US504904A - Multiphase motor - Google Patents

Description

(No Model.)

L. BELL. MULTIPHASE MOTOR.

v No. 504,904. Patented Sept. 12, 1893.

UNITED STATES PATENT OFFICE.

LOUIS BELL, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEW YORK.

MULTIPHASE MOTOR.

SPECIFICATION forming part of Letters Patent No. 504,904, dated September 12, 1893.

Application filed November 4, 1892. Serial No. 150,965. (No model.) v

To all whom it may concern.-

Be it known that I, LOUIS BELL, a citizen of the United States, residing at Boston, county of Suffolk, State of Massachusetts, have invented a certain new and useful Improvement in Multiphase Motors, of which the following is a specification.

In starting multiphase motors, as for example three-phase motors, having a closed circuited secondary member, it is found that the best starting torque is obtained when the resistance of the secondary element is considerably higher than would satisfy the best running conditions. This is because the resistance of the secondary best suited 110 efficient running is so low that the primary rush of current flowing through it on starting from rest is large enough to exercise a de-- magnetizing effect on the field so great as to materially decrease the starting torque. It has therefore been not unusual to connect with the secondary element a starting resistance which later is removed from circuit. When the secondary element is the stationary part of the motor, this is very simply done by connecting properly in circuit with it an ordinary rheostat. In such case, however, collecting rings are required on the revolving member in order to supply to it the primary current. If on the other hand the secondary member is the revolving part of the motor, and a fixed non-rotating rheostat is used, sliding connections are again necessary in the circuit of the rheostat.

It is desirable to avoid the sliding contacts altogether, and this is the main object of my present invention. To that end I make the primary member the fixed part of the motor, and use a starting resistance which revolves with the secondary member. The resistance is preferably non -induotive in character, though my invention in its broadest terms includes all suitable current impeding means for reducing the increased primary flow of current in the secondary until the machine speeds up. A switch for short circuiting the resistance is provided which also travels with the armature or revolving member, and which may be thrown while the motor is running manually, or automatically by a wide variety of speed responsive devices, such as have been used or suggested in the electrical art to secure a like function in other connections.

Acentrifugal or other mechanical governor, however, is preferred. This switch may have a movement along the armature shaft, or a rotary movement around the shaft, the essential thing being that it may be thrown while the armature is running. From the above it will be understood that. my invention does not comprise broadly the application of a starting resistance to the secondary of a multiple phase motor, as this, when coupled with sliding connections either for the primary current, or for the resistance, or both, has been alreadyin use, but its chief aim is to do away with sliding connections altogether, and such an arrangement is, so far as now known, broadly new to me, so that while the structure shown and specifically covered in some of my claims is believed an especially good one, yet it is my intention to include within the broader statements of myinvention many other modifications as well.

In the accompanying drawings Figure 1 shows in diagram one member of a multiphase motor containing my invention, and Fig. 2 shows the same similarly in diagram, but with a different type of winding. Fig. 3 shows in side elevation and section the short circuiting switch. Fig. 4 is an end view of the moving member of the switch seen in Fig. 3, looking in the direction in which the arrow points. Fig. 5 is a similar view of the fixed portion of the switch, and Fig. 6 illustrates in section one form of automatic switch.

A represents the secondary member of a multiphase motor, which will be mounted on a shaft B and form the revolving element. The type selected for illustration is a threephase motor, though the invention is by no means limited to that alone.

In Fig. 1 the winding shown is what is known as the Y winding. It comprises three coils designated by the numbers 1-1, 2-2, 3-3, each surrounding the armature ring or core, and with their respective entering and leaving ends spaced substantially one hundred and twenty degrees apart. Corresponding ends of each of these coils are connected to a common ring C, and through this ring to one another. The other ends of the coils are brought to contacts a, b, c, and

these contacts are connected by resistances D, i

E, and F. Hence it will be seen, when the contacts are not bridged by the switch, each coil is connected to its neighbor through a resistance, which will usually be so proportioned as to make the resistance of the armature ten or a dozen times the normal.

Fig. 2 shows a different form of winding, commonly known as the delta winding, in which each coil has its opposite ends respectively connected to one end of the other coils making what may be regarded as a series connection of all three, and in the connections between the coils are included properly proportioned resistances D, E, and F, as before. As seen in this figure coil 1 is connected to coil 2 through resistance F, coil2 to coil 3 through resistance D, and 3 to 1 through resistance E. Around each of these resistances is a short circuit interrupted at insulated contacts m, a so that when these contacts are bridged by a low resistance connection the resistances are short circuited.

In Fig. 3 a manual switch is shown. The contacts a, I), care fixed upon a support I mounted on the armature shaft, and are of course insulated from one another. Splined 0n the shaft so as to move longitudinally but not radially is a collar K carrying contacts (1 adapted to engage the fixed contacts. To insulate the contacts from the shaft, but to permit them all to be electrically connected together, they are placed upon a conducting ring 0 separated from K electrically by insulating material P. A hand lever Q is shown to throw the switch, and the contacts are made of interlocking fingers, insuring a good and firm connection.

In order that the starting up of the machine may be entirely automatic I prefer to use, as shown in Fig. 6,a device which will throw the switch and short circuit the resistances at exactly the moment that proper speed has been attained. To do this it is only necessary that some reliable speed responsive device control the switch; hence while that shown is a good construction, it may be departed from widely. The moving member of the switch K is carried by an arm R pivoted at r, and moved by a cam projection 3 upon a collar S free to slide radially on the shaft under the action of the centrifugal device T, and against the stress of a spring U bearing at one end against collar S, and at the other end against a fixed collar V, to which one of the toggle arms of the governor is also pivoted.

That I claim as new, and desire to secure by Letters Patent, is-

1. The combination in an electric motor of a closed circuited secondary member forming the revolving part of the motor, with current impeding means carried by, or fixed relatively to, said revolving member for reducing the primary current liowingin said secondaryiir cident to starting the motor, and means for removing said impeding means from circuit when the proper speed has been attained, as set forth.

2. The combination in an electric motor of a closed circuited secondary member forming the revolving part of the motor, with a noninductive resistance or resistances carried by, or fixed relatively to, said revolving member, and means for removing said resistance from circuit when proper speed has been attained, as described.

3. The combination in an electric motor of the inductive type, of a revolving secondary member having a closed circuited winding thereon, a resistance in said winding and moving therewith, and a switch for removing said resistance from circuit at will while the machine is running, as set forth.

4. The combination in an electric motor of a closed circuited revolving secondary member having a winding comprising two or more coils, as for example an ordinary three-phase winding, with a resistance orresistances moving therewith, and through which the circuit of the respective coils is or maybe completed, and a switch for removing said resistance or resistances from circuit at will, as described.

5. The combination in an electric motor of a closed circuited revolving secondary member having a plurality of coils thereon, each of which is connected to the others through a resistance moving therewith, and a switch adapted to remove all said resistances from circuit simultaneously while the machine is running, as described.

6. The combination in an electric motor of a revolving secondary member having a wind ing comprising a plurality of coils, and resistances moving therewith connecting one end of each coil to the proper end of its neighboring coil, short cireuiting connections around such resistance respectively, and a switch for removing said resistance from circuit while the machine is running, as set forth.

7. The combination in an electric motor of a closed circuited secondary member forming the revolving part of the motor, a resistance moving with such member and impeding the primary flow of current therethrough incident to starting the motor, a switch, and a speed responsive device automatically throwing said switch so as to remove the resistance from circuit when the proper speed has been attained, as set forth.

8. The combination in an electric motor of a closed circuited secondary member forming the revolving part of the motor, a resistance moving with such member and impeding the primary flow of current therethrough incident to starting the motor, a switch and a centrifugal speed responsive device automatically throwing said switch so as to remove the resistance from circuit when the proper speed has been attained, as set forth.

In witness whereof I have hereto set my hand this 28th day of October, 1892.

LOUIS BELL.

Witnesses:

N. F. HAvEs, ALEC F. MACDONALD.

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