US 3368137 A
Description (OCR text may contain errors)
Feb. 6, 1968 3,353,137
HIGH CURRENT INTENSITY RECTIFIERS USING BAR-TYPE CONDUCTORS Filed May 11. 1964 I. G. KENNARD ET AL 4 Sheets-Sheet 1 Fig.
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I. G. KENNARD ET AL Feb. 6, 1968 3,368,137
HIGH CURRENT INTENSITY RECTIFIERS USING BAR-TYPE CONDUCTORS Filed May 11. 1964 4 Sheets- Sheet 2 Fig. 5.
Fb. 6, 1968 KENNARD ET AL HIGH CURRENT INTENSITY RECTIFIERS USING BARTYPE CONDUCTORS Filed May 11, 1964 I 4 She etS-Sheet 5 w. w ll 1|..FIIITIJ 2 W w -ILLi q p u L f I; nofihctw L 2 T Feb. 6, 1968 I. G. KENNARD ET AL 3,368,137
HIG H CURRENT INTENSITY RECTIFIERS USING BAR-TYPE CONDUCTORS Filed May 11, 1964 4 Sheets-Sheet 4 Fig. 9.
United States Patent HIGH CURRENT INTENSITY RECTIFIERS USING BAR-TYPE CONDUCTORS Irving Graham Kennard, Colerne, and Sydney Arthur Stevens, London, England, assignors to Westinghouse Brake and Signal Company, Limited, London, England Filed May 11, 1964, Ser. No. 366,245
Claims priority, application Great Britain, May 17, 1963,
It) Claims. (Cl. 3218) ABSTRACT OF THE DISCLGSURE High current intensity rectifying apparatus including bar type conductors that pass through inductive cores having coils thereon. In a first embodiment of the invention, the bar conductors are connected in series in the branch arms of a rectifier network energized by the center-tapped secondary winding of a supply transformer. In this case, the core-mounted coils comprise D-C control windings. In a second embodiment, the bar conductors comprise secondary windings inductively energized by AC primary coils on the cores, said secondary windings being connected in the branch arms of the rectifier network, respectively.
This invention relates to improvements in heavy current electrical apparatus and in particular although not exclusively, to transformers for low voltage high current rectifier circuit arrangements as well as to transductors for controlling such rectifier arrangements, and to combined transformers and transductors in low voltage high current installations.
Rectifier arrangements of this kind are suitable for supplying the plating current to electro-plating baths, tinning lines, galvanizing lines and similar types of equipment.
Heretofore, the construction of such transformers and transductors has been expensive as it requires the use of a large Winding machine to produce the required winding of the heavy current conductor and the operation of shaping this conductor is also expensive.
According to the present invention there is provided heavy current electrical apparatus in which the heavy current circuit comprises solely straight bar conductors, insulated if and where necessary, with inductive coupling core means mounted thereupon and carrying at least one winding for the generation or reception of electrical energy.
The invention is suitable, more specifically, for the construction of a low voltage, high current, secondary system for use with low voltage rectifiers, such as those in a multi-phase rectifier circuit arrangement, in which the rectifiers are arranged to be controlled by saturable reactors mounted on the main rectifier A.C. bus-bars.
The invention will now be described, by way of example only, with reference to the accompanying drawings.
FIGURE 1 illustrates somewhat schematically a transformer having a single bar secondary with a plurality of cores mounted thereon and each provided with its own primary winding,
FIGURE 2 illustrates a modification of the arrangement shown in FIG. 1 suitable for a low voltage rectifier circuit arrangement using a center tap circuit and suitable for bi-phase rectification, two bar shaped secondaries are threaded through the requisite number of primary cores, each of which has its own primary winding, and suitable bridging pieces are provided for connecting the circuit to the rectifier limbs.
FIGURE 3 shows a modification of the arrangement shown in FIG. 2, in which the secondaries are so arranged ice as to form a substantially U-shaped construction suitable for fitting into an oil tank for cooling purposes.
FIGURE 4 illustrates a further modification of the invention as applied to a transformer system combined with a regulator,
FIGURE 5 illustrates the application of the invention to a three-phase transformer arrangement where the secondary windings are arranged inter-star. The vector diagram of such a transformer arrangement being illustrated above the figure.
FIGURE 6 illustrates the application of the invention to a series transductor.
FIGURES 7 and 8 illustrate further arrangements of transductors, and
FIGURE 9 illustrates a combined transformer and transductor arrangement embodying the invention.
Referring to FIGURE 1, there is shown a simple form of transformer having a bar type secondary 1. Three primary windings are shown at 2 and each is wound on a separate core 3, the secondary 1 passing through each core. The primary windings 2 are shown as being connected in parallel, but they may also be connected in series. In effect, the single bar secondary 1 passing through them becomes, as it were, a series secondary connection of all the cores placed around it. It is advantageous, in practice to connect the primary windings in parallel to the supply since, by doing so, it causes all the magnetic fluxes in the numerous cores to be equal to one another. By arallel connection of their equal primary windings there is produced an equal voltage per turn upon their windings 2 and all the cores 3 will, therefore, operate at the same flux density. The series connection of the secondar produces an equal load coupling on all the primaries so that all the primary currents will be equal and the desirable result is achieved of equating the flux densities and the primary current densities.
For low voltage high current rectifier arrangements it is not usual to use a bridge circuit but, instead, an alternative circuit such as a center-tapped circuit arrangement. Considering the matter for one phase only, a center-tapped circuit is required which, in effect, requires the minimum of two secondary turns with the mid-point of the two turns brought out as the center tap.
FIGURE 2 illustrates one such arrangement; in FIG. 2, two bar secondaries 1 are threaded through the required number of cores 3 each of which again has its own primary winding 2. The right-hand end of the upper bar, as shown in the drawing, is connected by a suitable bridging piece 4 to a further, outer, bar 5 which passes outside the core rings 3 to another suitable bridging piece 6 shown at the left-hand end of the lower secondary bar passing through the rings. In this way the left-hand end of the first secondary bar and the right-hand end of the second secondary bar pass through the rings 3 to the outer bar connections 4, 5, 6 and to a half wave rectifier U1, U2 as shown in dotted lines. A connection made at any point of the system joining the right-hand end of the first bar 1 to the left-hand end of the second bar 1 forms the required center-tap CT. Although each of the individual bars passing through the ring cores is only loaded on alternate half-cycles, the behaviours of the pair in loading the primary winding 2 of each ring core is as if the combined half cycles of current have passed through one bar only. A more convenient mechanical construction of the layout is shown in FIG. 3. In FIG. 3 the bar secondarie 1 are formed integrally, or by cross connecting by flat plates in one plane, to form a substantially U-shaped structure in which, before adding the center-tap connection CT, each bar conductor 1 through the ring cores 3 forms the legs of the U-shape. Only one joining connection 4 is then necessary at the top of the U-structure to complete effectively two turns through each ring core, and the center-tap connection CT is made to such joining bar, as shown. Any desired number of ring cores may be placed on each of the vertical leg sections of the U-shaped structure which has the advantage of providing a construction which is conveniently suited to fit in a cooling tank 9 containing, for example, an insulating and cooling oil. With such a arrangement the conventional three secondary connections, that is, the two outer connections and the mid-point, may be brought out vertically through a lid to the tank merely by extending the bar connections 1.
It will be appreciated that the arrangement just described can be arranged for use with a three-phase power supply by merely using three similar assemblies which can be conveniently placed side by side in the same tank. The primary windings on each set of ring cores may be connected in parallel between one phase line and neutral, thus forming a star connected primary, when all three transformer assemblies are joined together. Alternatively, the windings on the ring cores of eachlgroup may be joined in parallel across respectively the;R and Y, Y and B and B and R lines of the supply, soithat the complete assembly forms a delta connected primary system.
The secondary system may be arranged as illustrated by FIG. 3 with the center-tap points bonded together or, alternatively, the connection between the beginning of one winding and the end of another winding can be omitted and four connections brought out per phase, either for the purpose of utilizing an inter-phase reactor, or for use with appropriate transductor connections. Furthermore, rectifiers such as those shown at U1 and U2, may be mounted on external extensions of the secondary bars.
Means for regulating the output of a transformer and rectifier system such as that just described with reference to FIG. 3 may also be provided, and may be in the form of a regulator of an auto-transformer or double wound type, having two variable output connections per phase.
FIG. 4 illustrates one convenient manner in which this can be done for one phase. In FIG. 4, the secondary bar is again shown at 1 and has mounted upon it five ring cores 3. Three of these ring cores have their primary windings 2 connected in parallel with the mains supply, whilst the remaining two of them, shown at the righthand side of the drawing, are connected across the two variable outputs of a regulating transformer T which is of the single winding or auto-type. The transformer T has two movable contacts or brushes 7 and 8, connected to respective ends of the two primary windings 2. Assuming that all the ring cores 3 are of the same size and all the primary windings 2 are also of the same size, the result will be obtained that when the regulating transformer T has one output brush 7 connected to one end of its winding and the other ouput brush 8 connected to the other end of its winding, so as to excite the two primary windings 2 connected to it in phase with the other three primary windings, the output secondary voltage will be the sum of the voltages delivered by the coupling with all five ring cores. When the output brushes 7 and 8 are mid-way along the winding of the transformer, the secondary conductor 1 will have generated in it an output voltage of three-fifths of its value, and when the output brushes are at the opposite extreme ends of the transformer winding, the output volt age developed in the secondary 1 will be one-fifth of the maximum; that is to say, three rings will develop a voltage of one polarity and the other two will develop a voltage of the opposite polarity.
'It will be appreciated that if the number of ring cores connected directly to the mains and to the regulating transformer T are made the same the range of regulation obtainable will be from a 100% to zero.
It will be further appreciated that the arrangement illustrated by FIG. 4 is for a single bar secondary 1 only, and that it may be modified for two bar secondaries passing through all the ring cores as, for example, in the configuration illustrated by FIG. 2 or FIG. 3. The system may, of course, be multiplied by three to form a threephase system with the adjustable output brushes of the requisite regulating transformers mechanically coupled together so that each phase behaves as the other two in respect of ratios of outputs.
FIG. 5 illustrates a specific modification of a threephase system for use in a three-phase half wave rectifier circuit arrangement using a transformer whose secondary windings are arranged inter-star; the layout is illustrated in FIG. 5, together with the vector diagram. The core phases are shown at R, Y and B, and the appropriate connections at Y1, B1 and R1, in conjunction with the R, Y and B windings and the neutral line N.
Alternatively, or in addition to a regulating transformer, such as that shown at T in FIG. 4, transductors may be used for low voltage heavy current control either alone or in conjunction with such transformers. These transductors may be either of the autoor the non-selfexcited type. The latter type of transductor may be used advantageously in low voltage high current equipment in conjunction with a rectifier arrangement in which the rectifiers are arranged in some form of multi-phase half wave circuit.
To do this it is necessary to place two bar secondaries through each ring core of magnetic material and then to connect the two bars with reversed polarity, so that one half cycle of the AC. supply to one rectifier limb passes in one direction through the ring cores, and the next half cycle to another limb of the rectifier passes in the opposite direction through the rings.
FIG. 6 illustrates a transdu-ctor arrangement having two bar conductors 1, with one bar carrying current during each alternate half cycle and the magnitude of its current controlled ampere turn wise by the magnitude of excitation current and the number of turns on a DC. control winding 22 on each of the magnetic ring cores.
In FIG. 6 the bar conductors 1 each pass through two magnetic ring cores 3, each core 3 has a control winding 22 upon it and these windings are connected in series and form the DC. control for the transductor. The two conductors 1 are fed from a transformer T2 of which only the secondary winding is shown in dotted lines, one end of the secondary winding is connected directly to one end of the upper bar conductor 1 and the other end of the secondary winding of the transformer T2 is connected to the opposite end of the lower bar conductor 1, as shown in the drawing; the other ends of the two bar conductors are connected to rectifiers U1 and U2 forming the positive terminal of the rectifier arrangement, whilst the center tap CT on the secondary winding of the transformer T2 forms the negative terminal of the rectifier circuit arrangement.
As usual for non-self excited transductors an even number of cores 3 is necessary and the direct current excitation windings 22 as mutually reversed in phase with respect to the alternating current bars 1. These two windings are then connected in series (as shown) or in parallel, as desired.
It is possible to join the bar connections in several ways so that the resultant current flow in two of them per phase will have the same magnetic effect as an alternating current flowing in one bar through the ring cores of magnetic material, and FIG. 6 shows only one way in which this can be done.
FIGS. 7 and 8 illustrate further arrangement differing from FIG. 6 only in mechanical layout. In FIG. 7 the control windings 22 have been omitted for the sake of clarity and, also, in FIG. 8. In FIG. 8 it will be noted that instead of the center-tap secondary winding on the transformer T2 for a bi-phase system, the secondary winding has been divided into two isolated windings and the effective alternating current in the two bar conductors 1 through each transductor ring core 3 is formed by the outgoing conductor of one half of the bi-phase and the return conductor of the other half of the bihase.
p In FIGURE 8 the transformer T2 is shown as though, in effect, it had a secondary winding of several turns wound on the core in a conventional manner. In the large majority of applications the transductor system will be required to regulate the output current down to substantially zero output voltage as in the case, for example, of the power supply for a timing line. The secondary linkages of the transformer T2 will therefore, be the same in magnitude as the alternating current linkages of the transductor system connected in series with it as, under zero output voltage conditions, the transductor will have to absorb exactly the transformer secondary voltage. The effective current magnitude through them is also exactly the same, as they are effectively in series.
In the case of a bridge type rectifier circuit it will be appreciated that it is only necessary to thread the required number of transformer ring cores and transductor ring cores onto one loop shape system of bus bars and to connect the two alternating current terminals of the rectifier bridge appropriately. An arrangement analogous to that of FIG. 8 may be developed as illustrated in FIG. 9. For clarity of understanding in FIG. 9, the magnetic ring cores 3 forming the transformer T2 of FIG. 8 are shown at the bottom of the loop in FIG. 9 and those forming the transductor are shown at the top of the loop, the arrangement being somewhat similar to that already described with reference to FIG. 3, so as to lend itself readily to mounting in an oil tank, if required, with three outgoing bus bar connections passing through the lid of the tank and providing a mounting for the rectifiers U1 and U2, two of the bus bars being specifically for the rectifier connections and one for the return direct current connection. It will be appreciated that it is immaterial whether the ring cores forming the transformer are at the bottom, and those forming the transductor are at the top, or even whether those for the transformer are on one side and those for the tranductor are on the other side; it is even possible to intermix the transformer and transductor ring cores if desired, the only essential feature being that the polarity rules must be observed, that is to say, all the transformer primary windings must be so phased with respect to the secondary bars that the output voltages generated in the secondary bars add, while in the case of the transductor bars, which must be of an even number, one half must have their control windings coupled in one phase in relationship with respect to the bars, and the other half must be coupled in opposite relationship with respect to the bars, so that no matter whether the two groups are connected in series to make a series transductor, or in parallel to make a parallel transductor, the transformation ratio from the bus bars to the control winding is zero for the fundamental. In practice, it will generally be convenient for the transformer primary winding of each ring core to be connected in parallel and, in like manner, for the control windings of each of the two groups of transductor ring cores also to be connected in parallel in order to keep the size of the conductor to be wound on each ring core down to a low value.
It will be appreciated that simple bus bar fabrication methods may be employed in the construction of the transformers, transductors and the combined assemblies, and that by dividing the magnetic ring cores into a number of parallel-assembled cores, with parallel connected primary or control windings, the advantage is achieved of windings with small gauge conductors which can be wound very simply. Moreover, these can be divided into a number of standardized parts resulting in simple and economical manufacture. In addition to achieving the advantages of a robust bar type of construction, advantages may also be achieved in the winding of the ring cores.
This may be done using a toroidal winding machine and the transformer primary and transductor control windings may be wound on such machine on an uncut core which has been prewound of cold rolled grain orientated steel strip. It may be advantageous to use cores not with a circular window as illustrated in the drawings but with a rectangular window and then to concentrate the winding into two compact coils one on each of the two longer limbs of the rectangular windowed core. Alternatively, using uncut cores, the windings may be applied by a spin bobbin technique.
A particularly advantageous method of fitting the windings to the cores is to make use of so-called cut G-cores having a rectangular window, and to assemble these cores with a clamped band through two bobbin wound coils which have been wound previously on a conventional coil winding machine.
Irrespective of the method employed for assembling the coil windings on the cores, the final result of a rectangular shaped ring of strip wound core material together with its primary or control winding or windings is then threaded onto the bus bar system and supported from its neighbor with suitable moulded spacing pieces.
In the case of the transformer cores it is advantageous that the two coils on one core should be arranged for series or parallel connection in order to provide for a two voltage system so that the same stock items can be connected appropriately for the type of mains supply with which they are required to operate. In some cases, ring transductors with conventional transformers may provide the optimum arrangement.
The invention is particularly, but not exclusively, suitable for multi-phase rectifier circuit arrangements in which the rectifiers are arranged to be controlled by saturable reactors mounted on bus bars connecting the transformer secondary windings to the rectifiers, the rectifiers also being mounted on the bus bars with the center-taps of each secondary formed between the saturable reactors and the rectifiers.
Having thus described our invention what we claim is:
1. Rectifying apparatus for supplying rectified current to a pair of output terminals, comprising:
a pair of equally poled rectifier elements connected at one end with a first one of said output terminals;
a pair of bar conductors each connected at one end with the other ends of said rectifier elements, respectively, the other ends of said bar conductors being connected with the second output terminal;
hollow core means mounted concentrically on said bar conductors;
and means generating a flow of alternating current in said bar conductors, said pair of bar conductors constituting means for carrying half-cycles of current in opposite directions on successive half-cycles of the alternating current whereby D.C. magnetization and saturation of said core is precluded.
2. Apparatus as defined in claim 1, wherein said means generating a flow of alternating current comprises transformer means connected between said other ends of said bar conductors and said second output terminal, said transformer means including a center-tapped secondary winding the ends of which are connected with said bar conductors, respectively, the center tap of said secondary winding being connected with said second output terminal.
3. Apparatus as defined in claim 2, wherein said means generating a flow of alternating current in said bar conductors comprises alternating-current primary winding means mounted on said core means for effecting flux reversals therein, thereby generating by transformer action the alternating current flow in said bar conductors.
4. Apparatus as defined in claim 3, wherein said core means comprises a plurality of first hollow cores each receiving both of said bar conductors, respectively, said second output terminal being connected with a first one of said bar conductors at one end thereof and with the other of said bar conductors at that end thereof which is adjacent the other end of said first bar conductor.
5. Apparatus as defined in claim 4, wherein each of said bar conductors defines in longitudinal section a U- shaped configuration, said first hollow cores being arranged upon the vertical leg portions of said U-shaped bar conductors.
6. Apparatus as defined in claim 5, and further including a pair of additional hollow cores arranged upon the vertical leg portions of said U-shaped bar conductors, each of said additional cores receiving both of said bar conductors, respectively, and direct-current control winding means for controlling the flux density of said additional hollow cores.
7. Apparatus as defined in claim 3, and further comprising means including additional rectifier element, bar conductor and core means cooperating with said pairs of rectifier elements, bar conductors and core means to define a poly phase rectifier system.
8. Rectifying apparatus for supplying rectified current to a pair of output terminals, comprising:
input transformer means including a secondary winding connected intermediate its ends with a first one of said output terminals;
a pair of equally-poled rectifier elements adapted for connection at one end with the other output terminal;
a pair of bar conductors connected at one end with the other ends of said rectifier elements, respectively, the other ends of said bar conductors being connected with the outermost ends of said secondary winding, respectively;
and means for regulating the current flowing through said bar conductors, comprising hollow core means mounted concentrically about said bar conductors, and direct-current control winding means for controlling the flux saturation of said core means, said pair of bar conductors constituting means for carrying half-cycles of current in opposite directions on successive half-cycles of current supplied by said input transformer, whereby D.C. magnetization and saturation of said core by current through said bar conductors is precluded.
9. Apparatus as defined in claim 8, wherein said bar conductors are adjacent each other, and further wherein said core means comprises a pair of hollow cores each mounted concentrically about said pair of bar conductors, one end of said secondary winding being connected with one end of a first one of said bar conductors, the other end of said secondary winding being connected with that end of the other bar conductor that is adjacent the other end of said first bar conductor.
10. Apparatus as defined in claim 8, wherein said secondary winding includes first and second isolated sections, and further wherein said core means comprises a pair of hollow cores each receiving one of said bar conductors, respectively, and further including an additional pair of bar conductors extending through said pair of hollow cores, respectively, each of said additional bar conductors being connected at one end with said first output terminal and at the other end with the inner end of that section of: the secondary winding that is connected at its outermost end with the bar conductor passing through the core containing the other auxiliary bar conductor.
References Cited UNITED STATES PATENTS 3,175,175 3/1965 Hauck 336-- 1,301,636 4/1919 Arnold 336-175 3,011,118 11/1961 Brandt 321-25 3,013,199 12/1961 Hollingsworth et a1. 321-25 X 3,042,849 7/1962 Dortort 32127 3,059,171 8/1962 Storsand 321-26 X 3,252,072 5/1966 Gnanella 3218 FOREIGN PATENTS 1,018,995 11/1957 Germany.
JOHN F. COUCH, Primary Examiner.
W. H. BEHA, Assistant Examiner.