DE2036497A1 - Residual current circuit breaker - Google Patents

Description

The invention relates to a residual current circuit breaker with a summation current transformer, the primary windings for connection to the monitoring circuit and a secondary winding, to which the excitation winding of a switch mechanism for a switching device acting release magnet is connected.

The AC response current of a residual current circuit breaker with a summation current transformer increases if the switch is additionally influenced by a direct current residual current due to the premagnetization of the converter due to the DC residual current. Furthermore, such a residual current circuit breaker does not trip at all if it is only traversed by a direct current residual current is, as is known, to induce a voltage in the secondary winding of the summation current transformer an alternating current in the Pri ~ märwickiung is required. Even the changes in flux, which one or more primary windings of the summation current transformer flowing through, chopped direct current generated by half-wave rectification of alternating current in the converter are not so large, that a voltage sufficient to trigger the residual current circuit breaker is induced in the secondary coil of the summation current transformer will.

The invention is based on the object of remedying this and the use of residual current circuit breakers of the above-mentioned type also in circuits with, for example, thyristor-controlled DC motors to ermoj.iclien, in which because of the thyristor- control, in addition to AC residual currents, DC residual currents can also occur.

To solve this problem, a residual current circuit breaker is the initially mentioned type according to the invention characterized in that a capacitor in series or in parallel with the secondary winding of the summation current transformer and the excitation winding of the tripping

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magnet is switched.

From the German patent specification 279 545 it is known at the Secondary winding of a current transformer a capacitor to achieve the lowest possible phase deviation towards 180 ° to be connected between the primary and the secondary stream. Such a deviation of the two currents from the phase angle is probably 180 ° E.g. important for measuring devices with current transformers, for residual current circuit breakers However, it does not matter, so that the parallel connection of a capacitor to the secondary winding of the Summation current transformer in a residual current circuit breaker, which should be designed to save space and costs as much as possible, so far was considered unnecessary and has not become known.

In contrast, the invention is based on the knowledge that the series or parallel connection of a capacitor to the secondary winding of the summation current transformer of a residual current circuit breaker the voltage oscillations generated by a fault current consisting of a pulsating direct current in the independent circuit have a sufficient amplitude to actuate the release magnet and thus trigger the switch. Particularly It is beneficial if the one from the capacitor, the secondary winding of the summation current transformer and the excitation winding of the release magnet existing circuit at least approximately on resonance is matched.

The invention and its advantages are based on the drawing explained in more detail in an exemplary embodiment:

Figure 1 shows schematically a residual current circuit breaker. FIG. 2 shows the magnetic characteristic of the summation current transformer in the switch according to FIG. 1.
Figures 3 and 4 show oscillograms.

Figure 1 shows a residual current circuit breaker for monitoring the Lines R / U and Mp of an electrical system.

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, VPA 70/4023

This residual current circuit breaker 2 has a summation current transformer 3 with primary windings 4 and a secondary winding 5. the Primary windings 4 are in the "monitored lines R / U" and Mp, the secondary winding 5 of the summation current transformer 3 is on the excitation winding 9 Ces tripping magnets 8 connected. This tripping magnet 8, which can be a holding magnet or a working magnet can, acts through a mechanical connecting part 8a on the switch lock 10, which via a switch rod 10a into the to be monitored lines E / U and Mp lying switch 11 operated.

In parallel with the secondary winding 5 of the summation current transformer 3 and the excitation winding 9 of the tripping magnet 8, a capacitor 6 is switched on. Instead of the capacitor 6, a condenser 7, indicated by dashed lines in FIG. T, can also be connected in series with the windings and 9 be switched. The one from the capacitor 6 or 7 and the Windings 5 and 9 existing resonant circuit is tuned to resonance or at least approximately to Eesonanz.

The mode of operation of the capacitor 6 or 7 is based on the figures 2 to 4 explained:

The flux j> or the time t are plotted on the ordinate of the diagram according to FIG. 2 and the fault current I n is plotted on the abscissa. If an alternating current fault current flows through the summation current transformer 3 in accordance with the dashed curve 12 in FIG. At a corresponding level of this alternating current, the entire magnetic characteristic curve 13 consisting of the hysteresis loop is passed through and the flux change Λ j> ^ that occurs is very large, so that the voltage induced in the secondary winding of the summation current transformer according to the induction law is so large that it corresponds to the response voltage of the Trip solenoids 8 exceeds and the residual current circuit breaker trips without difficulty. The switch is triggered even if the capacitors 6 and 7 are not present in the circuit consisting of the coils 5 and 9.

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VPA 70/4023

Does the. Residual current, on the other hand, has the character of a pulsating direct current in accordance with the solid curve 14 in FIG. 2 (One-way direct current), so is the magnetization of the summation current transformer s 3 run through the hysteresis loop in FIG. 2 only up to the remanence point 15. The change in flux Δ Α remains small and the induced in the secondary winding 5 of the summation current transformer 3 The voltage does not reach the response value of the tripping magnet 8, so that the switch does not trip.

This case is shown graphically in the oscillogram according to FIG. The curve 16 shows the course of the fault current I ^ over time, the curve located between the trigger lines 18 and 19 represents the time course of the voltage TL on the excitation winding 9 of the release magnet 8. As can be seen, the curve 17 nowhere extends beyond the release lines 18 and 19. '

By switching on the capacitor 6 in parallel with the windings 5 and 9 or the capacitor 7 in series with the windings 5 and 9, a resonant circuit is created, and especially when this is coordinated Oscillating circuit at least approximately at resonance, the voltage IL on the excitation winding 9 of the release magnet 8 is raised so far, that the switch is triggered even with a fault current consisting of pulsating direct current.

These relationships are illustrated by the oscillogram according to FIG. 4 _f in which the same curves have the same reference symbols as in FIG. As can be seen, the curve 20, which indicates the time dependence of the voltage IL on the excitation winding 9 of the tripping magnet 8, protrudes beyond the tripping line 19, so that the residual current circuit breaker triggers even with a pulsating direct current according to curve 16 in FIG. The shape and height of the curve 20 depends on the size of the capacitor 6 or 7 used in FIG.

If the trigger magnet 8 is a holding magnet, in which the draw depends on the current direction in the field winding, it is advantageous to dimension the capacitor 6 or 7 so that the aperiodic borderline case in the secondary circuit is avoided and

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VPA 70/4023

the amplitudes of curve 20 in FIG. 4 "on both sides of the zero line are about the same.

4 figures

1 claim

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Claims (1)

VPA 70/4025 Claim Residual current circuit breaker with a summation current transformer, the primary « Windings for connection to the circuit to be monitored and a Has secondary winding to which the excitation winding of a trigger magnet acting on a switch lock for a switching device is connected, characterized in that a capacitor in series or in parallel with the secondary winding of the summation current transformer and the excitation winding of the release magnet is connected. 109886/0745