WELDER BACKGROUND

1. TECHNICAL FIELD

The present invention relates to an AC arc welder for manual welding with a built-in voltage reducing device, and also relates to a DC arc welder with a built-in feature of manual welding capable of outputting a voltage that is lower than the no-load voltage and that corresponds to a voltage to prevent electric shock in an AC arc welder.

2. BACKGROUND ART

When commercial power is supplied to an AC arc welder for manual welding that does not contain a voltage reducing device, a high no-load voltage of 80 V to 90 V is applied to the output side. If the operator accidentally touches a charged portion such as a welding rod holder or a welding rod while welding is not in progress and the no-load voltage is being applied, he/she may get an electric shock or be injured. To avoid this hazard that when the operator accidentally touches a charged portion such as a welding rod holder or a welding rod, he/she may get an electric shock or be injured, the law requires that while welding is not being performed, the voltage reducing device should cut the main circuits of the welder, and apply to the output side a low voltage of 30 V or less, which is within the safety limit. The law also requires that an AC arc welder for manual welding should be equipped with a voltage reducing device and that the voltage reducing device should be subjected to daily checks and regular maintenance.

These conventional AC arc welders for manual welding with either a built-in or external voltage reducing device are known to have a function as follows. When the operator turns on the inspection switch to inspect the voltage reducing device as daily checks before using the arc welder, it is inspected whether or not the voltage reducing device can apply a low voltage of 30 V or less, which is within the safety limit, to the output side when welding is not in progress (see, for example, Patent Literature 1). In the actual workplace, however, the operator can use the AC arc welder for manual welding without the above-de scribed daily checks before using the welder. In addition, it is impossible to determine whether or not the voltage reducing device was inspected before using the welder. If the operator neglects the daily checks before using the welder, the AC arc welder can be used even when the voltage reducing device is in an imperfect condition. In this situation, if the operator accidentally touches a charged portion such as a welding rod holder or a welding rod, he/she may get an electric shock or be injured.

In the case of DC arc welders for manual welding and DC arc welders for manual and other types of welding, the Industrial Safety and Health Law does not require that these welders be equipped with a voltage reducing device or that the voltage reducing device be inspected. Even so, in order to improve safety, some DC arc welders are equipped with a voltage reducing device that applies a voltage lower than the no-load voltage to the output side. However, even this type of DC arc welder does not have an inspection switch to inspect the voltage reducing device because of the lack of such laws (see, for example, Patent Literature 2). In order to avoid the hazard that when the operator accidentally touches a charged portion such as a welding rod holder or a welding rod, he/she may get an electric shock or be injured, some AC arc welders for manual welding are known to automatically inspect the voltage reducing device before welding is started (see, for example Patent Literature 3). Figs. 4 and 5 are schematic configuration views of conventional AC arc welders for manual welding equipped with a voltage reducing device.

The welders in Figs. 4 and 5 cut the main circuits on the secondary and primary sides, respectively. Fig. 6 is a schematic configuration view of a conventional AC arc welder for manual welding (hereinafter "AC welder") equipped with not only a voltage reducing device but also an automatic inspection device to inspect the voltage reducing device. As shown in Figs. 4 and 5, the AC welders include power switch 101 that receives AC power, transformer 104 that transforms the AC power, welding rod holder 107 that holds a welding rod, and voltage reducing device 111 that prevents electric shock. Voltage reducing device 111 includes inspection switch 114 to inspect the voltage reducing device, output control unit 116, low voltage supply unit 117, output condition detection unit 123, and main circuit breaking switch 124. Output control unit 116 controls the welding output. Low voltage supply unit 117 outputs a safe voltage lower than the no-load voltage. Output condition detection unit 123 detects the output state of the AC welder. Main circuit breaking switch 124 cuts the main circuits (chiefly, transformer 104). The AC welder creates an arc between base material 108 and welding rod 109 held in welding rod holder 107.

Voltage reducing device 111 having the above-described configuration operates as follows. In general, in the case of manual welding, welding rod 109 is held in welding rod holder 107, and an arc is created between base material 108 and welding rod 109. Unlike CO2 and TIG welders, welding is not started by pressing the torch switch. For this reason, unless voltage reducing device 111 is operating properly, a no-load voltage of 80 V to 90 V is applied between welding rod holder 107 and base material 108 when welding is not in progress (when no arc is present). In this situation, if the operator accidentally touches a charged portion such as welding rod holder 107 or welding rod 109, he/she may get an electric shock or be injured. To avoid this hazard, output condition detection unit 123 detects whether welding is in progress or not. When welding is not in progress, output control unit 116 turns off main circuit breaking switch 124 to cut the main circuits, thereby controlling low voltage supply unit 117 to apply a low voltage of 30 V or less, which is within the safety limit.

The principal difference between the welders shown in Figs. 4 and 5 is the location of main circuit breaking switch 124 to cut the main circuits. Main circuit breaking switch 124 is located on the secondary side of transformer 104 in Fig. 4, and is located on the primary side of transformer 104 in Fig. 5. The Industrial Safety and Health Law requires that voltage reducing device 111 having such a configuration should be subjected to the inspection of the operating conditions before use each day. To facilitate the inspection before use, voltage reducing device 111 is equipped with inspection switch 114. When the operator turns on inspection switch 114, output control unit 116 controls low voltage supply unit 117 and main circuit breaking switch 124 to switch the output voltage. Then, output condition detection unit 123 detects the output, thereby inspecting whether a low voltage of 30 V or less, which is within the safety limit, and the no-load voltage can be properly applied to the output side. In an AC welder equipped with the conventional voltage reducing device 111, the inspection of voltage reducing device 111 is done by the operator. This means that the operator can start welding even if he/she skips the inspection.

The AC welder shown in Patent Literature 3 will now be described as follows. Fig. 6 is a schematic configuration view of another conventional AC welder. The AC welder shown in Fig. 6 principally differs from that shown in Fig. 5 in including inspection device 125 to inspect the voltage reducing device before use. Inspection device 125 includes inspection controller 126 to control the inspection of the voltage reducing device before use, and inspection switch 127 to inspect the voltage reducing device before use. Inspection device 125 is connected to voltage reducing device 111, thereby preventing the operator from starting welding without turning on inspection switch 127 in order to operate inspection controller 126. Thus, the operator needs to operate inspection controller 126 to start welding, ensuring the inspection of voltage reducing device 111. However, even the AC welder shown in Fig. 6 requires the operator to take the trouble to turn on inspection switch 127 in order to operate inspection device 125. Moreover, the provision of inspection device 125 increases the cost.

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication No. S59-209481
Patent Literature 2: Japanese Unexamined Patent Publication No. S61-186169
Patent Literature 3: Japanese Unexamined Utility Model No. S52-115620

SUMMARY

The present invention is directed to provide an AC or DC welder for manual welding in which a voltage reducing device is inspected not by the operator turning on the inspection switch but automatically in response to the detection of power on of the welder. As a result, the welder can be inexpensive and yet ensure the inspection of the voltage reducing device before the welder is used. The welder according to the present invention is equipped with a voltage reducing device and includes a power switch to start up the welder; a start-up detection unit which detects the start-up of the welder; and an inspection control unit which controls the inspection of the voltage reducing device based on the detection result of the start-up detection unit. In the welder of the present invention, the inspection control unit automatically starts the inspection of the voltage reducing device when the power switch is turned on to start up the welder, and the start-up detection unit detects the start-up of the welder. The welder according to the present invention is equipped with a voltage reducing device and includes an inspection control unit, an output control unit, a first transfer instruction unit, a second transfer instruction unit, and a welding condition change unit.

The inspection control unit controls the inspection of the voltage reducing device. The output control unit controls the output of the welder. The first transfer instruction unit gives instructions to put welding conditions into a changeable state. The second transfer instruction unit gives instructions to transfer the welding conditions from the changing state to an unchangeable state. The welding condition change unit changes the welding conditions. When the welding conditions are in the changeable state, the output control unit stops the output of the welder. When the welding conditions are transferred from the changeable state to the unchangeable state, the inspection control unit automatically starts the inspection of the voltage reducing device. As described above, the welder of the present invention allows the voltage reducing device to be automatically inspected at the start-up of the welder. This eliminates the need to provide an inspection switch or device to inspect the voltage reducing device. As a result, the welder can be inexpensive and yet ensure the inspection of the voltage reducing device before the welder is used.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a schematic configuration view of an inverter DC arc welder for manual welding according to a first exemplary embodiment of the present invention.

Fig. 2 is a schematic configuration view of an inverter DC arc welder for manual welding according to a second exemplary embodiment of the present invention.

Fig. 3 is a schematic configuration view of an AC arc welder for manual welding according to a third exemplary embodiment of the present invention.

Fig. 4 is a schematic configuration view of a conventional AC arc welder for manual welding where the main circuits are cut on the secondary side of the welder.

Fig. 5 is a schematic configuration view of another conventional AC arc welder for manual welding where the main circuits are cut on the primary side of the welder.

Fig. 6 is a schematic configuration view of another conventional AC arc welder for manual welding, which is equipped with an inspection unit to inspect the voltage reducing device.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will now be described with reference to drawings. In the drawings, the same components are denoted by the same reference numerals, and the description thereof may be omitted.

FIRST EXEMPLARY EMBODIMENT

The first exemplary embodiment of the present invention will now be described with reference to Fig. 1. Fig. 1 is a schematic configuration view of an inverter DC arc welder (hereinafter, "DC welder") for manual welding according to the first exemplary embodiment. In the DC welder shown in Fig. 1, commercial power is supplied to primary rectifying circuit 2 via power switch 1 which turns on/off the input of the commercial power. The commercial power supplied to primary rectifying circuit 2 is converted to DC power by primary rectifying circuit 2. The DC power is then converted to AC power by inverter circuit 3. The AC power is converted by transformer 4 to the AC power that can be used for arc processing. The AC power is in turn converted to DC power by secondary rectifying circuit 5, and is outputted to welding rod holder 7 and base material 8 via reactor 6. The output of the DC welder is controlled by inverter circuit 3 so as to be a predetermined output current set value based on the detection results of current detection unit 9 and voltage detection unit 10. Inverter circuit 3 is controlled by output control unit 16 described later.

The DC welder shown in Fig. 1 is equipped with voltage reducing device 11 including start-up detection unit 12, inspection switch 14 to inspect the power supply preventive device, inspection control unit 15, and output control unit 16. Start-up detection unit 12 detects that power switch 1 is turned on and the DC welder is started. Inspection switch 14 is disposed in operation unit 13 so that voltage reducing device 11 can be inspected even after the DC welder is stared. Inspection control unit 15 receives the output of start-up detection unit 12 and the output of inspection switch 14, and in turn issues an instruction to inspect voltage reducing device 11. Output control unit 16 controls low voltage supply unit 17 and inverter circuit 3 based on the instruction from inspection control unit 15. Low voltage supply unit 17 supplies a low voltage of 30 V or less, which is within the safety limit. Inverter circuit 3 applies a no-load voltage. Operation unit 13 includes, in addition to inspection switch 14, welding condition change unit 20, display unit 21, and operation display control unit 22. Welding condition change unit 20 changes welding conditions.

Display unit 21 displays the welding conditions that are set or changed by welding condition change unit 20 and error messages. Operation display control unit 22 controls display unit 21 and other components. In order to detect the output state of the DC welder, output control unit 16 receives detection information from current detection unit 9 and from voltage detection unit 10. The instruction to inspect voltage reducing device 11 involves the following steps. First, low voltage supply unit 17 is controlled to output a voltage, and this voltage is detected to determine whether or not low voltage supply unit 17 is operating properly. Next, inverter circuit 3 is controlled to output a no-load voltage between welding rod holder 7 and base material 8, and this voltage is detected to determine whether or not the no-load voltage is outputted properly. When the DC welder having the above configuration is powered on, voltage reducing device 11 is automatically inspected as follows. When the operator turns on power switch 1 of the DC welder, start-up detection unit 12 detects that the DC welder is powered on and started, and then outputs the information to inspection control unit 15. Upon receiving the information from start-up detection unit 12, inspection control unit 15 outputs to output control unit 16 an instruction to inspect voltage reducing device 11.

In accordance with the instruction from inspection control unit 15, output control unit 16 operates low voltage supply unit 17 which applies a low voltage of 30 V or less, which is within the safety limit, first without driving inverter circuit 3. In this case, if current detection unit 9 does not detect as large a current as during welding, and voltage detection unit 10 detects a low voltage of 30 V or less, which is within the safety limit, output control unit 16 determines that low voltage supply unit 17 is operating properly. Otherwise, low voltage supply unit 17 is determined to be out of order. In this case, output control unit 16 controls operation display control unit 22 in operation unit 13 to output an error signal to display unit 21, which in turn displays error messages. After determining that low voltage supply unit 17 is operating properly, output control unit 16 controls inverter circuit 3 to apply a no-load voltage between welding rod holder 7 and base material 8. If current detection unit 9 does not detect as large a current as during welding, and voltage detection unit 10 detects a no-load voltage, output control unit 16 determines that the main circuits of the DC welder are operating properly. Otherwise, at least part of the main circuits (including primary rectifying circuit 2, inverter circuit 3, transformer 4, secondary rectifying circuit 5, and reactor 6) is determined to be out of order.

In this case, output control unit 16 controls operation display control unit 22 in operation unit 13 to output an error signal to display unit 21, which in turn displays error messages. When the inspection of low voltage supply unit 17 and the main circuits is properly ended, it is ready to start welding, and a low voltage of 30 V or less, which is within the safety limit, is being applied between welding rod holder 7 and base material 8. At this moment, if the operator turns on power switch 1 of the welder, absent-mindedly forgetting that welding rod holder 7 has welding rod 27 and that either welding rod holder 7 or welding rod 27 is in contact with base material 8, it is dangerous because the welding current flows to the output circuit. In the present first exemplary embodiment, however, output control unit 16 receives the information from current detection unit 9 and from voltage detection unit 10. Hence, even if power switch 1 of the welder is turned on and the inspection of voltage reducing device 11 is started while welding rod 27 or welding rod holder 7 is in contact with base material 8, the voltage detected by voltage detection unit 10 is 30 V or less. In other words, when low voltage supply unit 17 applies a low voltage of 30 V or less, which is within the safety limit, voltage detection unit 10 detects a lower voltage (for example, larger than 5 V and not larger than 30 V). This (for example, not larger than 5 V) allows detecting that welding rod 27 or welding rod holder 7 is in contact with base material 8.

Then, output control unit 16 controls operation display control unit 22 in operation unit 13 to output the error signal to display unit 21, which displays error messages. Output control unit 16 stops the welding output so as to stop the welding current, thereby preventing a dangerous situation from occurring. As described above, the welder according to the present first exemplary embodiment is equipped with voltage reducing device 11 and includes power switch 1, start-up detection unit 12, and inspection control unit 15. Power switch 1 is used to start up the welder. Start-up detection unit 12 detects the start-up of the welder. Inspection control unit 15 controls the inspection of voltage reducing device 11 based on the detection result of start-up detection unit 12. In the welder of the present first exemplary embodiment, inspection control unit 15 automatically starts the inspection of voltage reducing device 11 when power switch 1 is turned on to start up the welder, and start-up detection unit 12 detects the start-up of the welder. In this configuration, start-up detection unit 12 which detects the start-up of the DC welder allows voltage reducing device 11 to be inspected automatically when the DC welder is powered on.

This eliminates the need to turn on inspection switch 114 as in the conventional welder shown in Fig. 6, or to provide inspection device 125. As a result, the welder can be inexpensive and yet ensure that voltage reducing device 11 is inspected before the welder is used. Start-up detection unit 12 can detect the start-up of the DC welder depending on whether or not commercial power has been supplied to the DC welder. As a result, the DC welder does not require complicated additional devices, thereby being simple and inexpensive to manufacture. Voltage reducing device 11 receives the output state of the DC welder. In this configuration, it can be detected that welding rod 27 or welding rod holder 7 is in contact with base material 8 while voltage reducing device 11 is being inspected. As a result, it is prevented to provide a welding output while welding rod 27 or welding rod holder 7 is in contact with base material 8. This further improves safety during welding operations.

SECOND EXEMPLARY EMBODIMENT

A second exemplary embodiment of the present invention will now be described with reference to Fig. 2. Fig. 2 is a schematic configuration view of a DC welder for manual welding according to the second exemplary embodiment. The DC welder of the present second exemplary embodiment principally differs from the DC welder of the first exemplary embodiment in that voltage reducing device 11 is automatically inspected when the welding conditions have been changed and confirmed. The DC welder of the present second exemplary embodiment inspects voltage reducing device 11 automatically also when power switch 1 is turned on to start up the DC welder as in the first exemplary embodiment. Fig. 2 differs from Fig. 1 in that operation unit 13 includes first transfer instruction unit 18 and second transfer instruction unit 19, and that information from first transfer instruction unit 18 and from second transfer instruction unit 19 is inputted to operation display control unit 22. First transfer instruction unit 18 gives instructions to put welding conditions into a changeable state. Second transfer instruction unit 19 gives instructions to bring the welding conditions out of the changeable state.

In the DC welder having the above-described configuration, voltage reducing device 11 is automatically inspected as follows when the welding conditions of the DC welder have been changed and confirmed. When the operator operates first transfer instruction unit 18 to put the welding conditions into the changeable state while the DC welder is in operation, operation display control unit 22 sends a signal to output control unit 16, informing that the welding conditions have been put into the changeable state. Upon receiving the signal from operation display control unit 22, output control unit 16 controls inverter circuit 3 and low voltage supply unit 17 to stop the output of the no-load voltage and the low voltage of 30 V or less, which is within the safety limit. As a result, the welding conditions can be safely changed. After welding condition change unit 20 has changed the welding conditions, second transfer instruction unit 19 gives instructions to bring the welding conditions out of the changeable state. Then, operation display control unit 22 sends a signal to inspection control unit 15, informing that the welding conditions have been brought into an unchangeable state.

Upon receiving this signal, inspection control unit 15 controls output control unit 16 to start the inspection of voltage reducing device 11. As described above, the welder of the present second exemplary embodiment includes first transfer instruction unit 18 and second transfer instruction unit 19 in addition to the welder according to the first exemplary embodiment. In this welder, output control unit 16 stops the output of the welder when the welding conditions are in a changeable state. When the welding conditions are transferred from a changeable state to an unchangeable state, inspection control unit 15 automatically starts the inspection of voltage reducing device 11. This configuration allows voltage reducing device 11 to be automatically inspected after the welding conditions are changed and confirmed. Furthermore, this configuration eliminates the need to provide inspection device 125 to inspect the voltage reducing device before use. As a result, the welder can be inexpensive and yet ensure that voltage reducing device 11 is inspected before the welder is used.

The description of the inspection of voltage reducing device 11 is omitted because it is substantially the same as in the first exemplary embodiment. The description of the control of stopping the output when welding rod 27 or welding rod holder 7 comes into contact with base material 8 during the inspection of voltage reducing device 11 is also omitted because it is substantially the same as in the first exemplary embodiment. In this configuration, even if welding rod 27 or welding rod holder 7 accidentally comes into contact with base material 8 while the welding conditions are being changed, an error is detected to stop the output to the main circuits of the DC welder. This further improves safety during welding operations.

THIRD EXEMPLARY EMBODIMENT

A third exemplary embodiment of the present invention will now be described with reference to Fig. 3. Fig. 3 is a schematic configuration view of an AC arc welder (hereinafter, "AC welder") for manual welding according to the third exemplary embodiment. While the first and second exemplary embodiments show DC welders, the present third exemplary embodiment shows an AC welder. Unlike the DC welders shown in Figs. 1 and 2, the AC welder shown in Fig. 3 does not include any of the following: primary rectifying circuit 2, inverter circuit 3, secondary rectifying circuit 5, reactor 6, and current detection unit 9, but instead includes main circuit breaking switch 24. Main circuit breaking switch 24 is provided in voltage reducing device 11 so as to facilitate prior-to-use inspection of voltage reducing device 11. In order to avoid the hazard that if the operator accidentally touches a charged portion such as welding rod holder 7 or welding rod 27, he/she may get an electric shock or be injured, output condition detection unit 23 detects whether or not welding is in progress.

When welding is not in progress, output control unit 16 turns off main circuit breaking switch 24 so as to cut the main circuits, and also controls low voltage supply unit 17 to apply a low voltage of 30 V or less, which is within the safety limit. This further improves safety during welding operations. The description of how to automatically inspect voltage reducing device 11 at the start-up of the AC welder is omitted in the present third exemplary embodiment because it is substantially the same as in the first exemplary embodiment. The description of how to automatically inspect voltage reducing device 11 when welding conditions have been changed and confirmed is omitted in the present third exemplary embodiment because it is substantially the same as in the second exemplary embodiment. As described above, the welder according to the present third exemplary embodiment is equipped with voltage reducing device 11, a- " ~.„oS inspect n control unit 15, output control unit 16, first transfer instruction unit 18, second transfer instruction unit 19, and welding condition change unit 20. Inspection control unit 15 controls the inspection of voltage reducing device 11. Output control unit 16 controls the output of the welder.

First transfer instruction unit 18 gives instructions to put welding conditions into a changeable state. Second transfer instruction unit 19 gives instructions to transfer the welding conditions from a changeable state to an unchangeable state. Welding condition change unit 20 changes welding conditions. In the welder according to the present third exemplary embodiment, when the welding conditions are in a changeable state, output control unit 16 stops the output of the welder. When the welding conditions are transferred from the changeable state to an unchangeable state, inspection control unit 15 automatically starts the inspection of voltage reducing device 11. This configuration allows voltage reducing device 11 to be automatically inspected after the welding conditions are changed and confirmed. Furthermore, this configuration eliminates the need to provide inspection device 125 to inspect the voltage reducing device before use. As a result, the welder can be inexpensive and yet ensure that voltage reducing device 11 is inspected before the welder is used.

In the AC welder of the present third exemplary embodiment, output condition detection unit 23 supplies the welding output voltage to output control unit 16. This can stop the output when welding rod 27 or welding rod holder 7 accidentally comes into contact with base material 8 in the same manner as in the first and second exemplary embodiments. This further improves safety during welding operations. Output condition detection unit 23 can detect an output state by using current detection unit 9, voltage detection unit 10, or a phase detection method, taking advantage that the voltage phase on the output side is delayed with respect to the input side under load conditions.

INDUSTRIAL APPLICABILITY

Thus, the welder according to the present invention allows the voltage reducing device to be automatically inspected at the power-on of the welder, without turning on the inspection switch to inspect the voltage reducing device before use or without providing the inspection device to inspect the voltage reducing device before use. The voltage reducing device can also be automatically inspected after welding conditions are changed and confirmed. This safe and inexpensive welder equipped with the voltage reducing device is industrially useful.

REFERENCE MARKS IN DRAWINGS
1 power switch
2 primary rectifying circuit
3 inverter circuit
4 transformer
5 secondary rectifying circuit
6 reactor
7 welding rod holder
8 base material
9 current detection unit
10 voltage detection unit
11 voltage reducing device
12 start-up detection unit
13 operation unit
14 inspection switch to inspect the power supply preventive device
15 inspection control unit
16 output control unit
17 low voltage supply unit
18 first transfer instruction unit
19 second transfer instruction unit
20 welding condition change unit
21 display unit
22 operation display control unit
23 output condition detection unit
24 main circuit breaking switch
27 welding rod

What is claimed is:

1. A welder equipped with a voltage reducing device, the welder comprising: a power switch for starting up the welder; a start-up detection unit for detecting start-up of the welder; and an inspection control unit for controlling inspection of the voltage reducing device based on a detection result of the start-up detection unit, wherein the inspection control unit automatically starts the inspection of the voltage reducing device when the power switch is turned on to start up the welder and then the start-up detection unit detects start-up of the welder.

2. The welder of claim 1 further comprising: an output control unit for controlling an output of the welder; a first transfer instruction unit for giving instructions to put welding conditions into a changeable state; a second transfer instruction unit for giving instructions to transfer the welding conditions from the changeable state to an unchangeable state; and a welding condition change unit for changing the welding conditions, wherein when the welding conditions are in the changeable state, the output control unit stops the output of the welder, and when the welding conditions are transferred from the changeable state to the unchangeable state, the inspection control unit automatically starts the inspection of the voltage reducing device.

3. A welder equipped with a voltage reducing device, the welder comprising: an inspection control unit for controlling inspection of the voltage reducing device; an output control unit for controlling an output of the welder; a first transfer instruction unit for giving instructions to put welding conditions into a changeable state; a second transfer instruction unit for giving instructions to transfer the welding conditions from the changeable state to an unchangeable state; and a welding condition change unit for changing the welding conditions, wherein when the welding conditions are in the changeable state, the output control unit stops the output of the welder, and when the welding conditions are transferred from the changeable state to the unchangeable state, the inspection control unit automatically starts the inspection of the voltage reducing device.

4. The welder of one of claims 1 to 3 having a function of detecting a contact between a welding electrode and an object to be welded, wherein when it is detected that the welding electrode and the object to be welded are in contact with each other while the voltage reducing device is being inspected, the output of the welder is stopped.