SU862349A1 - Single channel device for controlling gate converter - Google Patents

Description

(54) SINGLE-CHANNEL DEVICE FOR CONTROLLING VENTILAL CONVERTER

one

The invention relates to electrical engineering and can be used in thyristor converters of alternating voltage to constant voltage, in which the cathodes of the thyristors have a common point.

Single-channel control devices are known, which contain a three-phase pulse generator, which form circuits, phase-shifters, a pulse distributor, built according to the circuit of a thyristor ring counter with a separate synchronization angle 1.

Such a single-channel device is very complex due to the presence of many circuit elements, which leads to a decrease in reliability, and the synchronization circuit filter becomes the cause of asymmetry of the output voltage.

Of the known single-channel control devices of a valve converter, the closest to the technical essence is a single-channel device for controlling a valve converter with a cathode group of thyristors 2, which contains series-connected reference voltage generator, pulse shaper and diode distributor

pulses with a cathode group and a pulse transformer. In such a device, the control voltage is compared with the reference voltage.

The disadvantage of such a device is complexity, low reliability of operation, the presence of asymmetry due to the variation of the parameters of elements included in the reference voltage generator, the effect of changes in the converter supply voltage on the magnitude of the load current.

The aim of the invention is to simplify

10 devices and increase its reliability.

This goal is achieved by the fact that a relay element with an output key and a load current sensor, the output of which is connected to the input of the relay element through a source, are inserted into a single-channel device for controlling a valve converter with a cathode thyristor group, containing a diode distributor of pulses and a control voltage source 15 control voltage, and the key of the relay element is included in the neutral wire of the diode pulse distributor.

A measuring shunt can be used as a load current sensor. The relay element can be made on a DC amplifier, Schmidt trigger and transistor switches.

The drawing shows the principle circuit of a single-channel control unit of a valve converter with a cathodic thyristor group.

The single-channel control device of a valve converter with a cathode group of thyristors contains a current sensor 1, 8 of which a measuring shunt is used, connected in series with the load 2 of a valve converter. The output of current sensor 1 is connected to the input of the relay element 3 and in series with the source 4 of the control voltage. Key 5 is inserted into the neutral wire of the diode distributor of 6 pulses. The diode distributor 6 pulses contains a three-phase transformer 7 and diodes 8-10.

The windings of the transformer 7 are turned on into a star with a neutral wire, the primary windings are connected to the power network, and the secondary windings through diodes 8-10 are connected to the control electrodes of the corresponding thyristors 11–13. The zero point of the secondary windings through the limiting resistor 14 and the key 5 is connected to the cathodes of the thyristors 11 -13 valve converter.

The device works as follows.

The control voltage U is applied to the input of the relay element 3 from the source 4 of the control voltage. The key 5 of the relay element 3 is closed as the condition is satisfied:

and - ct D,

where KZ ios.v11noe voltage sensor 1 load current 2; 2D width of the hysteresis loop of the relay element 3 (selected less than the ripple amplitude of the voltage sensor 1 of the load current 2).

The value of T / (U, equal to O at the initial moment of time. The pulse distributor 6 applies the unlocking signal to that of the thyristors I -13, on the anode of which there is the highest potential. If the highest potential on the anode of the thyristor 11, then the unlocking signal passes through Circuit: End of phase A winding of pulse distributor 6, diode 10, control electrode of thyristor 11, cathode of thyristor 11, switch 5, limiting resistor 14, common point of diode distributor. Thyristor 11 opens and phase A is applied to load 2. narrows under the influence of the voltage of phase A. The voltage from the current sensor 1 increases and

and - CE D

the relay element 3 is triggered and the key 5 opens, removing the unlocking voltage from the thyristor 11. When it reaches the maximum, the load current 2 and, accordingly, the voltage of the current sensor 1 begin to decrease under the effect of decreasing phase voltage A. If the conditions are:

and - k1 d

the relay element is activated, and the key 5 is closed.

A diode distributor b of pulses delivers a unlocking signal to thyristor 12, the anode of which is at the highest potential across the circuit: the end of the winding phase B of distributor 6, diode 9, control electrode of thyristor 12, cathode of thyristor 12, switch 5, limiting resistor 14, common point diode distributor 6. The thyristor 12 opens and the voltage of the phase B is applied to the load 2. The current tl of the load 2 under the action of the voltage of the phase B increases. As in the case of operation of the thyristor 11, the key 5 opens, and then closes.

A diode distributor of 6 pulses supplies a triggering signal to the thyristor 13, the anode of which is now at the highest potential across the circuit: the end of the winding of phase C of the distributor 6, diode 8, control electrode of the thyristors 13, cathode of the thyristor 13, switch 5, resistor 14, common point diode distributor 6. The thyristor 13 opens and phase 2 voltage is applied to load 2

Further, the work process is repeated. Thus, the device operates in a self-oscillating mode with a frequency of 3f, where f is the frequency of the mains supply.

With a large input control voltage and the voltage Ts k3 of the current sensor 1 does not have time to reach the value of U + + D during the operation of one thyristor, the relay element does not work and the key 5 remains closed. The distributor 6 pulses feeds unlocking signals to each of the thyristors 11-13 during the time that the thyristor anode is at the highest potential, which ensures the maximum voltage on the load until the voltage LL K11 reaches the value and + A.

After that, the auto oscillatory mode discussed above is set.

The use of the proposed single-channel device for controlling a valve converter provides the following advantages over existing devices:

ease of manufacture, minimal cost, and reliable operation by significantly reducing the number of elements included in the device;

the high symmetry of the output voltage, which is determined by the symmetry of the network voltage, since there are no asymmetry elements in the device.

Claims (2)

1.Labuntsov, V.A., et al. Magnetic and semiconductor control system of a valve converter. Electricity, 1965, No. 2, p. 29-35. 2. USSR author's certificate No. 568137, cl. H 02 R 13/16, 1977 (prototype).