DE2920188B1 - Circuit arrangement for monitoring contactors - Google Patents

Description

Claims: 1. Circuit arrangement for monitoring the main current paths of contactors with a measuring element lying in the course of a line to be switched, characterized by the following features: 1. With the drive part (excitation coil 8) a first signal transmitter (16) is connected to the contactor (4); 2. with the measuring element A second signal transmitter (17) is connected (current transformer 13, 14, 15); 3. both signal transmitters (16, 17) are connected to an evaluation circuit (20); 4. the evaluation circuit (20) emits an output signal if there is no signal from the first signal generator (16) a signal from the second signal generator (17) is present.

2. Circuit arrangement according to claim 1, characterized by the following Features: 1. In the case of an electromagnetically operated contactor (4), the first signal transmitter (16) controlled by the excitation voltage of the contactor (4); 2. the second signal generator (17) is determined by a current measuring device assigned to the line (1, 2, 3) to be switched (13, 14, 15) controlled.

3. Circuit arrangement according to claim 1, characterized in that the evaluation circuit (20) a trigger signal for an upstream circuit breaker (12) gives.

The invention relates to a circuit arrangement for monitoring the Main current paths of contactors with one lying in the course of a line to be switched Measuring element.

While known bodies of this type, which are commonly part of of switchgear can be of the most varied types, especially to serve the To record the respective existing load, the invention is based on the object the correspondence between the switching status of the operating circuit of the contactor and to monitor the switching status of the main current paths. This is supposed to be for the purpose happen, an unintentional start-up or continued operation of To signal equipment in spite of contrary or missing switching commands and, if necessary, to prevent.

This object is achieved according to the invention by the following features: 1. A first signal transmitter is connected to the drive part of the contactor; 2. with a second signal transmitter is connected to the measuring element; 3. Both signal transmitters are on an evaluation circuit connected; 4. the evaluation circuit gives an output signal if, in the absence of a signal from the first signal generator, there is a signal from the second Is present.

This circuit arrangement is in principle different for contactors Drive type suitable, d. H.

for example for pneumatically, fluidically or electromagnetically operated Sagittarius.

In the latter, most commonly used type of shooter the first signal transmitter can be from the excitation voltage of the contactor and the second signal transmitter controlled by a current detection device assigned to the line to be switched be. The evaluation circuit then responds to the dangerous state, that the main current paths of the contactor carry a current, although an excitation voltage for the contactor is not available. To remedy this condition as quickly as possible, it is advantageous to design the evaluation circuit in such a way that it emits a switch-off signal for a circuit breaker upstream of the contactor. Whose response gives Reason for checking whether the contactor is faulty. The cause can be B. a weld or gluing the main contacts or blocking the drive part of the contactor be.

The invention is described below with reference to that shown in the figure Embodiment explained in more detail.

In a three-phase cable run with phase conductors 1, 2 and 3 is a contactor 4 with main contacts 5, 6 and 7 switched on by an electromagnetic Drive system can be actuated, the excitation coil of which is denoted by 8. The cable run with the phase conductors 1, 2 and 3 is used to feed an electric motor 10, the is provided for driving any work machine 11. In normal operation can the motor 10 by connecting the excitation coil 8 to a suitable, not Switch the control voltage source shown on and off. Switching off succeeds but not when the main contacts 5, 6 and 7 of the contactor 4 are in the on position are blocked, e.g. B. by welding as a result of an overload or by a mechanical faults within the drive system of contactor 4. This allows Hazards of the most varied kinds may be connected. A shutdown of the engine 10 is generally made possible by a circuit breaker 12 that is still present be, but only with a considerable and therefore dangerous loss of time, because the Operator of the motor 10 and the contactor 4 to that often at some distance and locked, housed circuit breaker 12 does not have immediate access or is not even informed of its presence.

Claims (1)

This hazard is caused by an automatically acting circuit arrangement prevented. For this purpose, the circuit arrangement includes a with the excitation coil 8 of the Contactor 4 connected signal generator 16 and another, with current transformers 13, 14 and 15 connected signal generator 17 for the phase conductors 1, 2 and 3. The operating voltage the excitation coil 8 and the output variables of the current transformers 13, 14 and 15 are through the signal generator 16 or 17 converted into signals that are available for further processing in an evaluation circuit 20 are suitable. The evaluation circuit 20 compares the signals of the signal generator 16 and 17 and thus erfßat the incident that in one or load currents flow across all phase conductors, although contactor 4 is not energized. The output signal of the evaluation circuit 20 is a suitable output element 21, e.g. B. a relay supplied. In the example shown, the relay controls 21 a warning lamp 22 and at the same time the release of the circuit breaker 12. Despite blocking of the contactor 4, the motor 10 is thus disconnected from the mains.