DE1233469B - Arrangement for limit value detection of a direct current - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CI .:

G05f

German class: 21c -46/31

Number: 1233 469

File number: S 75310 VIII b / 21 c

Filing date: August 16, 1961

Opened on: February 2, 1967

For the safety monitoring of nuclear reactors, radiation measuring devices such as ionization chambers, used that are interconnected with limit monitors. This facility causes ζ. B. the triggering of an alarm system or the automatic shutdown of a reactor, if that The signal from the radiation measuring device exceeds the value set in the limit indicator.

In the past, magnetic amplifiers were used for similar measuring purposes, in which the inductances capacitors were also connected in parallel. Sensitivity and shutdown accuracy of such However, facilities left something to be desired. For shutdown purposes in heavy current engineering are also overcurrent transformers with an iron core with an approximately rectangular magnetization characteristic has been proposed. Today work in the weak and ultra-fine current measuring technology against it Limit indicators mostly based on the yes-no principle with the help of flip-flops fitted with tubes or transistors. This means that the output voltage can only assume two inherently constant values. This Behavior does not allow conclusions to be drawn about the signal state, and incorrect changes to the The limit indicator itself is only displayed when the error finally results in the triggering of the tilting process indicates. But it can also work in the opposite direction, so that it works at all the tipping process is not triggered if the signal rises to the danger level. A Loss of the input signal from the sensor is also not reported.

To avoid the resulting uncertainties, it is desirable to have a device whose working condition can be checked at any time with the greatest possible sensitivity and response accuracy can. The present invention solves this problem and relates to an arrangement for detecting limit values of a direct current using transformers that can be pre-magnetized by the direct current, where a capacitor is connected in parallel, especially for safety circuits of Nuclear reactors. According to the invention, the transformer has a rectangular magnetization characteristic and the capacitor has such an electrical capacitance that a resonance tuning to the frequency the alternating voltage applied to this oscillating circuit via a resistor only when The limit value of the direct current to be detected is reached.

The advantages mentioned over the prior art result from the basic principle of the

Arrangement for limit value detection of a
Direct current

Applicant:

Siemens Aktiengesellschaft, Berlin and Munich, Erlangen, Werner-von-Siemens-Str. 50

Named as inventor:
Herbert Troeger, Baiersdorf

lying invention, which consists in the fact that the tilting properties a pre-magnetizable choke, which in a known manner on a steep change in inductance the same due to the rectangular characteristics of the magnetic core used, combined with the voltage increase that can be achieved by an oscillating circuit in the case of resonance are. One that realizes this basic idea

he circuit example (see Fig. 1 and 2) works as follows:

The direct current taken from the radiation measuring device 12 feeds the windings 14 and 15, which are wound together with the windings 4 and 5 as well as 24 and 25 on a magnetic core with rectangular characteristics. An adjustable capacitor 3 is connected in parallel to the windings 4 and 5. The resulting oscillation circuit is connected to an alternating voltage source via a resistor 2

z. B. connected to a frequency of 50 Hz. The series resistor 2 gives the arrangement flowing current has the character of an impressed current that occurs at resistor 2 and at the oscillating circuit, consisting of the windings 4 and 5 and the capacitor 3, leads to corresponding voltage drops.

When the direct current is switched off, this oscillating circuit is not tuned to resonance. When switching on of the ionization chamber current, which has a pre-magnetizing effect, changes the inductance of the Windings 4 and 5, so that the oscillation circuit is thereby tuned to resonance. However, since due to the square wave characteristics of the magnetic core, the alternating current resistance and thus the voltage collapses on coils 4 and 5 after crossing the kinks of the magnetization curve, the oscillation circuit suddenly goes out of resonance.

709 507/287

Claims (2)

The combination of the properties of a parallel resonant circuit and the tilting behavior of a choke winding applied to an iron core with a rectangular characteristic result in a considerable increase in sensitivity compared to a simple circuit without capacitor 3. So z. B. such a limit indicator ready to be controlled with 100 μΑ. Another advantage is that the mentioned tilting process only takes about 30 ms in contrast to conventional magnetic flip-flops, which need about 300 ms. The voltage occurring at the output windings 24 and 25 then has approximately the course according to FIG. 2, which is plotted as a function of the control current. The shape of this curve can be changed by setting the capacitor 3 and, to a certain extent, also by the resistor 2. In any case, by increasing the control current, a voltage maximum is reached which, when the control current continues to rise, is followed by a slight decrease again with a sudden voltage collapse, which is reproducible with an accuracy of l% under correspondingly constant operating conditions. To avoid the transmission of an alternating current component to the same circuit, the bias windings are connected in opposite series in a known manner. As already mentioned, the output signal is taken from this oscillating circuit transformer via the windings 24 and 25 and fed to the transformer 32, which is connected to the amplifier 33 with its output winding. This intermediate transformer 32 is necessary so that the direct current flowing in the input circuit of the amplifier 33 does not have a disruptive effect on the main transformer. The amplifier 33 can be a tube or transistor amplifier and is connected to the triggering device, a relay 38, via the output transformer 34. This DC relay 38, which is connected to the transformer 34 via the rectifiers 35 and 36 and the smoothing capacitor 37, is preceded by a measuring device 39 as part of a measured value comparison arrangement, as described below, which allows the operating status of the entire device to be monitored at any time. The use of such limit indicators is of course not limited to nuclear reactors, rather it is appropriate wherever monitoring devices such. B. thermocouples, weak signal direct current is supplied. Other circuit arrangements that differ from that in FIG. 1 are also conceivable. What they all have in common, however, is the principle of superimposing the resonance amplification of an oscillating circuit and changing the inductance with the aid of a pre-magnetizing direct current signal using the tilting behavior of the inductance, which is caused by the rectangular characteristic of the magnetic core used. It should be noted that, of course, the use of a series resonant circuit in a corresponding circuit is possible. Patent claims: 1. Arrangement for limit value detection of a direct current using by the Direct current bias transformers to which a capacitor is connected in parallel, in particular for safety circuits of nuclear reactors, characterized in that the transformer has a rectangular magnetization characteristic and the capacitor has a Such electrical capacitance has that a resonance tuning to the frequency of the one Resistance to this oscillation circuit applied alternating voltage only when reaching the to detected limit value of the direct current takes place. 2. Arrangement according to claim 1, characterized in that up to a maximum Value approximately steadily increasing and then steeply decreasing output signal via an intermediate transformer to an amplifier which is connected upstream of a display and trigger system. Considered publications:
German Patent Nos. 815 200, 916 650;
German Auslegeschrift No. 1104 599;
Kerntechnik magazine, 1960, no. 12, pp. 408 to 410. 1 sheet of drawings 709 507/287 1.67 © Bundesdnickerei Berlin