US2310145A - Single or polyphase switch arrangement - Google Patents

Description

Feb. 2, 1943. M. ZUHLKE 2,310,145

SINGLE OR POLYPHASE SWITCH ARRANGEMENTS Filed 00 2a, 1940 WITNESSES: INVENTOR WW Marcel Zubllre.

72/60 kflrm- ATTORNEY Patented Feb. 2, 1943 UNITED STATES PATENT OFFICE SINGLE OR POLYPHASE SWITCH ARRANGEMENT Pennsylvania Application October 26, 1940, Serial No. 362,987 In Germany November 28, 1939 3 Claims. (Cl. 175363) This invention relates above all to improvements in singleor polyphase switch arrangements in which a conductor or each of the supply conductors coming from an alternating current supply system is branched ofi to two contact devices, the latter being series-connected with saturable chokes having highly saturated magnet cores, by the desaturation of which a current weak interval is brought about which facilitates the interruption of the current. The duration of the above-mentioned current weak interval is dependent upon the voltage applied to the winding in the case of saturable chokes having a predetermined number of turns and a predetermined core cross-section. The longer the current weak interval lasts the greater the certainty as to the irregularity in maintaining a predetermined moment at which the contacts are broken and on the other hand the smaller the utilization factor of the switch arrangement will be. It may therefore be desirable in the case of the same operating voltage to adjust the duration of the current weak interval difierently or to maintain the duration of the current weak interval for all voltages as constant as possible in the case of difierent high operating voltages.

According to the invention two saturable chokes may be provided and change-over devices, with the aid of which the saturable chokes may be changed over in such a manner that on the one hand they are arranged in series with one another in the conductor between the alternating-current terminal and the tapping point and on the other hand in the branch conductors between the tapping point and each of the two contact devices. The number of the branch conductors and of the saturable chokes as well as of the contact devices may also be greater than two so that any combinations of series or parallel connection of the saturable chokes are possible. Such arrangements may among other things be employed for supplying electrolytic baths with energy.

In the accompanying drawing are shown embodiments of the invention, in which Figs. 1 and 2 show a converter system operating at a voltage capable of being regulated in the ratio 1:2, and

Fig. 3 shows a converter system for a threephase current with a transformer to be alternately connected in a star or delta.

Figs. 1 and 2 show a single-phase arrangement in two switching conditions. From this singlephase arrangement, polyphase arrangements of any number of phases may be easily developed. I i denotes the primary winding of a transformer Whose secondary winding is subdivided into two parts l2 and 12' whose winding ends lead to detachable terminals l3l6. With the aid of connecting pieces H, the two secondary windings may either be connected as shown in Fig. 1 in parallel or as shown in Fig. 2 in series so that an operating voltage varying in the ratio 1:2 is available. The detachable terminal It may, for instance, be connected to a middle wire of the direct-current system, the load being applied between the middle wire and the outers or in the case of a three-phase current system to the neutral point of a transformer winding. From each of the detachable terminals 13 and I4 extends a conductor to the saturable chokes l8 and I9 through so-called connectors 2| and 23 respectively. The magnet cores of the saturable chokes consist preferably of a fiatwise wound strip of a high grade magnetic steel and whose magnetization curve is as little as possible inclined in the unsaturated region to the flux axis, which curve presents when passing from the unsaturated region to the saturated regions sharp bends and runs in the saturated regions practically parallel to the axis of the magnetic energization. The number of turns and the core cross-section of the saturable choke is so chosen that the magnet core is unsaturated in the neighborhood of the zero value only in the case of very small instantaneous values of the current.

To the saturable chokes are connected the branch conductors which extend to the contact device 25 or to the contact device 26 through connectors 22, 24. The contact devices are combined with one another and with a common drive to form the contact device 29 which contains also additional devices, such as, for instance, capacitors, resistances which may be connected in parallel relation to the individual contacts in order that the increase in voltage recurring at the contacts when opening the same may be retarded so as to prevent a burning off of the contacts or a wandering of the material of the same. Instead of contact devices also discharge devices, for instance, tubes may be employed. According to Fig. 1 the connectors 23 and 24 are closed, whereas the connectors 2| and 22 are open. The saturable chokes l8 and I9 lie therefore in the branch conductors between the tapping point and the contact devices 25 and 25. The latter may be alternately closed and opened so that, for instance, the contact device 25 carries all positive half waves of the alternating current to be converted and transmits the same to the direct-current conductor 21 running perpendicularly to the plane of the drawing, whereas the contact device 26 would carry all negative half waves and transmit the same to the direct-current conductor 28. According to Fig. 2 the connectors 2| and 22 are closed and the connectors 23 and 24 are open. The saturable chokes I8 and I9 are therefore connected in series, the tapping point lies behind the two saturable chokes. In this case the saturable choke i8 is traversed by the operating current in a direction opposite to that of the choke shown in Fig. 1. Consequently, auxiliary windings (if any) of the saturable chokes, for instance, biasing windings which are supplied with direct current or alternating current and which may serve for the magnetic control of the cores of the saturable chokes so as to adapt the same to different conditions of load or for regulating the direct voltage to a further extent by varying the biasing current, must also be changed over at least for the saturable choke i3 when changing over the main conductors,

The connectors Zl-Zd, by means of which the change-over connections are broken or established may be preferably provided with solid contacts and a contact bridge rising perpendicularly from the contact surface and particularly in the case of power current arrangements in the conductors as laid. This arrangement of the connectors permits a laying of the conductors according to an approximately straight line, whereas when employing the usual change-over switches the laying of the conductors would be complicated.

The movable parts of the change-over devices may be driven by compressed air pistons through cranks, cams, eccentrics or the like. It is preferable to provide the compressed air control valves with interlocking devices, by means of which faulty switching operations are prevented with certainty.

In case the switch arrangement according to Figs. 1 and 2 is intended for converting purposes, a starting device 33 may be provided to facilitate the putting into operation, consisting of a number of resistances which are disconnected one after the other. A very simple arrangement may be attained by the fact that the connector 25 and 23 lying before the tapping point serve at the same time as short-circuiting devices for the starting resistances. The starting device itself is capable of being changed over with the aid of change-over switches 3|, 32 to one or the other conductor which is to be operated.

The converter system according to Fig. 3 has six contact devices I to '6 arranged in Graetzconnection and which are closed and opened in accordance with the proper sequence with the aid of a synchronous driving motor (not shown). A preferably capacitive parallel path (not shown) is connected in parallel relation to each contact device. The saturable chokes l8 and I9 which may also be provided with auxiliary windings for the magnetic bias are series-connected with the contact devices of each phase. This system serves, for instance, to exchange energy between a three-phase current supply circuit iii and a direct-current supply circuit 20. To the threephase current supply circuit is connected the primary winding i i of a transformer whose secondary winding supplies the Switch arrangement with energy. The secondary winding i2 may be alternately connected in star or delta. To switch over from star to delta or vice versa and at the same time to switch over the saturable coil, the

switch devices 33 to 39 may be employed which may be coupled with one another by a common shaft ii) or by a common rod. In one of the two direct-current conductors is arranged a reactance coil ii. The changing-over ratio of the series-connected turns of the saturable chokes is also in this case 1:2, whereas the changing-over ratio of the voltages is 1: 3. It follows that with a star connection the current weak interval lasts longer than when employing a delta connection. This is of particular advantage as regards a greater reliability of operation and consequently the capability of carrying heavy loads and the greater possibility of regulating in operation at higher voltages.

The changing over of the transformer at the secondary side has the advantage that the relative leakage voltage of the transformer is reduced in the low-voltage step so that in the diiferent switch steps the times of short-circuit difier switch steps the times of short-circuit dififers from one another to a lesser extent. Besides, in

the case of a simultaneous changing over of the saturable coils, for instance, according to. Figs. 1 to 3 all changing-over operations may take place in a single circuit arrangement, whereby among other things diiiiculties as to the insulation of a driving device common to all changeover devices may be avoided.

What is claimed is:

l. A conversion system for transferrin electric energy between a polyphase alternating-current circuit and a direct-current circuit comprising a polyphase transformer having windings connected to the polyphase circuit and windings for connection to the direct-current circuit, switching means for connecting said second mentioned windings either in polygon or in star, two switching contactors bridge connected between each effective phase terminal and the direct-current circuit, said switching contactors being connected to opposite sides of the direct-current circuit and being alternatively periodically conductive, two saturable commutating chokes connected between each phase terminal and the associated contactors and switching means for establishing a bridge connection between the phase terminal and the contactors either intermediate the reactors or outside the reactors, and an interlock between said bridge connecting means and said switching means.

2. An electric current converting system for transferring energy between an alternating-current circuit and a direct-current circuit comprising a transformer, a plurality of transformer windings on said transformer, means for connecting said windings to produce either of a plurality of terminal voltages of different orders of magnitude, two switching contactors for periodically connecting the terminal potential of said windings to the direct-current conductors of opposite polarity, two saturating commutating reactors associated with said switching contactors, circuit means for connecting said contactors in bridge relation exclusive of said reactors, a second circuit for connecting said contactors in bridge relation including said reactors, switching means for selectively establishing the operativeness of said bridge circuits, conductor means for applying the terminal voltage of said transformer windings intermediate the reactors, a second conductor means for applying said terminal voltage to both reactors in series, a second switching means for selectively energizing said conductor means, and means for interlocking said first and.

second switching devices whereby said first mentioned bridge circuit can only be rendered operative when said second mentioned conductor is energized.

3. An electric current converting system for transferring energy between an alternating-current circuit and a direct-current circuit comprising a transformer, a plurality of transformer windings on said transformer, means for connecting said windings to produce either of a plurality of terminal voltages of different orders of magnitude, two switching contactors for periodically connecting the terminal potential of said windings to the direct-current conductors of opposite polarity, two saturating commutating reactors associated with said switching contactors,

circuit means for connecting said contactors in bridge relation exclusive of said reactors, a sec ond circuit for connecting said contactors in bridge relation including said reactors, switching means for selectively establishing the operativeness of said bridge circuits, conductor means for applying the terminal voltage of said transformer windings intermediate the reactors, a second conductor means for applying said terminal voltage to both reactors in series and a second switching means for selectively energizing said conductor means, a starting impedance and means for connecting said starting impedance to either of said conductor means.

MARCEL ZUI ELKE.

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