Electricity: measuring and testing – Electromechanical switching device – Relay
Reexamination Certificate
2000-02-07
2001-11-06
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Electromechanical switching device
Relay
C324S536000, C361S085000, C361S088000
Reexamination Certificate
active
06313636
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for determining switchgear-specific data at contacts in switchgear, in particular contactor contacts, and/or for determining operation-specific data in a network connected to the switchgear or contactors, in which a so-called contact follow-through travel at a switching path is detected as an equivalent criterion for erosion, and a resilience change during a shutdown cycle is measured in each case to determine an erosion of contact facings of contact pieces and is converted to a remaining service life, for which purpose a time measurement of an armature movement from a start of the armature movement to a start of contact opening is carried out for a switchgear drive having an armature, a magnet coil and an associated yoke, wherein the armature movement is determined from the measured time, the resilience is determined therefrom, the measurement of the contact opening is detected on a load side of the monitored switching device and the armature movement start is signaled from the voltage of the magnet coil. The invention also relates to an associated apparatus for carrying out the method.
German Published, Non-Prosecuted Patent Applications DE 44 27 006 A1, DE 196 03 310 A1 and DE 196 03 319 A1 describe methods for determining a remaining contact life of contactors, in which contact wear, that increases over the course of the electrical contact life, is detected from a time difference between a start of the armature opening movement and a start of contact opening. A present value of the so-called contact follow-through travel is determined in that case with the aid of a microprocessor and specifically adapted electronic circuits for detecting required measurement variables, and reduces as a result of erosion from its new value (=100% remaining contact life) to its minimum contact life (=0% remaining contact life). The contact follow-through travel is defined as that movement distance through which the magnet armature travels between the start of armature opening and the start of contact opening during the shutdown cycle.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for determining switchgear-specific data at contacts in switchgear and/or operation-specific data in a network connected to the switchgear and an apparatus for carrying out the method, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and apparatuses of this general type and which include additional functions in the method.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for determining at least one of switchgear-specific data at contacts in switchgear or contactors and operation-specific data in a network connected to the switchgear or contactors, which comprises detecting a so-called contact follow-through travel on a switching path as an equivalent criterion for erosion; measuring a resilience change during a shutdown cycle in each case in order to determine an erosion of contact facings of contact pieces and converting the resilience change to a remaining contact life, by performing a time measurement of an armature movement from a start of the armature movement to a start of contact opening for a switchgear drive including an armature, a magnet coil and an associated yoke; determining the armature movement from the measured time, determining the resilience from the armature movement, detecting a measurement of the contact opening on a load side of the monitored switching device and signaling an armature movement start from a voltage of the magnet coil; and determining switching, operating and fault states at the switching device and in an electrical network, in addition to the resilience, from the resilience detection signals by measuring the voltages at the magnet coil of the switching device drive and at switching poles of the switching device, in particular at an artificial star point.
In accordance with another mode of the invention, there is provided a method which comprises detecting an electrically on/off operating state of the contactor drive.
In accordance with a further mode of the invention, there is provided a method which comprises detecting the number of switching operations.
In accordance with an added mode of the invention, there is provided a method which comprises detecting a phase failure or a network voltage failure.
In accordance with an additional mode of the invention, there is provided a method which comprises detecting contact welding.
In accordance with yet another mode of the invention, there is provided a method which comprises additionally deriving any short circuit present in the network from the resilience detection signals.
In accordance with yet a further mode of the invention, there is provided a method which comprises avoiding faulty evaluations in the determination of the remaining contact life of the switching contacts by the detection of the phase failure and/or the network voltage failure.
In accordance with yet an added mode of the invention, there is provided a method which comprises supplying signals for the electrical on/off contactor drive through an optocoupler to a microprocessor for further evaluation.
In accordance with yet an additional mode of the invention, there is provided a method which comprises counting the number of electrical on/off signal changes in a microprocessor.
In accordance with again another mode of the invention, there is provided a method which comprises identifying a phase failure when the contactor is connected, by using a microprocessor.
In accordance with again a further mode of the invention, there is provided a method which comprises identifying a network voltage failure with a microprocessor through a voltage divider at the artificial star point.
In accordance with again an added mode of the invention, there is provided a method which comprises identifying contact welding when the contactor is switched off and network voltage is present.
In accordance with again an additional mode of the invention, there is provided a method which comprises identifying a short circuit by using a magnetic sensor system to detect a magnetic field.
With the objects of the invention in view, there is also provided an apparatus for carrying out the method, comprising an evaluation circuit and a microprocessor for determining contact follow-through travel from time signals, the microprocessor also processing signals relating to a network state; and units actuating the microprocessor for evaluating at least one of network voltage and phase voltage, the units containing a device for detecting arc voltages, in particular at an artificial star point.
In accordance with another feature of the invention, the device for detecting the arc voltages operates without a reference-ground potential.
In accordance with a further feature of the invention, there is provided a high-pass filter associated with one of several line phases at the artificial star point. The filter may be a passive high-pass filter, an active high-pass filter or a series circuit including a passive and an active high-pass filter.
In accordance with a concomitant feature of the invention, the evaluation circuit for determining the arc voltage without a reference-ground potential has measurement lines for each line phase at the artificial star point for additional detection of phase voltages.
Within the context of the present invention, the existing electronics can be used on one hand to identify specific fault states in the remaining contact life detection and to avoid an incorrect evaluation and, on the other hand, to obtain useful data for switchgear monitoring, such as specific states of the switching device or of the electrical network connected to the switching device. This extension of function means that the further measured data can be obtained with minimum additional complexity and by using a microprocessor, which is normally already present.
The invent
Elsner Norbert
Pohl Fritz
Greenberg Laurence A.
Lerner Herbert L.
Metjahic Safet
Nguyen Vincent Q.
Siemens Aktiengesellschaft
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