The present invention relates to a circuit breaker for high-voltage currents.
As it is known, circuit breakers for high-voltage currents must be actuated quickly and promptly. In order to meet this requirement, the use of direct actuators of the electromechanical type would entail devices of unacceptable size; accordingly, systems for accumulating mechanical energy are generally used. Energy accumulation occurs over a few hundred seconds. Energy is then used and delivered over a few tens of milliseconds.
This solution in any case entails using complex, expensive and bulky devices which cannot be integrated with the circuit breaker poles they must operate. In particular, if the energy is accumulated in steel springs, which have a great mass, it is not possible to connect them directly to the movable assembly of the pole of the circuit breaker, because their mass would significantly limit the speed and the operation time of the circuit breaker, unacceptably penalizing its performance.
In such situations it is necessary to resort to stroke multiplier mechanisms interposed between the spring and the movable element of the circuit breaker, which further complicate the actuation mechanisms and make it practically impossible to integrate it with the pole of the circuit breaker.
As regards the poles of circuit breakers, in the conventional art the use of porcelain insulators leads to great limitations. This solution necessarily entails using two porcelain insulators equipped with aluminum flanges (which are cemented to the insulator in a complicated manner), which respectively contain the arcing chamber and the insulating drive rod; the entire unit is assembled by means of plates and covers which are expensive and bulky.
Patent application nr. FR-A-2589001 discloses a mechanism for operating circuit-breaker and suitable for causing a circuit-breaker to perform a rapid opening-closing-re-opening cycle. A first spring is coaxially arranged around an operating rod that moves the movable contacts of the circuit breaker. A second spring is arranged around a cylinder that surrounds the first spring.
Patent application nr. EP 788126 discloses a switch for hieh-voltage current, which is provided with a movable contact that can be actuated by means of an actuation rod made of insulating material. The actuation rod accommodates a spring, which is operatively connected between the actuation rod and the body of the insulator that accommodates the switch.
Patent nr. US-5504289 discloses a switching mechanism for a high voltage circuit breaker. The disclosed mechanism comprises a first spring and a second spring that is positioned coaxially with the first spring. An operating rod member is operatively associated to said springs and to the movable contacts of the circuit breaker.
Main aim of the present invention is to provide a circuit breaker for high-voltage currents which allows to eliminate the complicated stroke multiplying mechanisms required to transmit motion to the movable parts of the pole of the circuit breaker.
Within the scope of this aim, an object of the present invention is to provide a circuit breaker for high-voltage currents which allows to reduce the energy required to transmit motion to the movable contacts of said circuit breaker so as to improve its performance in terms of speed and promptness of intervention.
Another object of the present invention is to provide a circuit breaker for high-voltage currents with a pole having a smaller number of components, a reduced weight and, insulation levels being equal, smaller size.
Further but not last object of the present invention is to provide a circuit breaker for high-voltage currents which is highly reliable, has reduced testing times, is relatively easy to manufacture and at competitive costs.
This aim, these objects and others which will become apparent hereinafter are achieved by a circuit breaker for high-voltage currents according to the following claim 1.
Further characteristics and advantages of the present invention will become apparent from the following detailed description of preferred but not exclusive embodiments. of the circuit breaker according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
With reference now in detail to Figures 1, 2 and 3, the circuit breaker according to the invention comprises a pole which is constituted by an insulator 4, by fixed contacts 1 and by movable contacts 2. An electric power tap 3 protrudes from the insulator and supports a movable contact holder 10 by means of an intermediate flange 11.
Inside the insulator 4 of the pole there are provided elastic means which are conveniently constituted by two springs 6 and 7, respectively for opening and for closure, which are made of insulating material. Advantageously, in the opening spring 6 one end is connected to a movable drive rod 5, which is also made of insulating material and which, by actuating the movable contacts 2, allows to open and close the circuit breaker, and the other end is fixed to the flange 11. In the closure spring 7, one end is coupled to sliding support means 12 which are connected, by means of a tube 13, to circuit breaker actuation means 8, and the other end is connected to the flange 11. In particular, the tube 13 is coupled to the drive rod 5 through engagement means 16 which are fixed to the tube 13 and have a pawl that engages a slot formed in the rod 5.
The circuit breaker actuation means 8, according to the present invention, comprise a gearmotor 31, a worm screw 36, two electrical engagement devices 34 and 35, and two engagement means 19 and 20 and are directly connected to the flange 9 of the insulator 4 by means of the flange 14. In this manner they are rigidly coupled to the base of the insulator 4.
Starting from the conditions of Figure 1, in which the circuit breaker is open and the closure spring 7 is loaded, i.e., is tensioned, the energization of the electromagnet 35 releases the engagement means 19: in this manner, the closure spring 7 can move freely and moves upward the tube 13 which, by being coupled to the drive rod 5 through the engagement means 16, also moves the rod 5 in its upward movement. The rod 5, by actuating the movable contacts 2, closes the circuit breaker and loads, by compressing it, the opening spring 6 which is rigidly coupled thereto.
At the end of the actuation, as shown in Figure 3, the pawl of the engagement means 16 is released by the stroke limiter 17 and the drive rod 5 engages the engagement means 20; in this manner, the opening mechanism is made independent of the closure mechanism.
The gearmotor 31 starts by means of the stroke limiter switch 32 and can reload the closure spring 7 which, at the end of its loading, engages the engagement means 19; the wheel of the gearmotor disengages from the worm screw 36 and the gearmotor stops due to the stroke limiter 33.
Opening of the contacts, which can be performed if necessary also during the reloading of the closure spring, occurs by energizing the electromagnet 34. In this manner, the engagement means 20 are released and the opening spring 6, as it is released, pushes down the rod 5, which opens the contacts.
With the circuit breaker according to the invention it is possible to perform quick opening-closure-opening with the following sequence.
Starting from an operating condition in which the circuit breaker is closed and the closure and opening springs are loaded, the following occurs:
By energizing the electromagnet 35, the engagement means 19 are released and the circuit breaker, as described above, closes. In this situation, the opening spring is loaded and the insulating rod 5 is engaged with the engagement means 20.
By re-energizing the electromagnet 34, the circuit breaker reopens.
Auxiliary contacts 18 of the insulator are switched at each actuation.
A second embodiment of the circuit breaker according to the invention is now described with reference to Figure 4. In this embodiment too, the opening and closure springs, now designated by the reference numerals 3 and 4, are contained in the insulator 5 of the pole of the circuit breaker and are made of insulating material. In particular, in the opening spring 3 one end is fixed to a flange 30 and the other end is fixed to an insulating rod 50 which, by actuating the movable contacts 2, allows to open and close the circuit breaker. In the closure spring 4, one end is fixed to the flange 30, while the other end is connected to a system constituted by a linkage 61 and a lever 62.
In this embodiment, the actuating means comprise two electric engagement devices 39 and 41 and a gearmotor 42. Starting from the situation shown in Figure 4, in which the circuit breaker is open,the closure spring 4 is loaded (compressed) and the opening spring 3 is released, energization of the electrical engagement device 40 releases the kinematic chain 62, 61 and 4. The closure spring 4 is released and, by elongating, pushes the lever 62 which, by means of the linkage 63 and the levers 64 and 65, moves upward the rod 50, which causes the closure of the contacts and the loading (by compression) of the opening spring 3.
At the end of the closure actuation, the lever 64 engages the electrical engagement device 41; at the same time, the lever 66 disengages the lever 64 from the lever 62, making the opening mechanism independent of the closure mechanism. The gearmotor 42 can thus reload the closure spring 4. At the end of the loading action, the spring 4 engages the electrical engagement device 40 and the gearmotor 42 disengages from the lever 62 by means of a disengagement device 43.
The opening of the contacts, which can be performed if necessary also during reloading of the closure spring, occurs by energizing the electrical engagement device 41, which releases the lever 64. The opening spring 3 is no longer retained and is released, pushing the rod 50, which opens the contacts.
According to this embodiment, it is possible to perform quick opening-closure-opening by means of the following sequence:
Another advantage of the circuit breaker according to the invention is the fact that the insulator of the pole is monolithically made of composite material coated with polymeric material. Accordingly, this allows to reduce the number of components of the pole, its weight and, insulation levels being equal, its size.