Electricity: circuit makers and breakers – Toggle mechanisms
Reexamination Certificate
2003-03-20
2004-08-17
Donwan, Lincoln (Department: 2832)
Electricity: circuit makers and breakers
Toggle mechanisms
C200S400000, C218S022000
Reexamination Certificate
active
06777635
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a very high-speed electrical switchgear apparatus having the function of a limiting circuit breaker.
STATE OF THE PRIOR ART
In the document EP 0,309,311 a limiting circuit breaker is described with high-speed opening control of the contacts by Thomson effect, each pole-unit of which circuit breaker is equipped with a movable assembly having a movable main bridge forming a main circuit with a pair of stationary main contacts connected to current input terminal strips, and a movable arcing contact bridge forming, with a pair of stationary arcing contacts, an arcing circuit connected in parallel with the main circuit. A Thomson effect thrust means drives the movable assembly for opening of the main circuit and of the arcing circuit. A latching device holds the movable assembly in the open position against the bias of return springs tending to return the movable assembly to the closed position. A second Thomson effect thruster serves the purpose of unlatching the latching device.
All the circuit breaker openings, whether it be simple operations or openings on faults, are caused by the Thomson effect actuator which therefore has to be dimensioned for a very large number of cycles. The Thomson effect actuator drives the contacts over the whole opening travel. Furthermore, the Thomson effect actuator requires its own electric power supply and, in case of failure of the latter, there is no subsidiary means of operating the apparatus. Moreover, the apparatus thus designed is very specific with respect to low-voltage power circuit breakers of conventional design which constitute the vast majority of the range, so that its cost remains high. Finally, the openings and closings by means of the Thomson effect actuator are extremely snappy, regardless of the type of fault. The mechanism of the apparatus therefore suffers considerably during the opening and closing cycles.
To limit shocks, it has been proposed in the document FR 2,377,086 to subdivide the electric power storage means by capacitors providing the power supply for the Thomson effect actuator into two parts. In case of opening under normal conditions, only one of the two parts is used whereas in case of an electric fault, both the parts of the energy storage means are used, a greater power then being available.
To operate Thomson effect limiting circuit breakers, electric short-circuit detection processes are known supplying a short-circuit detection signal very quickly and very reliably enabling high-speed operation of an electromechanical relay performing unlatching of a mechanism of the circuit breaker. The document DE 3,642,136 describes such a detection process using a current intensity signal and a current intensity differential signal to make a very quick decision as to the existence of a short-circuit. Early short-circuit detection combined with the speed of reaction of the Thomson effect actuator gives the circuit breaker a high-performance limiting function enabling it to break almost infinite prospective currents. However, the limiting function is only achieved by tripping of the circuit breaker, so that it does not enhance down-line selectivity in a distribution panel.
Circuit breakers are moreover known opening whereof is achieved by a spring-loaded mechanism and having a very short response time when tripping occurs on a fault. It has notably been proposed, in the document EP 780,380 A1, to use the mechanical reaction arising from electrodynamic compensation of the compensated contact means to bring about automatic tripping. The opening pawl comprises disengageable actuating means causing self-unlatching of the latch in the presence of a short-circuit current exceeding a calibration threshold defined by a spring, said self-unlatching being commanded from a mechanical reaction generated by the electrodynamic compensation effect and causing very fast rotation of the latch to unlatch the opening pawl before the trip means operates. To further improve the above device, it has been proposed, in the document FR 2,781,921, to add thereto electromagnetic limiting means performing separation of the contact fingers to limit very strong currents pending opening of the mechanism. The circuit breaker obtained has very high performances, but separation of the contact fingers by electromagnetic reaction cannot take place before the current intensity has exceeded a limiting threshold.
SUMMARY OF THE INVENTION
The object of the invention is therefore to remedy the shortcomings of the state of the art so as to propose an extremely reliable, relatively compact, low-cost limiting circuit breaker with very high-speed opening, enabling separation of the contacts and a limiting effect to be achieved without the current intensity having exceeded a limiting threshold.
For this purpose, the object of the invention is to provide an electrical switchgear apparatus comprising:
a first contact connected to a first terminal strip for connection to an electric power circuit;
a cage movable between a closed position and an open position;
a second contact electrically connected to a second terminal strip for connection to the electric power circuit, the second contact being movable with respect to the cage between a contact position and a separated position, the second contact being in contact with the first contact when the cage is in the closed position and the second contact is in the contact position,
a drive mechanism of the apparatus movable between a closed position and an open position, comprising:
an energy storage spring loaded when the drive mechanism is in the closed position and unloading when moving the drive mechanism from the closed position to the open position;
an opening latch, locking the drive mechanism in the open position;
an electromechanical relay for operation of the opening latch;
a kinematic transmission system between the energy storage spring and the cage to drive the cage from the closed position to the open position when the drive mechanism moves from the closed position to the open position;
an electromechanical actuator comprising a movable assembly moving between a rest position and an active position and driving the second contact from the contact position to the separated position going from the rest position to the active position, when the cage is in the closed position.
The presence of a drive mechanism independent from the actuator first of all makes it possible to limit the number of operations that have to be performed by the high-speed actuator since certain of the openings will be able to be performed by actuating the mechanism latch. In addition, the actuator only has to supply the energy required for moving the second contact to the separated position. When opening is confirmed by an unlatching order of the opening latch, the mechanism drives the contact support to the open position which has the effect of separating the movable contact even further from the first contact. In other words, a part of the travel of the movable contact with respect to the stationary contact is performed by the opening spring of the mechanism. The dimensioning of the actuator and associated electronics is thereby greatly simplified.
The redundance of the opening functions in addition enables downrated operation when malfunctioning of the electric power supply or power electronics associated to the very high-speed actuator, or even of the actuator itself, occurs. In this case, the circuit breaker in fact acts as a conventional limiting circuit breaker. The global reliability of the breaking function of the apparatus is thereby improved.
Furthermore, in so far as closing is performed by the mechanism, it is possible in case of closing on a fault to achieve immediate separation of the contacts by means of the actuator.
Preferably the apparatus in addition comprises a contact pressure spring urging the second contact to the contact position when the second contact is near to the contact position.
According to a first embodiment, the contact pressure spring bears on the movabl
Baginski Pierre
Brun Grégoire
Ferrand Jean-Paul
Joubert Jacques
Pellegrin Christian
Donwan Lincoln
Fishman M.
Parkhurst & Wendel L.L.P.
Schneider Electric Industries SAS
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