US3361956A

US3361956A - Voltage regulating transformer systems

Info

Publication number: US3361956A
Application number: US330813A
Authority: US
Inventors: Joseph G Sola
Original assignee: Basic Products Corp
Current assignee: Basic Products Corp
Priority date: 1963-12-16
Filing date: 1963-12-16
Publication date: 1968-01-02
Anticipated expiration: 1985-01-02

Description

Jan. 2, 1968 r SOLA 3,361,956

VOLTAGE REGULATING TRANSFORMER SYSTEMS Filed Dec. 16, 1963 4 Sheets-Sheet l AND CONTROL UNIT SENSING INVENTOR. g/o SEPH G4 Sou? NEW 4 4,222

ATTORNEYS Jan. 2, 1968 J SQLA 3,361,956

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% HARMONIC VOLTAGE INVENTOR. dos [P4 6? Jam Jan. 2, 1968 J. G. SOLA 3,361,956

I VOLTAGE REGULATING TRANSFORMER SYSTEMS Filed Dec. 16, 1965 4 Sheets-Sheet 4 Fig.6

INVENTOR ATTORNEYE United States Patent 3,361,956 VULTAGE REGULATING TRANSFORMER SYSTEMS Joseph G. Sela, River Forest, 111., assignor to Basic Products Corporation, Elk Grove Village, 111., a corporation of Wisconsin Filed Dec. 16, 1963, Ser. No. 330,813 9 Claims. (Cl. 323-45) This invention relates to electric regulators and especially to line voltage regulators.

Among the problems of previous line voltage regulators has been the use of moving parts, the relatively slow response thereof to changes in line voltage and load, and sensitivity of the regulator to frequency change and waveform distortion. Previous types of line voltage regulators have in many instances relied upon motor driven variable ratio autotransforrners for maintaining a prescribed output voltage value when line voltage and load changes occur, such motor driven devices being slow in operation and requiring moving parts which are subject to wear. Ferro-resonant type line voltage regulators are generally restricted to power sizes of the order of kva. and less and are inherently sensitive to the frequency of the applied voltage. Also, there will be a change in output Voltage with frequency changes. Furthermore, although they can be adjusted to have good regulation for changes in line voltage, they cannot also be adjusted for satisfactory regulation for changes in load impedance. Additionally, they produce waveform distortion which may or may not require external filtering for correction. Previous types of static regulators using saturable devices, such as magnetic amplifiers or semiconductor devices (e.g., controlled rectifiers), operate by gating portions of the line voltage from a load. Although their response may be fast and the devices static, they can produce undesirable distortion of the output voltage requiring bulky, expensive and external filtering.

One of the objects of the present invention is to provide a regulating transformer which has relatively fast response, good output waveform, and requires no moving parts.

Another object of the invention is to provide an arrangement wherein the material and parts required per kva. of regulated power is relatively small compared with previous static devices.

In one aspect of the invention, an A.C. source is pro vided with at least two A.C. magnetic circuits, each circuit having an A.C. main winding means and an auxiliary winding means connected in series therewith. In one form, only one of the AC. winding means has an auxiliary winding means associated therewith and at least one of the magnetic circuits has a DC. saturating means. One of the magnetic means has an air gap located in a portion thereof in such a manner that it will affect only the A.C. flux produced by the winding means. The air gap serves to reduce the cyclic variation of the reluctance for the circuit concerned. Preferably, each A.C. winding means has an auxiliary winding associated therewith, one being in boost relation and the other in bucking relation. A DC. saturating means is provided for both.

In another form of the invention, the magnetic circuits can be located on a single core in which case the shunt does not necessarily require an air gap therein. It is preferred, however, that an air gap be employed so as to obtain minimum distortion and adequate regulation. For best performance, the auxiliary winding turns should be so related to the core area cross section that with maximum output to the load, the core will operate below saturation. It is desirable that the harmonic content of the output be not more than about 3% when a sine wave source is employed.

In one form of core structure, the shell has a center leg with bifurcated ends, the bifurcated ends having the DC. saturating winding thereon. The shunt means is located near the center of the center leg, and the main winding means with its auxiliary winding means is located on either side of the shunt.

The DC. saturating means can be connected to a suitable control circuit responsive to the output voltage. It may control the saturating windings together or only one at a time. The device is dependent upon D.C. saturation of either half of the magnetic core means. When no DC. is impressed upon the saturating means, the input voltage divides between the two primary or main winding means. If DC. is applied to only one part of the magnetic structure, the input voltage is transferred to the main winding of the other part of the magnetic structure, so that the volts per turn of the auxiliary winding on the part having DC. applied will .be reduced while the volts per turn of the auxiliary winding on the unsaturated part increase. As one auxiliary winding voltage aids the input voltage and the other opposes, the output voltage will be controlled by application of DC. to the desired portion of the magnetic structure.

These and other objects, advantages and features of the invention will become apparent from the following description and drawings which are merely exemplary.

In the drawings:

FIG. 1 shows a schematic wiring diagram;

FIG. 2 shows one form of the invention;

FIG. 3 shows another form of the invention;

FIG. 4 shows a still further form of the invention;

FIG. 5 is a graph showing the relation between k and percentage of third harmonic at 54,000 lines per square inch input flux density; and

FIG. 6 is a still further form of the invention.

Referring to FIGS. 1 and 2, in one embodiment of the invention, the main winding comprises at least a pair of windings 10, 11 on core means 12. Auxiliary windings 13, 14 are connected to the main windings 10 and II. The shunt 14A is schematically shown as located between main winding portion 11 and its auxiliary winding 14 and main winding 10 and its auxiliary portion 13. The auxiliary windings 13 and 14 are arranged so that one will be in bucking relation to the load and the other in aiding relation to the load. The source of A.C. 33 is connected across leads 15, 16 to

points

17 and 18 between main winding means 10, I1 and 13, 14. When the windings are on a single core, the shunt may be solid, but it is preferable that there be an air gap therein so as to provide minimum distortion.

At least one end of core 12 is arranged to have DC. control Winding means 19, 20 associated therewith for the purpose of saturating or controlling the saturation of that portion of the core. It is preferable to use a second DC. control winding arrangement 21, 22. The DC. control winding means may be controlled by a sensing and control arrangement 23, which is connected across load 24, the sensing and control means 23 being any conventional means. The load is connected across the outer ends of auxiliary windings 13 and 14 by

leads

25 and 26.

Referring to FIG. 2, the core means 27 may take the form of a shell although it can take other shapes. The center leg 22} has bifurcated

end portions

29, 30 at each end thereof. The DC. control windings 21 and 22 are on the bifurcated portions of end 29 and the DC. control windings 19 and 20 are on the bifurcated end portion 3t), each pair being in opposed relation.

The auxiliary windings 13, 14 are shown in heavier lines for clarity in description. Main windings 1t) and 11 are connected together by means of a lead 31, and shunt means 32 and 33A are located between the main winding means 10 and 11. The source 33 is connected by means of

leads

15, 16 to

points

17, 18 of the main winding means and load 24 is connected by means of

leads

25 and 26 to the ends of the auxiliary winding means 13 and 14, respectively.

Describing the operation of the arrangement shown in FIG. 2, A.C. is applied to the main windings 10 and 11 from source 33, causing a flux to exist in the

center legs

34, 35 of the core. These fluxes may not be equal in magnitude or in phase, the difference fluxes passing through shunts 32, 33A. With no control current applied to the DC. windings on either side, line voltage 33 -is substantially passed to the load 24 without appreciable change in magnitude. When DC. is applied to control windings 19, 20, the portion 35 of the core becomes saturated and the source voltage 33 then appears mainly on main winding 10, producing a flux through core section 34 and the shunt so as to energize only auxiliary winding 13. Since auxiliary winding 13 is connected in boosting relation, the result is that the load voltage at 24 rises to a value above the source voltage 33. On the other hand, if control current is applied to control windings 21 and 22, portion 34 of the core becomes saturated and the line voltage 33 is now applied to main winding 11, so that the flux passes through portion 35 and through shunts 32 and 33A to energize auxiliary winding 14. Since auxiliary winding 14 is connected in bucking relation, the load voltage at 24 becomes less than the line voltage 33. By suitably controlling the currents in the DC. windings, the relationship between the line voltage 33 and load voltage 24 can be varied over the range of boosting and bucking turns ratios determined by windings 13 and 10 and windings 11 and 14.

Merely by way of example, referring to FIG. 2, the core for a kva. regulator may be 3 /2 inch stack of 29- gauge laminations M-lS hot rolled steel. The longitudinal dimension may be 8" and the cross dimension 7". The center or middle core is 3%. wide and is located between the two end legs. The bifurcated portion has an opening or window of 1%" width by 1% thick. The shunts are one inch wide and are located between the center portion and the outer legs with a gap of 0.010 between each shunt and the shell. The main windings each have 57 turns, and the "boosting auxiliary winding has 12 turns. The auxiliary bucking winding for bucking has 2 turns. The control windings each have 112 turns.

The aforementioned regulator maintained a constant output voltage of 115 volts at 60 c.p.s. for a range of input voltage from 104 to 127 volts. The maximum percentage of harmonics of the output voltage has a third harmonic of 3.6% of the fundamental at the maximum line voltage condition and at full load. With an air gap in the shunt of 0.025", the maximum value of the third harmonic was 2.7% of the fundamental of the output voltage at the maximum line voltage condition and at full load.

In FIG. 3, a pair of cores 100, 101 having

main windings

102, 103 are shown. Auxiliary windings 104 and 105 are connected to the ends of

main windings

102 and 103, and the load 1.06 is connected to terminal 107 and 100A of the auxiliary windings. The

D.C. control windings

108 and 109 are arranged to be connected to a source of control, DC. The DC. control windings preferably are split in two parts, one on each of the two center legs. Each core 100, 101 has two center legs, and the outer legs have air gaps 109A, 110, 111 and 112.

Describing the operation of PEG. 3, source voltage 113 is applied to the

main windings

102 and 103 in series. With no control current in either structure, the source voltage is passed through the two transformers to the load 106 without substantial alteration. If control current is applied to windings 108, the center legs become saturated and the line voltage 113 now appears mainly across winding 103. Since the windings 103 and 105 act in boosting relation, load voltage 106 then rises above the line voltage 113. If control current is applied to control winding 109, the line voltage will appear across winding 102 and since

windings

102 and 104 are connected in bucking relation, the load voltage 106 will be forced below the line voltage 113. By adjusting the control current in

windings

108 and 109, a range of relationships between line and load voltage can be obtained within the turns ratio limits of the main and auxiliary windings on the two structures.

FIG. 4- shows a still further form of the invention wherein shells 120, 121 have interiorly disposed cores 122, 123, respectively. The shells and cores may be so dimensioned that the desired air gaps in the shunts will be at 124, 125, 126, 127. The A.C. source is connected across main windings 12 8, 129 by leads 130, 131, the main windings being serially connected together by lead 132. The boost auxiliary winding 133 is connected in series with the load 1.34 by lead 135 and with its main winding by lead 136. Bucking auxiliary winding 137 is connected to load 134 by lead 135A and with its main winding 129 by lead 138.

The DC.

control windings

139 and 140 are wound on the center cores only, said windings being suitably con nected to the DC. control circuits.

The arrangement of FIG. 4 Will operate in a manner similar to the previously described forms.

Referring now to the embodiment having an air gap, regulation will be dependent upon the DC. ampere turns, the air gap in the shunt and the number of aiding and opposing turns. The regulating range increases as the number of DC. ampere turns increases.

It has been found that the regulating range decreases as the air gap increases. Thus, when the air gap increases, from no gap to a 0.050" gap, the regulating range decreases to less than one half its range at no gap. The regulating range increases as the number of aiding and opposing turns increases. However, the increase in range for a given increase in turns becomes less as more turns are added.

In the form where auxiliary windings are wound directly over the main windings, the leakage reactance will be ery low. Because of the close coupling of the main and auxiliary windings, the line power factor is very high, and may be 97% or better.

It was ascertained that the total harmonics can be held under 3% for an input regulating range of 110% of nominal voltage. It appears that there are two primary sources of harmonics, A.C. saturation caused by the auxiliary winding ampere turns and 'by a certain combination of main winding and DC. flux. The major portion of the output distortion is caused by the third harmonic voltage. The third harmonic voltage, caused by auxiliary winding A.C. saturation, is a maximum when no D.C. flux is present in the core, the amount of third harmonic voltage distortion in the output being dependent upon such A.C. saturation level.

The following relationship gives the auxiliary winding current required to produce a particular percentage of third harmonic output voltage:

The value of k depends upon the percentage of third harmonic output voltage. L is the inductance of the auxiliary windings in series.

Thus tang =3.19N2A 10B I=Load current in amps.

N =Number of aiding and opposing turns A =Net cross section of the core in square inches L zLength of air gap in inches L =Length of magnetic path of core in inches ,u=Etfective permeability of the core L=Inductance in henrys k=Third harmonic content factor (see FIG. 5

From the above equation, it is possible to determine the maximum load current which will produce less than a 3% third harmonic voltage in the output. For 3% third har monic voltage k=.03.

The values of k, shown in FIG. 5, are for a fixed input fiux density. If the input flux density is increased, k increases slightly, thus allowing larger load current for the same percentage of third harmonic voltage. If the input flux density is reduced, the value of k decreases, thus allowing less load current for the same percentage of third harmonic voltage.

It is difficult to analyze the second source of harmonics which is caused by a combination of primary and DC. flux. It is dependent upon the input flux density, the air gap and the number of aiding and oppoisng turns. The output harmonic voltages under these conditions are a maximum, when half of the core under the aiding winding is partially saturated with DC. For this condition the output harmonics increase directly as the opposing turns increase. The harmonics increase as the input flux density increases and decreases .as the air gap is increased.

The'form shown in FIG. 6 is a five legged core arrangement 150, the center leg 151 having air gap 152, theouter legs having

D.C. windings

153, 154 on each of the

outer legs

155, 156 and 157, 158 respectively. The outer legs are also wound with A.C. windings over the legs two at a time, the

primary windings

159 and 160 being Wound around

legs

155, 156 and 157, 518 respectively. The primary windings are series connected by lead 160A and to the source 161A, the source being connected to leads 163, 164. The bucking or opposing winding 165 also is wound on

legs

157, 158 in the same direction as the A.C. winding and is connected to the A.C. winding at point 162. The boost or aiding winding 165A is connected at point 161 to the A.C. winding on

legs

155, 156. The opposite end of the bucking winding is connected by lead 166 to one portion of the output or load 166A. The opposite end of boost winding 165A is connected by lead 167 to the other side of the output 166A. The DC.

windings

153 and 154 are connected to a DC. control means (not shown) as previously described. The direction of DC. winding 153 is such that the DC. ampere turns produced by the winding on the two

legs

155, 156 are in a direction to produce saturation of

legs

155, 156. Likewise, the direction of DC. windings 154 on

legs

157, 158 is in a direction to produce saturation of

legs

157, 158 without producing a DC. flux in the center leg 151.

In the operation of the regulator with neither D.C. winding energized, the input voltage is transferred directly to the output with little change in magnitude because the buck and boost winding 165, 165A cancel the effect of each other. However, if one of the DC. windings, for example, winding 154, is energized to saturate

legs

157, 158, the buck winding 165 is disabled and the boost winding 165A operates in its magnetic circuit. The effect is to produce an increase in the output voltage. On the other hand, if D.C. winding 153 is energized to saturate

core legs

155, 156, the boost winding A is disabled and the buck winding 165 operates to decrease the outputvoltage over the input voltage. During this operation, the A.C. flux path is shifted from between the outer legs in accordance with the degree of saturation produced by the DC windings. If one of the DC. windings saturates one pair of outer legs, such as

legs

157, 158, the A.C. flux is then confined mainly to the

legs

155, 156, linking the turns 159 of the primary winding and producing the appropriate voltage in the boost winding 165A. By this means, the output voltage can be controlled by applying independent DC. to the DC. saturating windings for a fixed value of primary voltage. Conversely, for varying values of primary voltage, the output voltage can be maintained constant by suitably controlling the limits of current in the DC. saturating windings.

It should be apparent that various changes may be made in the details of the circuit and structures without departing from the spirit of the invention except as defined in the appended claims.

What is claimed is:

1. In an A.C. voltage regulator, the combination including load means, an A.C. source, at least two A.C. magnetic circuits, each of said magnetic circuits having an A.C. main winding and at least one of said circuits having an auxiliary winding connected in series with its main winding, at least one of said magnetic circuits having D.C. saturating means, said main winding means being connected serially, means connecting said A.C. source across said serially connected main winding means, means connected said auxiliary winding means to said load means and the other side of the load to said other main winding means, at least one of said magnetic circuits having an air gap located in a portion thereof to affect only A.C. flux produced by the main winding, said air gap serving to reduce the cycling variation of the reluctance of the circuit in which it is located, and means for applying DC. to said saturating means.

2. In an A.C. voltage regulator, the combination including load means, an A.C. source, a pair of A.C. magnetic circuits, each of said magnetic circuits having an A.C. main winding and an auxiliary winding connected in series with its main winding, said main windings being connected serially, at least one of said magnetic circuits having D.C. saturating means, said A.C. source being connected across said serially connected main winding means, means connected said load across said main winding and auxiliary windings, at least one of said magnetic circuits having an air gap located in a portion thereof to aifect only A.C. flux produced by the main winding, said air gap serving to reduce the cyclic variation of the reluctance of the circuit in which it is located, and means for applying D.C. to said saturating means.

3. In an A.C. voltage regulator, the combination including load means, an A.C. source, a pair of A.C. magnetic circuits, each of said magnetic circuits having an A.C. main winding and an auxiliary winding connected in series with its main winding, said main windings being connected serially, each of said magnetic circuits having D.C. saturating means, said A.C. source being connected across said serially connected main winding means, means connecting said load across said main winding and auxiliary windings, at least one of said magnetic circuits hav ing an air gap located in a portion thereof to aifect only A.C. flux produced by the main winding, said air gap serving to reduce the cyclic variation of the reluctance of the circuit in which it is located, and means for applying DC. to said saturating means.

4. In an A.C. voltage regulator, the combination including load means, an A.C. source, magnetic core means, a pair of main winding means, at least one of said winding means having an auxiliary winding means serially connected therewith, air gap shunt means between said main winding means, at least one D.C. saturating winding means for controlling the saturation of that part of said core means associated with at least one of said main winding means, at least part of each of said main Winding means being series connected together and to the source, parts of said main winding means and said serial- 1y connected auxiliary winding means being connected across said load means, and means for applying DC. to said saturating winding means.

5. In an A.C. voltage regulator, the combination including load means, a magnetic core means having a shell and a center leg with bifurcated ends abutting said shell, magnetic shunt means located between said shell and said center leg inwardly of said bifurcated ends, main winding means on either side of said magnetic shunt means each having an auxiliary winding means serially connected therewith, means for connecting an A.C. source to a point between each of said main winding means and its auxiliary winding means, means connecting said load means across said auxiliary winding means, DC. control winding means on said bifurcated ends, and means for applying DC. to said DC. control winding means.

6. In an A.C. voltage regulator, the combination including load means, a magnetic core means having a shell and a center leg with bifurcated ends abutting said shell, magnetic shunt means with an air gap located between said shell and said center leg inwardly of said bifurcated ends, main winding means on either side of said magnetic shunt means each having an auxiliary winding means serially connected therewith, means for connecting an A.C. source to a point between each of said main winding means and its auxiliary Winding means, means connecting said load means across said auxiliary winding means, DC. control winding means on said bifurcated ends, and means for applying DC. to said DC. control winding means.

'7. In an A.C. voltage regulator, the combination including load means, an A.C. source, a single core means providing a pair of A.C. magnetic circuits, each of said magnetic circuits having an A.C. main winding, said main windings being connected serially, an auxiliary winding connected in series with each main winding, said A.C. source being connected across said serially connected main winding means, means connecting said load across said main winding and auxiliary windings, D.C. saturating means on said core means, at least one of said magnetic circuits having an air gap located in a portion thereof to effect only A.C. flux producedby the main winding, and means for applying DC). to said saturating means.

8. In an A.C. voltage regulator, the combination including load means, an A.C. source, a five legged core means having two pairs of legs and a center leg with an air gap therein, D.C. saturating winding means on each of said pairs of legs, main winding means on each of said pairs of legs, said main winding means being serially connected, said A.C. source being connected across said serially connected main winding means, an auxiliary boost winding means on one of said pairs of legs connected to said main winding means and to one side of said load means, an auxiliary buck winding means on the other pair of said legs and connected to said main winding means and said load means, and means for selectively applying DC. to said DC. saturating winding means, energization of either one of which shifts A.C. flux to the center leg.

9. In an A.C. voltage regulator, the combination including a shell type core means providing a pair of A.C. magnetic circuits, each of said magnetic circuits being provided with a main winding and a series connected auxiliary winding, one of said auxiliary windings beng connected in boosting and the other in bucking relationship with respect to its associated main winding, means connecting said main windings in series, means for connecting said series connected main windings across a source of A.C. power, means for connecting said auxiliary windings to a load, and DC. control winding means associated with each of said magnetic circuits for controlling the A.C. flux transfer between said main and auxiliary windings thereby to control the output voltage to said load.

References Cited UNITED STATES PATENTS 1,902,466 3/1933 Ratkovszky 32345 2,665,406 1/ 1954 Carmichael 32345 2,847,639 8/1958 Howe 32345 2,985,817 5/1961 Bird 32356 1,414,652 5/1922 Kirke 32345 1,997,657 4/1935 Schmutz 32345 3,172,031 3/1965 Sola 32356 3,188,555 6/1965 Essinger 32389 FOREIGN PATENTS 527,536 4/1954 Belgium.

JOHN F. COUCH, Primary Examiner.

W. E. RAY, Assistant Examiner.

Claims

1. IN AN A.C. VOLTAGE REGULATOR, THE COMBINATION INCLUDING LOAD MEANS, AN A.C. SOURCE AT LEAST TWO A.C. MAGNETIC CIRCUITS, EACH OF SAID M AGNETIC CIRCUITS HAVING AN A.C. MAIN WINDING AND AT LEAST ONE OF SAID CIRCUITS HAVING AN AUXILIARY WINDING CONNECTED IN SERIES WITH ITS MAIN WINDING, AT LEAST ONE OF SAID MAGNETIC CIRCUITS HAVING D.C. SATURATING MEANS, SAID MAIN WINDING MEANS BEING CONNECTED SERIALLY, MEANS CONNECTING SAID A. C. SOURCE ACROSS SAID SERIALLY CONNECTED MAIN WINDING MEANS, MEANS CONNECTED SAID AUXILIARY WINDING MEANS TO SAID LOAD MEANS AND THE OTHER SIDE OF THE LOAD TO SAID OTHER MAIN WINDINGS MEANS, AT LEAST ONE OF SAID MAGNETIC CIRCUITS HAVING AN AIR GAP LOCATED IN A PORTION THEREOF TO AFFECT ONLY A.C. FLUX PRODUCED BY THE MAIN WINDING, SAID AIR GAP SERVING TO REDUCE THE CYCLING VARIATION OF THE RELUCTANCE OF THE CIRCUIT IN WHICH IT IS LOCATED, AND MEANS FOR APPLYING D.C. TO SAID SATURATING MEANS.