US1212125A - Switch for heavy alternating currents. - Google Patents

Description

W. BURSTYN.

SWITCH FOR HEAVY ALTERNATING CURRENTS.

APPLICATION FILED JAN.I4, 1915.

1,212,125.. Patentd Jan. 9, 1917.

11 ness e5 In vemor 422% I i/m WALTHER-BURSTYN,- OF BERLIN, GERMANY.

SWITCH FOR HEAVY ALTEBNATING CURBENTS.

Specification of Letters Patent.

Patented Jan. 9, i917.

Application filed January 14, 1915. Serial No. 2,268.

To all whom it may concern:

Be it known that I, WALTHER BURSTYN, a subject of the Emperor of Austria-Hungary, residing at Berlin, in the German Empire, have invented a new and useful Switch for Heavy Alternating Currents, of which the following is a specification.

The present invention relates to improvements in switches for alternating currents of some power, say, beginning from a few amperes and 100 volts. This switch may be an electromagnetic, or a pneumatic, or a hydraulic switch the electrodes of which are adapted to be opened at a speed not depending on the speed of the hand.

Heretofore alternating current switches have been built so as to open the contacts wide and with high speed in order to get a reliable and quick extinction of the interruption arc, in the same way as it is usual for direct current. The present invention is based on the fact that the same effect may be obtained farbetter in a different way,

viz. by opening the contacts so slowly that their distance at the moment of the next' ward the voltage is not able to jump the gap again. The same effect is obtained if the contacts are not initially opened a distance greater than said critical distance.

There are different reasons why knife switches are not suitable for application according to this method. One reason is that a small opening distance of the contacts cannot accurately'be adjusted. Another reason is, that just at the moment of the break the electrodes of the switch form edges which, on account of their small heat capacity, are considerably heated by the are even if the latter is of short duration. In consequence they would soon burn away and necessitate a readjustment of the small gap. Furthermore, they would reduce the quenching effect for which, as is well known, cold electrodes are a. requirement. A third reason is that the quenching effect requires the arc to be inclosed, as far as possible, between two large metal masses, which cannot be done by means of edges and points. That is the reason why plate spark gaps are used in wireless telegraphy as quenching spark gaps.

As a consequence of these considerations, for automatic switches I propose contact pieces of a slight convexity as illustrated, partly in section, in Figure 1 of the accompanying drawing. Fig. 2 shows an electromagnetic relay according to this invention, while Fig. 3 illustrates a modification of the relay construction shown in Fig. 2.

The surface of the contact piece may correspond approximately to a segment of a sphere, and both contact pieces may be alike in shape, or one of them may be fiat. The diameter of the contact pieces is to be chosen rather large, for instance 10 to 20 millime- L ters for a current of 100 amperes. Like the electrodes of quenching spark gaps, they ought to be made of a metal that conducts heat well and does not readily oxidize. The electrodes are preferably made of copper and coated with silver.

As heretofore stated comparatively cold electrodes of large mass and good conductors of heat and electricity are required for producing the quenching effect necessary to extinguish the issuing arc. Furthermore, when interrupting alternating currents, if the electrodes or contacts are separated beyond the critical distance, the issuing arc will possess a considerable length and develop great heat and cannot be extinguished by a quenching efl'ect. Consequently the electrodes must be quickly opened to a distance not exceeding thecritical distance, i. e. the distance beyond which the quenching effeet will not extinguish the issuing arc, and which is determined on the one hand by the fact that the operating voltage prevailing at the electrodes after the interruption has taken place will jump a distance that is too small and hence will again close the circuit, and on the other hand by the fact that for mechanical reasons a very small distance cannot be securely maintained. Practically the critical distance has been found to be I from one-half to two millimeters. The only practicable means toquickly open the contacts is by an electrical or mechanical operating means which acts independently of the speed of the movement of the handy because hand operation cannot be depended upon and has been found to be inaccurate.

In the illustration of an electromagnet c relay according to thiS invention, shown 1n Fig. 2, a3 is an alternating current generator, '10 indicates the current consumer -(lamps, motors, etc.), m is the electromagnet of the relay, a is the armature of the electromag- 5 net, 0 are contact pieces of the described construction, 1'" is a stop that prevents the contacts from separating from each other beyond a distance of about half a millimeter,

b is a battery, and t a key. By closing and opening the key If the pieces 0 are caused to contact-or to open. I As a matter of course after the break is actually eflected the contacts may be fur ther'separated from each other. This may be considered desirable in order to prevent dust and the like matter from bridging-the contacts, which'may possibly happen when the distance between the contacts is small. An electromagnetic relay that meets this requirement is illustrated in Fig. 3, in which like reference letters are used for like parts as in ig. 2. The armature of this relay opens the contacts preliminarily quickly a short distance and thereafter the contacts move. apart more slowly. A relay is illustrated which interrupts the alternating current when-the key t is closed and the magnet m therefore attracts the armature a with a predetermined steady force or pull so that the switch will operate independently of the speed of movement of the hand.

When the armature e is attracted by the magnet m, the contact pieces 0 quickly open till the armature meets the stop 1". At this 5 moment the distance between the contacts ought to be equal to the critical distance. However, with this modification the stop 7' is not arranged immovable as in Fig; 2 but is carried by a pivotally mounted doublearmed lever h which is balanced by means of the weights g, g, and is drawn by a weak spring 8 against the screw stop 2 provided in a stationary post. By the action of the magnet m the'lever h is caused to give way under the pressure of the armature a, and to partake in its movement thereby exerting a checking action on the same. In consequence, the speed of the m oving armature is diminished, and the further opening of the contacts 0 proceeds but slowly.

The same effect may be obtained if the movement of the armature is checked by a pneumatic or hydraulic brake instead of by an inertia efi'ect. For breaking voltages up- :56 ward of 1000 volts, a ingle pair of contacts will not do any longer, but several pairs of contacts must be connected in series.

What .I claim is 1. In a switch for heavy alternating our- 60 rents, the combination of switch contacts having surfaces consisting of metal, such as silver, which is a good conductor of electricity and heat and does not readily oxi-' dize, one of said surfaces being slightly con- 66 vex, and means operating independently of the speed of movement of a hand to open said contacts to such an extent thatat the moment of the next minimum value of the alternating current the contacts will not be farther apart than the distance beyond which the quenching and cooling effect of the electrodes will not extinguish the result ing arc, whereby when the contacts are opened the resulting arc will be extinguished in consequence of the quenching and cooling efiect produced at the moment the value of the alternating current is at its minimum, and means for closing said contacts.

2. In a switch for heavy alternating currents, the combination of switch contacts having slightly convex surfaces consisting of a metal which is a ood conductor of electricity and heat an does not readily oxidize, means for causing the contacts to in- 8/5 itially open a small distance with a quick I movement so that at the moment of the next minimum value of the alternating current the contacts are not farther apart from each other than from one-half to two millimeters so that the issuing arc is extinguished in consequence of the quenching effect produced by the electrodes, said means thereafter causing a further separation of the electrodes.

3. In a switch for alternating currents, the combination ofswitch contacts, means for initially separating one of said contacts from the other a predetermined distance so that at the moment of a succeeding minimum value of thealternating current the issuing arc will be extinguished in consequence of the quenching efltect produced at the'moment the current passes zero, and means for resisting-the separation of said contacts after said initial movement.

4. In a switch for heavy alternating currents, the combination of switchv contacts, means for initially separating one of the contacts from the other a predetermined dis tance so that at the moment of a succeeding minimum value of the alternating current the issuing arc will be extinguished in consequence of the quenching effect produced at the moment the current passes through zero 5 value, and means for resisting the further separation of said contacts after the said initial separation.

5. In a switch for heavy alternating our rents, the combination of switch contacts,

electric means capable of causing the separation of one of said contacts from the other, said means causing an initial separation for a predetermined distance so that at the moment of the next mimimum value of the alternating current controlled by said switch the issuing arc will be extinguished in conse quence of the quenching effect produced at the moment the current passes through zero value, and mechanical means permitting ing current controlled by said switch the contacts Will be only from one half to two millimeters apart and the issuing arc Will be extinguished in consequence of the quenching efiect produced at the moment the current passes through zero value, and means for resisting the further separation of said contacts after said initial movement. 20

DR. WALTHERBURSTYN. Witnesses:

HENRY HASPER,

WOLDEMAR HAUPT.

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