SU1141506A1 - Device for protection of pulse thyristor d.c.converter - Google Patents

Abstract

DEVICE FOR PROTECTION pulse thyristor DC-DC converter, in SEB vklyuchayuschego- main thyristor soedinenny series with the output circuit of the transducer comprising a linear contactor, contacts of which are intended to be included in series with the main thyristor and the coil through a capacitor intended for connecting parallel output terminals of the converter and through starting contact to one of; input; Converter terminals, characterized in that, in order to increase reliability, a current sensor, a discharge and auxiliary thyristors, a zener diode and a choke are inserted, while the cathode of the discharge thyristor is connected to the other side of the capacitor and the coils of the linear contactor through the choke. the capacitor and through the Zener diode is connected to the anode of the auxiliary thyristor, and the terminals of the current sensor to be connected in series with the main thyristor are connected to, respectively, Aulus yuschemu electrode auxiliary thyristor and its cathode connected to the control electrode of the discharge; thyristor.

Description

The invention relates to a converter technology, in particular to the field of protection of pulsed thyristor converters of direct current, used in electric transport, in particular in mine electric locomotives. A device for protection against disruptions of pulsed thyristor converters, consisting of a working impulse sensor and a logic circuit with a power source, triggered by the absence of a single pulse in the sequence of current pulses, is known. Dani device has a sufficiently high speed Сl. However, the design of such a device is complex, the application is not always justified, since in the event of a breakdown of the switching unit of the converter during installation of the engine mode for any reason other than a short period of time, it is not usually dangerous for the power components of the converter, and protection against stalling is not a requirement for speed. The closest to the invention to the technical essence is a device for protection of a pulse thyristor converter of constant current Kaj, the main thyristor connected in series with the output circuit of the converter and a switching node connected in parallel to the main thyristor, containing a line contactor, contacts of which are connected in series / with the main thyristor, and the coil is connected through a capacitor in parallel with the output terminals of the converter and connected to the one through a starting co} of the input terminals of the transducer L2J. However, the known device has the disadvantage of expressing a decrease in the supply voltage on the contact coil when the converter control ratio is close to unity, i.e. at the output voltage approaching the mains voltage. The holding force of the contactor box is so strong that it makes it possible to disconnect it spontaneously. This reduces the reliability of the converter as a whole and makes it necessary to limit the maximum 6 duty cycle during its operation, which is not always permissible. The purpose of the invention is to increase the reliability of the protection device. This goal is achieved by the fact that a device for protecting a pulse converter of a direct current including a main thyristor connected in series with the output circuit of the converter contains a linear contactor whose contacts are intended to be connected in series with the main thyristor and the coil through a capacitor parallel to the output pins of the converter and through the starting contact to one of the input pins of the converter, a current sensor, bit and all the thyristor aid, the zener diode and the choke, the cathode of the discharge thyristor is connected to the combined capacitor and linear contactor coils through the choke, the anode is connected to another capacitor lead and connected to the auxiliary thyristor anode through the diode, and the current leads to be connected in series with the main thyristor is connected respectively to the control electrode of the auxiliary thyristor and its cathode connected to the control electrode of the discharge thyristor. A moving vehicle with a thyristor electric drive is a source of increased danger. When the output voltage is close to the maximum, a breakdown in the operation of the converter cannot always be seen visually. Therefore, the converter must be equipped with a device that automatically disconnects it from the network in order to avoid loss of controllability, the consequence of which is the impossibility of quickly reducing speed and putting it into dynamic engine braking mode without switching power equipment. FIG. 1 is a schematic diagram of a converter with a protection device; in fig. 2 - experimental dependence of the voltage on the coil of the contactor U on the relative voltage at the output of the thyristor npeo6pa30BaTejpi

for the known device (curves B, C for different values of the capacitance) and the proposed device (curve A) in FIG. 3 - diagrams of the output voltage of the converter (voltage on the device capacitor. U,).

Converter 1 ss derkit main thyristor 2 and node 3 switching. The current sensor 4 includes a current transformer 5 with shunt resistance and a diode. Load 6 is connected to the converter output

with zero valve 7, in parallel with which the coil 8 is connected linearly. a contactor and a capacitor 9 connected in series with it, parallel to which, in turn, is connected a chain of discharge thyristor 10 and throttles P. The anode of the thyristor 10 through the zener diode 12 and the auxiliary thyristor 13 is connected to the control electrode, and the control electrode of the auxiliary thyristor 13 is connected via a diode to the output of a current transformer 5. Dp of the converter start-up serves as a button 14, by means of which a coil of a linear contactor is connected to the mains.

The device works as follows.

Pressing button 14 turns on

Line contactor 8 and through it.

I contact to the converter is energized. At the same time, the supply voltage is also supplied to the converter control system, which can be carried out using any of the well-known circuits. The converter starts to work, in case of a pulse voltage at its output, the coil 8 of the line contactor will be fed by a recharging current of the capacitor 9. If there is voltage at the output of the converter, the capacitor. will be charged with the polarity shown in FIG. 1, and in the absence of voltage, it is discharged to the load. 6

When the converter is operating with a minimum output voltage. (Fig. 3 capacitors 9, as can be seen from Fig. 36, manages to completely discharge for the duration of the pause output; this voltage. With an increase in output-jj of the voltage (Fig. Sv), the following occurs: boundary mode (Fig. 3g), , capacitor 9, having broken off, again

starts to charge. However, in this case, the control pulse from the current transformer, acting on the thyristor 13, will not turn it on, because at this moment the voltage on the capacitor 9 does not exceed the breakdown voltage of the Zener diode 12. This allows you to exclude the mode of operation of the device at which the switching of the thyristor 10 would be unreliable. In this case, the magnitude of the voltage on the capacitor at which the thyristor will be reliably switched off depends on the capacitor capacitance value, the size of the chokesel and the type of discharge thyristor 10 (switching the thyristor 13 is facilitated by the presence of a zener diode). FIG. (curve A) this mode is characterized by a certain voltage dip on the coil, which, however, does not exceed 3–5% and does not have a noticeable effect on reliable holding, since the reliable holding voltage for contactors of the type used in the device is 50–60 % nominal voltage

With a further increase in the output voltage (Fig. 3 d) at the time of the occurrence of the control pulse on the thyristor 10, the voltage on the capacitor 9 is higher than the breakdown voltage of the zener diode 12 and the thyristors 13 and 10 are sequentially turned on. The recharge of the capacitor 9 from the polarity indicated in FIG. 1, to the opposite. Due to the oscillatory recharge of the capacitor through the choke 11, the thyristors 13 and 10 are locked, after which the capacitor 9 begins to recharge. The voltage across the capacitor 9 is as shown in FIG. 3 e. A voltage oscillogram on the same capacitor during operation of the known device is shown on 3 W for comparison. Due to the periodic recharging of the capacitor 9 during normal operation of the converter, the voltage on the coil 8 of the linear contactor will remain practically: • unchanged throughout the entire range of operation of the converter.

With the breakdown of the converter, i.e. in the absence of commutation of the main thyristor, the capacitor 9 will be charged, after which it will not be discharged, control pulses

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the thyristor 13 will also not be supplied, the current in the coil of the line contactor will stop, resulting in its disconnection.

Thus, in the proposed device, in comparison with the known supply voltage, the coil of the linear contactor does not decrease at the output voltage of the converter, which is close to the maximum, since in the whole range of output control-. voltage converter

41506

the voltage on the coil of the line contactor is maintained sufficient to securely hold it in the on state. This increases the reliability of the protection device. The scope of application of the proposed device is also expanding.

The use of the device allows to increase the safety of operation of the rail mine electric conveyor with thyristor pulse converters.

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Claims (1)

DEVICE FOR PROTECTING A DC PULSE THYRISTOR CONVERTER, including · the main thyristor connected in series with the output circuit of the converter, containing a linear contactor, the contacts of which are designed to be connected in series with the main thyristor, and the coil through the capacitor is designed to connect in parallel to the output terminals of the converter and through the start contact to one of the 'input; converter leads, characterized in that, in order to increase reliability, a current sensor, a discharge and auxiliary thyristors, a zener diode and a choke are introduced, while the cathode of the discharge thyristor is connected through a choke to the combined terminals of the capacitor and the coil of the linear contactor, the anode is connected to another terminal of the capacitor and through zener connected to the anode vspomogatelnogo1tiris- ~ torus, and current sensor conclusions _Λ pre- designated for inclusion posledo- 3 consistently with the main thyristor are connected. respectively, to the control electrode of the auxiliary thyristor and its cathode connected to the control electrode of the discharge thyristor. Sil ,,,, 1141506 Figure 1