SU1495897A1 - Device for protection of semiconductor converter - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase the reliability of a device for protecting a semiconductor converter against internal short circuits during valve breakdown, by improving the selectivity of fuses. When the short circuit current passes through the fuses 1, included in the circuit of the punched valve 2, the currents of each of them are different at the melting stage of the fusible inserts. By a certain point in time, the dynamic resistance of the fuse 1 in the branch with less resistance becomes significantly greater than the dynamic resistance of the fuse 1 in the parallel branch. When making resistances of branches containing fuses and connected in parallel with different ratios in the range of 1.3–2, the selectivity of protection is improved due to the fact that, due to the non-simultaneous burning of fuses 1, the integral of the fuses is determined by all parallel-connected fuses 1 and arc integral - one fuse. 1. 2.il.

Description

The invention relates to electrical engineering and can be used to protect power converting installations used in electrical terms, electrolysis, electric drive and other areas.

The purpose of the invention is to increase the reliability of a device for protecting a semiconductor converter against internal short circuits during the breakdown of ventilators by improving the selectivity of fuses

FIG. 1 is a schematic of the device for protecting a semiconductor converter in FIG. 2 - timing diagrams for the operation of the device.

The device for protection (Fig. 1) contains two branches connected in parallel with each other with fuses 1, which are connected to the circuit of each of the valves 2 of the protected converter.

The fuses 1 are the same and are connected to each other and the protected transformer by means of a current lead - 3 of them.

I The busbar resistances b are made different for the connectors.

1 fuse with each other parallel to the fuse 1, and the ratio To the maximum resistance of the branch to the minimum. Satisfies the condition: 1 ,.

The device is based on the fact that the selectivity coefficient Kg of the fuses is determined by the following pressure:

KC

one

de

.t

+ -tflS TP

one

i dt

f

(one)

BY

- Joulev arc burning integral;

Oft

i i dt

PA

-Joulev integral melting;

- respectively, the burning and melting time of the insert.

In this case, the smaller the selectivity coefficient, the better the selection of protection in case of breakdown of the valve.

Consider the process of disabling short-circuit current (short-circuit) device

the breakdown of one of the valves 2 (Fig. 2).

With the passage of current short circuit through the fuses 1 included in the circuit of the broken valve 2, the currents of each of them at the melting stage of the fusible inserts are different, and in this case inpi i pr, where 1 1p, is the current of the fuse in the circuit, where the resistance of the power busbars is less, is the current fuse in the circuit where the resistance of the current busbar is greater.,

  V

In this case, the dynamic resistance of the fusible plugs changes in accordance with the expression

R,

0

five

0

five

0

five

0

five

R

(2)

-k, -, -, -; o

where K „- dynamic resistance

 fuse insertKHJ R is the resistance of the fuse link in the initial state.

By the time t, the dynamic resistance of the fuse in the branch with lower resistance becomes significantly greater than the dynamic resistance of the fuse in the parallel branch. If we take into account that by this time 90-95% of the melting integral has been used, then it becomes a 1 m Yush distribution, therefore, iflp is in the region. falls sharply, and the current increases sharply. If the current drops to zero, then the arc in this fuse, as a rule, does not occur, since the temperature of the fusible elements is insufficient for its occurrence. At the site current short circuit off with one fuse.

Thus, the melting integral is determined by two fuses, and the arc integral is determined by one fuse, which leads to a decrease in the selectivity coefficient of a pair of fuses.

If the current i „p does not fall to O, and an arc also occurs in the first fuse, as shown by experimental and calculated data, the arc of a pair of fuses remains smaller than in the case of uniform distribution of current.

With a uniform distribution of current between the fuses, the process of disconnecting the short-circuit current. flows along the dotted curve (Fig. 2), and the arc burning integral significantly increases.

The effect of improving the selectivity is achieved if the resistances of the branches of the fuses differ from each other by no less than 1.3 and not more than 2 times.

Formula

Device to protect the semiconductor converter from internal short circuits during valve breakdown, containing intended

for connecting in series with each of the valves of the protected converter, each of which

made in the form of N branches connected in parallel, consisting of conducting busbars and connected in series with them, one in each of the branches of identical hoops

fuses, characterized in that, in order to increase reliability by improving the selectivity of the operation of fuses, in each of the circuits

busbar resistance

different branches are made different, and the ratio To the maximum resistance of the branch to the minimum satisfies condition 1 ,.

FIG. 2

Claims (1)

Claim A device for protecting a semiconductor converter from internal short circuits during the breakdown of valves, comprising intended to be connected in series with each of the gates of the protected converter circuit, each of which 5 is made in the form of N branches connected in parallel, consisting of conductive buses and connected in series with them one in each of the branches of the same fuse: fuses, characterized in that, in order to increase reliability by improving selectivity I fuse in each of the current supply circuit 15, the resistance of tires of different branches are made different, the ratio K of the maximum to the minimum resistance branches satisfy the condition 1.3 ≤ k ≤ 2.