USRE12180E - Method of controlling electric motors - Google Patents

Description

' N0.12,18o. REISSUED BBQ. a, 1903.

M. WADDBL-L.

METHOD OF CONTROLLING ELECTRIC MOTORS.

APPLICATION FILED IAB. 10, 1902.

UNITED STATES Reissued December 8, 1903.

PATENT OFFICE.

MONTGOMERY. WADDELL, 0F NEW-YORK, N. Y., ASSIGNOR TO THE GEN- ERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK.

METHOD OE CONTROLLING ELECTRIC MQTORS.

SPECIFICATION formingpart of Reissued Letters Patent No. 12,180, dated December 1903- Orlginal Hm BBBJBB, dated January 15, 1901. Application for reissue filed March 10, 1902- Serlal No. 97,668.

To all whom it may concern:

Be it known that I, MONTGOMERY WAD- DELL, a British subject-,residing at New York, county of New York, and State of New York, have invented certain new and useful Improvements in Methods of Controlling Electric Motors; and I do hereby declare the following to'be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appert'ains' to make and use the same.

My invention relates to a novel method of controlling electric motors, whereby the motor when loaded may be readily actuated from the electrical source of power or when in operation may be instantly or gradually stopped or its speed of rotation diminished without the application of mechanical braking devices. It is'well known that an electric motor when loaded cannot be readily 0perated from the actuatingdynamo to run on constant potential, owing to the motor forming a dead short-circuit, until it obtains its speed and maintains an equal potential to that of the feeding-conductors. To obviate this difllc ulty, it has heretofore been customary to interpose resistances in series with the electric source of power and the motor and then gradually reduce the resistances to nothing, by which time the motor would have received its full speed and would have acquired the same potential as that of the conductors.

The purpose of my invention is to substitute in series for the resistances referred to a second motor. of smaller size, wh'ich'motor, having a comparatively inappreciable load to carry, will at once attain its full speed and full potential. The speed of the small motor is then diminished by mechanical means or otherwise, thereby lowering itscounter electromotive force and permitting a current to flow through it and through the large motor,

the latter beginning to operate when this current reaches a certain point. The speed of the small motor being still further decreased, the potential of the large one will increase until when the' small motor is stopped the large one is running on full potential, whereupon the small motor may he cut out of the circuit. By my method I am also enabled to stop the large motor without the application of brakes thereto, the interruption of the In the drawing, A is an ordinary type of I motor provided with the field-coils L and armature O. l v B indicates the terminals of a dynamoelectric machine or its equivalent, of any convenient construction, and interposed in series between the dynamo-electric machine B and the motor A is a small motor G, provided with a cut-out switch I) and a brake E, operated by the brake-lever F.

In starting up the 'motor A the small motor G is introduced in lseries by means of the switch D. It immediately attains its full speed and total electromotive force fromthe source of power. I The brake-lever F is thereupon applied, reducing the speed of motor G, thereby causing its counter electromotive force to drop and permitting the current to flow through it and through the large motor A. The application of the brake is continued and the speed of the small motor further diswitch into the position shown in the dotted lines in the drawing.

It is evident that the switch and the means for controlling the speed of the small motor G may constitute one and the same device, so as to be operated bya single manipulation.

The motors may be shunt-wound or may be wound in series, according to the purpose for which they are to be employed. It is preferable, however, to have shunt-fields for e the small motor G, as they-can then be on before the main switch is closed.

While I have shown the secondary motor as entirely independent of mechanical connection with the primary motor, it is evident that the two may be built in together uponthe same frame and framework without departing from the spirit of my invention.

Having thus described my invention, what I claim, and desire to secure by Letters Patent, is

l. The method of varying the speed of an electric motor which consists in placing in series with its armature the armature of a dynamo electric machine, generating by dynamic induction in the armature of said dynamo-electric machine a counter electromotive force, and varying the counter electromotive force so generated, substantially as described.

2. The method of starting, operating, and controlling an electric motor at anyspeed desired which consists in exciting its field, supplying its armature with current, passing the current supplied to said armature through a regulatingarmature in series therewith, causing said regulating-armature to cut lines of force, and varying. the rate of cutting of lines of force by said regulating-armature, substantially as described.

3. The method of operating an electric motor at any speed desired which consists in exciting its field, supplying its armature with current, passing the current supplied to said armature through a regulating-armature in series therewith, causing said regulating-armature to cut lines of force, and varying the speed of said regulating armatnre by subjecting it to a load, substantially as described.

4. The method of controlling electric mo tors which consists in supplying to the motor a current of electricity, and producing by magnetic induction in the circuit between the source of supply and the motor, a variable magnetically-induced counter electroniotive force independently of that of the motor, substantially as set forth.

5. The method of controlling electric motors which consists in supplying to the motor a current of electricity, and producing by magnetic induction in the circuit between the source of supply and the motor a variable m'agnetically-induced counter electromotive .force independently of that of the motorand opposing the current from the source of supply, substantially as set forth.

6. The method of varying the electromotive force at the terminals of a translating device, which consists in developing in series with the translating device by means of a revolving winding an electromotive force between the source of supply and the translating device which is variable at will, substantially as set forth. I

Y 7. The method of obtaining from a source of electromotive force a different and controllable electromotive force at the terminals of a translating device with a minimum waste of energy, consisting in placing in the path of the current leading to the translating device the armature of a dynamo-electric machine, and operating said machine as a motor to reduce the electromotive force at the terminals of the translating device, substantially as set forth.

MONTGOMERY WADDELL.

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