Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1998-03-02
2000-02-08
Paladini, Albert W.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
324422, 340644, H01H 7312
Patent
active
060231106
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to switching equipment with an electromagnetic contactor and a circuit breaker which is located ahead of the contactor. The contactor has an operating magnetic circuit with a magnetic core, an operating coil and an armature which moves in dependence on the current flow through the operating coil. Furthermore, the contactor has a number of contacts which are influenced by the armature.
BACKGROUND OF THE INVENTION
Electromagnetic contactors are known and have been used for a long time, for example as switching means between a voltage source and an electric motor. One problem with such contactors is that one or a few of the contact pairs of a contactor may become fixed to each other by welding, and the risk of this is greater at high currents. Such welding together of contact pairs may, for example, be caused by contact bouncing when closing the contactor towards a high making current of an electric motor.
The fact that one or more contact pairs become fixed by welding may entail serious harmful effects. Upon an opening signal to a contactor with a welded-together contact pair, the armature will move a certain distance in the opening direction, because of the resilience in the mechanical coupling, and then stop in an intermediate position. This may cause arcs in the contact pairs which are not welded together, and fire, explosion or other damage to the contactor and other equipment. In many applications, it may also, and independently thereof, cause serious consequences that a contactor does not open when, according to a supplied opening signal, it should have opened.
SUMMARY OF THE INVENTION
The object of the invention is to provide switching equipment of the kind mentioned in the introductory part of the description, in which the risk of damage and other inconvenience, which may otherwise arise during an incomplete opening of the contactor caused by welded-together contacts, is eliminated in a simple manner.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained in greater detail in the following with reference to the accompanying FIGS. 1-4 wherin.
FIG. 1 shows switching equipment according to the invention, connected in the supply conduit of an ac motor.
FIG. 2 shows the composition of the control equipment of the contactor.
FIG. 3 shows the control circuit included in the control equipment.
FIG. 4 shows how some of the quantities occurring in the switching equipment vary with time during an opening operation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows switching equipment according to the invention connected to the line between a three-phase motor M and an alternating-voltage power supply network N. The switching equipment comprises contactor equipment CE and a circuit breaker BR located ahead of the contact equipment (by "ahead of" is meant that the circuit breaker is arranged between the contactor equipment and the supply network.) The function of the switching equipment is to connect, in dependence on a control signal s.sub.c, the motor to or disconnect the motor from the supply voltage. The control signal may be obtained in a known manner from superordinate control equipment or be supplied manually. The contactor equipment is usually adapted to also to serve as thermal overload protection means for the motor and then receives an opening signal from a current-sensing protective circuit (not shown). The circuit breaker BR, which in a known way is adapted to trip at overcurrents, serves as overcurrent protection device. As shown in the figure, the circuit breaker also receives a tripping signal s.sub.d from the contactor equipment for opening of the circuit breaker if contacts of the contactor have become fixed by welding.
In the usual manner, the contactor equipment has a bank of contacts 10 which, in the three-phase application shown, has three contacts, one for each phase. Via a resilient mechanical link 14, the contacts are mechanically connected to the armature 13 of the operating magnet 11 of the contactor, which magne
REFERENCES:
patent: 5204633 (1993-04-01), Ahladas et al.
patent: 5243291 (1993-09-01), Umemura
patent: 5455733 (1995-10-01), Waggamon
patent: 5774323 (1998-06-01), Innes et al.
Henrion Claude
Johansson Gunnar
Stephansson Paul
Vefling Harald
ABB Research Ltd.
Paladini Albert W.
LandOfFree
Switching equipment does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Switching equipment, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching equipment will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1683395