US718910A - Process of controlling electric motors. - Google Patents

Description

PATENTED JAN. '20, 1903.

W. H. CHAPMAN. PROGESSOF CONTROLLING ELECTRIC MOTORS.

APPLICATION FILED OUT. 22, 1902.

10 MODEL.

Urvrrnn STATES PATENT OFFICE.

WILLIAM H. CHAPMAN, OF PORTLAND, MAINE.

PRQCESS F CONTROLLING ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 718,910, dated January 20, 1903.

Application filed October 22, 1902. Serial 110.128.315. (No model.':

To to whom it may concern:

Be it known that I, WILLIAM H. CHAPMAN, a citizen of the United States of America, and a resident of Portland, Cumberland county, State of Maine, have invented certain new and usefullmprovements in Processes of Controlling Electric Motors, of which the following is a specification.

My invention relates to a process of controlling electric motors, and it is particularly adapted to motors which have to be frequently reversed, such as those used on elevators, 850.

The object of the invention is to avoid com- 7 plete interruption of the working circuit of the motor and to do away with sparking at contact-surfaces, which is liable to weld them together.

The invention consists, essentially, of connecting each armature-terminal of the motor with each pole of the line from which the current is derived through suitable resistance and simultaneously and equally increasing the resistance between one of said terminals and the positive pole of the line and decreasing the resistance between said terminal and the negative pole of the line and reversing this operation as to the other terminal.

The invention also includes a method of short circuiting the armature terminals, whereby retarding effect is produced in the motor doing the work of a mechanical brake.

I illustrate my invention by means of the accompanying drawing, which shows a controller,partly in detail and partly diagram matically, which is adapted to carry out my process as applied to elevator or other like motors which have to be frequently reversed.

B B and C O are four sets of rheostat-segments composed of thin copper sheets separated by mica and all clamped together in the iron supporting-frames A A, from which they are insulated by mica in the usual manner. Between the two sets of segments B O is one wide brass segment i, and also between the two sets B O is another wide brass segment i, and these wide segments each constitute a common terminal segment of each of the two sets between which it is placed and serving as a means of connecting them together. Each set of rheostat-segments is connected in the usual way to a series of resistance-coils, and the resistance of these coils in the successive steps increases by regular gradations from the outer extremes of each set to a point about three-fourths way toward the inner extremes, which are located at the wide segment at the center portion of the supporting-castings A A, and the resistance of the coils in the last one-fourth of each set decreases by regular gradations to the central wide segment. \Vhile the resistance of each step at the outer or innerextreine may be, say, three one-hundredths of an ohm, the resistance of each step at the point three-fourths way from outer to inner extreme is as high as fifty ohms.

D and D are inverted-L-shaped levers or rheostat-arms, each pivoted at g g. The vertical portions of these levers have brass fingers Z) and b pivoted to them and actuated by springs t to press them into contact with the segments B B and O and C. The levers are mechanically connected by rod H, so as to move in unison. Means are provided for bringing the levers D and D back to a central or normal position when they are free to move. For this purpose I provide compressionsprings 3', one on each of the two rods m and m. The lower ends of the rods are pivoted to the levers, and their upper ends slide freely in the brackets 13 and p. The tendency of these two springs is to bring the arms D and D normally to a central position when they are not acted upon by the solenoids. Solenoids are provided for operating the levers D and D to slide the contact-fingers along the rheostat. The horizontal ends of the levers are pivotally connected with links I and I, and these in turn are pivotally connected to the iron coresj and j of the solenoids K and K, which are mounted on an iron casing attached to the slate F.

L and L are two dash-pots, whose pistonrods are pivotally connected to the levers D D.

In directing the operation of my controller I make use of a two-point switch having the lever N and segments 0 and O. This switch admits current directly from the line to either one of the two solenoids at will.

T is the service-switch, which is kept closed during the hours of service of the motor to be controlled. From this switch the running current or current for driving the motor is distributed by wires to the various circuits, which may be classified as follows: the armature-circuit, the solenoid-circuit, and the shunt-field circuit. In the armature-circuit is included the armature of the motor, the two levers D and D, the fingers b, the resistances at O and C or at B and B or such portion of them as may not be cut out by the fingers b, and the series winding of the motor. The'solenoid-circuit has two branches, one of which includes the winding of solenoid K, one contact-point of the two-point switch, and the lever of the switch. The other branch includes the solenoids K, the other contactpoint of the two-point switch, and the lever of this switch. The field-magnet circuit is derived directly from the terminals of the switch T and contains simply the shunt field of the motor.

Besides the working circuits or circuits for passage of live current from the line, as above described, there is another local circuit established when the levers D and D are at the central position or at a short distance either side of the same, and this local circuit may be called the armature short circuit. This circuit includes the armature, the two levers D and D, the contact-fingers b, a portion of the resistance lying adjacent to the wide segment in each of the frames A and A, and the cross-connection wire W, which connects one segment of the set E with one segment of the set C. WVhile these levers D and D are in the central position, all the resistance at B, O, B, and C is in circuit from one pole of the line to the other pole of the line and allows only a very feeble current to flow through the resistances and none through the armature. When the lever N is turned to segment 0, it energizes the solenoid K, pulling the two levers D and D over to the right. When the levers D and D arrive at the extreme end of the series of segments-for instance, to the rightall resistance is cut out and the armature-circuit receives its full current, said current passing through the wires 1 2, fingers Z), lever D,wire 3, thence through the armature,through Wire 4, lever D, fingers b, wire 5 and 6, through the series winding,and by wire 7 to the other pole of the line. The movement of the levers to the right is retarded by the dash-pot L, and thus the current is admitted gradually to the armature, which is caused to rotate, the shunt-field circuit being energized whenever the s witch T is closed. To stop the motor, the lever N is brought to central position, solenoid K stops pulling, and the spring .9 brings the levers back to central position. When the levers approach the central position, the armature short circuit is established and a current is generated in this circuit by reason of the armature revolving by its momentum within the influence of the excited field. In other words, the motor becomes a generator and its momentum is checked by the current that it generates, which acts as a brake to make it stop quickly, and the quickness of the stop can be adjusted by placing the crossconnection wire at different points on the series of segments. If, for instance, this wire were connected from one wide segment to the other wide segment at the centers of frames A A, it would give a dead short circuit and stop the armature almost instantly,while the more this wire is removed from the center the slower will be the stop, as more resistance is thereby included in the armature short circuit, thus reducing the amount of current that is generated in this circuit. means I am enabled to take the Work from the mechanical brake, the retarding action of the armature being sufficient to stop the motor and its action being superior to that of a mechanical brake, since it produces an elastic or yielding stopping action instead of a sudden jerk, as in the case of an ordinary brake.

I claim-- l. The herein-described process of controlling electric motors, consisting of connecting each armature-terminal with each pole of the line through suitable resistance and simultaneously and equally increasing the resistance between one of said terminals and the positive pole of the line and decreasing the resistance between said terminal and the negative pole of the line and decreasing the resistance between the other terminal and the positive pole and increasing the resistance between the latter terminal and the negative pole.

2. The herein-described process of controlling an electric motor which consists in placing suitable resistance between the armatureterminals and between each armature-terminal and each line-terminal and then gradually changing the resistance from armatureterminal to armature-terminal and simultaneously and gradually changing the resistance from both armature-terminals to the line-terminals inversely to the change between the armature-terminals.

3. The herein-described process of controlling an electric motor which consists of placing the two armature-terminals in connection through suitable resistances with each other, and with the two poles of the line and then gradually changing the resistance from armature terminal to armature terminal while simultaneously changing by equal and opposite amount the resistance from armature-terminals to line-terminals.

Signed at Portland, Maine, this 19th day of September, 1902.

WVILLIAM II. CHAPMAN.

Witnesses:

S. W. BATES, EDNA A. SEWALL.

By this I

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