US1753116A - Electric-motor starter - Google Patents

Description

April l, 1930. w. T. HOLMES ELECTRIC MOTOR STARTER Filed Jan. 7, 1928 L YM /IL J, ff

ATTORNEY.

'n the armature current.

' dated Patented Apr. 1, 1930 WILLIAM T. HOLMES, or

SAID WILLIAM T. HOLMES, DECEASED, ASSIGNOR TO BALTIMORE, MARYLAND; DAISY N. HOLMES, EXEGUTRIX OF MONITOR CONTROLLER GOM- LPANY, OF BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND ELECTRIC-MOTOR STARTER 1 Application ed January 7, 1928. Serial No. 245,156.

rhis invention relates to electric motor starters of the class wherein the cutting out of the starting resistance is controlled by current iiow in the armature circuit of the motor. In the patent to IVhittingham, No. 1,135,870, pril 13, 1915, is shown a starter in which a centrally pivoted contactor is rocked to closing position by a magnet having its coils connected across the line in a circuit independent of the armature circuit of the motor, and a magnet, having its coils in series with the armature circuit, acts in opposition to the first mentioned magnet and prevents the closure of the contactor until the armature current falls to a predetermined value. This starter operates satisfactorily under all werking conditions; but under very unusual conditions, as may be brought about by temporary grounds or short circuits on the supply circuit, the voltage at the terminals of the magnet which rocks the contactor to closed position, may be lowered to such an extent that it will not overpower the series magnet and close the contactor when the current in the coils of the series magnet is at the predetermined value where, under ordinary conditions, the contactor would close. In the present invention, the main and auxiliary contactors are moved to their closed positions and held in such positions by magnets, the coils of which are connected across the line, but they are not acted upon or retarded by series coils, as in the patent referred to, and therefore will be held in their closed positions even witha very large drop in line voltage. The timing of the closure of the auxiliary contactors, in the present invention, is attained by the use of relays, each having a magnet connected in shunt to a part of the starting resistance, whereby the relay is controlled by Each relay controls the circuit of a. magnet for closing an auxiliary contactor and operates to close said circuit whenthe armature current falls to a predetermined value. By this arrangement, the time of closure of the auxiliary contactors is controlled by the armature current, but there is no magnetic force applied to the contactors tending to open the same, and hence the magnets which close the contactors will hold them cuit through the resistance, and auxiliary con- A tactors b and c, for cutting out the resistance.

These contactors are adapted to be closed by magnets l, 2, and 3, which magnets are mounted upon metalbases 122% ant 3a, respectively. rIhe starting resistance is connected to the bases of the magnets, as shown, thus dividing if he resistance into sections r and 1. The armature circuit extends from the starting resistance by conductor 4 to the armature m, and thence to the supply wire L. The field 7 ofthe motor is connected to the supply wire L, and also by conductor 5 to the base 1a of the magnet 1. rI'he contactors a, Z), and 0 are adapted to engage stationary contacts 6, 7, and 8, respectively, which contacts are connected by conductor 9 to the supply wire L, as i shown. T he contactors are pivotrally mounted upon the magnet bases, as shown, and are therefore electrically connected to said bases.

It will be seen that when the contactor a closes against the Contact 6, current will flow from the supply wire L, through the contactor fr and the base la to the field of the motor through the conductor 5, and also to the armature of the motor through the entire resistance It. When the auxiliary contactor Z2 closes, current will flow from the stationary contact 7 through contactor b and magnet base 2a to the section r of the starting resistance, and v thence to the motor, thus short circuiting the section r of the starting resistance. When the contactor c closes, current will flow through stationary contact 8 and this contactorthrough base 3 directly to the motor, thus short circuiting the section r of the resistance.

The coils of the magnets l, 2and 3, when in circuit, are connected across the line and receive the .tull line voltage. ,The `circuit ot' the magnet 1 is controlled by a hand switch L, so that immediately upon closure oi? the switch the contactor a will close; but the circuits oit the magnets 2 and 3 of the auxiliary contactors are controlled by relays Z and CZ',

so that said contactors close in succession at predetern'iined current values in the armature circuit ot' the motor.

The circuits ot the relay magnets 10 and 11 are connected in shunt to portions of the starting resistance. The relay Z comprises the magnet 10, mounted upon a suitable base 10, connected to the base 1, and an armature 1.2, which is constantly urged away from the magnet. by a spring 13. rthis armature is adapted to engage a stationary con-tact 14, but is normally `held out of engagement with said contact and in close relation to the pole of the .magnet 10 by an extension a on the main contacter fr. The relay d is similar to the rel-ay d, and its armature 15 is adapted to engage a stationary Contact 16,` but. is normally held out of engagement with said contact :by an extension 7) on the auxiliary contacter Thelbase 11a of the relay magnet 11 is `electrically connected to the base 2"L yot the magnet 2.

The switch blade 18 ot the switch .72, is connected by conductor 19 to the supply wire L, and this bla de is adapted to engage stationary contacts 2O and 21 practicall i at the same time. A conductor 22 connects the contacts 21 with the coils of the shunt magnet- 1, and these coils are connected by conductor 23 to 'the supply wire L. Hence, when the switch -k is closed, the magnet 1 will be energized and the main contacter will engage the stationary contact 6 `and close 'the armature circuit through the entire resistance. A conductor 24 connects the contact 20 with the coil of the relay magnet 10, and a conductor .25 extends from this *coil to an adjustable contact member 26, which engages the resistance section Hence, when the switch L closes, the magnet of 'the relay Z will be strongly .energized by current flowing through the circuit just traced to the resistance and thence to the motor. The contactor a, in closing, releases the armature 12; but the current flowing through the magnet 10 holds the armature 12 away from the contact 14 until the current 1n the coil of the magnet 1'0 falls to a predetermined value, when the magnet releases the armature and the latter is moved by the spring 13 into engagement with the contact 14.

It is to be noted that when the switch 7L is closed, the magnety coils of 'the relay Z are connected in shunt to that portion of the "starting resistance which is included between the base V1a the point where the adjustable arm 26 engages the resistance. Hence, the 'armature current will divide between said portion of the resistance and the coil of the magnet 10, and the latter will hold the armature 12 until the current in the armature circuit o the motor falls to a predetermined degree, when the armature 12 will move away from the magnet 10 and engage the contact 14. The time of release of the armature 12 by the magnet may be varied by adjustment of the spring 13 or adjustment of the arm 26 to include more or less ot' the starting resistance in parallel with the coils of the relay magnet.

When the armature of the relay cl engages the contact 14, it closes a circuit through the shunt magnet 2 of the auxiliary contactor b, and also a circuit through the coil of the magnet 11 of the relay CZ. Thus, the contact 14 is connected by conducto-r 27 to the coil of the magnet 2, and thence by conductors 28 and 23 to .the supply wire L. The circuit of the magnet 11 of relay d extends from the Acontact v14., through yconductor 27 to conductor 29, thence through the magnet coil and by conductor 30 to the adjustable arm 31 which engages the section r of the starting .resistance. It will be seen that when the relay armature 12 engages the contact 14, current will flow through the main lcontacter a to the vbase 10L of the relay CZ, thence through armature 12 to the contact .14, from whence current will flow through the coils of mag- Vnet 2 and through the coils of the magnet 11 of rela-yd. The auxiliary contactor Z) will be immediately mov-ed to the closed position by the magnet 2, and the extension o of the contacter will be moved away from the armature 15 of the relay. The main contactor will cut -out the section r of the starting resistance, and the coils `of the relay magnet will remain .in parallel with la part of the section r of the starting resistance. When the armature current tal-ls to a predetermined value, the relay al will release its armature 15 and the .latter willengage the contact .16, thereby closing the circuit through the magnet 3, which controls ythe auxiliary contactor 0. This circuit extends .from 'the contactor b, through the base 11a of the relay to the armature 15, thence to contact 16, thence through conductor 32Vto the 'coils ot' magnet 3, and thence through conductors l33 and `23 to the side L of the supply circuit. Upon the closure of this mag-net circuit the contactor 0 will instantly close and short circuit the section r of the 'starting resistance. l

From the foregoing, .it will seen that upon closure of the manually operable switch It, the main contactor a will close instantly, but `the time of closure of the auxiliary contactors will be determined by the volume of current in the armature circ-uit. The .shunt connected magnets 1, 2, and 3, which close the contactors, may be made of Vsuch strength that they will hold the contactors closed even with a very considerable drop .in voltage, as may occur with grounds .and short circuits on the line, er from other causes. Thus, in the starter described, the cutting out of the starting resistance is controlled bythe current in the armature circuit, but the contactors are held in their closed positions by magnets which are not affected by fluctuations el' the `armature current, and hence they will stay closed under all Working conditions of the motor and will be released only when there is a very heavy drop in voltage en the line, or when the switch h is opened to stop the motor.

Then the switch L is opened, it will interrupt the circuit of the magnet l and the latter will release the main contacter, and it will also open the circuit through the relay magnet 10, and current will thus be cut eil' from the meter. The main contacter, in opening, Will move the relay armature l2 away from the contact 14 and into close relation to the magnet l0, thus interrupting the circuit through the magnet 2 of the auxiliary contacter Z), and also through the relay magnet 1l. The centactert will move the relay armature 15 out of engagement with contact 16, thus interrupting the circuit through the magnet 3 or' contacter c, and the latter will tall back to its normal position.

In Fig. 2 of the drawing, I have shoxvna modified ferm et starter, comprising a main contacter and an auxiliary contacter, in which the switch arm of the current-centrelled relay is not held in normal position mechanically by a contacter.

-eterring to Fig". 2, S indicates the starter and lvl indicates a motor controlled by the starter. A main contacter 0,2 is adapted to be closed by a shunt magnet 35, and the auriiliary contacter c2 is adapted to be closed by a shunt magnet 36. A relay (Z2 controls the circuit et' the magnet 36. lThe starting resistane is connected te the bases and 36 et the magnets and 38, respectively, and the field circuit 37 et the meter is connected te the base 35 and to the supply wire li', as shown. The contactors a2 and 02 are adapted te engage fixed contacts 3S and 39, respectively, which latter' are connected by a Wire 40 to the supply Wire L. A conductor 4l leads from the supply Wire L to a relay Contact 42, vwhich is adapted te be engaged by the relay armature 43, but the latter is normally held out of engagement with said Contact by an adjustable spring 44. A circuit extends trom conductor 41, through a normally open push button switch l), by Way et conductors 43 and 44 to the coils or" relay magnet 45, and thence by conductor 46 to adjustable contact I?, which engages the resistance section r at a point intermediate the bases 35a and It `vill be evident that when the push buttm switch P is closed, current will new Jfrom th supply Wire L through the circuit just cf te the resistance r3, and thence through meter armature m te the supply Wire L', and

the magnet Will be energized. This magnet will move the switch arm 43 out of engagement With a contact 48 and into engagement with the contact 42.` l/Vhen the switch arm 43 engages contact-42, a circuit Will be completed through the magnet 35 et the main contacter as follows: 'from supply Wire L, through conductor 4l te switch arm 43, thence through the base 49 et' the relay magnet to conductor o0, thencethrough conducter 5l to a normally closed stop push button switch 52, thence through conductor 53 t0 the coils el magnet 35, thence 'through conductor te the side la el the supply circuit. The magnet 35 Will cause the main contacter te close, and .when sai-d contacter closes, it

will complete the motor circuits and alsoy complete holding circuits threu 'h the magnets 45 and 35, so that these magnets will remain energized after the operator releases the push button switch l). Thus, When the main contacter closes, it connects the side L oi the supply circ it to contact 55, which is connected by conductor 5G to conductor 44, and hence current 'from the supply Wire la can 'flow through the contacter and conductor 44 to the relay magnet 45 alter the start push button l? has been released, and the relay magnet will hold the switch arm 43 in engagement vith contact 42. The main contacter will also connect a contact 57 with the supply Wire L, an-d current will llevv from said contact throughconductors 58 and 5l to the stop push button switch 52, thence through the shunt magnet 35 to theA supply wire L. The magnet 35 will therefore be energized even vai'ter the relay magnet 4o releases the switch arm 43.

By reason et the circuits thus traced, the closure o'li the start push button switch Will cause the relay switch te close a circuit through the magnet oi the main contacter, and the latter' Will immediately close the motor circuits and the magnet of the coils et the relay switchvvill be included in shunt to that portion et the starting resistance which lies between the bases 35a and the adjustable contact `member 4?. l/Vhen the current in the armature circuit falls to a predetermined value, the relay magnet releases the switch arm 43, Which is then drawn by the spring-44 into engagement With the contact 43. This completes a circuit through the shunt magnet36 or" the auxiliary contact-or c2 as follows: from the supply Wire'L.v through main contacter andcenducters 58 and to the base 49 of the relay, thence through switch arm 43 and contact 48 to conductor 59, thence through coils et magnet 36 and by conductors 60 and 54 to the supply ivire L. The magnet 36 Will cause the contactor c2 to close, thus cutting out the starting resistance and at the same time closing ay holding circuit through the magnet 36. This latter circuit extends from a contact 61,

which the main contacter engages, through conductor 62 to. the wire 59, thence through coils of magnet 36 and by conductors 60 and 54; to the supply wire L.

It will be evident that in the starter of F ig. 2, the time of closure of the auxiliary contacter, which cuts out the starting rcsistance, is controlled by the armature current, which divides between the relay magnet and a part of the starting resistance. lt will also be evident that when the circuits of the magnets 35 and 36 are made up the contactors will immediately close. These magnets may be Wound so as to retain the contactors in their closed positions, notwithstanding wide changes in the line voltage, and it will be evident that the magnets are not affected by fluctuations in armature current.

To stop the motor, it is merely necessary to open the stop push button switch 52, which interrupts the circuit through the main contactor magnet and its contacter, in opening, opens the circuit through the relay magnet and the circuit which extends through the base of said magnet to the magnet 36 of the auxiliary contractor. lence, upon opening the stop push button switch. the parts will move to the position shown in the drawing.

lhat I claim is:

l. The combination with a supply circuit, of a motor starter comprising a starting resistance, main and auxiliary contactors, magnets for closing the contactors, said magnets having circuits independent of the armature circuit of the motor, a relay comprising a switch member adapted to close the circuit of the magnet of the auxiliary contacter and a magnet having windings in parallel with part of the resistance for controlling the movement of said member, said main centactor adapted to normally hold said member close to the relay magnet and to release said member and connect the same to the supply circuit when said main contacter closes.

2. The combination with a supply circuit, ot' a motor starter comprising a starting resist-ance, main and auxiliary contactors, magnets for closing the contactors, said magnets having circuits independent of the armature circuit of' the motor, a relay comprising a magnet having windings in parallel with part of the resistance and an armature nermal'ly held in close relation to the relay magnet by said main contactor, said main contactor, in closing, adapted to release said armature, and the latter adapted to close the circuit of the magnet of the vauxiliary contactor when released by the relay magnet.

3*. The combinati-on with a supply circuit, of a motor starter comprising a starting resistance, a ser-ies of contactors, magnets for closing the contactors, said magnets having circuits independent of the armature circuit of the motor, relays associated withV the several contactors in the series except the last vIiP/53,116

one, each relay comprising a magnet having windings in parallel withpart of the start ing resistance and an armature normally held in close relation to the relay magnet by the Vcontactor with which it is associated and adapted to be released when the contacter closes, and the armature of eaca relay adapt@ ed to close the circuit of the magnet of the next contactor in the series when released by the relay magnet.

il. The combination with a supply circuit, of a motor starter con'iprising a starting resistance, a series of contactors, magnets for closing the contactors, said magnets having circuits independent of the armature circuit olf the motor, relays asseciated with the seycral contactors in the series except the last one, each relay comprising a magnet having windings in parallel with part of the starting resistance and an armature normally held in close relation to the relay magnet by the contacterv with which it is associated and adapted to be released when the contactor closes, andthe armature of the relay associated with the first contactor in the series adapted to close the circuit of the magnet ot' the next contactor in the series and also to close the circuit of the relay magnet associated with the latter contactor. v

5. The combination with a supply circuit, ct a motor starter comprising a starting resistance, main and auxiliary contactors, magnets tor closing the'contactors, said magnets having circuits independent of the armature circuit of the motor, a relay comprising a switch member normally tending to close the circuit of the magnet of the auxiliary contactor and a magnet having windings in parallel with part only of the resistance for controlling the movement of said member, said main contact-or adapted to normally bear against and hold said member in open postion and to release said member and connect the same to the supply circuit when said main contacter closes.

In testimony whereof I hereunto alix my signature. l

VILLIAM T. HOLMES.

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