US1682000A - Rectification of alternating currents - Google Patents

Description

Aug. 28, 1928. 1,682,000,

Ta A. WILLARD ET AL 'RECTIFICATION OF ALTERNATING GURRENTS Filed Nov. 15, 1924 22M BY amzwa g A ORNEY Patented Aug. 28, 1928.

insane earner en ice.

UNITED s'rnres THEODOBE A. WILLARD, 0F CLEVELAND, @310, AND FREDERICK S. MGCULLOUGH, OF WILKINSBURG, PENNSYLVANIA.

BECTIIIGATION 0F ALTERNATIITG CUBRENTS.

Application filed November 13, 1924. Serial I80. 749,661.

This invention relates to the rectification of alternating currents, and particularly to the rectification of such currents as to pro duce a substantially constant direct current, capable of use, for instance. in the plate circuit of a vacuum tube.

The primary object of the invention is to provide a rectifier permitting of the use of houselighting currents in the plate clrcuit of a vacuum tube radio set, partlcularly receiving sets, whereby the usual plate or B battery may be dispensed with.

A further object of the invention is to provide a method and means of rectification of alternating currents wherein the resulting direct current is substantially constant A further object of the invention is to in crease the rectifying period of a one way rectifier, and thereby obtain effioiency greater than heretofore attainable with one way rectifiers. Furthermore, due to the longer rectifying period, the operation of the rectifier is more nearly constant, and the hum due to current changes more easily eliminated.

A further object oi the invention is to establish a resonant circuit including a rectifier,

- and to'shift the phase of the current in the resonating circuit from one point to another with respect to the supply current with each reversal of current flow in the supply circuit.

A further object of the invention is to use a rectifier for automatically varying the capacity of a resonating circuit. 7

To this end, the inventlon consists, generally, in establishing a capacity couphng across a rectifier, i. e., in parallel with the rectifier, and to couple this capac ty and rectifier in series with a second capacity. he resulting operation, as well as other ob ects and advantages, may be more readlly understood and appreciated by referenceto the accompanying drawings, in which:

Fig. 1 is a circuit diagram, illustrating an embodiment of the invention;

Fig. 2 is a diagrammatic circuit, not embodying the invention, but provlded for the purpose of developing the principle of the invention, illustrating a resonant circuit;

Fig. '3 is a diagram illustrating the effect of operating the circuit of Fig. 2 below resonance frequency;

Fig. 4 is a similar diagram, illustrating the efiect ofoperating the circuit of Fig. 2 above resonance frequency;

Fig. 5 is a view similar to Figs. 3 and 4,-

illustrating the wave elfects of the circuit of Figs. 1 and 9;

1 Figs 6, 7 and 8 are diagrams illustrating rect1fy1ng periods of usual one-way rectifiers, usual two-way rectifiers, and my invention utilrzinga one-way rectifier, respectively;

Fig. 1s a diagram similar to Fig. 1, showmg a slight practical modification.

Referring to Fig. 1 of the drawings, X designatcs a transformer, Y a suitable rectifier, and Z is a filtering circuit.

The transformer has a core 5 on which is a primary winding 6 and a secondar wind- 111g 7. At L in the core is a leak. he primary 6 may be connected in an alternating current circuit G, such as-the usual houselighting circuit. ii

One side of the secondary 7 is connected to one electrode 8 of the rectifier Y, which 1s shown as consisting of a hot cathode tube, but the invention is not restricted to use with any one particular type of rectifier. The other electrode 9 of the rectifier is connected with one side 10 of any preferred or standard filter circuit Z, which may include a choke and suitable condensers, and the load circuits P and P, the other side of the filter circuit connecting through wire 11 with the other end of the secondary.

In parallel with or shunted across the rectifier, is a capacity, such as condenser C. In series with the rectifier and condenser C is a second condenser C The circuit including the secondary 7 of the transformer, the rec-' tifier and capacity C in parallel, and the con: denser C" form a resonating circuit, The condenser C while being in series with capacity C, 1s connected across the load circuit. The provision of the leak L in the transformer, from a practical standpoint, is necessary to accomplish resonance in the circuit.

This is the general nature of the invention. Its operation may be best understood by ref erence, first, to Fig. 2, showing a simple resonating circuit embodying a transformer having the core leak L, the secondary 7 and condenser C When switch K in the alternating primary circuit G is closed, the current and voltage will, if the capacity C is such that the circuit will operate below resonance frequency, pass through the variations graphically illustrated in Fig. 3. In this figure, V represents the supply voltage, Va the condenser voltage, and lathe condenser current. Space t indicates the period ing to its theory, we vary the capacity in the resonant circuit during the operative period of the rectifier, from the condition shown in Fig. 3 to the condition shown in Fig. 4, thereby lengthenin the rectifying period. Then, at the end of t 1e rectifying period, the capacity of the resonant circuitis changed to bring about the conditions existing in Fig. Referring now to Fig. 1, it will be seen that during the idle period of the rectifier, condensers C and C are in series. During the active period of the rectifier, the condenser C is partially short circuited by the rectifier.

There is, consequently, more capacity in the resonance circuit during the active period of the rectifier than during its inactive period, inasmuch as one condenser has a greater capacity than two condensers in series.

We thus utilize the rectifier to automatically modify the capacity of the resonant circuit. In so doing, we may vary the circuit conditions from that illustrated in Fig. 3 to that illustrated in Fig. 4, and vice versa.

We thereby increase the rectifying period and shorten the period during which the rectifier is not functioning. The resulting current variations are i lustrated in Fig. 5, wherein the symbols are identical with those used in Figs. 3 and 4.

Referring to Fig. 5, the following operation would take place. Durin the first charging period the rectifier is lnoperative and V0 is, according to Fig. 3. If this condition persisted, then 25 would be according to dotted line 7'. But the rectifier shunts the condenser, partially short circuiting it. Therefore, the condition of Fig. 4 takes place, and the time of charging the condenser t is longer than 15 At the end of 25 the rectifier becomes inoperative. and, instead of F (dotted line) the condition of Fig. 3 takes place and the time t is smaller than t It will thus be seen that periods .25", t and It will always be longer than periods t t etc.

The result is that the rectifier is much more constant than the usual type of rectifier and the hum due to current changes can thus be more easily eliminated.

The effect of the load resistance, such as a detector and amplifier tubes, and designated as P and P, is to act as a partial shunt on C but this shunt is operatlng always and, due to the filtering cI rcuits, the currentdrawn from C has a constant value. Hence, the effect of the. load is merely to drop the base line in Fig. .5 to the position indicated by the heavy dotted line A-A, without materially affecting the length of the operative periods of the rectifier.

Fi s. 6,7 and 8 illustrate the wave forms or recti er periods of the usual one-way rectifier, the usual two-way rectifier, and our present rectifier, respectively. It will be seen from these figures how much more nearly our invention approaches the constant of the two-way rectifier than the usual one-way rectifier. I

In Fig. 9, we have illustrated a practical embodiment of the invention, wherein the. condenser C? is omitted, and one electrode of the rectifier is grounded on the core of the transformer b wire 8'. The same effect is then obtained etween the core of the transformer and the secondary winding as where a separate condenser C is used. therwise, Figs. 1 and 9 are identical. In Fig. 9, we have dotted in a condenser to indicate that there is a capacit coupling acrossthe electrodes of the recti er. 4

Various changes and circuit modifications ma be made in the circuits and apparatus uti izing the principles of our invention as herein set forth within the contemplation of the invention and under the scope .of the ap-- pended claims.

We claim as our invention:

1. Means for effecting the rectification of alternating currents including a resonant circuitin which there is a rectifier, a capacity in parallel with the rectifier, and a capacity in series with the rectifier and said first mentioned capacity.

2. Means for effectin therectification of alternating currents inc uding a transformer having primary and secondary windings, a rectifier in circuit with the secondary, a capacity shunted across the rectifier, a capacity in series with the first capacity and the rectifier and a filter circuit shunted across said second capacity.

3. Means for effectin the rectification of alternating currents inc uding a transformer having a core and primary and secondary windings, the core having a leak between said primary and secondary windings, a resonant circuit in which the secondary is included, and a rectifier and capacity connected in parallel included in the resonant circuit.

4. The method of rectifyin alternating currents with a one-wa recti er consisting in increasing'the recti ying period for the rectifier beyond one half cycle phase period of the supply current and decreasin the non rectifying period of the rectifier elow the other half cycle phase period of the supply current.

5. The method of rectifying alternating currents consisting in establishing a resonant circuit for therectifier and varying the capacity of said circuit by means of the rectifier to increase the rectifying period beyond a half cycle of the supply current and decrease 5 the idle period of the rectifier for each half cycle of the supply current.

6. The combination with a rectifier having input and output electrodes, of an inductance connected across the input, a pair of con- 10 densers connected in series across the inductance, a connection between the two condensers and one of the electrodes of the rectifier, a filter circuit connected with one side of the inductance and one of the electrodes, and means for impressing a voltage on the inductance.

In testimony whereof we hereunto affix our signatures. Y

THEODORE A. WILLARD. v FREDERICK S. v M CCULLOUGH.

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