US2006970A - Control of constant current circuits - Google Patents

Description

y 2, 1935- c. G. sun's 2,006,970

CONTROL OF CONSTANT CURRENT CIRCUITS Filed Sept. 25, 1935 Fig. I.

3 /Constant Current Transformer? Fig. 2.

Inventor; Chaunce g GSuits His A tornqg- Patented July 2, 1935 CONTROL OF CONSTANT CURRENT CIRCUITS Chauncey G. Suits, Schenectady, N. Y., assignor to General Electric Company, a corporation or New York Application September 23, 1933, Serial No. 690,704

4 Claims.

My invention relates to alternating current circuits of the constant current type, including a source of constant current and a load supplied thereby. It is the object of my invention to provide a circuit of this character having improved means for causing regularly recurring variations in the eiIective value of the current supplied to the load.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 is a circuit diagram of one embodiment of my invention; and 2 is a circuit diagram showing a modification thereof.

In Fig. l I have shown at i a constant cu;- rent transformer which may be of any well known form, such for example, as that commonly employed for the supply of constant current lighting circuits. The primary 2 of this transformer is supplied from the constant potential source 3, 4 of alternating current, which source may, for example, be a cycle, volt commercial lighting circuit. The secondary 5 of the transformer connects with the load circuit 8 which is shown containing a plurality of load devices I which may be are or incandescent lamps. A constant current lighting circuit of this type is well known particularly in street lighting systems employing arc lamps in which case the current supplied is maintained commonly at a value of approximately 6.6 amperes; it will be understood, however, that where the load devices or lamps require a lower current suitable adjustments or changes in the construetion would be made in the transformer so as to give the desired current in the load circuit.

For ordinary lighting purposes it is desirable that the lamps shall operate to give a constant illumination, but in certain other cases where it is important that the lamps shall be readily distinguishable from other lamps in the vicinity, it is desirable that the light from the lamps shall undergo variations in intensity in some easily recognized manner. For example, if the light from the field border lamps of an airport is caused to vary in some regular manner a pilot approaching the airport is at once able to dis-.

tinguish those lamps from 'all other lamps in the vicinity and thereby locate the landing field with less difllculty. Moreover each airport so equipped may have its field border lamps varied at a diflerent frequency, thus facilitating the recognition of each particular port as distingulshed from the other ports.

In accordance with my invention 1 have provided the load circuit with means for producing regularly recurring variations in the efiective value of the alternating current supplied to the load, which means is entirely electrical in operation; that is, it has no relatively moving parts and operates in response to the electrical condition of the load circuit. For this purpose I have provided a variable shunting means connected across the load circuit whereby a variable portion of the current supplied by the transformer is shunted around the load circuit. The shunting means which I have provided is the saturable core reactor 9 having the saturating winding l 0 which reactor connects with the 0pposite sides of the load circuit by the leads it. The current transformer I2 having its primary winding l3 connected in serieswith the load circuit has its secondary winding is connected to supply alternating current to the non-linear resonant circuit l5 which comprises the capacitor IS, the resistor l1, and the self-saturating reactor l8. In accordance with the value of the capacitance, resistance, and inductance in this circuit the circuit becomes resonant with a predetermined voltage supplied thereto by the secondary l4 and hence in accordance with the value of the current supplied to the load sircuit. The circuit [5 therefore is a voltage sensitive non-linear resonant circuit since the co dition of resonance in the circuit is dependent upon the voltage applied thereto. The current supplied to the saturating winding is of reactor 9 and hence the reactance produced by this reactor is varied in accordance with the current traversing the resonant circuit l5. Various means may be employed for energizing the saturating winding ID to vary with the current in circuit 15. In Fig. 11 have shown the saturating winding ID connected through the full wave rectifier l9 which is arranged in series in circuit P5. In Fig. l I have represented reactor 9 in a purely diagrammatic manner; it will be understood, however, that this reactor may be of the form shown in Fig. 1 of my Patent 1,885,- 155, November 1, 1932, or if desired instead of employing a reactor having a single core I may employ two separate transformers as represented by Fig. 2 of the aforementioned pateht.

The operation of the apparatus shown in Fig. 1 will be readily apparent from the above description. Assuming that the current in the saturating winding l0 of reactor 9 is a mini-'- mum, the impedance offered by the reactor to the shunt circuit is a maximum, and hence maximum current is being supplied to the lamps I. When this maximum load current occurs the voltage in the secondary ll of the current transiormer I2 is a maximum. The non-linear resonant circuit I5 is constructedto become resonant at this maximum applied voltage and hence the current flow in the circuit l5 rises to a maximum and supplies a maximum current to the saturating winding it of the reactor. The re actor now becomes saturated in which condition the impedance ofiered thereby to the shunt circuit drops to a minimum; hence the current in the shunt circuit rises to a maximum. Since the transformer l is constructed to supply a constant current the current which is not shunted by the reactor is insuflicient to illuminate lamps 1 to their full brilliancy or may be insufllcient even to make them visible. The resulting diminution in current in the load circuit now produces a diminished voltage applied to the non-linear resonant circuit l5 which diminished voltage is insumcient to preserve a condition oi resonance in that circuit. Accordingly the current supplied to the saturating winding falls to the original minimum value. Thus the cycle or operation is completed. It will be understood that a timeelement is involved due to the well known characteristics of saturable core reactors, and in accordance with the particular apparatus employed the number of light pulsations produced by the lamps 1 may vary over ,a considerable range, the periodicity of pulsation being in all cases materially less than the periodicity of the alternating current supply. It will be observed that the above described apparatus for causing the variations in the load current is entirely electrical in operation being devoid of 'any relatively? moving parts and being free from any interruption of the circuit where sparking may occur which might give rise radio interference.

In the modified form of my invention shown by Fig. 2, the non-linear resonant circuit is connected across the load circuit 6 whereby it is responsive to the voltage supplied to the lamps rather than being responsive tothe current supplied thereto. In view of the close similarity of the operation of this form of my invention to that shown in Fig. 1 and described above, it is thought to be unnecessary to give a detailed explanation of the operation of this form.

I havev chosen the particular embodiments described above as illustrative of my invention and it will be apparent that various other modifications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent 01 the United States, is:

1. In combination, a constant current transformer, a load circuit connected to be supplied therefrom, a saturable core reactor connected to shunt said load circuit, and means including a voltage sensitive non-linear resonant circuit constructed to pass from a non-resonant to a resonant condition, in response to a predetermined increase in current in said load circuit for varying the saturation of said reactor.

2. In combination, a constant current transformer, a load circuit connected to be supplied therefrom, a saturable core reactor provided with a saturating winding and connected to shunt said load cn'cuit, a current transformer connected in the load circuit and a voltage sensitive non-linear resonant circuit connected to be energized from said transformer and constructed to become resonant at a predetermined voltage supplied thereto for supplying current to said saturating winding.

3. In combination, a source of supply of alternating current, a lamp circuit, a constant current transformer connecting the source with the lamp circuit and means for causing the current in the lamp circuit to undergo regularly recurring variations, said means comprising a saturable core reactor provided with a saturating winding and connected to shunt the lamp circuit, a transformer having its primary connected in series in the lamp circuit, a voltage sensitive non-linear resonant circuit including a selfsaturating'reactor connected to be supplied from the secondary of said transformer and constructed to become resonant at a predetermined voltage supplied thereto and a rectifier in said nonlinear resonant circuit connected in circuit with said winding.

4. In combination, a constant current transformer, a load circuit connected to be supplied therefrom, a saturable core reactor provided with a saturating winding and connected to shunt said load circuit, a voltage sensitive nonlinear resonant circuit including a self-saturating reactor connected across said load circuit whereby it becomes resonant with a predetermined increase in current in the load circuit and means including a rectifier for supplying curtrent to said winding from said resonant circui CHAUNCEY G. SUITS.

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