US2351681A - Constant current control - Google Patents

Description

June 20, 1944. HAUG 2,351,681

CONSTANT CURRENT CONTROL Filed Dec. 24, 1942 Patented June 20, 1944 2,351,681 CONSTANT CURRENT CONTROL Eugene H. Haug, Chicago,

and mesne assignment Bank, Chicago,

Ill., assignor, by direct s, to La Salle National 111., as trustee Application December 24, 1942, Serial No. 410,102

(Cl. run-419) 6 Claims.

My invention relates to electric regulating circuits and more particularly to such circuits utilizing electric resonant circuits oi. the constant potential to constant current type for regulating the current as may be required.

Resonant type of constant current transformation devices are old in the art, having been known since the time of Boucherout in 1893 who demonstrated their operation. But these resonant circuits were of no practical value in series constant current lighting circuits due to the fact that input voltage variations cause variations in the current output.

The modern incandescent lamp is primarily a constant-voltage device, that is, at constant-voltage supply, the life of the lamp is greater than at constant current supply, assuming the same percentage fluctuation from constancy. The reason is: a variation of voltage at the lamp terminals, by p percent, gives a variation of current of about 0.619 percent, and thus a variation of power of about 1.6p percent, while a variation of current in the lamp, by p percent, gives a variation of voltage of about i 0.6 percent, and thus a variation of power of about percent. Thus, with the increasing use of incandescent and vapour discharge lamps in series constant current operation, the constancy of the current becomes of increasing importance.

Heretofore there have been proposed several arrangements for controlling the constant current in the output circuit of the resonant type of constant current transformers. All these arrangements will not automatically regulate to hold the current constant with both constant potential input variation and load variation. Furthermore all prior arrangements require antihunting and other devices to stabilize the automatic regulation. The addition of these antihunting devices lowers the efficiency and dependability of the constant current transformer.

It is the object of my invention, therefore, to provide an improved constant current regulator which will hold the current constant although the constant input potential .may vary or the amount of load in the constant current circuit may vary, or both the input voltage and the load may vary simultaneously.

-In accordance with my invention, a resonant constant potential to constant current transcircuit connected to a line 4 by means of lead 1 forming device has the constant current output special type of automatic ratio changing transformer which regulates in a manner to hold the current in the output circuit vary, or both input ratio transformer may For a together in connection with the accompanying drawing, and its scope will be pointed out in the appended simultaneously. I and 2 indicates the constant potential supply which may vary 15 percent. Reactor 3 is connected at one terminal to supply line I and at its other terminal to reactor 5 by means of line 4. Reactor 5 has one of its terminals connected to line 4 and the other terminal to line 9. A capacitor 8 is connected to and to line 2 by means of reactor 3, reactor 5, and capacitor -6 are of equal reactance, hence in resonant condition. III is the automatic ratio change transformer of which II and I 2 are the two primary windings and H the secondary winding. Primary winding II has one of its ter- 2l, and its other Primary winding I I2. Secondary l4 terminal connected to line 22. I has more turns than primary of transformer I0 is connected to the load 23 by means of leads 2-4 and 25. Current transformer l5 has one terminal of its primary I 6 connected to line 2, and its other terminal connected to line iii. The secondary ll of current transformer l5 has one of its terminals connected to rectifier 20 by means of lead l9, and its other terminal connected to oxide rectifier 20 by means of lead It. Rectifier output terminals are connected to the D. C. winding 29 of saturatins transformer 28. Reactance winding 30 of primary windings, the current will divide saturating transformer I has one of its terminals connected to line It by means of lead II, and its other terminal connected to line II.

The operation of the above described apparatus is as follows: a constant potential to lines I and 2 will be transformed into constant current to lines I and I. This constant current is fed to the primaries Ii and I2, and the current in windings II and II will be of a value depending upon the respective impedance of each winding. The current to the load 2! from the secondary ll will depend upon the ratio of primary ampere turns to the secondary ampere turns. The current transformer I, which has its primary it connected in series circuit relation to the output of the resonant constant current device an to the primaries Ii and ii of the automatic ratio changing transformer lil, has the function of introducing a voltage supply to rectifier 20 that is proportional to the output current of the resonant constant current device. Hence the output circuit of rectifier 2| introduces a current to the direct current winding 2! of saturating reactor 18, which is also proportional to the output current of the resonant constant current device. The direct current winding 20 therefore saturates the core 32 proportional to the output current of the rectifier 20 and therefore controls the reactance of winding III of the saturating reactor proportionally to the output current of the resonant constant current device. Since the primary ll of transformer III is connected in series circuit relation with reactance winding 30 of the saturating reactor 28 and the output circuit of the resonant constant current device, the current introduced to winding I! of transformer 28 will therefore be proportional to the reactance value of the winding 30 of saturating transformer 20. should the supply voltage feeding lines I and 2 increase. the current output of the resonant constant current device will increase proportionally in lines 8 and I. This will increase the current to transformer l5, thereby increasing the voltage to the rectifier It, and thereby increasing the direct current output of rectifier III to the direct current winding 29 of saturating transformer 28, thereby decreasing the reactance value of winding 3| and thereby increasing the current to primary ii of transformer ill. Since the current fed to the primaries II and I2 is approximately constant the current to each of these primaries will be proportional to their respective impedances. Hence, the current will be transferred from winding II, which has more ampere turns, to primary II, which has less ampere turns, and therefore decreasing the flux in the core 33 of transformer l0, and which in turn decreases the voltage of secondary It in a manner to hold the current constant to the load II.

A decrease in the value of supply voltage to lines I and 2 effects the control in the reversed order, and thereby holds the current constant in the load circuit.

Mathematically the operation of the automatic ratio changing transformer is as follows: the secondary voltage of a transformer depends upon the flux density interlinking the secondary (neglecting impedances and losses). Th flux density depends upon the primary ampere turns. In the automatic ratio changing transformer we have two primary windings and one secondary winding. If the primary has 800 turns on one winding and 400 turns on the other winding, and a constant current of i5 amperes is fed to these two these respective windings proportional to their respective impedances. The 800 turn primary will take 5 amperes and the 400 turn primary will take 10 amperes, respectively. Thus, 800 5 amperes=4000 ampere turns, and 400x10 amperes=4000 ampere turns. or a total of 8000 ampere turns. Now suppose that a series impedance of twice the value of the impedance of the 400 ampere turns is connected in series circuit relation with the 400 ampere turn, so that both primary windings will have the same impedance, the 400 turn primary will take 7.5 amperes, and the 800 turn primary will take 7.5 amperes. We will then have 400x7.5 or 3000 ampere turns from the 400 turn primary winding, and 800x or 6000 ampere turns from the 800 turn primary winding, which makes a total of 9000 ampere turns of both primary windings acting together. Therefore, with no impedance in the 400 turn primary we have a total ampere turns from both primary windings of 8000 ampere turns, while if the primary with 400 ampere turns has an added impedance of twice the value of the 400 ampere turn winding the total ampere turns of both primary windings will be 9000 ampere turns, or an increase of 1000 ampere turns.

Figure 2 illustrates a circuit similar to Figure 1 except for a different type of constant potential to constant current transformer and parts therein corresponding to like parts in Figure l are designated by the same reference numerals.

In Figure 2 the T resonant circuit of Figure 1 is replaced by a monocyclic square including a pair of reactors 3 and l and a pair of condensers 6 and 6a. This resonant transformer functions in substantially the same manner as the transformer of Figure l and the operation of the remainder of the circuit is the same.

While I have described what I at present consider the preferred embodiment of my invention, it will .be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with an alternating current supply, a resonant type of constant potential to constant current transformer, an automatic ratio changing transformer having two primary windings and one secondary winding, and a load, a saturating reactor connected in series circuit relation to one of the primary windings of said ratio changing transformer, and means to control the saturation of the reactor to maintain the current flow to the load substantially constant.

2. In combination with an alternating current supply, a resonant type of constant potential to constant current transformer, an automatic ratio changing transformer having two primary windings and one secondary winding, and a load, a saturating reactor connected in series circuit relation to one of the primary windings of said ratio changing transformer, and means responsive to the flow of current from the resonant transformer to control the saturation of the reactor.

3. In combination with an alternating current supply, a resonant type of constant potential to constant current transformer, an automatic ratio changing transformer having two primary windings and one secondary winding, and a load, a

into 75 saturating reactor connected in series circuit relation to one of the primary windings of said ratio changing transformer, and means responsive to the total flow of current to the two primary windings to control the saturation of the reactor.

4. In combination with an alternating current supply, a resonant type of constant potential to constant current transformer, a transformer having two primary windings with different numbers of turns connected in parallel to the resonant transformer, a load circuit connected to the secondary winding of the last named transformer, a saturating reactor connected in series with one of said primary windings, and meansto control the saturation at the reactor,

5. In combination with an alternating current supply, a resonant type of constant potential to constant current transformer, a transformer having two primary windings'with different numbers of turns connected in parallel to the resonant transformer, a load circuit connected to the secondary winding of the last named transformer, a saturating reactor connected in series with one of said primary windings, and means responsive to the flow of current between the resonant transformer and the primary windings to control the saturation of the reactor.

6. In combination with an alternating current supply, a resonant type of constant potential to

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