the arc current.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. 1 is a block diagram showing an embodiment of the SCR AC welding power supply apparatus according to the present invention, as shown in the first coil portion (S1) and the electric shock prevention for arc current generation on the secondary output side of the main transformer (T) The second coil unit S2 for voltage generation is provided, and the SCR 1 and the smooth reactor 2 are connected in series to the first coil unit S1. In addition, a non-contact relay 4 is connected to the second coil portion S1. The shunt 3 and the polarity discrimination circuit 15 are connected to the output terminal u of the first coil part S1, and the load discrimination circuit 17 is connected to the output terminal v. The rear end of the load discrimination circuit 17 is connected to a switching circuit 18 for switching the start control circuit 13 and the electric shock prevention circuit 19 to each other.

The electric shock prevention circuit 19 drives the non-contact relay 4 provided in the above-described second coil part S2. On the other hand, in the polarity discrimination circuit 15, the motor driving circuit 16 and the motor-mounted variable resistor 11 are sequentially connected, so that the control current from the control power supply 20 is regulated by the variable resistor 11 and the amplifier Amplified by (10) and input to the operational amplifier and constant current circuit (8). On the other hand, the minute change of the arc current detected by the shunt 3 is input to the operational amplifier and the constant current circuit 8 through the full wave rectification circuit 6 via the amplifier 5.

The operation amplification and constant current circuit 8 is a microcurrent change signal from the shunt 3 and the polarity discrimination circuit described above with respect to the reference voltage from the reference signal setting circuit 7 according to the command of the start control circuit 13. The signal of the control power supply 20 adjusted by 15 is added or subtracted to drive the SCR trigger generation circuit 14 through the emitter follower 12. The SCR trigger generation signal 14 triggers the gate terminal of the SCR 1 connected to the secondary side first coil portion S1 of the main transformer T1, that is, the arc current generating coil S1.

In the figure, reference numeral 9 denotes a start sensitivity adjusting circuit and 21 denotes a control power switch.

2a and 2b is an internal configuration showing the appearance and use of the control bar 22 for remote control of the output current according to the present invention, both ends of the adjustment bar 22 in contact with the welding holder and the base material, respectively 23 is provided, and the diode 24 and the resistor 25 are provided in series inside. The adjustment bar 22 determines whether electricity is supplied to the internal diode 24 in the forward or reverse direction depending on the contact direction, and whether or not the adjustment bar 22 is energized is detected by the polarity discrimination circuit 15 to drive the motor. The volume of the motor-mounted variable resistor 11 is adjusted by the furnace 16. Accordingly, the trigger current generated by the trigger generation circuit 14 of the SCR can be controlled according to the contact direction of the adjustment bar 22.

Referring to the operation of the present invention, first, since the output terminal U and V are opened before starting the welding operation in the ON state of the control power supply switch 21 or at the time of stopping the welding operation, the load discrimination circuit 17 This is determined as no load, the start control circuit 13 is cut off by the switching circuit 18, and the electric shock prevention circuit 19 is turned on to conduct the relay 4 of the second coil S2 for electric shock prevention voltage generation. Therefore, one line of the two coils S2 is connected to the output terminal V and the other line is connected to the output terminal U through the relay 4 so that a safe electric shock voltage of about 25 V or less induced in the second coil S2 is obtained. It is output between the output terminals u and v, ie, the base material and the welding holder or the welding rod.

On the other hand, when the welding start and the operation during the welding is described, when the welding electrode and the base material is contacted to electrically connect the output terminals U and V, the load discrimination circuit 17 determines the load as the load by the switching circuit 18. The electric shock prevention circuit 19 is cut off, and a welding start signal is sent to the start control circuit 13. At this time, the start sensitivity adjusting circuit 9, which enables to realize a smooth start, drives the SCR trigger generation circuit 14 through the emitter follower 12 together with the start control circuit 13. Once welding is started, since the load condition is continued, the detection result of the load discrimination circuit 17 is also not switched to no load, so the arc current through the first coil S1 continues. At this time, even if the operator unnecessarily fluctuates the gap between the welding rod and the base material slightly, the shunt 3 detects the minute change in the arc current according to the change in the arc length, and the amplifier 5 and the full-wave rectifying circuit 6 By inputting into the operational amplification and the constant current circuit 8 through the feedback control of the trigger generation of the SCR trigger generation circuit 14 to obtain a stable arc current.

On the other hand, when the operator wants to remotely control the arc current, the contact holder 23 between the both ends of the output current adjusting adjustment bar 22 is contacted with the welding holder and the earth wire (base metal) respectively connected to the output terminals U and V in a specific direction. Let's do it. Then, the polarity determination circuit 15 determines this and rotates the volume control motor in the direction of increasing or decreasing the welding current by the motor driving circuit 16 so that the signal of the control power supply 20 is adjusted by the variable resistor 11. The amplifier 10 is input to the operational amplifier and the constant current circuit 8 through the amplifier 10. Therefore, in the operational amplification and constant current circuit 8, the signal from the circuit 6 according to the signal of the reference signal setting circuit 7 and the arc length change and the welding current remote control circuit 10 according to the welding start signal of the start control circuit 13. Amplification and constant current control are performed by receiving the signal from the circuit, and the SCR trigger generation circuit 14 is driven through the emitter follower 12 to trigger the output current adjustment SCR 1 on the secondary side of the main transformer T. Phase control the output current. The output current phase-controlled by the SCR 1 outputs a uniform half-wave rectified without ripple through the reactor 2, so that a good output without interruption of the welding current can be obtained.

Referring to the operation at the end of welding or stopping, when the worker separates the welding rod from the base material in order to finish welding, the arc voltage increases as the arc length between the secondary output terminals U and V becomes long. At this time, when the arc voltage reaches a predetermined set value, for example, when the arc voltage is increased to about 30 mm of the arc length and rises to 60 V, the load discrimination circuit 17 determines that there is no load and switches it through the switching circuit 18. The signal to the start control circuit 13 is turned off to cut off the output current adjustment SCR 1, and instead, the electric shock prevention circuit 19 is operated to provide a non-contact relay 4 with a safe electric shock prevention voltage of about 20 V and the output terminal U. Output to V.

As described above, according to the present invention, the secondary output current of the main transformer is directly phase-controlled by the SCR, thereby simplifying the circuit construction and the device, and improving the stability and control characteristics of the arc current, compared to a conventional movable coil type AC welder. Excellent AC arc welder can be obtained. In addition, by using the electric shock prevention circuit on the primary side of the main transformer separately, a part of the secondary side is used as an electric shock prevention voltage, so that the welding current and the electric shock prevention current can be switched at the time of welding, and the start sensitivity at the start of the arc is also significantly increased. The welding work can be done simply and efficiently. In addition, the operator can perform the welding operation simply and efficiently during the operation. In addition, when the operator wants to adjust the welding current during the operation, the gate signal of the SCR is controlled by adjusting the rotational direction of the small motor that adjusts the variable resistance by determining the polarity according to the selection of the contact direction of the adjustment bar. Therefore, it is possible to continuously adjust the output current instead of stepping up, which makes the welding work more smooth and the welding result can be further improved.

Claims (2)

In the AC arc welding machine having the first coil S1 for arc generation and the second coil S2 for electric shock prevention voltage on the secondary side of the main crank T, the first coil S1 includes an SCR ( 1) and the smooth reactor 2 are connected in series, and the load discrimination part 17 which discriminates the load part of the output terminals u and v of the main transformer T, and at the time of opening the said output terminals u and v are opened. Turn off the gate trigger signal of the SCR (1) to cut off the welding current flowing in the first coil (S1), conducting the second coil (S2) to output a low voltage for the electric shock prevention, and the output terminal (u, v) And a switching unit 18 which cuts off the second coil S2 at the time of short-circuit and turns on the gate trigger signal of the SCR 1 to output a predetermined art current, and the load discrimination unit 17 provides a welding rod. As the arc length increases as the distance from the base material increases, and the load voltage rises to a predetermined value, it is determined as no load and the gate trigger signal of the SCR 1 is determined. Program and AC arc welder, comprising a step of outputting a low-voltage-proof lightning. 2. The welding machine according to claim 1, wherein a contactor (23) is formed at both ends, and the secondary output terminal (u,) of the mate lance (T) of the output current control adjusting bar (22) having a diode (24) therein. and a polarity discrimination circuit 15 for detecting a change in polarity according to the contact direction of v), and at the rear end of the polarity discrimination circuit 15 for forward and reverse driving of the rotational direction of the volume control motor of the control power supply 20. An AC arc welding machine, characterized in that the motor drive unit 16 is connected to control the gate trigger signal of the SCR (1) to remotely control the arc current.