JPS6243787B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric shock prevention device for an arc generating power source used as a power source for gouging or direct current manual welding that adjusts the output current. This prevents workers from accidentally touching a holder that is exposed to electrical shock and receiving an electric shock.

Generally, in gouging and DC manual welding,
When replacing carbon electrodes or welding rods, there is a risk of electric shock if a worker accidentally touches a holder that generates secondary no-load voltage, so it is safe to touch the holder while work is not in progress. A shock prevention device is added to the power supply, which short-circuits the electrode rod to the base material at the start of work, thereby creating the main circuit and obtaining the high no-load voltage necessary for arc generation. We are striving to ensure safety. In addition, this electric shock prevention device maintains the no-load voltage in the main circuit for a predetermined period of time after an arc breakage occurs, and prevents electric shocks after that predetermined time. The circuit is configured to step down the voltage to a low voltage.

FIG. 1 shows an example of the output voltage waveform during operation of the electric shock prevention device having such a configuration.

Further, FIG. 2 shows a block diagram of a thyristor phase control type gouging and manual welding power source equipped with a conventional electric shock prevention device, and FIG. 3 shows the electric circuit of the electric shock prevention device in the block diagram.

In Fig. 2, 1 is a power supply circuit, 2 is a thyristor circuit, 3 is an output current detection circuit, 4 is a reference signal generation circuit, 5 is a comparison amplifier circuit, 6 is an ignition circuit for the thyristor circuit 2, and 7 is an electric shock prevention circuit. , 8a are normally open contacts of the firing signal relay of the thyristor circuit 2.

Further, in FIG. 3, 9 is a transformer for generating electric shock prevention voltage, and the secondary induced voltage of this transformer 9 is transmitted through a rectifier circuit of a rectifier diode 10 and a resistor 11.
It is rectified and smoothed by the smoothing circuit of the capacitor 12. 13 is a resistor for generating a signal when the output is short-circuited; 1
4 is a Zener diode, 15 and 16 are NPN type transistors, 17 is a PNP type transistor, 18
~20 is an input resistor for transistors 15 to 17,
21 to 23 are bias resistors for the transistors 15 to 17, 24 and 25 are collector resistors of the transistors 15 and 17, 26 is a capacitor charged via the resistor 25, and 27 is a protection diode for the transistor 16. In addition, 8 is the above-mentioned normally open contact 8
It is a relay with a.

In the power supply equipped with this conventional electric shock prevention device, the thyristor circuit 2 is not fired during work stoppage.
The electric shock prevention voltage from the transformer 9 is taken out to the output terminal.

When the electrode comes into contact with the base material at the start of work, current flows through resistor 13 and transistors 15 to 17 are turned on.
As a result, the relay 8 is turned on, the comparison amplifier circuit 5 and the ignition circuit 6 are connected, the thyristor circuit 2 is ignited, and an arc is generated.

Next, when the work is stopped, the electrode rod is pulled up and the arc is cut, and the voltage across the resistor 13 becomes zero, and the transistors 15 and 17 are turned off. In addition, the transistor 16 is turned off after a predetermined time due to a voltage drop due to the discharge of the capacitor 26, and after that predetermined time, the relay 8 opens the connection between the comparison amplifier circuit 5 and the ignition circuit 6, and the no-load voltage is applied to the output terminal. It disappears and the electric shock prevention voltage is extracted.

This kind of operation prevents electric shock accidents, but as you can see from the above configuration,
The electric shock prevention circuit 7 includes a transformer 9, a diode 10, a resistor 11, and a capacitor 12 for electric shock prevention voltage.
In particular, the need for the transformer 9 to be separate from the transformer for the power supply circuit 1 causes the equipment to become larger and more expensive, making it difficult for manufacturers who place emphasis on miniaturization and lower prices in technological development. was a factor that needed to be resolved.

In view of these problems, the present invention provides an electric shock prevention device that is smaller in size and lower in price.

Hereinafter, one embodiment of the electric shock prevention device of the present invention will be described using the drawings of FIGS. 4 to 8.

FIG. 4 shows a block diagram of a power source for gouging and direct current manual welding equipped with an electric shock prevention device according to an embodiment of the present invention. In FIG. 4, 1 to 6 are the same parts as 1 to 6 in FIG. 2. shows. 2
8 is a current detection relay drive circuit, 29 is a voltage detection relay drive circuit, 30 is an electric shock prevention voltage signal generation circuit that generates an electric shock prevention voltage signal, and 31 is an electric shock prevention circuit.

5 shows an example of a specific electric circuit of the current detection relay drive circuit 28 shown in FIG. 4. In FIG. 5, 32 is an operational amplifier, 33 is an input resistance of the operational amplifier 32, and 34 is an operational amplifier
2 is the feedback resistor, 35 is the operational amplifier 32
, and 36 is the output resistance of the operational amplifier 32. 37 is an NPN type transistor, 38 is a bias resistor of the transistor 37, 39 is a Zener diode, and 40 is a current detection relay.

In this current detection relay drive circuit 28, when a signal proportional to the output current detected by the output current detection circuit 3 is input to the operational amplifier 32 via the input resistor 33, this signal is compared and amplified by the operational amplifier 32, and the operational amplifier The output signal of 32 switches the transistor 37, and the current detection relay 40
control.

FIG. 6 shows an example of a specific electric circuit of the voltage detection relay drive circuit 29 shown in FIG.
In the figure, 41 is an operational amplifier, 42 is an input resistance of the operational amplifier 41, 43 is a feedback resistance of the operational amplifier 41, 44 is a grounding resistance of the operational amplifier 41, and 45 is an output resistance of the operational amplifier 41. 4
6 is a Zener diode, 47 is an NPN type transistor, 48 is a bias resistor for transistor 47, 49 is a voltage detection relay, 50 is a variable resistance for adjusting starting sensitivity, and 51 is also a starting sensitivity adjusting resistor.

In this voltage detection relay drive circuit 29, the voltage applied via the input resistor 42 is applied to the operational amplifier 41.
The output signal of the operational amplifier 41 is used to switch the transistor 47 and control the voltage detection relay 49.

FIG. 7 shows an example of a specific electric circuit of the electric shock prevention circuit 31 shown in FIG. .
55 is an NPN type transistor, 56 is a base resistance of the transistor 55, 57 is a bias resistance of the transistor 55, 58 is a Zener diode, 59
is a relay. Further, 40a is a normally open contact of the current detection relay 40, and 40a is a normally open contact of the voltage detection relay 49. In addition, in FIG. 4, 59a
is the normally open contact of relay 59 of electric shock prevention circuit 31, 5
9b is a normally closed contact of the relay 59.

8a to 8d show the output voltage waveform of the power supply shown in FIG. 4 and the timing chart of the relays 40, 49, and 59, and using these FIGS. Explain the operation.

During the work stoppage, the current detection relay 40 and the voltage detection relay 49 are in the OFF state, the relay 59 is in the ON state, and the ignition circuit 6 receives the electric shock prevention voltage signal output from the electric shock prevention voltage signal generation circuit 30. It has been entered.

In this state, when the electrode rod is brought into contact with the base material,
The terminal voltage drops to nearly zero, which turns on the voltage detection relay 49, short-circuits both ends of the capacitor 52 of the electric shock prevention circuit 31, turns off the NPN transistor 55, and turns the relay 59 off. Therefore, instead of the electric shock prevention voltage signal of the electric shock prevention voltage signal generation circuit 30, the ignition circuit 6 receives the electric shock prevention voltage signal.
The output signal of the comparison amplifier circuit 5 is now input. That is, the thyristor circuit 2, the output current detection circuit 3, the comparison amplifier circuit 5, and the ignition circuit 6 constitute a closed loop control system, and the output determined by the reference signal generation circuit 4 is provided to the ignition circuit 6. In this state,
Arc voltage (load voltage) is generated, voltage detection relay 49 is turned off, and current detection relay 40 is turned on.

In addition, when the electrode rod is separated from the base material and the arc is cut when the work is stopped, the current detection relay 40 is turned OFF.
After a predetermined period of time, the arc 59 is turned on due to a voltage drop due to the discharge of the capacitor 52. During this predetermined time, the aforementioned closed-loop control system is configured and the output current is zero, so the input to the comparison amplifier circuit 5 is only the reference signal from the signal generation circuit 4, and the thyristor circuit 2 is at full capacity. It is in the ignition state, and the output voltage is the no-load voltage.

After a predetermined period of time, the relay 59 of the electric shock prevention circuit 31 is turned on, the ignition circuit 6 is coupled to the electric shock prevention voltage signal generation circuit 30, the comparison amplifier circuit 5 is disconnected, and the output terminal is connected to the electric shock prevention voltage. is taken out.

In the electric shock prevention device of the present invention, several hundred A, several tens of meters
Since it is difficult to detect a short-circuit current of several amps at the time of starting with a V output current detection circuit and use this as the starting signal for the electric shock prevention device, the starting signal is obtained by voltage detection, and arc breakage is detected. Detection is obtained by current detection.

As is clear from the above explanation, according to the electric shock prevention device for an arc generating power supply according to the present invention, there is no need to add a separate transformer etc. for electric shock prevention voltage, and the entire device can be made smaller. Prices can be lowered.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the output voltage waveform of a power source for gouging and direct current hand welding equipped with a general electric shock prevention device, and Figure 2 is a block diagram of a power source for gouging and direct current manual welding equipped with a conventional electric shock prevention device. FIG. 3 is an electrical circuit diagram of the electric shock prevention device in the block diagram of FIG. 5 to 7 are electrical circuit diagrams of the main parts of the block diagram shown in FIG. 4, and FIGS. 8 a to d show the output voltage of the power supply shown in the block diagram of FIG. 4 and FIGS. 5 to 7, respectively. 2 is a timing chart showing the relationship between the operation of the main components of the circuit shown in FIG. 2... Thyristor circuit, 6... Ignition circuit, 28... Current detection relay drive circuit, 29... Voltage detection relay drive circuit, 30... Electric shock prevention voltage signal generation circuit, 3
1... Electric shock prevention circuit, 40... Current detection relay, 49
...Voltage detection relay, 59...Relay.

Claims (1)

[Claims] 1. A thyristor circuit that controls the output current flowing between output terminals for arc generation, an output current detection circuit that detects the output current and outputs a signal proportional to the magnitude of the output current, and a standard that outputs a reference signal. a signal generation circuit; a comparison amplifier circuit that compares an output signal from the output current detection circuit with a reference signal from the reference signal generation circuit; and a comparison amplifier circuit that controls firing of the thyristor circuit based on the output of the comparison amplifier circuit. a voltage detection relay drive circuit that detects a short circuit between the output terminals and drives the voltage detection relay; and a current detection relay that operates based on a signal when the output current detection circuit detects an output current. a current detection relay drive circuit that drives the electric shock prevention voltage signal generation circuit that outputs the electric shock prevention voltage signal, and a voltage detection relay that drives the voltage detection relay to permit signal supply from the comparison amplifier circuit to the ignition circuit. At the same time, the supply of the electric shock prevention voltage signal from the electric shock prevention voltage signal generation circuit to the ignition circuit is prohibited, and the signal supply from the comparison amplifier circuit to the ignition circuit is prohibited after a predetermined time after the driving of the current detection relay is stopped. 1. An electric shock prevention device for an arc generation power source, comprising an electric shock prevention circuit that prohibits the electric shock prevention voltage signal generation circuit from supplying an electric shock prevention signal to the ignition circuit.