DE2043008C3 - Residual current circuit breaker - Google Patents

Description

The invention relates to a residual current circuit breaker with a summation current transformer, the Has primary windings for connection to a circuit to be monitored and a secondary winding, and with a release magnet which acts on a Sciialtschloß for a switching device and whose excitation winding lies in one diagonal of an electrical bridge circuit, in one of which Branch is the secondary winding of the summation current transformer and its other diagonal with connections is provided for feeding alternating current.

From the German Offenlegungsschrift 19 05 505 a residual current circuit breaker with a summation current transformer is known whose secondary winding is in a branch of an electrical bridge and whose Primary windings are connected in the circuit to be monitored. In one diagonal of the bridge there is a trigger element, which acts on a switch located in the circuit to be monitored acts while an alternating current source is connected to the other bridge diagonal.

The bridge is balanced when im to be monitored Circuit no fault current flows. Due to a fault current flowing in the circuit to be monitored becomes the premagnetization of the magnetic core of the current transformer and thus the inductive resistance the secondary winding of the current transformer changed so that the electrical bridge circuit is no longer balanced and a current flows in the diagonal of the bridge with the trigger element, through which the trigger element responds when the switch is actuated in the circuit to be monitored. The well-known residual current circuit breaker speaks not only to an alternating current residual current, but also to a direct current residual current in the circuit to be monitored.

The invention is based on the object of the trigger sensitivity to improve such a residual current circuit breaker, so that this switch also is suitable for monitoring circuits in which a relatively low direct current or AC fault current can occur.

A residual current circuit breaker is used to solve this problem of the type mentioned at the beginning, characterized by a further summation current transformer with primary windings for connection to the circuit to be monitored, the secondary winding in a bridge branch and which is so strapped that Voltages induced in the secondary windings of the two summation current transformers within the bridge circuit are opposed to each other.

This residual current circuit breaker is more sensitive because the two summation current transformers in the event of a residual current are biased in the opposite direction, so that the bridge is severely detuned. The trigger In other words, the double signal is available for triggering. However, it flows in the idle state no current through the excitation winding of the release magnet.

The invention is based on the drawings of exemplary embodiments explained in more detail:

The F i g. 1 and 2 show a schematic representation of two embodiments of fenler current circuit breakers according to the invention. The residual current circuit breaker 2 according to FIG. 1 has two summation current transformers 3 and 4 with primary windings 5 and 7 and secondary windings 6 and 8. The primary windings 5 and 7 are z. B. in two monitored lines R / U and Mp, while the secondary windings 6 and 8 are connected in an electrical bridge consisting of these secondary windings and ohmic resistors S and 10.

The primary windings 5 and 7 of the summation current converter 3 and 4 are wound in the same direction and connected in series so that the current in the circuit to be monitored flows through the primary windings 5 of the summation current converter 3 and the primary windings 7 of the summation current converter 4 in the opposite direction. The secondary windings 6 and 8 have the same »; Winding direction and are switched in the bridge so that their winding directions match within the bridge. Therefore, voltages Lk and Lh, which are induced in the secondary windings 6 and 8 by current flowing in the primary windings 5 and 7, are opposite to each other within the bridge.

In one diagonal of the secondary windings 6 and 8 and the ohmic resistors 9 and 10 existing bridge is an excitation winding 11 of a tripping magnet 12 schaitet, which is mechanically on a Switching mechanism 13 acts, which via a switching rod 14 has a circuit breaker 15 in the to be monitored Circuit operated. The other diagonal is connected to connections 16 for the supply of alternating current. A capacitor 17 is located in one of the connecting lines.

The bridge consisting of the secondary windings 6 and 8 and the ohmic resistors 9 and 10 is balanced in the normal operating state, so that no current through the excitation winding 11 of the trip magnet 12 flows.

If an alternating current fault current or a direct current fault current occurs in the lines RIU and Mp, the magnetic cores of the summation current converters 3 and 4 are biased in opposite directions, so that the bridge is severely detuned and the release magnet 12 triggers the switch lock 13, which opens the circuit breaker 15. The residual current circuit breaker according to FIG. So I have an increased trigger sensitivity.

In Fig. 2, the primary windings 5 and 7 of the summation current transformers 3 and 4 are wound in the same direction

and connected in series in such a way that the current in the circuit to be monitored flows through the primary windings of both summation current transformers 3 and 4 in the same direction.The secondary windings 6 and 8 also have the same direction of rotation and are connected in a bridge branch in such a way that their winding directions within the bridge are opposite are, so that the voltages Lk and Lk induced in the secondary windings 6 and 8 are again opposite to one another within the bridge circuit.

In the bridge circuits according to FIGS. 1 and 2 can be the bridge diagonals for the excitation winding 11 of the release magnet 12 and for the connections 16 can also be swapped for feeding in alternating current. Instead of two summation current transformers with the same direction wound primary windings and secondary windings wound in the same direction can be used in one embodiment Residual current circuit breaker also uses two appropriately switched summation current transformers whose primary windings or their secondary windings are wound in opposite directions.

Instead of the ohmic resistors 9 and 10, inductances and capacitances can also be used will.

1 sheet of drawings

Claims (1)

Claim: Residual current circuit breaker with a summation current transformer, the primary windings for connection to a circuit to be monitored and a Has secondary winding, and with a trip magnet, which is on a switch lock for a switching device acts and its excitation winding in one diagonal of an electrical bridge circuit is, in one branch of which the secondary winding of the summation current transformer is and whose the other diagonal is provided with connections for feeding in alternating current, characterized by a further summation current transformer (4) with primary windings (7) for connection to the circuit to be monitored, its secondary winding (8) in a bridge branch and which is connected in such a way that in the secondary windings (6,8) of the two summation current transformers (3,4) induced voltages within the bridge circuit are opposed to each other.