US2800623A - Series-transductor apparatus - Google Patents

Description

July 23; 1957 M. BELAMIN ,8 23

SERIES-TRANSDUCTOR APPARATUS Filed Sept. 25, 1952 2 Sheets-Sheet DQJQQ AQ 16 pzloq. A21 17 y 1957 M. BELAMIN 2,800,623

SERIES-TRANSDUCTOR APPARATUS Filed Sept; 25. 1952 2 Sheets-Sheet 2 United States Patent SERIES-TRANSDUCTOR APPARATUS Michael Belamin, Nurnberg, Germany, assignor to Siemens Schuckertwerke Aktiengesellschaft, Berlin Slemensstadt, Germany, a corporation of Germany Application September 25, 1952, Serial No. 311,395

Claims priority, application Germany October 3, 1951 12 Claims. (Cl. 321-48) My invention relates to premagnetized saturable reactor devices, briefly called transductors, and more particularly to transductors of the series type. Such series transductors are applicable, as such or as a component part of a circuit combination, for such purposes as controlling, regulating, translating, releasing a periodic or alternating electric current.

It is among the objects of my invention to devise series transductors capable of a more versatile performance than heretofore available and suitable for issuing current pulses of constant amplitude which are accurately controllable as to phase position and duration relative to the cycle of a periodic or alternating voltage.

These and more specific objects, as well as the means provided by my invention for achieving them, will be set forth in the following with reference to the drawings, in which- Figs. 1 and 2 are explanatory circuit diagrams of series reactors according to the prior art;

Fig. 3 is an explanatory diagram of current and voltage curves relating to transductors according to Figs. 1 and 2 as well as to those according to the subsequent illustrations;

Figs. 4 to 7 show respective circuit diagrams of series transductors according to the invention;

Fig. 8 shows the circuit diagram of a contact converter with series transductors according to the invention; and

Fig. 9 is a coordinate diagram of current and voltage curves explanatory of the operation of the apparatus of Fig. 8.

A series transductor comprises two saturable reactors whose respective main windings are electrically series connected and whose respective magnet cores are premagnetized by direct current in opposing directions, relating to the magnetizing direction of the current flowing in the main windings. The premagnetization, as a rule, has a magnitude beyond the saturation knee ofv the magnetic characteristic. In the known series transductors, the two saturable reactor portions are equal and their re spective premagnetizations have the same strength. In those transductor designs Where each reactor portion has its own core with a pertaining premagnetizing winding, the two premagnetizing windings are equally excited and, like the main windings, are usually series connected with each other though in mutually inverse polarity relations to the respective main windings.

Such a known series transductor is illustrated in Fig. 1. As shown, the transductor has two saturable reactor portions 10, 20 with respective main windings 11, 21 and respective premagnetizing windings 12, 22. The premagnetizing windings 12 and 22 are series connected in a direct-current circuit of normally constant terminal voltage which includes an adjustable resistor 14 and a stabilizing inductance coil 15. The main windings 11 and 21 are connected in series with a load 16 to an alternating current supply, for instance a utility line of the 2,800,623 Patented July 23, 1957 customary frequency of 50 C. P. S. or 60 C. P. S Instead of providing two separate reactors each with its own core, the series transductor may be given a single, three-legged core 17 with a single premagnetizing winding 13 on the center leg, as shown in Fig. 2. Such a three-legged core may be looked upon as being a combination of the two magnet cores shown in Fig. 1.

Series transductors of these known types impart to the alternating current of the main-winding circuit a squaretopped, for instance, substantially rectangular or trapezoidal wave shape as exemplified in Fig. 3 by curve i. This curve represents the current in dependence upon the angular degrees of the current cycle and is given an idealized shape, neglecting particularly the finite width of the magnetic hysteresis characteristic of the core material. The two half waves of the trapezoidal current i are congruent due to the fact that the two reactor portions are equal and have the same strength of premagnetization. The duration of each trapezoidal half wave between two successive zero passages, which coincide with the moments at which the alternating voltage u passes through its peak value, is equal to the period of a half cycle of this voltage, and hence corresponds to the interval or angle 1r.

The equality of the amplitudes of the positive and negative trapezoidal current pulses is due to the magnetizing conditions. The-two saturable reactors of the series transductor are excited by the same direct-current magnetomotive force, and this force determines the height of the trapezoidal half waves. The equal widths of the trapezoidal half waves result from the fact that no direct current component can be transmitted from the direct current side to the alternating current side of the apparatus.

In comparison with the known series transductors explained in the foregoing, it is a more specific object of the invention to provide a series transductor for generating a current pulse of substantially constant magnitude whose pulse duration may be given any desired length different from that of the half wave period of the alternating voltage.

Another, subsidiary object is to make such a pulse accurately adjustable or displaceable relative to the cycle period, for instance, for controlling or regulating the ignition time points of gas discharge tubes or the make time points of mechanically or magnetically driven contact converters.

Another, more specific object of the invention is to provide an accurately controllable pulse-issuing device of highly reliable constancy of operation for the saturation control of the commutating reactors in contact converters.

To achieve these objects, and in accordance with my invention, I apply to the two saturable reactor portions of a series reactor respectively different magnitudes of premagnetization with respect to the pertaining main reactor windings. That is, the two reactor portions are .given respectively different ratios of their direct-current ampere turns or magnetomotive force to the turns number of their main windings. According to a more specific feature of my invention, this difference is obtained by giving one reactor portion a turns ratio of main winding to premagnetizing winding difierent from the corresponding ratio of the other reactor portion. According to another, alternative feature, both reactor portions have the same winding-turns ratio but the circuit of one of the premagnetizing windings has a direct-current magnitude different from that in the other premagnetizing circuit.

The asymmetry thus introduced into the transductor circuit has the result of eliminating the above-mentioned congruence of the positive and negative half waves of the trapezoidal current. A consideration of the modification imposed by this asymmetry upon the shape of the current curve may start from the fact that the transductor as such does not have a valve effect and that, therefore, the algebraic average values of the positive and negative currents must be equal. Hence, the areas defined by the positive and negative portions of a current wave must also be equal. Such a current wave is exemplified in Fig. 3 by the trapezoidal curve i. As explained, the area F1 beneath a positive wave portion is equal to the negative area F2. Since the amplitudes of the two trapezoids are different, their widths must also be different to satisfy the requirement for equality of the areas F1 and F2. Considering the positive and negative wave por' tions individually, it will be recognized that each represents a current pulse of substantially constant magnitude whose duration is no longer determined by the halfcycle period of the alternating voltage impressed upon the series transductor. Consequently, the provision of magnetically unequal reactor portions offers the possibility of generating current pulses of any desired length different from a half wave which, when using a highquality iron material in the core, maintain a virtually constant current magnitude during the entire duration of the pulses. Especially suitable for this purpose are types of iron with a so-called rectangular loop characteristic, that is whose magnetic characteristic in the unsaturated region is as little as possible inclined toward the flux axis and enters into the saturated region with a sharp knee to thereafter extend substantially parallel to the axis of the exciting current. Such reactor cores are preferably wound up from strips of a nickel-iron alloy and have a toroidal shape.

Especially advantageous embodiments of series transductors according to the invention are illustrated in Figs. 4 to 7, in which the same reference numerals as in Fig. 1 are used for respectively similar elements.

In the transductor according to Fig. 4, the two saturable reactors and 20 have the same structural design. That is, the pertaining magnet cores are similar, the main windings have the same number of turns, and the premagnetizing windings 12, 22 are also equal as regards their number of turns. However, the two premagnetizing windings 12 and 22 are traversed by direct currents of different magnitudes and hence induce in the cores respective premagnetizations (i. e. magnetomotive forces) of different magnitudes. For this purpose, the two premagnetizing windings 12 and 22 are not series-connected but lie in parallel relation to each other. The parallel branch circuit of winding 22 includes an additional adjusting resistor 24 and a separate stabilizing coil 25. The difference in the magnitudes of the premagnetizing currents results in a corresponding difference between the currents flowing in the main windings, since these currents always assume the value required for compensating the premagnetizing current up to the moment when the reactor enters into the unsaturated condition. In Fig. 3, the different values of the premagnetizing currents for producing different amplitudes of positive and negative pulses, respectively, of the trapezoidal current i are denoted by distances i and i respectively.

In the series transductor shown in Fig. 5, the two saturable reactors 10 and 20 have the same turns ratio of main winding to premagnetizing winding. The two premagnetizing windings 12 and 22 are series connected with each other. However, part of the direct current is shunted away from one of the premagnetizing windings. In the illustrated example, the winding 12 is thus supplied with a reduced direct current by diverting part of the current through a parallel circuit equipped with a separate adjusting resistor 24 and a separate stabilizing coil 25, This parallel circuit extends across the entire series connection of the winding 12 with the adjusting resistor 14 and the stabilizing coil 15. The current thus shunted from the premagnetizing winding 12 may preferably be utilized for some other purpose; for instance it may be supplied to a load such as a separate magnet or relay winding 26 not active in the performance of the transductor proper.

In the embodiment of Fig. 6, the main windings 11 and 21 of the two saturable reactors 10 and 20 have the same numbers of turns, while the respective premagnetizing windings 12 and 22 have different numbers of turns, this being indicated by winding 12 having a shorter length than winding 22. The premagnetizing windings are series connected into the direct current circuit and hence are traversed by the same premagnetizing current. Alternatively, however, the two premagnetizing windings may be given the same numbers of turns while providing different turns numbers in the two main windings 11 and 21. In either case, the two saturable reactors 10 and 20 have different translation or turn ratios. For instance and as shown, if the two reactors are premagnetized by direct current of the same magntiude, flowing through the series connected windings 12 and 22, then the premagnetizations effective upon the respective main windings 11 and 21 of the two reactors are different, and this difference may be calculated on the basis of the difference in the turns ratios. If the calculated values of premagnetization are denoted by i and i then the same conditions, in principle will result as for the embodiments according to Figs. 4 and 5. Consequently, the curve i in Fig. 3 typifies in principle also the transductor current in an embodiment of the type explained with reference to Fig. 6.

This applies also to a series transductor as illustrated in Fig. 7. In this embodiment, the saturable reactors 10 and 20 are shown to have annular cores. Each core has an auxiliary winding 18 or 19; and both cores have a premagnetizing winding 23 in common. The windings 18 and 19 are series connected to the direct current supply and hence traversed by the same premagnetizing current. The polarity of connection of windings 18 and 19 is such that their premagnetizing effects have the same sense relative to the alternating-current circuit of the main windings 11 and 21. In contrast, the common premagnetizing winding 23 has a cumulative magnetizing effect relative to the main winding on one of the cores but an opposing magnetizing effect relative to the main winding on the other core. Consequently, one core is subjected to the sum and the other to the difference of the common premagnetization and the pertaining auxiliary premagnetization. As a result, and in analogy to the embodiments previously described, the ratio of the direct current fluxes in the core of the two reactors to the turns numbers of their respective main windings is different. In consequence, the two main windings are subjected to respectively different strengths of premagnetization as is again exemplified in Fig. 3 by the two values i and i The adjusting resistors 14 and 24 serve the purpose of limiting the current and may, therefore, be substituted by any other current-limiting means, for instance vacuum tubes. Such a vacuum tube is shown at 1411 in Fig. 6. Such a regulation of one of the branch currents in the direct current circuit of the transductor affords obtaining a continuous variation of the direct current flux conditions. This causes a variation in the pulse duration and hence also in a phase displacement of the steep flanks of the pulse wave. In such a manner, by electric differentiation preferably of the ascending (left-hand) front flank (i. e. by transforming the rate of current change at the pulse front, into a corresponding voltage pulse), a peaked voltage pulse of a continuously regulatable phase position may be produced. Such a voltage pulse is advantageously suitable, for instance, for controlling the ignition of a gas discharge device even if exacting requirements as to accuracy of timing are to be met.

The premagnetizing direct current may be supplied to the series transductors by means of a bridge circuit, for instance, a full-wave rectifier bridge energized from the alternating-current supply of the transductor main circuit. The various features described in the foregoing may be used individually as well as in any desired combination with each other. Constant current pulses of predetermined or adjustable duration are advantageously applicable, for instance, .for the control of relays and releasing devices, or for the premagnetization or reversal of magnetlzatron in saturable reactors of allvkinds, especially those used in contact rectifiers and converters, or for counting circuits, pulse-responsive switches, latching magnets and other pulse-responsive electric apparatus.

Fig. 8, for example, shows the application of an asymmetrical series transductor for premagnetizing the commutating reactors in a contact rectifier in a three-phase Y connection.

Connected to the secondary winding 1 of a power transformer with three phases R, S, .T, whose primary winding is notillustrated, is the main winding 27 of a commutating reactor 2 in series with a synchronous contact device 3 which opens and closes in synchronism with the alternating supply current so that only one half wave of the current can flow through each phase circuit. Only the circuit element pertaining to phase R of the three phase circuits are designated by reference numerals, as the two other phase circuits are similar in design and operation except that they function in the proper cyclical sequence to apply a substantially continuous rectified current to the load 5. The three contact devices are periodically actuated, for instance by a mechanical transmission schematically represented by a dot-and-dash line 10a, from a synchronous motor 10 energized from the power supply of the apparatus. Instead of a mechanical drive actuated by a synchronous motor, an electromagnetic control device may be used, for instance as illustrated and described in the copending application Serial No. 278,385, filed March 25, l952, by E. Rolf for Electric Contact Converters, and assigned to the assignee of the present invention.

The circuit of load 5 is-shown to include a smoothing reactor 6 and a load switch 7, as well as an auxiliary load 8 which remains effective as a base load when switch 7 is open.

The core of each commutation reactor 2 is equipped with auxiliary windings 28 and 36 which provide the reactor with respective components of direct-current premagnetization as explained presently.

The commutation reactor in each phase circuit of the rectifier has a high reactance only temporarily during the commutation intervals when the magnetic flux. in the reactor core changes between opposingly-directed saturation values, while the reactance is negligibly small at all other times when the core is saturated. As a result, when contact device 3 is closed, the reactor depresses the current flowing through the pertaining contact device 3 at small instantaneous current values in the vicinity of a current zero passage, thus flattening the current wave to a step of a very small residual current magnitude (step current). The synchronous contact device 3 is so phased as to open its circuit at a moment (break moment) during the step interval.

The auxiliary windings 28 and 36 provide a resultant direct-current premagnetization which controls the current step as to phase position and step-current magnitude to secure optimum circuit interrupting conditions.

When the contact device 3 closes its contact, it is desired to have the pertaining commutating reactor 2 so premagnetized that it again reverses its saturation and thus provides a high reactance at the contact closing moment (make moment). Therefore, another current step (make step) is efiective immediately subsequent to the make moment of the contact device 3 to secure optimum voltage conditions or also for-controlling the output voltage of the rectifier. The make premagnetization of the commutation reactor 2 is also controlled by iliary windings. As a rule, however, the resultant premagnetization efiective during the make performance is to be different from the afore-mentioned break premagnetization. For that reason, the auxiliary winding 36 is energized by a constant-current pulse of the proper amplitude and the proper phase timing to secure the desired difference between the make premagnetization and break premagnetization of the commutation reactor.

This current pulse is supplied to the winding 36 by an asymmetrical series transductor 70 composed of two satur able portions with respective main windings 71 and 72. The winding turns ratio of the respective main windings to the pertaining premagnetizing windings 71' and 72' is smaller in one reactor than in the other as explained above. The main windings 71 and 72 of the two reactors are series-connected and, for adjusting a desired phase position of the premagnetizing pulses in winding 36, are connected in a phase-shift circuit energized from the power transformer. In the illustrated embodiment, the transductor 70 for the commutation reactor 2 of phase R is connected to respective auxiliary transformer windings 1a of the phases T and S. The connection of the transductors for the commutation reactors of the two other phases is analogous, that is the transductor for each phase is energized from the auxiliary transformer windings pertaining to the two other phases in accordance with a cyclical circuit arrangement.

The premagnetizing windings 71' and 72' of the three series transductors are series-connected in a common direct current circuit which is energized from a constant voltage source 29 and includes a smoothing and stabilizing inductance coil 30 and an adjusting resistor 31. The same direct-current circuit also includes the auxiliary windings 28 of the commutation reactors in all three phases.

The time curve of the premagnetizing current i produced by each series transductor 70 and applied to the auxiliary winding 36 is represented in Fig. 9 by curve i in dependence upon time t. The zero-current axis is indicated by a horizontal dot-and-dash line. Due to the asymmetry of the series transductor, a positive pulse of short duration and a negative pulse of long duration will result. The long negative pulse has a smaller amplitude so that the two areas, defined by the two curve portions and by the dot-and-dash zero line, are of equal size. The current curve i has lines of symmetry at those time points t t, where the voltage u across the transductor reverses its direction. The positive pulse, serving as a constant component of the make magnetiza tion, is to be given a duration and phase position with respect to the alternating-voltage cycle that is effective upon the commutation reactor during the period of time in which the pertaining contact device 3 may close its circuit within the available range of voltage control. With a three-phase Y connection as illustrated, the maximum control range is a electrical, counted from the time point of voltage equality between the decaying phase current and the incipient phase current. The corresponding duration of the positive transductor pulse from a to a that is from 0 to 90, is obtained by a corresponding selection of the number of winding turns, the cross sections of the reactor cores, and the magnitude of the auxiliary voltage u. The correct timing of the current pulse requires a phase position of the auxiliary alternating voltage, for instance u so that this auxiliary voltage intersects the zero line at a moment occurring (a -tx /2 later than the moment of voltage equality between the decaying and incipient phase currents. It follows for the present example that the auxiliary voltage u leads the phase voltage UR (shown by a dotted line in Fig. 9) by about For accurately dimensioning the strength of the premagnetization, the above-described trapezoidal premagnetization effective in the auxiliary winding 36 is supplemented by a superim-' posed continuous direct-current premagnetization by means of the winding 28 which, as explained, may be included in the direct current circuit of source 29.' This continuous component of premagnetization is denoted in Fig. 9 by V It acts in the same sense as the negative pulses and results together therewith in a constant component VA- of the break magnetization. In contrast, the difference between the positive pulses and the supplemental premagnetization V provides the resultant constant component VE of the make magnetization.

For improving the shape of the current step, each commutation reactor 2 may have its core inductively linked with a shaping circuit 33 which, in the illustrated simplest case, consists of a resistor and a capacitor seriesconnected with each other across an auxiliary winding on the reactor core. If desired, the converter may also be provided with auxiliary premagnetizing circuits that cooperate with the main reactor winding 27 to provide further components of premagnetization in dependence upon the voltage drop occurring across the series connection of the main winding 27 and the pertaining contact device 3. Two such auxiliary circuits are shown at 32 and 42. Each circuit comprises a resistor and a valve of opposed polarity to that of the other circuit. Both circuits extend parallel to each other between a tap point of winding 27 and the load-side point of contact device 3. Auxiliary circuit 32 serves to improve the adaptation of the reactor premagnetization to the requirements of the break performance. Circuit 42 performs a similar function for the make performance. The valve of circuit 42 may be controllable as shown in the drawing. Such auxiliary circuits permit adapting the converter to most exacting accuracy requirements as, is more fully explained in the above-mentioned copending application to which reference may be had for further details if desired.

It should be understood that such and other auxiliary circuit means are not essential to the invention proper and that apparatus according to the invention may be modified in various other respects and may be given embodiments other than those herein specifically illustrated and described, without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim:

1. A transductor apparatus, comprising two transductor portions having respective saturable cores having angular saturation curve knees and having main and premagnetization reactor windings disposed on each of said cores and electrically series-connected with each other, said portions having direct-current premagnetizing means inductively linked with said respective cores in mutually opposing senses relative to said main windings and operative to magnetize said portions beyond said saturation curve knees, one of said portions having a ratio of premagnetization to main-winding-turns difierent from said ratio of said other portion.

2. A transductor apparatus, comprising an alternatingcurrent circuit, two transductor portions having respective saturable cores having angular saturation curve knees and having main and premagnetization reactor windings disposed on each of said cores and electrically seriesconnected with each other in said circuit, direct-current circuit means inductively linked with said two cores in mutually opposing senses relative to said circuit for magnetizing said cores beyond said saturation curve' knees and having respective ampere turns, the ratio of said ampere turns to the number of main-winding turns of one of said transductor portions being different from said ratio of the other portion.

3. A transductor apparatus, comprising a circuit, two electrically asymmetrical transductor portions having respective saturable cores having angular saturation curve knees and having respective main and premagnetization windings disposed on each of said cores and electrically series-connected with each other in said circuit, each of said portions having direct-current circuit means inductively linked with said core and having in said core for magnetizing said cores beyond said saturation curve knees and relative to said circuit a magnetomotive force opposed to that in said other core, said circuit means of one of said cores having a current larger than said other circuit means.

I 4. A transductor apparatus, comprising two transductor portions having respective saturable cores having angular saturation curve knees and having respective main reactor windings disposed von said cores and electrically seriesconnected with each other, each of said portions having a premagneti'zing winding on said core, direct-current circuit means connected with said two premagnetizing windings for magnetizing .said cores beyond said saturation curve knees and having in said premagnetizing windings respectively. ditterent magnetizing polarities relative to said main windings, one of said transductor portions having a turns ratio of main winding to premagnetizing winding different from said ratio of the other portion.

5. A transductor apparatus, comprising two electrically asymmetrical transductor portions having respective saturable cores having angular saturation curve knees and having respective main reactor windings disposed on said cores and electrically series-connected with each other, each of said portions having a premagnetizing winding on said core, two direct-current circuits of constant terminal voltage connected to said respective premagnetizing windings for magnetizing said cores beyond said saturation curve knees, one of said circuits having a current control member for varying the current in one premagnetizing windingrelative to the current in the other.

6'. In combination, a contact converter comprising a load circuit having a saturable commutation reactor and a periodic contact device series-connected with each other, said reactor having a premagnetizing circuit, and means comprising a series transductor having two transductor portions series-connected in said premagnetizing circuit and operative to provide it with premagnetizing excitation pulses of unequal positive and negative wave durations.

7. In combination, a contact converter comprising alternating-current supply means, a load circuit connected with said supply means and having a saturable commutation reactor and aperiodic contact device series-connected with each other, said reactor having premagnetizing winding means,.and means comprising a transductor having two transductor portions series-connected between said supply means and said winding means for providing said winding means with premagnetizing pulses.

8. In combination, a contact converter comprising alternating-current supply means, a load circuit connected with said supply means and having a saturable commutation reactor and a periodic contact device seriesconnected with each other, said reactor having two premagnetizing windings, a direct-current circuit of normally constant voltage connected with one of said windings to provide a constant component of premagnetization, and means comprising a transductor having two transductor portions series-connected between said supply means and said other winding to provide said other winding with a premagnetizing pulse of unequal positive and negative half-wave-durations alternately cumulative and differential with respect to said constant component.

9. In combination, a contact converter comprising alternating-current supply means, a load circuit connected with said supply means and having a saturable commutation reactor and a periodic contact device seriesconnected with each other, said reactor having premagnetizing winding means, phase-shift means connected with said supply means, a transductor having two series-connected transductor portions connecting said phase-shift means with said winding means and operative to pass through said winding means a pulse wave of unequal half-Wave durations in a given phase relation to the make and break intervals of said contact device, the short pulse of said wave being coincident with the make interval and the long pulse being coincident with the break interval, whereby said reactor is differently premagnetized due to said pulses during said respective make and break intervals.

10. A combination according to claim 9, comprising a direct-current circuit of normally constant voltage also connected With said premagnetizing winding means of said commutation reactor to provide said reactor with a continuous and constant component of premagnetization, and said pulses being alternately cumulative and differential relative to said constant component.

11. A combination according to claim 9, comprising a direct-current circuit of normally constant voltage also connected With said premagnetizing Winding means of said commutation reactor to provide said reactor with a continuous and constant component of prernagnetization,

10 said direct-current circuit having relative to said Winding means a polarity of connection at which said constant component has the sense required for said break interval.

12. In a combination according to claim 8, said transductor portions having respective direct-current prernagnetizing windings series-connected in said direct-current circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,778,725 Oswald Oct. 21, 1930 2,039,044 Wolfert et al Apr. 28, 1936 2,466,864 Prati Apr. 12, 1949 2,558,572 Logan June 26, 1951 2,611,114 Fisher Sept. 16, 1952 2,680,831 Belarnin June 8, 1954 2,693,569 Diebold Nov. 2, 1954

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