US560735A - Alternating-current generator - Google Patents

Description

W. S. MOODY. ALTERNATING CURRENT GENERATOR.

(No Model.)

No. 560,735. Patented May 26, 1896.

ITNSSES UNITED STATES PATENT OFFICE.

TVALTER S. MOODY, OF LYNN, MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NETV YORK.

ALTERNATlNG-CURRENT GENERATOR.

SPECIFICATION forming part of Letters Patent No. 560,735, dated May 26, 1896.

I Application filed January 17, 1896- Serial No. 575,828. (No model.)

To all whom, it may concern.- as to compound or overcompound properly, Be it known that I, \VALTER S. MOODY, a the excitation coming on too slowly when the citizen of the United States, residingat Lynn, current falls and falling off too slowly when in the county of Essex, State of Massachuthe load drops. Another objection to the 5 5 setts, have invented certain new and useful use of the single exciter is that with alter- Improvements in Regulating Alternatingnators having large armature selfinduction Current Dynamo Electric Machines, (Oase (which is true of the majority of those in use) No. 323,) of which the following is a specitithe field-current is very much larger at low cation. load than at no load, so that in case of a IO My invention relates to the regulation of alsmall amount of overcompounding, such as ternating-current dynamo-electric machines, ten per cent. or so, there may be one hundred and more particularly to the compounding of per cent. or even one hundred and fifty per such machines for change of potential upon cent. increase in the field-current. A single change of load. The objects thus pointed compound-wound eXciter furnishing, say, one I 5 out have been attained to a greater or less hundred and ten volts when fullload is on the perfection by other forms of apparatus; but alternating-machine at a light load or no load some of these devices have been objectionmust run at a potential of about fifty volts able for various reasons. One principal or less. W'ith this condition of weak field in method in use has been to use a separate exthe exciter the current in its field-magnet 2o citer for such machines and to commute a winding will be extremely unstable and may part of the current of the main machine and fall below the critical point, so that the mapass it around the field-magnets of the exchine will lose its excitation entirely. This citer, so that the potential of the eXciting-curfact has been practically demonstrated within rent rises with the increase of load, and thus my knowledge in large machines in commermore current is passed around the field-magcial use. This and other disadvantages of nets of the main machine, and its potential the methods commonly in use I have overis likewise raised. Another method has been come by means of the present invention, in to commute a part of the main current and which I employ two exciting-machines. One pass it around the field-magnets of the maof these machines furnishes to the field-mag- 8o 0 chine itself. This latter arrangement necesnets of the main machine all of the current sitates a somewhat large commutator and the which they receive. The armature of this commutation of a considerable portion of the machine has no connection with its own fieldmain current,while the single-exciter method magnets, but they are separately excited by of compoundinghas several objections,among a second eXciter-machine. It is in a sense a 35 others being the fact that the increase or decompound-wound machine, in that the windcrease of field strength in the exciter brought in g upon its field-magnets, which derives curabout by the commuted main current acts rent from the second eXciter-machine, is a to increase or decrease the current through winding of high resistance, like an ordinary the shunt-winding of the exciter-machine, shunt-winding, and will be hereinafter re- 0 0 and thus produces a sort of geometric proferred to as the shunt-winding. It regression in the change of potential. This is sembles that class of winding in that a commorc objectionable from the fact that the paratively constant current is maintained current in the shunt-field winding does not through it. Upon the same field-magnets is respond quickly to the change of electromowound a compounding-coil, which derives its 9 5 5 tive force at the terminals of the winding, energy from the main circuit. In some cases but requires a certain length of time to reach I prefer to mount a transformer upon the its corresponding value on account of self-inarmature of the main machine and send curduction and resistance, which, added to the rent from the secondary of this transformer lag from hysteresis, prevents the electromothrough a synchronous commutator mounted 5c tive force in the main machine being quickly upon the shaft of the main machine; but for adjusted to the varying current demand so this I may substitute other arrangements, in

that case particularly where a stationary transformer is used. By this arrangement I provide a method of compounding free from the disadvantages and objections which I have pointed out. The main exciter cannot fall below the critical point in its field exciration, because the auxiliary exciter furnishes to the shunt-winding a current sufficient at all times to maintain it above this point. This current being independent of that flowing in the armature of the main exciter, it responds freely to changes in the load upon the main. dynamo, as the compounding-coil may be of relatively-greater effect with the kind of excitation to which I have just referred. The current in the shunt-winding of the main exciter being independent of its own armature, the changes in the field strength produced by the compounding-coil do not directly affect the shunt-coil, and therefore the sluggishness or lack of coincidence between the demand for current and the increase of potential due to the compounding-coil does not occur, and the proportionate amount of compounding is not disturbed by this reactive influence of the shunt-coil. It is of course designed to adjust the amounts of the shuntwinding and the compounding-coil to the particular degree of overcompounding desired.

The method of operation, as will be seen from the above statement of invention, is, briefly, to supply the main dynamo fieldmagnets withcurrent from an armature rotating in a field of force produced by a constant magnetizing-current independent of the armature itself, and a second magnetizing force derived either directly or inductively from the main machine, by which is meant either the dynamo itself or the circuit supplied by it. In speaking of this independent field of force it is,of course understood that the armature reaction is not referred to, but that there is no electrical connection between the main eXciter-armature and its own fieldmagnets.

The accompanying drawings show diagrammatic embodiments of my invention, Figure 1 being a representation of the combination of machines that I have described with a transformer carried upon the armature of the main dynamo. Fig. 2 is a modified form in which a stationary armature is employed and a synchronous commutator is used to furnish the compounding-coil with direct current derived from the main circuit.

Referring now to the drawings by letter, A is the armature of the main dynamo-electric machine to be regulated. B indicates the fieldmagnets. d b are the mains from the armature, provided with a pair of collecting-rings. A single-phase alternator is indicated; but nothing in my invention would exclude its application to alternating-machines of other numbers of phases.

0 is the transformer to which I have referred, mounted upon the armature of the main machine and connected with its armature-winding at G O. From the secondary of this transformer leads pass to the commutator 0 mounted upon the shaft of the main machine and provided with the usual brushes. From these brushes leads pass to the compounding-coil EF and between these leads a resistance R is shown, which may or may not be adjustable, but ordinarily is of fixed amount. The shunt-coil of the main exciter is indicated at FF, and within the field-coils furnished by these two coils rotates the armature of the main exciter EA in circuit with the field-magnets B of the main machine. The shunt-coil is furnished with current from the armature EA of the second or auxiliary exciter, whose field-magnet FF is in series with its own armature. A regulating-resistance R for determining the voltage of the main machine and incidentally that of the exciters is interpolated in the circuit at any suitable point.

In Fig. 2 the same reference-letters indicate like parts; but the transformer C is in the main circuit and is stationary. It supplies energy to the armature MA of the synchronous motor M, acting as a rotary eonverter, the field-magnets of which are supplied with current from the auxiliary exeiter. The portion of the main current transmitted by induction through the transformer O is fed to the armature of this converter and is there rectified by the commutator and fed to the compoundingcoil EF The electrical operation of the devices just described will be readily apparent to those skilled in the art, while the advantages of the method of operation have been pointed out above.

It is manifest that another source of current for supplying the constant excitation of the main exciter might be substituted for the auxiliary dynamo which I have shown. Such a source of current is indicated in Fig. 1 in dotted lines, a storage -battery being diagrammatically shown at S with a resistance R in its circuit for adjusting the electromotive force, although any other means might of course be used.

In addition to the advantages which I have already stated I am enabled by the combination of apparatus and method of operation which I have illustrated and described to dispense with potential-responsive magnets as employed in many forms of regulator now in use, and I also dispense with contacts to be opened and closed by the action of such potential-responsive devices, thus overcoming the objections not only to these devices but to the auxiliary arrangements so often necessary to eliminate the sparking in their operation.

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

1. The method of compounding alternatingcurrent dynamo-electric machines for change of potential under change of load, which consists in supplying to the field-magnets cur= rent from an armature revolving in a compound field of force independent of the armature itself, part of such field of force supplied by a separate excitation substantially fixed in amount, and part by a commuted current derived from the main machine.

2. The method of compounding alternatin gcurrent dynamo-electric machines for change of potential under change of load, which consists in supplying to the field-magnets current from an armature revolving in a compound field of force independent of the armature itself, part of such field of force supplied by separate excitation substantially fixed in amount and part by a commuted current derived inductively from the main machine.

In combination, an alternating-current dynamo-electric machine, an exciter-armature in circuit with its field-magnet winding, a coil of high resistance upon the field-magnets of the exciter, an external source of current for the coil, and another coil upon the field-magnets, the latter coil deriving its energy from the alternator.

4:. In combination, an alternating-current dynamo-electric machine, an exciter-armature in circuit with its field-magnet winding, the latter armature having no electrical connection with its own field-magnet winding, a coil upon the exciter field-magnets in circuit with a source of substantially constant electromotive force, and a compounding-coil upon the exciter field-magnets deriving energy by induction from the main circuit.

5. In combination, an alternating-current dynamo-electric machine, an exciter-armature in circuit with its field-magnet winding, an auxiliary exciter supplying a field-magnet coil upon the main exciter with substantially constant electromotive force, a compounding coil upon the field-magnets of the main exciter, and a synchronous commutator rectifying part of the main current and supplying it to the compounding-coil.

(3. In combination, an alternating-current dynamo-electric machine, a main exciter-armature in circuit with its field-magnet winding, an auxiliary exciter, a synchronous converter, a high-resistance coil upon the fieldmagnets of the main exciter, electrical con nections from the auxiliary exciter to the high-resistance coil and the field-magnets of the converter, and a compounding-coil upon the field-magnets of the main exciter and in circuit with the converter.

In witness whereof I have hereunto set my hand this 14th day of January, 1896.

WALTER S. MOODY. lVitnesses:

JOHN XV. GrBBoNEY, HENRY M. HOBART.

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