DE1250527B - - Google Patents

Description

SUNBESREPUBLiK GERMANY

Int. Cl.

H © lh

GERMAN

PATENT OFFICE

IDENTIFICATION

»0 527 German class: 21c- 35/07

Number:

File number:

Registration date:

S 100074 VIII d / 21 c
October 13, 1965
September 21, 1967
April 4th 1968

Display day:
Issue date:

The patent specification corresponds to the patent specification

The previous synchronous switches have energy storage devices that are used for switching off shortly before Current zero crossing and for switching on again immediately after the current zero crossing takes effect reach. The mechanical solutions generally operate valves or latches solved, whereupon the switching movement under the action of compressed gas drives and / or springs comes about. If charged capacitors are used as energy storage devices, the Switching movement caused mostly with the help of electrodynamic drives. Regardless of the type of Drive system, only 1 ... 2 ms (milliseconds) are available for the movement of the contacts, which requires very great forces. It also makes it difficult to use capacitors at high voltage recharge quickly. There is therefore a need for a simple synchronous switch, in which there is sufficient time to initiate the movement. ao

The synchronous switch according to the invention is characterized by an extinguishing contact system on which a holding force generated electrodynamically by the current to be switched off acts, and by one of the current to be switched off Current-influenced waste magnet system, its armature, which is held in the switched-on state, through the switch-off command is released and then in the vicinity of the one preceding the synchronous switch-off Current zero drops, as a result of which a switch-off force counteracting the holding force is built up will.

With reference to FIG. 1 shows the principle of synchronous control in a synchronous switch according to the invention explained;

F i g. 2 shows a section through a switching chamber of a synchronous switch according to the invention Solenoid contact,

F i g. 3 shows a further embodiment of a holding contact for a synchronous switch according to the invention and

F i g. Figures 4 and 5 are side and elevation views, respectively, of a three-pole switch in accordance with the invention.

The shifted short-circuit current / (see FIG. 1) starts at time t ₀ , goes through zero for the first time at time Z _{1 and for} the second time at time t z. If the overcurrent protection responds between t ₀ and Z _1, for example at time t *, a drop-out magnet system that is to be switched off / fed is mechanically released. The armature then drops in the vicinity of ii and opens a valve, whereupon the pressure ρ and thus the pressure on a piston synchronous switch

Patented for:

Siemens Aktiengesellschaft, Berlin and Munich, Erlangen, Werner-von-Siemens-Str. 50

Named as inventor:

Dr.-Ing. Fritz Kesselring, Küsnacht (Switzerland) - -

Acting force

P (t) = p-A

{A = piston cross-section) increases according to the dash-dotted line and reaches the value P after, for example, 3 ms. The compressive force p now acts on the movable switching contact, which, however , is initially held by the electrodynamic holding force F, which is proportional to Z ² , so that the switch-off movement can only start when the electrodynamic force F becomes smaller than the actuating force p. If the hatched working area in FIG. 1 is selected so that the movable contact reliably reaches the extinguishing distance s at time t _z , then a synchronous disconnection occurs. Currents with a maximum holding force P less than P are interrupted asynchronously. Several milliseconds are thus available to build up the maximum switch-off force p , whereas this has to be done in fractions of a millisecond in the case of the synchronous switches known up to now. The value of 3 ms is advantageous because then a short half-wave of z. B. 5 ms duration can still be safely interrupted.

In Fig. 2, 1 is the high pressure chamber and 2 is the low pressure chamber, both of which are made of insulating material. 3 is a highly conductive metal plate to which the upper main contact 4 is connected in a gas-tight manner. The massive main contact ring 4 has segments 4a at the bottom. 5 is the movable pipe contact to which the current is supplied at its upper end through the sliding contact 6 . At its lower end it is connected to the two movable windings 7 of the solenoid contact. With la three fixed turns of the solenoid contact are designated; the turns 7 and la have the same sense of winding. With the pipe contact 5 a differential piston 8 is firmly connected, which is expediently made of "Teflon". It slides inside the main "

809 534/100

I.

contact 4 and is vented through the openings 9. With 10 the movable main contact is referred to; it consists of a plurality of contact fingers IOa and the contact housing 10b. The contact fingers IOa are pressed by the spring 11 against the segments 4a of the upper main contact 4 and against the lower main contact 12 . The lower main contact 12 is in turn conductively connected to the turns la of the solenoid contact. The contact fingers IOo are supported by a ring 13 . The contact jo IOb housing has two opposite approaches IOC, which cooperate with the later-described operating rod 34th

The lower arc electrode is denoted by 14. The annular magnet system 15 provided with air gaps is attached to the main contact 4. 16 is the associated waste anchor, which is firmly connected to the valve rod 17 , which also carries the two valve plates 18 and 18 o; at its lower end it engages in the slot of a spring 19 , via which it is connected to the movable main contact 10 . 20 is the tubular valve housing. Corresponding to the bore 21 in the metal plate 3 , the valve housing has a circular opening 22 . The power supply to the lower main contact 12 takes place via the tube 23 which carries the connection 24 and the high-pressure connection 25. A corresponding pipe 26 with the connection 27 and the low-pressure nozzle 28 serves to discharge the switching gases from the low-pressure chamber 2. The U- shaped line 29 establishes the connection between the connection 27 and the metal plate 3 via the plug-in contacts 30 ; it is provided with an insulation which serves to avoid a flashover caused by the hot, ionized gases after this line. 31 is the upper arc electrode attached to conductive spacer 32 ' ; this carries the sealing lining 33 at its dome-shaped end.

To actuate the movable main contact 10 , the insulating rod 34 is used, which is inserted into the interior of the high-pressure chamber 1 via the rubber sleeve 35 and encloses the movable main contact 10 like a fork. If the left end of the actuating rod 34 is moved downwards, the movable main contact 10 moves upwards into the switch-off position and vice versa. The high and low pressure chambers 1 and 2 are connected to one another by the two-part insulating ring 36 after the sealing rings 37 and 38 have been pressed together, and the metal plate 3 is thus also fixed in its position. The ring 39 serves to seal the pipe contact 5 against the metal plate 3, while the ring 40 seals the turns 7 and la of the solenoid contact against each other. The upper valve disk 18λ has an elastic rubber sleeve 41 which slides in the cylinder 42.

The mode of operation of the switch is as follows: If a small current is to be interrupted, the left end of the actuating rod 34 is moved downwards (see F i 2. 2). The movable main contact 10 moves upwards, the contact fingers IOa being withdrawn from the lower main contact 12 , so that the current is commutated to the solenoid contact 7, la; at the same time the armature 16 of the magnet system 15 is released. Since the holding force is small as a result of the small current in the solenoid contact 7, la , the armature 16 falls under the effect of the high pressure on the valve disk W> a 527

while the valve disk 18 is pressed onto the lower end of the valve housing 20. At the same time, the cuff 41 is lifted inwards from the cylinder 42 (position indicated by dotted lines) and the space 21 is vented. The high pressure now acts on the lower side of the differential piston 8, whereby the pipe contact 5 and the associated windings 7 of the solenoid contact are moved upwards. After the solenoid contact is disconnected, an arc occurs between electrodes 14 and 31 . The high pressure gas flows into the pipe contact 5 and causes the arc to be extinguished the next time the current passes zero.

It is switched on by moving the actuating rod 34 upwards at its left end. As a result, the movable main contact 10 moves downwards into the position shown and, shortly before the end position, also takes the armature 16 of the magnet system 15 with it via the spring 19 and the valve rod 17. As a result, the armature 16 is pressed onto the pole faces again. At the same time, however, the valve 20 switches over; the high pressure gas flows into the space 21 and generates a pressure on the upper surface of the differential piston 8 , whereby the pipe contact 5 with the turns 7 is pressed against the turns la. There is thus a contact pressure generated by the differential piston 8 even without current.

Even in the case of synchronous disconnection, after the main contact 10 has been moved , pressure is exerted on the lower surface of the differential piston 8 . In contrast to an asynchronous shutdown, however, the movement of the pipe contact 5 and the solenoid windings 7 can only begin when the holding force of the solenoid contact 7, la is less than the compressive force acting on the differential piston 8. The forces and masses are now coordinated with one another in such a way that the extinguishing distance s (see Fig. 1) is reliably reached in the time available. Since the arc is blown immediately inward and thus onto the arc electrodes 14 and 31 after the turns 7 are separated from la , the holding force of the solenoid contact drops almost instantly to zero, which increases the hatched working area in FIG.

In order to achieve short switch-off paths and a high level of voltage security, it is expedient for the interruption points to be under high pressure in the switched-off state. This is achieved in that the upper edge of the pipe contact 5 is pressed against the seal 33 in the disconnected position shown in dotted lines. On the other hand, in order to avoid main valves in the supply line to the high pressure chamber 1 , which would result in additional expenditure and a considerable time delay, the high pressure chamber 1 should also be sealed off from the low pressure chamber 2 when it is switched on. This is done with the aid of the seal 40 between the movable windings 7 and the fixed windings la of the solenoid contact.

Should for any reason (complicated network fault, cargo handling fault or the like) once the synchronous Shutdown do not come about, the arc burns after the current zero crossing continues during a full half-wave. If the current is relatively low, the interruption takes place in the next Siiom zero crossing. At higher short-circuit currents, however, due to the high switching

Claims (1)

1 260 work on a considerable overpressure in the low-pressure chamber 2. As a result, the rubber sleeve 411 is pressed against the cylinder 42 and now acts as a type of differential piston. The valve rod 19 is suddenly moved downwards. the pressurized gas flows into space 21 and causes the extinguishing contact system to be switched on again immediately, as a result of which the arc is extinguished and the switching gases flow out of the low-pressure chamber 2. Shortly before the next current zero crossing, the armature 15 drops again, whereupon the final synchronous shutdown takes place. in Fig. 3 again means 51 the pipe contact corresponding to 5 in FIG. 2, which carries the nozzle-shaped contact piece 52 at the lower end. The fingers 53 of the fixed mating contact are pressed against the support ring 55 by the spring 54 in the switched-off state. The power is supplied via the connection 56, which also carries the arc electrode 57. With their upper end, the contact fingers 53 snap into the groove 58, whereby the tubular contact 51 is held in the switched-on position. The pressing force per finger 53 against the groove 58 is proportional to Z2 according to the formula 25 to operate the switch according to the invention at lower voltages even with compressed air. You then have the advantage that the circuits are quiet and the air remains dry. The synchronous control with the aid of a switch-off force which builds up in a few milliseconds and which counteracts an electrodynamic holding force of the extinguishing contact system results in a very simple and space-saving construction of a synchronous switch. As a result of the electrodynamic contact pressure, a high short-circuit resistance of the extinguishing contact system is achieved, since it is not difficult to keep the contact voltage Uk = Rk-i for each value of the current 1 to be switched off lower than the melting voltage Us associated with the respective contact material. In the case of point-like contact, as can occur in the worst case with solenoid contact, the contact resistance Rk is calculated according to the following formula: Rk ^ 1.8 · 10-e, IO-8 kp, where η is the number of fingers / their length and d means the mean distance. If the force ρ on the lower surface of the differential piston 59 is greater than the holding force F caused by the falling current / the pipe contact 51 is accelerated upwards. The mode of operation corresponds in principle to that on the basis of FIG. 2, with the difference that a small contact overlap has to be traversed. In the F i g. 4 and 5 mean 61 the complete switching chambers corresponding to FIG. 2, 62 and 63 +0 are the upper and lower connections. The pipe sockets 64 and 65 are inserted into the hollow post insulators 66 and 67 and sealed by the elastic rings 68 and 69. They are connected to the compressed gas connection lines 70 and 71, respectively. The compressor 72 is arranged between the lines 70 and 71. The release shaft 73 carries fork-like levers 74 into which the isolating actuating rods 75 open, corresponding to 34 in FIG. 2. 76 is the resilient rubber sleeve. The release shaft 73 can either be moved by hand with the aid of the lever 77 or in a manner known per se by an electromagnet or a small pressurized gas drive. 78 is the grounded base. The fork 79 attached to the insulating actuating rod 75 encloses the movable main contact 80 corresponding to the main contact 10 in FIG. 2. If the actuating rod 75 is moved to the left by stretching the rubber sleeve 76 (see 35 in FIG. 2), the fork 79 can be brought into the pins 81 in a simple manner to engage. The mechanical connection is then ensured by the lever 74 even when the chambers 61 are pressurized. The chambers 61 can be exchanged in a simple manner by pulling them out. With the low gas content (e.g. SF6), the loss of gas when changing a chamber can be accepted without further ado. However, it is possible, where H is the hardness (for copper ^ 7000 kp / cm2), P the pressing force (holding force). So that the solenoid contact works properly, the holding force should be P = ki2 ^ 100 kp for i = 10 000 A, from which follows 100 k = IO8 10- This results in: Rk = 1.8 · IO-8 7000 10- «· ι2 Uk = Rki = 1.8 · 10- 1 <7000 io-e = 0.15 V, regardless of i, because the right-hand side of the equation is a constant. Since the melting voltage for copper is Us = 0.42 V, there is a very high level of protection against welding. In the case of the known tulip contact, the conditions are even more favorable due to the larger number of contact points. The control element in the form of a waste magnet system excited by the main current is very simple and therefore also reliable. To use too much switching work, which occurs in unfavorable cases and which causes a pressure surge in the low-pressure chamber, to initiate rapid reclosing, should represent the simplest method for reliably protecting the switching chamber against overload. The special type of mechanical actuation of the main contact has already been used in a similar way in vacuum switches with glass vessels. In the synchronous switch according to the invention, in addition to releasing the armature of the drop-out magnet system, it also has the further advantage of a simple switch position indicator. Patent claims: 1. Synchronous switch, characterized by a quenching contact system on the one