US2143745A - Constant potential transformer - Google Patents

Description

J. G, SOLA Jan. 10, 1939.

CONSTANT POTENT IAL TRANSFORMER Filed Aug. 31, 1938 2 heeisSheet l Jan. 10, 1939; J. G. SOLA 2,143,745

CONSTANT POTENTIAL TRANSFORMER Filed Au 31, 1938 2 Sheets-Sheet 2 Patented Jan. 10, 1939 PATENT OFFICE CONSTANT ro'rsn'rmr. TRANSFORMER Joseph G. Sola, Oak Park, IlL, assignor to Sola Electric 00., Chicago, 11]., a corporation of Delaware Application August 31, 1938, Serial No. 227,626

12 Claims.

' My invention relates to an improved constant potential transformer by means of which variations of input voltage over a wide range of limits may take place without affecting the output voltage to any substantial extent.

One of the objects of my invention is to provide a constant potential transformer which is compact as a unit and which may be economically manufactured. in It is another object of my invention to provide a transformer of this type in which the emciency and input power factor are high while the temperature rise of the magnetic core is low.

A further object of my invention is to provide if) a transformer, the outputvoltage wave of which will have very little distortion and the device will be satisfactory for various commercial-applications.

The invention consists of the novel construc- 20 tions, arrangments and devices to be hereinafter described and claimed for carrying out the above stated objects and such other objects as will appear from the following description of certain preferred embodiments illustrated in the accompanying drawings, wherein,-

Fig. 1 is a sectional view of one form of construction that may be used;

Fig. 2 is a diagrammatic illustration of the wiring arrangement that may be used in connec- 30 tion with a construction such as that shown in Fig. 1;

Fig. 3 is a sectional view of another form of construction embodying the principles of my invention;

35 Fig. 4 is a diagrammatic illustration of the wiring arrangement that may be used in connection with a construction such as that shown in Fig. 3;

, Fig. 5 is a diagram showing the vector relations 40 between the various voltages obtained in the illustrated constructions at different values of input voltage; and

Fig. 6 is a graph showing the relation between the magnitudes of various voltages obtained in 45 the illustrated constructions as the input voltage is varied.

Like characters of reference designate like parts in the several views.

Referring to Figs. 1 and 2, it will be seen that 50 a core type of transformer construction is illustrated, the closed magnetic circuit ID of which comprises a stack of I-shaped laminations II in abutting relation with the end legs l2a of a stack of E-shaped laminations l2, which may be held 5 together by any suitable means. On the end portion A of the core bar H, I have provided a primary winding I3, the terminals I4 and I of which are adapted to be connected with a source of alternating current, the voltage of which from 7 time to time may fluctuate or vary substantially. 5

On the end portion B of the core bar H, I have mounted a winding it, which is in spaced relation to but magnetically coupled with the winding 13, the winding is having terminal leads I1 and I8 and an intermediate tap l9. That part 10 of the winding IE between the lead l1 and tap l9 may be considered as an output or load winding, and the entire winding l6 between the leads I1 and I8 may be termed an intermediate winding. The magnetic core III is provided with a high leakage reactance path between the windings l3 and it which in the form shown comprises the central leg l2b of the E-shaped laminations and which terminates short of the core bar I l thereby providing a non-magnetic or air gap between 20 said leg l2b and the core bar I I. In this arrangement, a condenser 2| is connected by leads 22 across the terminals I1 and 18 of the winding IS. The lead II forms one side and the tap IS the other side of what may be termed an output or load circuit. In the arrangement shown, an auxiliary winding 23 is positioned over the winding 13 and is magnetically coupled therewith, the terminals 24 of said winding 23 being connected in series in the lead IQ of said output circuit.

In Figs. 3 and 4, I have illustrated my invention in connection with a well-known shell type of transformer having two closed magnetic circuits Ill and la comprising a straight central core bar 25 of I-shaped laminations, the sides of which are in abutting contact with the end legs 26a of the E-shaped laminations 26 and the end legs 21a of the E-shaped laminations 21, said parts being held in operative relation by any suitable means. On the end portion A, of the core 0 bar 25, I have mounted a primary winding 28 the terminals 29 and 30 of which are adapted to be connected to a source of alternating current, the voltage of which may fluctuate substantially from time to time. Another winding 3| is positioned on the end portion B of the core bar 25, the winding 3| being in spaced relation to but magnetically coupled loosely with the winding 28. A condenser 32 is connected across the terminals 33 and 34 of the winding 3i. Another winding 35 is mounted on the end portion B of the core bar 25, in the arrangement shown the winding 35 being positioned over and magnetically coupled tightly with the winding 3|. The terminal 36 of the winding 35 leads to one side of what may 5 be termed an output circuit. An auxiliary winding 31 is positioned on the end portion A of the core bar 28 and in the arrangement illustrated the winding 31 is positioned over and magnetically coupled tightly with the winding 28. A lead 38 connects the winding .31 in series with the winding 35, the lead 39 of the winding 31 forming the other side of the aforesaid output circuit. The winding 35 may be termed an output or load winding and the winding 3| may be considered as an intermediate winding. The closed magnetic circuits described are each provided with a high leakage reactance path between the windings 28 and 31 on the end portion A of the core bar 25 and the windings 3| and 35 on the end portion B of said core bar, which in the arrangement shown comprise the central legs and 4| 0! the respective E laminations 28 and 21. The shunts 40 and 4| terminate short of the adjacent sides of the core bar 25 thereby providing non-magnetic or air gaps 42 and 43 between the legs 40 and 4| and the core bar 25.

In Figs. 2, 4, 5 and 6 V0 represents the voltage across the output cucumv, shows the input voltage on the primary winding, V; indicates the voltage derived from the winding l8 between the lead l1 and tap l3,'and from the winding 35 forming parts of the respective output circuits, and Vpa is the component 0! the output voltage taken across the terminals of the auxiliary winding 23 or 31, as the case may be.

In Fig. 5, I have shown the vector relations of the various voltages in either arrangement at a certain power output and at diflerent values of primary voltage. The various voltages are either not primed or are primed to correspond to the difierent values of V, which is varied. As shown, V is nearly 180 out of phase with V, and hence the vectorial sum V0 of the two is approximately their numerical diflference.

In Fig. 6, I have illustrated graphically the relation in the constructions described between V5, V0, Vpa and V atma certain power output.

The principles upon which my improved transformer constructions operate will be clear from a detailed consideration of the construction shown in Figs. 3 and 4. The flux set up by applying a potential across the primary winding 28 will link with winding 3| and cause a definite reactance to be set up by that winding. As the voltage on the. primary winding is increased from zero to a higher level, the flux threading through winding 3| tends to increase in nearly direct proportion to theprlmary flux, due to the reluctance caused by the air gaps 42 and 43, a very slight amount leaking through the shunts 48 and 4|. As the induced E. M. F. reaches a higher value in winding 3| a critical point is reached where resonance takes place, since the reactance of the efl'ective inductance of the winding 3| and the capacity reactance of the condenser 32 are approximately equal at the frequency of the voltage impressed on the winding 28, that is to say,

where f is the frequency of the voltage impressed on the primary winding 28, L is the effective inductance of the winding 3|, and C is the capacity of the condenser 32. Under this resonant condition, a definite amount of current will fiow in the resonant circuit, comprising the winding 3|, condenser 32 and leads 33 and 34, and such current will be limited by the constants 01' that circuit, with the result that a potential will be set up across the winding 3! and a corresponding amount of magnetic flux will be set up in the end portion B of the core bar 25.

It is well known that the inherent characteristic of a resonant circuit is such that its power vector may be many times greater than that of the generator which supplies the energy to the resonant circuit; in this case the energy is supplied by the primary oi the transformer to the resonant circuit comprising winding 3| and condenser 32. By varying the primary voltage across winding 28 so that the magnetic density of section A thereof will still remain under the maximum magnetic density of section B of the core, with which the resonant circuit is associated, the change of flux density in section A of the core due to line variation in the primary will have no appreciable effect on the resonant circuit as the reluctance of the leakage path will be under that of section B of the core and flux will leak through the leakage path between the primary and resonant core portions, which leakage path comprises the shunts 40 and 4| and their respective nonmagnetic gap portions 42 and 43.

It is due to this leakage reactance path also that the co-efiicient of coupling between the primary winding 28 and the aforesaid resonant cir-'- cuit is reduced to a certain optimum value, thereby maintaining a balanced condition so that the resonant circuit will continue to oscillate with the maximum current therein at a frequency equal to the frequency impressed on the primary winding. Under this state of resonance, winding 3| will set up a magnetic field in the core portion B which will remain practically constant so long as the density in the magnetic field of the core portion A remains at a lower density than that of the core portion B. It follows that this substantially constant field strength in core portion B will produce also a substantially constant voltage across the terminals of winding 3| and condenser 32, and this voltage will remain at practically a constant level regardless of variation of voltage applied to the primary winding 28.

The aforesaid resonant circuit, therefore, becomes a constant primary source of voltage for any winding such as the winding 35 that is directly coupled to the winding 3|. This coupling can be effected in any desired way, for example, by means of an auto-type transformer arrangement as shown in Fig. 2, or by mounting the winding 35 over the winding 3| as shown in Fig. 4. In the Fig. 4 construction, the output voltage of the windings 35 will also have a practically constant level voltage independent of the voltage variation in the primary winding 28 so long as the circuit which includes the winding 3| remains in resonance.

The auxiliary regulating winding 31 is coupled to the portion A of the core and is used to change the percentage of regulation of V0 across the terminals 36 and 39 of the output circuit with a variation of V Since this auxiliary winding 31 on core portion A is directly coupled to the primary winding 28, the voltage induced will always be proportional to the turns ratio of primary winding 28 and the auxiliary winding 31.

A very constant level of voltage V. across the terminals 36 and 39 may be obtained by suitably apportioning the number of turns of said auxiliary winding 31 in relation to the number of turns in the winding 35. Any percentage of regulation of output voltage in relation to varia-. tions of V9 also may be obtained from terminals 36 and 89,-for example, an increase in the primary voltage on winding 28 will produce a decrease in output voltage V by properly arranging or apportioning winding 31 in relation to the winding 35.

The relation of voltages described has been upon the assumption that the transformer is on an open output circuit, that is to say, with no load on the terminals 36 and 39. If a load be applied on said terminals,.a magnetic fiux in the aforesaid resonant circuit will be developed corresponding to the load on said output circuit thereby unbalancing the magnetic fiux in section B of the core. This density change in core section B will in turn affect the stable relation of the flux in core sections A and B and also the leakage reactance through the aforesaid shunt paths thereby causing a greater amount of useful flux from core section A to thread through core section B, which compensates for the energy used by the consuming circuit and at the same time maintains the resonant circuit in the desired oscillating condition.

It will be readily understood that in transformers embodying the principles of my invention the primary' winding electrically connected to the source serves to induce voltage to the resonant circuit which is separated from the primary circuit by a high leakage reactance path, thereby providing a low co-eflicient of coupling between the primary and the resonant circuits. The aforesaid resonant circuit may be considered as the primary or main source of controlling energy to the winding 35 and hence'to the output or consuming circuit of the transformer. I

My improved constant potential transformers are compact and efiicient, and are of a small size relative to their power output as compared with other and more cumbersome and expensive apparatus intended for the same purpose. My improved transformers operate at an inherent high power factor, and the output voltage is very close to a pure sine wave.

My improved transformers may be used for many diflerent purposes. They are particularly advantageous in connection with commercial applications such as amplifiers for talking motion pictures, amplifiers for radio transmitters, mercury arc lamps, X-ray apparatus, etc.

I wish it to be understood that my invention is not to be limited to the specific constructions shown and described, except so far as the claims may be so limited, as it will be apparent to those skilled in the art that changes in the constructions and arrangements may be made without departing from the principles of my invention.

I claim:

1. In a constant potential transformer, the combination of a magnetic core, a winding on said core adapted to be connected to a source of alternating current of fluctuating voltage, a second winding on said core, said core providing a high leakage reactance path for a portion of the fiux to thread through one of the windings to the exclusion of the other winding, and means for maintaining the potential across the second winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including said second winding and a condenser, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the first winding.

2. In .a. constant potential transformer, the combination of a magnetic core, a winding on said core adapted to be connected to a source of alternating current of fluctuating voltage, a second winding on said core in spaced relation to said first winding, said core having magnetically disposed between said windings a magnetically permeable shunt with a non-magnetic gap portion, and means for maintaining the potential across the second winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including said second winding and a condenser, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the first winding.

3. In a constant potential transformer, the combination of a closed magnetic circuit comprising first and second core portions, a winding on said first core portion adapted to be connected to a source of alternating current of fluctuating voltage, a second winding on said second core portion, said circuit providing a high leakage reactance path for a portion of the flux to thread through one of the windings to the exclusion of the other winding, and means for maintaining the potential across the second winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including said second winding and a condenser, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the first winding, the magnetic density at maximum predetermined input voltage of the first core portion being less than the maximum magnetic density of the second core portion.

4. In a constant potential transformer, the combination of a closed magnetic circuit comprising first and second core portions, a winding on said first core portion adapted to be connected to a source of alternating current of fiuctuating voltage, a second winding on said second core portion in spaced relation to said first winding, said circuit having magnetically disposed between said windings a magnetically permeable shunt with a non-magnetic gap portion, and means for maintaining the potential across the second winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including said second winding and a condenser, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the first winding, the magnetic density at maximum predetermined input voltage of the first core portion being less than the maximum magnetic density of the second core portion.

5. A constant potential transformer comprising in combination a magnetic core, a primary winding on said core adapted to be connected to a source of alternating current of fiuctuating voltage, a load winding on said core adapted to be connected to an output circuit, said core providing a high leakage reactance path for a portion of the flux to thread through one of the windings to the and means for maintaining the potential across the load winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including a condenser and a third winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding, the third winding being in inductive relation to the load winding.

6. A constant potential transformer comprising in combination a magnetic core, a primary winding on said core adapted to be connected to a exclusion of the other winding,

source of alternating current of fluctuating voltage, a'loadwinding on said core in spaced relation to said primary winding and adapted to be connected to an'lnput circuit, said core having magnetically disposed between said windings a magnetically permeable shunt with a non-magnetic gap portion; and means for maintaining the potential across the load winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including a condenser and a third winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding, the third winding being in inductive regap portion, and means for maintaining the'potential across the load winding substantially constant regardless of fluctuations in the input voltage comprising a resonant circuit including a condenser and a third winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed upon the primary winding, the third winding being on the second core portion and in inductive relation to the load winding, the magnetic density at maximum predetermined input voltage of the first core portion being less than the maximum magnetic density of the second core portion. a a

8. A constant potential transformer comprising in combination a magnetic core; a primarywinding on said core adapted to be connected to a source of alternating current of fluctuating voltage, a load winding on said core adapted to be connected to an output circuit, said core providing a high leakage reactance path for a portion of the flux to thread through one of the windings to the exclusion of the other winding, a resonant circuit on said first core portion adapted to be connected to a source of alternating current of fluctuating voltage, a load winding on said second core portion and adapted to be connected to an output circuit, said core having magnetically disposed between said windings a magnetically permeable shunt with a non-magnetic gap portion, a resonant circuit including a condenser and a third winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding, the third winding being in inductive relation to the load winding, and an auxiliary winding'on'said first core portion in inductive relation to the primary winding and in series with the load winding, the magnetic density at maximum predetermined input voltage of said first coreportion being less the maximum density of said second core portion.

10. A constant potential transformer comprising in combination a magnetic core, a primary winding on said core adapted to be connected to a source of alternating current of fluctuating voltage, a second winding on said core provided with two leads and an intermediate tap, one of said leads and said tap leading to an output circuit, said core providing a high leakage reactance path for a portion of the flux tothread through one of the windings to the exclusion of the other winding, and means for maintaining insaid output circuit a substantially constant potential regardless of fluctuations in the input voltage comprising a resonant circuit including a condenser connected in series between the leads of said second winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding.

11. A constant potential trans former comprising in combination a magnetic core; aprimary winding on said core adapted to be connected to a source of alternating current of fluctuating voltage; a second winding on said core provided with two leads and an intermediate tap; said core having magnetically disposed between said windings a magnetically permeable shunt with a taining in said output circuit a substantially constant potential comprising a resonant circuit ineluding a condenser connected in series between the leads of the second winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding, and an auxiliary winding on said core in inductive relation to the primary winding and in series with the load winding.

12. A constant potential transformer comprising in combination a closed magnetic core comprising first and second core portions; a primary winding on said first core portion adapted to be connected to a source of alternating current of fluctuating voltage; a second winding on the second core portion and provided with two leads and an intermediate tap; one of said leadsand saidtap leading to an output circuit; said core having magnetically disposed between said windings a magnetically permeable shunt with a non-magnetic gap portion; the maximum density at maximum predetermined input voltage of said first core portion being less than the maximum density of said second core portion; and means for maintaining in said output circuit a substantially constant potential comprising a resonant circuit ineluding a condenser connected in series between the leads of the second winding, the resonant circuit operating at a frequency equal to the frequency of the voltage impressed on the primary winding, and an auxiliary winding on said core in inductive relation to the primary winding and in series with the load winding.

JOSEPH G.- SOLA.

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