US1554024A - Alternating-current-motor starter - Google Patents

Description

Sept. 15, 1925 W. E. PAUL \ALTERNATING CURRENT MOTOR STARTER Filed April 26, 1924 (L N, start/n9 0 ,2 22 o i /9 1 L I runn/ng 5 {@J /4 running star ting starting Inventor:

WHliam E. Paui,

y- M His Attorney."

Patented Sept. 15.1925;

UNITED STATES.

WILLIAM E. PAUL, OF SCHENECTADY, NEW YORK, ASSIGNOB 'IO GENERAL ELECTRIC PATENT. OFFICE.

COMPANY, A CORPORATION OF NEW YORK.

Application filed April 26, 1924. Serial No. 709,302.

To all whom it'may concern:

Be it known that I, WILLIAM E. PAUL, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Alternating-Current-Motor Starters, of which the following is a specification.

My invention relates to improvements in alternating current motor starters of the compensator type employing separately operable starting and running switch contact mechanism.

One of the objects of the invention is to provide a simple and effective arrangement involving a starting switch and a separatel operable running switch in connection Wit a starting auto-transformer, with the connections arranged in such a manner that the motor circuit will not be opened during the starting interval and the motor will be connected directly to the source of sup ly through the starting and running switclies for the normal runnin of the motor.

A further object of the invention is to pro vide an arrangement of the character indicated whereby two substantially similar plural pole switches may be employed, preferably two normally open substantially similar oil switches, one switch serving as a starting switch and the other'switch serving as a running switch, together with connec-' tions whereby the neutral of the auto-transformer is closed by contact mechanism of the running switch when the running switch is in the open position, the neutral is opened in the closed position of the running switch so that the motor is connected to the line through the taps of the auto-transformer when the starting switch is closed, the autotransformer serves as a reactor while the running switch is being closed, and the motor is connected directly to the line when both switches are closed.

A further object of the invention is to provide interlocking connections between the starting and rurming switches to prevent closing the starting switch unless the running switch is in the open position, so as to prevent connecting the motor directly to the line without employing the auto-transformer to s pply a red ced p ential for startin These and other objects of the invention A ployed in the system of Fig. 1, only so much of the structural features of the contact mechanism and the operating means therefor being shown as would seem necessary to an understanding of the invention, and Fig. 3 is an end view of the starting and running oil switch mechanism shown in Fig. 2.

Referring to the drawing, the electric motor 10 of the alternating current type is ar-' ranged to be started from the three phase alternating current source of supply 11, by means of the starting switch 12 in cooperation with the starting auto-transformer 13 and the running switch 14. The starting switch, the running switch and the autotransformer are connected in such a way that the closing of the starting switch will connect the motor to the source through the starting taps of the auto-transformer 13 and when the motor has come up to speed, the closing of the running switch 14 will connect the motor directly to the supply circuit.

The switches 12 and 14 are substantially similar switches, each having three circuit making movable contact members corresponding to the number of phases of the source of supply. As shown, the switches are of the four pole type, although the switch 12 is not provided with the fourth circuit making contact member, since this member is unnecessary, it being sufiicient to merely retain at least one of the pole terminals of the switch 12 for use in closing the neutral of the auto-transformer in cooperation with the fourth circuit makin contact member 15 of the running switc This contact member 15 of the running switch is arranged so as to be in the closed position normally while the other three contact members of the running switch are arranged to be in their respective open positions normally. The circuit making contact members of the starting switch are also arranged to be in their respective open positions normally. The conductors 16,.17 and 18 are provided for interconnecting corresponding pole terminals of the starting and the running switches, as shown, and the terminals of the startingauto-transformer are connected to these conductors respectively. The neutral of the auto-transformer is formed by attaching two of the other terminals of the auto-transformer to the pole terminals 19 and 20 associated with the fourth contact member 15 of the running switch. The connection from the remaining coil of th e auto-transformer is made to the pole terminals 21 associated with the running switch and the flexible jumper 22 is connected between the pole terminals 21 and the contact member 15 so that with the running switch in the open position the neutral of the autotransformer will be closed. Conductors 23, 24 and 25 permanently connect the taps of the starting auto-transformer with the motor. I

In order to prevent closing the starting switch unless the running switch is in the open position, I have provided a mechanical interlocking member 26 which cooperates with a cam surface 27 of the running switch and a pivotly mounted biased detent 28 connected with the starting switch.

By reference to Figs. 2 and 3 it will'be seen that the switches which I prefer to use are of the oil switch type, and in these figures only so much of the oil switch is shown as is necessary for the understanding of the invention. By reference to Fig. 2 it will be seen that I have provided the ordinary form of four pole oil switch with an arrangement whereby the circuit making contact member 15 makes engagement with its respective pole terminals in the open position of the switch, while the other contact members of the switch are out of engagement with their respective pole terminals. The flexible jumper 22 connects the pole terminal 21 of the starting switch (Fig. 3)

and this jumper is connected to the circuit making contact member 15' of the running switch by any suitable means such as the clamp 29. By reference. to Fig. 3, it will be seen vthat the interlocking connection between the starting and the running switches is conveniently-mounted on the casing of the switches and cooperates with movable parts ofthe operating mechanism of the switches so as to provide the protection heretofore referred to.

As thus constructed and' arranged and with the, parts in their respective positions shown inthe drawings, the operation of my invention is as follows:

In order to start the motor, the starting switch 12 will be first closed, thereby connecting the motor to the source 11 throtigh the starting auto-transformer 13 which serves as a step-down auto-transformer to apply a reduced potential to the motor for starting, because of the fact/that the neutral of the auto-transformer is closed through the running switch is in the open position.

When the motor has come up to a proper speed on the starting taps of the auto-transformer, the running switch 14 is closed. It

will be observed that during the intervalof closing the running switch the neutral of the auto-transformer is opened by reason of the fact that the circuit making contact 15 of the running switch will open the circuit through its contacts. However, this will not effect an interruption of the cur rent being supplied to the motor, since during this interval the motor will receive energy, through the starting auto-transformer serving as a reactor. This prevents a drop in speed and torque of the motor during the transition from the startingto the full running position. When the running switch is closed the motor is connected directly to the source of supply through the starting and the running switches.

If the starting switch is opened so as to disconnect the motor from the source of supply and stop the motor, the starting switch cannot be thereafter again closed unless the running switch is also returned to the open position. The interlocking member 26 is shifted by means of the cam 27 of the running switch so as to be in engagement with the pivoted detent of the starting switch, but when the running switch is in the open position the interlocking member 26 is returned to the position shown in the drawing by means of the biasing spring 30. It will also be observed that the interlocking member 26 does not interfere with the opening of the starting switch after the running switch is closed, because of the fact that the detent 28 will move about its pivoted connection with the starting switch against the action of its biasing spring.

The arrangement above set forth provides a very simple and effective means-whereby two substantially similar switches may be employed for connecting the motor to the supply circuitand whereby an'operation of the switches which. would likely cause injury to the motor is prevented. It will also be noted that the connection of the source of supply to the motor is maintained throughout the starting interval so that the speed and torque of the motor will not drop as in former arrangements in which the starting switch is opened prior to closing the running switch. If the running switch is opened after the motor is connected directly to the source, no damage results and although ordinarily it is not desirable to do this, however, under certain conditions it is desirable to have this feature in order to obtain temporarily a reduced speed without the necessity of first opening the starting switch. The reduction in the motor speed will be brought about, particularly if the motor is running under load, because tap voltage is applied to the motor, but it is to be noted that auto-transformers are ordinarily not designed for continuous running on the taps of the auto-transformer.

What I claim as new and desire to secure by Letters Patent of the United States, is: 1; A starter for polyphase alternating current motors, comprising a starting autotransformer, a starting switch having a set of normally open circuit making contact members corresponding to the phases of the' source of supply and an additional set of terminals, a running switch having a set of normally open circuit making contact members corresponding to the phases of the said source and an additional movable contact member arranged to be in the closed position normally, a flexible jumper from one of said terminals of the starting switch to the said additional contact member of the running switch for closing the neutral of the auto-transformer in the open position of the running switch, and connections whereby closing the starting switch connects the motor to the source of supply through the starting taps of the auto-transformer, subsequently operating the running switch toward the closed position opens the neutral of the auto-transformer so that the motor is connected to the source through the auto-transformer serving as a reactor during the interval of closing the running switch, and the motor is connected directly to the source through the starting and running switches when the running switch closes.

2. A starter for polypha'se alternating current motors, comprising a starting autotransformer, a normally open starting switch having at least one extra pole more than the number of conductors of the supp-1y circuit, a normally open running switch having a number of poles similar to the starting switch, conductors interconnecting corresponding terminals of the said switches through which the motor is supplied with current from the supply circuit, connections between one set of terminals of the auto transformer to the respective conductors bebeing closed in the open osition of the a running switch by means 0 a flexible connection from a terminal of the extra poie of the starting switch to the extra contact mem ber of the running switch, whereby the motor is connected to the source of supply through the starting taps of the auto-transformer by the closing of said starting switch,

the neutral of said auto-transformer is opened by the said contact member so that the motor is connected to the source through the auto-transformer serving as a reactor during the interval of closing the running switch, and the'motor is connected directly tothe source through the running is closed.

3. A starter. for three phase alternating current motors, comprising two normally open four pole switches having each three contact members for connecting the motor to a source of supply, one of said switches being a starting switch and the other being a running switch, a starting auto-transformer having one set of terminals of the said starting and auto-transformer connected to respective conductors between the said switches, the neutral of the auto-transformer being normally closed with the running switch in the open position by means of a connection from one terminal of the auto-transformer to the fourth contact member of the running switch and connections from the other terminals of the auto-transformer to the pole terminals of the said fourth contact mem ber of the running switch, the starting taps of the auto-transformer being permanently connected to the motor, whereby closing the starting switch connects the motor to the source through the starting taps of the autotransformer, the neutral of the auto-transformer is opened by closing the running switch thus causing the auto-transformer to serve as a reactor during the interval of closing, and the closing of the running switch connects the motor directly to the source through the starting switch.

4. A starter for polyphase alternating cur- .rent motors, comprising a starting autotransformer, a normally open starting switch, a normally open running switch arranged to close the neutral of the auto-transformer in the open position thereof, interlocking connections between the said switches for preventing the closing of the starting switch unless the running switch is open, and. connections whereby closing the starting switch connects the motor to the source through the starting tips of the autotransformer, operating the running switch toward the closed osition opens the neutral of the auto-trans ormer so that the motor is connected to the source through the autotransformer serving as a reactor during the interval of closing the running switch, and.

the motor is connected directly to the source through the starting and running switches when the running switch closes, 10

In witness whereof, I have hereunto set my hand this 25th day of April, 19%.

WILLIAM E. PAUL.

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