US2226041A - Constant potential to constant current transformation apparatus - Google Patents

Description

Dec. 24, 1940. HE. YOUNG ETAL 2,225,041

CONSTANT PQTENTIAL TO CONSTANT CURRENT TRANSFORMATION APPARATUS Filed Oct. 11, 1938 (7 1 s6 if q E IBN r19 INVENTORS Patented Dec. 24, 1940 PATENT OFFICE CONSTANT POTENTIAL TO CONSTANT CUR- RENT TRANSFORMATION APPARATUS Hugh E. Young and Eugene H. Haug, Chicago, 111. Application October 11, 1938, Serial No. 234,394

3 Claims. (Cl. 171-119) Our invention relates to constant potential to constant current transformation apparatus and it has particular reference to the regulation and over voltage protection of the constant current 5 circuit. It is to be noted that the two conditions just mentioned are, in general, incompatible, since the means employed for maintaining the current constant under varying load conditions also operates to maintain the current constant during open circuit conditions thus producing a very high voltage.

In United States Letters Patent No. 2,085,060, granted June 29, 1935, and United States Letters Patent Nos. 2,099,715 and 2,099,716 granted November 23, 1937, upon the application of Hugh E. Young, and in the co-pending application of Eugene H. Haug, Serial No. 191,390, filed February 19, 1938, there is described a regulating system including the use of electric valves whereby stable constant current regulation and suitable circuit protection is obtained from a resonant circuit. Our present invention constitutes a modification of that described and claimed in the foregoing application.

It is well known that if four equal reactances two capacitative and two inductiveare arranged to constitute a resonant square, and if constant potential is impressed across one diagonal of the square, constant current may be obtained in a circuit that is connected across the other diagonal of the square. We utilize this principle which is old and is commonly known as the monocyclic square-for the purpose of obtaining constant current.

35 This monocyclic square arrangement for obused in series with each other and of equal or approximately equal reactance, so more or less neutralizing each other, even small changes of frequency may cause very large variations in the result. Thus, in a resonating circuit of very small power loss, a small change of frequency at constant impressed E. M. F. may change the current over an enormous range. Thirdly, because the current in the constant current circuit is directly proportional to the impressed voltage and therefore a three percent variation in the applied voltage produces a three percent variation in the current in the constant current circuit. 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. Therefore, on account of the characteristics of the incandescent lamp and the three inherent electrical characteristics of the mono cyclic square mentioned above, it is very impracticable to use this form of apparatus inconstant current street lighting without having some form of electrical control in the monocyclic system which would counteract these three inherent electrical characteristics so detrimental to the operation of the lamp or lighting unit.

It is the object of our invention to incorporate additional electrical equipment and to construct the reactance in such a manner as to counteract the detrimental electrical characteristics of the monocyclic square arrangement in relation to lighting units. 7

It is a further object of our invention to limit the voltage in the ,constant current circuit to the operating voltagerating of the cable and connected apparatus.

It is a further object of our invention to provide a protection against harm from accidental contact in case of open circuit resulting. from a damaged circuit. Open circuits in series street lighting systems are unavoidable, especially on aerial circuits and itis very desirable from the standpoint of safety first that when an open circuit does occur the circuit be deenergized.

It is a still further object of our invention to provide an arrangement whereby the monocyclic square system for obtaining constant current may be made economically practical.

Proper operation of this type of constant current regulator required an exact balance of the four reactances. Since the capacity of the condensers in commercial manufacture may vary from the design value to a certain extent, the inductive reactances are so constructed as to compensate for the diflerences in the condensers. Also, when a proper balance of the four reactances is made, a resulting constant current may not be of such value as to give the exact rated lamp current. A special current transformation device is therefore incorporated in the monocyclic square in order to obtain the correct value of the load current.

In accordance with our invention the two inductive reactances of the monocyclic square are not wound on one and the same core and each is provided with a suitable number of taps for proper resonation. With such an arrangement no inequalities in the voltage across each reactor can exist and the constant current system remains stable thus eliminating all surges. The inductive reactances are so wound and'connected in the system that standard voltage variations will not affect the constance of the current. The current transformer is interposed between the monocyclic square and the load circuit so that any desired value of constant current can be obtained for the load circuit. Also, the current transformer is of such a construction in regards to the leakage reactance as to limit the open circuit voltage to a desired value. An automatic switch is incorporated between the regulator and the load circuit; the purpose of the switch being to furnish additional protection for open circuit conditions.

For a better understanding of our invention toing and its scope will. be pointed out in the ap- "\airgaps 40.

pended claims. The single figure of the accompanying drawing illustrates an arrangement embodying our invention for operating a constant current street lighting load from a constant potential supply.

Referring now more particularly to the drawing, ther is illustrated an arrangement for operating a constant current load 21 from a constant potential supply circuit I and 2. The load 21 is a number of street lighting units connected in series circuit relation. Across each street lighting unit is a film cutout 4| connected to the street lighting unit with wires 42 and 43. The object of the film cutout 4| is to complete the circuit upon failure of the street lighting unit 21.

The condenser 4 and the reactor 6 are connected in series circuit relation by means of line 5 and are in turn connected across the constant potential supply lines I and 2 by lines I and 3 re-v spectively. The condenser 8 and the reactor Ill are connected in series circuit relation by means of line 9 and are in turn connected to the alternating current supply lines and 2 by lines 46 and I3 respectively. Reactances 6 and ID are placed on the cores I2, the said cores |2 having Transformer 45 has its primary line H connected to line 5 and its primary line |5 connected to line 9. I The transformer secondary II has its line I8 connected to switchpoint 38 of automatic switch 44 and the line l9 connected to switchpoint 36 of automatic switch 44. Switchpoint 34 is connected to switchpoint 39 by means of line 28. Switchpoint 35 is connected to switchpoint 38 by means of line 29. The load 21 is connected to the Switchpoint 39 by line 2|, and the load line 20 is connected to switchpoint 31.

An automatic cutout 25 is connected in series circuit relation to switch operating coil 24 by means of line 23. One end of the automatic cutout 25 is connected to the load circuit 20 by means of line 26 and one end of the operating coil 24 is connected to line 2| by means of line 22.

.The general principle of operation of the above described constant current regulating system will be well understood by those skilled in the art. In brief, if an alternating constant potential is supplied to lines I and 2 a constant current will be obtained from lines l5 and I4. It will be noted that reactances 6 and I U have taps and therefore facilitates the resonation of these reactors with their respective condensers 4 and 8. It will be also noted that the core |2 which is broken by airgaps acts as one fiux path for both reactances 6 and It so that no unbalancing of the bridge circuit may be obtained thus precluding transmission of current surges to th constant current circuit l4 and |5. It will be further noted that the reactances 6 and H) are so wound and connected as to cause an increase in the leakage reactance and thereby hold the current in the lines l5 and I4 constant notwithstanding small variations in the line voltage.

The constant current lines l5 and I4 are connected to a current transformer which has a proper number of taps in order to obtain the desired value of constant current and also the desired value of leakage reactance in order to limit the open circuit voltage. It will be fur ther noted that the constant current circuit l8 and i9 has an automatic switch 44 interposed between itself and the load lines 20 and 2|. The function of this switch 44 being as follows: Upon an open circuit in the load circuit 2|] there is impressed upon the automatic cutout 25 a high voltage which functions to make this cutout conducting thereby energizing operating coil 24 of automatic switch 44. It will be noted that automatic switch 44 has switchpoints 31 and 38 connected by switch blade 30 and switchpoints 36 and 39 connected by switch blade 3|. In this normal operating position the load 21 is connected directly to the secondary ll of the current transformer 45 by switch blades 30 and 3|. However, in the trip position of the automatic switch 44 the switch blade 30 takes the position as indicated by dotted line 32 and the switch blade 3| takes the position as indicated by dotted line 33.

The automatic switch 44 prevents an open circuit voltage in the load circuit 20 by operating in the following sequence: First, the auto matic switch 44 short circuits the secondary leads I8 and I9 of the transformer 45; secondly, the automatic switch 44 disconnects-the load line 20 from the transformer secondary thirdly, the automatic switch 44 short circuits the load circuit 20. Upon the occurrence of a fault in the load circuit, the load or lighting circuit is immediately deadened, thereby obviating the danger of electrocution from this source. As a further safeguard, the switch is so designed that it can not be reclosed until the fault in the circuit has been first corrected.

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

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

1. In a constant current system-a pair of capacitative reactances and a pair of inductive rcactances, said inductive reactances being placed substantially on one and the same core, having airgaps between the said inductive reactances, one on each side, a circuit arrangement including the above inductive and capacitative react ances in the form of a bridge circuit in order to obtain constant current from constant potential, a variable ratio current transformer connected between the load and the bridge circuits and an automatic switching means for deenergizing the load circuit upon failure of the constant current in the load circuit. I

2. In an electrical system of the class described a regulator equipment comp-rising a reactance and a capacitance bridged in series across the supply mains and another inductance and capacitance also bridged likewise across said mains but with the inductance and capacitance in opposite sequence, each inductance comprising a coil and a U-magnet core therefor, the cores being disposed end to end with the tips of their arms spaced apart somewhat, in combination with a load transformer, the primary winding of which is connected across. between points located between the inductance and capacitance on the two bridging circuits respectively.

but with the inductance and capacitance in op-.

posite sequence, each inductance comprising a HUGH E. YOUNG.

EUGENE H. HAUG.

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