US1075579A

US1075579A - Motor-starter.

Info

Publication number: US1075579A
Application number: US46221808A
Authority: US
Inventors: Charles D Knight
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1908-11-12
Filing date: 1908-11-12
Publication date: 1913-10-14
Anticipated expiration: 1930-10-14

Description

G. D. KNIGHT.

MOTOR STARTER; APPLICATION FILED NOV. 12, 1908.

' PatentedOct. 14, 1913.

INSZE'NTUR CHARLES 17. KNIEHT.

WI TJYEE'SES" ductioirmotors of the UNITED STATES PATENT QFFICE.

'UHABLES D. KNIGHT, OE SCHENEGTADY, NEW YORK, ASSIGNOB, T GENERAL ELECTRIC COMPANY,

A CORPORATION OF NEW YORK.

MOTOR-STABTER.

Specification of Letters Patent.

Patented Oct. 14,1913.

Application filed November 12, 1908. Serial No. 462,218.

To all whom it may concern Be it known that I, CHARLES D. KNIGHT, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Motor Starters, of which the following is a specification.

This invention relates to means for controlling electric motor circuits and has for its object the provision of a device whereby an electric motor may be started and brought to. running speed in a safe and citicient manner.

My invention relates more specificallyto the starting of alternating current motors of the induction type. When starting inslip ring type, it is essential that the secondary circuit be closed through the necessary resistance before the closing of the primary circuit. It is desirable that means he provided for cutting the impedance out of the secondary circuit in a convenient manner. In carrying out my invention, therefore, I provide in connection with automatic means for cutting the resistance out of the secondary circuit, means'whereby the resistance may be automatically reinserted in the secondary circuit upon the opening of the rimary circuit. also provide means whereiiy the primary circuit cannot be closed until said resistance is inserted in the secondary circuit.

In the accompanying drawing I have shown my invention embodied in concrete form, the arrangement being somewhat diagrammatic in order to make the operation of my device more apparent.

Referring to the drawing, P represents the primary and S the secondary of an inv duction motor, of the slip ring type. I have shown a motor having three phase windings, although it is apparent that my invention is not limited to any particular number of phases. The primary circuit of the motor is closed by means of contactors A, B and C, one for each phase, having solenoids a, Z) and 0 respectively, actuating plungers, which plungers operate contacts to open the primary circuit at contacts 1, 2 and 3 respec tively. The plungers of solenoids a and c carry bridging contacts i and 5 respectively, arranged to bridge contacts 6 and 7 as shown, for a purpose hereinafter described. The impedance for the secondary circuit which I have shown as a resistance is diarranged to bridge the vided into three sections, D, E and F, one for each phase. These resistances are provided with contact studs 8, 9 and 10 arranged in a circle, the sections being separated by dead studs. The controlling memher for this resistance consists of three arms 11, 12 and 13, joined together by an operating disk 14: and arranged 120 apart. On each arm is arranged a bridging contact 15 contacts 16 successively and short circuit resistance 16 normally in series with coils a, b and 0. The controlling member is arranged so that it is always operated in the same direction, namely, a clockwise direction by means of a pawl 17 pivoted on an arm 18. This arm 18 is pivoted on the pivotal point of the con trolling member at 19, while its free endis actuated by means of the solenoid 20 in one direction and returned by the spring 21. The return movement of the solenoid is retarded by the dash pot 22. The make and break mechanism of the step by step sole noid operating mechanism consists of two pivoted arms 23, one of which is arranged to vibrate between the studs 24: and 25 while the other arm is engaged by the

stops

26 and 27 on the plunger of the solenoid.

The spring 28 draws the two arms toward each other: It is evident that the arm 23 will be moved into engagement with either stud 2a or 25 depending upon which side of the pivotal point the spring28 happens to be. It isalso apparent that as soon as the two points of support of the spring and the pivotal point of the rods pass out of line with each other, that the switch 23 will be snapped over witha quick movement. This type of mechanism' is well known and requires no further description. The limit switch 29 is arranged to be 'en gaged by each arm in turn as it arrives at the end of the adjacent section of the resistance.

anism. A shunt is arranged around this switch from the point 30 through conductor 31, contacts i and 5 to point 32, so that when the bridging contacts l-and 5'are in engagement with the contacts 6 and 7 respectively. the switch will be short circuited and the circuit of the solenoid operating mechanism closed.

The arrangement of circuits and mode of operation is as follows:

This switch opens the circuitbf the solenoid 20 and stops the operating mech- When the switch 1 33 is closed, the parts being in'the position shown, current will pass under phase X, through coils, a, Z) and c in parallel, thence through conductor 84, contacts 16 and conductor 35 backto phase Y. The circuit of the primary P is thus closed through contacts 1, 2 and 316mm the three phases X, Y and Z. At the same time current passes from phase X, through conductor 36, solenoid 20,, contact 25, switch 29 and conductor 35 back to phase Y. The solenoid 20 being energized, the arm 18 is moved to the left and the controlling arms 11, 12 and 13 stepped along to the next stud. When the circuit of the solenoid is broken at 25, the arm 23 of the vibrator snaps over to stud 24 and spring 21 returns the plunger which is re-' tarded by the dashpot 22. This movement continues in a well known manner, stepping the arms over the studs until the arm 11 reaches the limit switch 29 and opens the circuit of the solenoid 20. At this point, the resistance is cut out of the secondary circuit, and the motor is running at normal speed. If, now, the voltage should fail, the contactors A, B and C would open. When this happens the contacts 6 and 7 will be bridged and the circuit of thesolenoid 20 will be immediately closed through conductor 31, bridging contacts 4 and 5, and conductor 35, instead of through the limit switch. Upon restoration of voltage to the line the control arms will be moved forward, each arm moving on to the first step of the succeeding section of resistance. The resistance is thus all included in the secondary circuit so that upon the closing of the primary circuit the motor will be protected.

It is evident that when the primary circuit is opened, it cannot again close until the arms are brought'to the starting position to bridge contacts 16 and short circuit re sistance 16". This is so because the resistance 16 is of such a value that when it is in series with solenoids (1,6 and c, the latter will hold their contactors closed, but will I not be strong enough to close the contactors.

It will be seen that I have provided a very simple and efiicient starting device which adequately protects the motor against damage due to careless handling and the like. The motor will start and automatically come up to running speed and when the motor stops leave the apparatus in protected position.

While I have described my invention in connection with concrete mechanism for bringing about the desired result, it should be understood that I do not limit my invention thereby, sincevssious modifications will suggest themselves i6" those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

WVhat I claim as new and desire to secure by Letters Patent of the United States, is 1. The combination with an alternating current motor, of means for controlling the same comprising a primary circuit closing device, an impedance for the secondary circuit, an electro-magnetic device for gradually reducing said impedance by a movement in one direction and connections established upon the failure of voltage whereby the device is automatically moved in the same direction to insert impedance upon the restoration of voltage.

2'. T he combination with a polyphase motor, of means for controlling the same comprising a primary circuit closing device, an impedance for each phase of the secondary circuit, a controlling member having a varying element for each impedance, an electromagnetic device for moving said member in a direction to reduce the impedance, 2. switch for stopping said member at the limit of its movement, and connefitions established upon the failure of voltage whereby the member is moved inthe same direction to insert the impedance upon the restoration of voltage 3. The combination with a olyphase motor, of means for controlling t e same, comprising a primary circuit closing device, an impedance for the secondary circuit having concentrically arranged sections, one for each phase, a controlling member having an arm for each section, an electromagnetic mechanism for moving said member in a direction to reduce the impedance, means for stopping said member when it reaches the end of a section, and connections established upon the opening of the primary circuit by failure of voltage whereby said mechanism is energized to continue the movement of each arm to the next section upon the re storation of voltage.

l. The combination with a polyphase m0- tor, of means for controlling the same comprising a primary circuit closing device, an impedance for the secondary circuit having concentrically arranged sections one for each phase, a controlling member having an arm for each section, an electromagnetic device for moving said member in a direction to reduce the impedance, a switch for stopping said member when it reaches the end of a section and a shunt around said switch arranged to be closed upon the opening of the primary circuit by failure ofvoltage to continue the movement of each arm to the next section upon the restoration of voltage.

5. The combination with a polyphase motor, of means for controlling the same comprising a primary circuit closing device, an impedance for the secondary circuit having concentrically arranged sections one for each phase, a controlling member having an arm for each section, an electromagnetic device for moving said member in a direction to reduce the impedance, a switch forstopping said member when it reaches the end of a section, a shunt around said switch arranged to be closed upon the openin of the primary circuit by failure of v0 tag'e to continue the movement of each arm to the next section upon the restoration of voltage and connections whereby the primary circuit cannot be closed until the controlling arms are at the beginning of a section;

6. The combination with a polyphase motor, of means for controlling the same comprising a primary circuit closing device, an impedance for the secondary circuit having concentrically arranged sections one for each phase, a member having an arm for each section, an electromagnetic step by-step decopies of this patent may be obtained for in cents each, 'by addressing the Commissioner of vice arranged vto always more said member ance, a switch for stopping said member when it reaches the end of the section and a closed upon the o ening of the rimary circuit by failure 0 voltage to continue the movement of each arm to fthe beginning of the next section upon the restoration of voltage.

myhand this 10th day of November, 1908.

" CHARLES D. KNIGHT.

Witnesses: I v

BENJAMIN B. HULL, HELEN ORFORD.

taunts:

Wuhington, D. 0..

shunt around said switch arranged to be In witness whereof, I have hereunto set in the same direction to reduce the imped-