Inverter power source for tig welding

 

(57) Abstract:

The invention relates to the technical equipment used for arc welding, in particular to malagarasi - tion sources. Inverter power supply contains two parallel branches 1, 2. Each branch includes two after sequential included thyristor 3, 4, 5, and 6 correspond - ingly. The supply voltage is applied to the diagonal, education - private points of connection of the anodes and cathodes parallel wet - Wei 1 and 2. Between the points of connection of the anodes and cathodes of the thyristors 3, 4 and 5,6 included commutating capacitor 10. The primary winding of the output step-down transformer 9 to the middle point. Each Polubotko 7 and 12 included in the anode circuit of the thyristors 3 and 5. The power source provides a pulse-width modulation that allows you to change the duration of current flow in the load mode transformer for each half-cycle, thereby adjusting the welding current. 4 Il.

The invention relates to the technical equipment used for arc welding, in particular to small-sized power sources.

Known symmetric half-bridge inverter of the series type, used for welding (see And what her energy, applied to the welding zone through capacitors shoulders of the half-bridge that significantly impairs energy indicators. In addition, due to the fact that the welding current is controlled by varying the frequency of the inverter, the adjustment possibilities are limited, because at low currents increase ripple and worsens the arc.

Known symmetric bridge inverter serial type (see the same source, Fig. 1 g).

The disadvantages of this inverter, as described above, are the transfer of energy in the arc zone through the condenser, limited adjustment possibilities, since the current control is performed by changing the frequency inverter, as well as the deterioration of combustion stability of the arc at low currents due to the increase of the ripple current.

Known inverter power source for electric arc welding comprising two parallel branches, each of which includes a thyristor and Polubotko step-down transformer. Between the anode of thyristor switched capacitor (the source of the same, figure 1.d).

Describes the source is taken as a prototype in the preparation of this application.

The disadvantage of the prototype is limited ability to control ptx2">

Day solve this problem in the inverter power source for electric arc welding comprising two parallel branches, each of which includes two series-connected thyristor, and the supply voltage is applied to the diagonal formed by the connection points of the anodes and cathodes of parallel branches, a commutating capacitor and an output step-down transformer, the primary winding of the latter is included with the mid-point, and each Polubotko included in the anode circuit of the thyristors, and a commutating capacitor connected between a connection point of the anodes and cathodes of the thyristors parallel branches.

The claimed source is characterized by the following salient characteristics:

(a) each branch contains two series-connected thyristor;

b) each Polubotko transformer included in the anode circuit of thyristors;

C) the cathodes of the upper thyristors do not have a common point;

g) a commutating capacitor connected between a connection point of the anodes and cathodes of the thyristors parallel branches.

Conducted research on the patent and scientific literature revealed a number of technical solutions similar to AP the criteria of "novelty" and "technical level".

Testing of the prototype gives the right to argue about the health and industrial applicability of the claimed inverter power source.

In the drawings presents:

Fig. 1 is a circuit diagram of the inverter power source for TIG welding:

Fig. 2 - schedule power thyristors in standby (idle) mode;

Fig. 3 - schedule power thyristors mode pulse-width modulation;

Fig. 4 - schedule power thyristors mode with a combined impulse control.

Symbols used on the drawings-graphs and their definitions:

I1- current thyristor N3;

I2- current thyristor N4;

I3- current thyristor N5;

I4- current thyristor N6;

Uc- the voltage on the commutating capacitor;

tthemthe time pulse;

tp- the pause time;

T - the period of work;

Inverter power source for TIG welding has two parallel branches 1 and 2, each of which includes two series-connected thyristors 3, 4, and 5, 6 respectively. The supply voltage is applied to the diagonal, and (+) is supplied to the primary Polubotko 7 and 12 transform the public) parallel branches included commutating capacitor 10. The secondary winding of the transformer 9 consists of Polubotok 11 and 8, and Polubotko 11 and 8 through rectifier diodes 13, 14 and a smoothing inductor 15 is connected to the electrode 16, on the one hand, and article 17, on the other hand.

Inverter power source operates as follows.

In idle mode (Fig. 2) the control pulses alternately, simultaneously on two thyristor 3, 6 or 4, 5, and the capacitor 10 of the resonant charging on circuits: (+) source (not shown), Polubotko 7 of the transformer 9, the thyristor 3, the capacitor 10, the thyristor 6, (-) source; (+) source, Polubotko 12 of the transformer 9, the thyristor 5, the capacitor 10, the thyristor 4, (-) source. Thanks resonant circuit formed paleobotany 7, 12 and capacitor 10, a few cycles of the capacitor 10 is charged to a voltage necessary for normal operation of the inverter, and with a minimum speed of running in idle mode.

In the combustion mode of the arc, the following operation modes of the inverter.

1. The mode of operation is similar to the idle mode, but with much greater frequency, providing a continuous arc. This mode is characteristic of all neostem value of welding current. When this pre-idling for a few cycles, the capacitor 10 is charged to a voltage necessary for normal operation of the inverter, i.e., disconnection of the load current passing through the thyristor 4, 6 of the inverter. In the load mode when (+) on the left capacitor plate 10 control pulses to the thyristors 5 and 6, which are unlocked. As a result, the current begins to flow through the circuit (+) power source, Polubotko 12 of the transformer 9, the thyristors 5 and 6 (-) source. The second Polubotko 8 transformer current supplied to the load. The duration of current flow is determined by the control circuit, and when the maximum duration of the current transformer core 9 is not in saturation. To stop the current flow in the load control pulse is supplied to the thyristor 4, the voltage of the capacitor 10 is applied in the opposite direction to the thyristor 6, resulting in a current that flowed through him, begins to flow through the thyristor 4, and the capacitor 10 begins to recharge through the circuit: (+) source, Polubotko 12, the thyristor 5, the capacitor 10, the thyristor 4, (-) source. Until the voltage of the capacitor 10 is applied to the thyristor 6 in the opposite direction is the process Prairie on its plates will change the polarity and on the right plate will be (+). After cessation of current flow, the thyristor 5 is also restores the locking ability.

In the next cycle of the control pulses arrive on the thyristors 3 and 4, with the result that they are unlocked and the current flows through the circuit: (+) source, Polubotko 7 of the transformer 9, the thyristors 3 and 4, (-) source. With the secondary winding 11 of the current supplied to the load. Then to stop the current flow in the load, the control pulse is supplied to the thyristor 6, when the firing of the thyristor 6, the voltage of the charged capacitor 10 is applied in the opposite direction to the thyristor 4, resulting in the current flowing through it flows through the thyristor 6 and the capacitor 10 begins to recharge through the circuit: (+) source, Polubotko 7 of the transformer 9, the thyristor 3, the capacitor 10, the thyristor 6, (-) source. Until the voltage of the capacitor 10 is applied in the opposite direction to the thyristor 4, it is the process of restoring the locking ability in the forward direction. After the process of overcharging the thyristor 3 is locked, and the voltage of the capacitor 10 will change the polarity and on the left plate will be (+). Then, the control pulses are received on the thyristors 5 and 6 and the process repeats.

The proposed power supply both the thyristors 3, 4 and 5, 6 constant, but varies parametrically or by using a feedback delay time supply control pulses to the thyristors 4 and 6 that allows you to change the duration of current flow in the load mode transformer for each half-cycle, thereby adjusting the welding current. The source operation is illustrated by the plots of currents and voltages.

For normal operation of the source you want the regular inclusion of series-connected thyristors 3 and 4 occurred after you turn off the thyristors 5 and 6, and Vice versa, because the source can operate only under this condition. With decreasing welding current frequency of the pulsations is not reduced, which contributes to the stability of the arc.

Mode combined with impulse control.

In this case, in the load mode, in contrast to the previous pulse-width adjustment, the frequency of the alternate firing of series-connected thyristors 2, 4, 5, and 6 will change and can be represented parametrically, but managers must deal with a delay in relation to the control pulses to the thyristors 4 and 6. This delay determines the duration of a pause in the flow of current in Polubotko 2 and 12.

Thus, HC is it to reduce the length of the current pulses in Polubotko 7 and 12, because the duration of a pause is not changed. Therefore, with increasing frequency, the current will decrease. This method of control provides a stable arc and extends adjusting the operation of the inverter.

Inverter power source for electric arc welding comprising two parallel branches, each of which includes two series-connected thyristor, and the supply voltage is applied to the diagonal formed by the connection points of the anodes and cathodes of parallel branches, a commutating capacitor and an output step-down transformer, characterized in that each branch contains two series-connected thyristors, each Polubotko included in the anode circuit of the thyristors, and a commutating capacitor connected between a connection point of the anodes and cathodes of thyristors in parallel branches.

 

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