SU1459845A1 - Apparatus for limiting no-load voltages of welding transformer - Google Patents

Abstract

The invention relates to electrical apparatus, in particular, to control systems for electric welding equipment. The purpose of the invention is to increase the reliability of the device by obtaining a stable arc under various welding conditions. Device Contains a welding transformer with a thyristor switch in the primary circuit. The switch control circuit consists of two auxiliary sources, a zener diode, a thyristor, a resistor, and a capacitor. It is supplemented with a transistor, a capacitor and two resistors. When the supply voltage is applied, the switch control circuit is in working condition, but there is a safe voltage on the welding electrode. When the product touches the electrode, the switch is turned on. A rated operating voltage is applied to the electrode. When the arc is broken after a certain period of time, at the output of the welding transformer, the reduced no-load voltage for the person is set again. The use of a transistor in a switch control circuit eliminates the effect of interference on the operation of the welding power source. 1 il. f

Description

one

The invention relates to electrical apparatus, in particular, to control systems for electric welding equipment.

The purpose of the invention is to improve the reliability of the equipment by obtaining a stable arc under various welding conditions.

The drawing shows a circuit diagram of a device for limiting the no-load voltage of a welding transformer.

The device contains the first auxiliary source 1 connected

to the control electrodes of the thyristor switch 2 and its supplying circuit is controlled and the switch is bridged by an RC circuit of a series-connected resistor 3 and a capacitor. The secondary circuit of the welding transformer 5 includes a reactor 6, which serves to regulate the welding current, a welding object 7, an electrode 8 and a current transformer 9, the secondary winding of which is connected to the second auxiliary source 10. The output of the first auxiliary source 1 is bypass condensed C71

:about

00 4 O1

rum 11, and its positive output through resistor 12, capacitor 13 connected in parallel and resistor 14, thyristor 15 and zener diode 16 are connected to the plus of the second auxiliary source 10. A collector is connected to a common point of resistor 12 and capacitor 13 shunted by resistor 14

Switch 2. This provides the supply of a nominal voltage to the electrode 8, as a result of which a normal welding process is possible. However, the capacitor 13 after some time, determined by the value of the resistor 12, is charged, the thyristor 15 is closed, the voltage.

transistor 17, the emitter of which is connected to the base of transistor 17 sharply,

and it closes.

If the electrode 8 touches only randomly or briefly, then the limited voltage is again in the welding circuit. If the electrode 8 is not removed from the item to be welded 7, then as the voltage of the welding transformer 5 increases, the current in the secondary winding increases, and

20 consequently, the voltage on the secondary winding of the current transformer 9. When the voltage at the output of the second auxiliary source 10 value of the Zener diode 16

dinene with obp; it minus sources 1 and 10. The base of the transistor is connected to the common cathode point of the thyristor 15 and the anode of the Zener diode 16, and a resistor 18 is connected between the base of the transistor 17 and the common minus of the auxiliary sources 1 and 10. The capacitor 11 serves to smooth the voltage pulsations after the first auxiliary source 1. Resistor 12 serves to set the collector current of transistor 17 and, at the same time, to set a constant charging time for capacitor 13, resistor 14. provides a discharge for capacitor 13 and, at best, punch through and voltage e unlocks the time constant of its difference to the base of the transistor is supplied from the row. Resistor 18 provides a reliable second auxiliary source.

thirty

blocking of the transistor 17 in the absence of a control signal at its base.

The device works as follows.

When the supply voltage is applied to the input of the device at the output of the first auxiliary source 1, the voltage is sufficient to start the circuit. Thyristor switch 2. is in the off state, however, due to the presence of the RG chain,

40

10 throughout the entire welding process. Second auxiliary

consisting of a resistor 3 and a capacitor 4, an emf is induced in the secondary winding of the welding transformer 5, the value of which is determined by the pyram- eters of elements 3 and 4 and is selected from the conditions of safety requirements (not more than 12 V). When the electrode 8 touches the welded object 7 in the secondary winding of the current transformer 9, a voltage appears which, after being rectified by the second auxiliary source 10, is sufficient to unlock the thyristor 15. After turning on the thyristor 15, the voltage from the positive terminal of the first auxiliary source 1 through the resistor 12 , the capacitor 13 and the open thyristor 15 are supplied to the base of the transistor 17, which opens, ensuring the inclusion of the thyristor 10 contains a reactive element (energy storage) - a capacitor. Its capacitance is chosen so that after the welding current is interrupted, an unlocking signal is applied to the control electrode of the thyristor 15 for a while. resulting in a time delay of up to 4 s, during which a voltage of 60-65V is provided on the electrode. After this time, the thyristor 15 is closed, the base of the transistor 17 is de-energized, it is reliably locked with a resistor 18, and the voltage on the secondary winding of the welding transformer 5 is reduced to 12 V.

This delay is necessary to ensure uninterrupted work of the welder in case of accidental rebounds of the electrode.

The elimination of a relay element made in the form of a reed switch improves the reliability of the device, and the use of standard elements by 50

55

improves manufacturability, reduces overall dimensions and metal consumption.

Claims (1)

Claims An apparatus for limiting the no-load voltage of a welding path 10 during the entire time of the welding process. Second auxiliary Point 10 contains a reactive element (energy storage) - a capacitor. Its capacitance is chosen so that after the welding current is interrupted, an unlocking signal is applied to the control electrode of the thyristor 15 for a while. resulting in a time delay of up to 4 s, during which a voltage of 60-65V is provided on the electrode. After this time, the thyristor 15 is closed, the base of the transistor 17 is de-energized, it is reliably locked with a resistor 18, and the voltage on the secondary winding of the welding transformer 5 is reduced to 12 V. This delay is necessary to ensure uninterrupted work of the welder in case of accidental rebounds of the electrode. The elimination of a relay element made in the form of a reed switch improves the reliability of the device, while the use of standard elements according to 55 improves manufacturability, reduces overall dimensions and metal consumption. Apparatus of the Invention A device for limiting the no-load voltage of a welding transformer comprising a switch mounted in the primary circuit of a welding transformer consisting of thyristors and diodes, an RC-shunt circuit, the first and second auxiliary sources of direct voltage, the second of which is connected to the input the secondary winding of the current transformer, the primary winding of which in series with the reactor is included in the secondary winding circuit of the welding transformer, while the minuses are auxiliary Fresh sources are interconnected, the first capacitor and the first resistor connected in parallel, and the series-connected thyristor and zener diode, the anode of the latter connected to the cathode of the thyristor, the control electrode of which is connected to the cathode of the zener diode connected to the plus of the second auxiliary power source, characterized by that, in order to increase the reliability of the equipment by obtaining a stable arc under different welding conditions, a transistor, a capacitor and two resistors were inserted into the device, the input of the first auxiliary source is connected to the common points of the control electrodes of the thyristors and cathodes of the diodes of the thyristor switch, and the output is bridged by the second capacitor, a second resistor is connected to the positive output of the first auxiliary source, the collector is connected to the common point of the first capacitor and resistor transistor, and its emitter - to the common minus of auxiliary sources, the base of the transistor is connected to the common point of the cathode of the thyristor and the anode of the zener diode, A third resistor is connected between the base of the transistor and the common minus of the auxiliary sources.