US1331063A - hastings - Google Patents

Description

H. C. HASTINGS.

ELECTROMAGNETIC SWITCH.

APPLICATION FILED .IULYE, I919. I

Patented Feb. 17,1920.

2 SHEETS-SHEET 1 FISDDJ.

Inventor- Hammond C. Hastin H. c. HASTINGS. ELECTROMAGNETIC SWITCH,

APPLICAT ON FILED JULYB, I919. 1,331,063, Patented Feb. 17,1920.

2 SHEETS-SHEET 2.

D K B C 25 370/51)? and Com ensat/n 60/76.

urren I y P y inventor:

Hammond 0. Hastings,

His Att orney.

UNITED STATES PATENT OFFICE.

HAMMOND CHARLES HASTINGS, OF RUGBY, ENGLAND, ASSIGNOR TO GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK,

' ELECTROMAGNETIC SWITCH.

To all whom it may concern:

Be it knownthat I, HAMMoNn CHARLES HA TINGS, a subject of Great Britain, residi the starting, of electric motors,- it has been the practice to employ a plurality of lelectroma'g'netic 's witches, which close successively to'cut out sections of resistance from the motorcircuitand bringthe motor up to speed... Various means have been devised for controlling the operation of the switches so that they will only close when the current is at a proper value, that is, afterla switch has operated to cut out a section of resistance the next switch will not operate until the current has dropped to a safe value due to'the speeding up ofthe motor. a

A form of switch which hasfrequently been proposed for this purpose is one in which a shunt coil closesthe switch and a: series coil, instead of controlling theI-circuit of the shunt coil, positively prevents the switch from closing by actually holding it open,.that is, the shunt coil pulls against the series, or holding-out coil. The diiiiculty with this type ofswitch is that the value of current in the holding-out winding at which the switch will close depends upon the pull ofthe shunt coil, which of course will vary with the voltage and also with the temperature of the coil. In other words, the-setting of the switch, z. e.. the motor current value at which it closes. changes with change of voltage' It also closes at one value of current in the series coil when the shunt coil is cold and another when it is at its operating temperature which is ordinarily about degrees C.

The object .of the present invention is to obtain a lock-out magnet h'avinu a shunt closing coil and series lock-out coil in which the balance between the closing and holding open forces will not be aiiected by the varia- Specification of Letters Patent.

Application filed July 8, 1919. Serial No. 309,300.

will be free from the disadvantages inherent to the use of a common magnetic circuit for the series lock-out coil flux .and the look-out component of the shunt coil flux.

Referring to the drawings, Figure 1 'is a plan view of a contactor embodying my inout magnet having coil 16 and core 17 and a compensating magnet having shunt coil 18 and core 19. Coil 18 is connected in series with the shunt closing'coil l0, and isused for neutralizing the etlectof the variations in pull of the shunt closing magnet. The magnetic circuits of the three magnets are independent of each other. The lever 13 which forms the armature for the closing coil is shown having a projection 15 which forms the armature forthe magnets 16 and 18, but three separate armatures could be 'used, provided that they were rigidly fixed together. 7

p In Fig. 1 the contactor is shown in .the

.open position, the lever 13 resting against the stop 20 which is made otnon-magnetic material. .26 is a base of insulating mate rial, 23 and 24: contacts for carrying the main current, and 25 spring for producing wiping action between the contacts in a manner well known in the art. It will be seen that the pulls due to the compensating magnet 18 and lock-out magnet 16, are both opposed to the closing magnet 10. Theonly forces acting on the moving arm oi. the contactor when in the-open position are those due to gravity, lock-out magnet and compensating magnet tending to lock open. and the force due to the shunt coil 10 tending to c ose the contractor. No springs are used. The compensating andvlock-out magnets are both fitted with adjustable air gaps, so that the magnetic circuit of either can be altered without affecting the magnetic circuit of the shunt closing coil. The compensating magnet circuit is adjusted in the first place to give the necessarv compensating eflect-bv means of the adjustable iron cap 22. which is then permanently locked in position [on the core 19. As the coil 18 of this magnet is eerie rit -tee an eee ea a l 0 the same changes in current, due to heating and voltage variation, occur in both coils. The magnet circuit of 18 is proportioned so that any change in the pull of theclosing magnet is balanced by a corresponding change of the pull due to 18, over the workingsrafigeof the contacto'r. The cap 22 enables small adjustments to be made to compensate for variations in manufacture; The adjustableiron cap 21 of the series lock-out magnet is'used for adjusting the reluctance I .of the magnetic pathof this magnet, so that 'the lever l5'wfll be released and contactor sa'ting.magnet, assuming that this operates .at .the same leverage as the closing coil.

Both are. showrron the same sideof the 1101i- .zo'ntaLa-Xis, although one is opposed to the jother. --.OB'=cur rei'1t corresponding to maxi- .mum line volts when, coil is cold.- OD:CUI' rent corresponding to minimum line volts ,lwhen .coil is 'atits maximum temperature.

AGzchange in the pull of the closing coil due .to maximum variation in temperature and line volts. AEIQlOSlIli force opposed to gravity and the series 100 -out coi when shunt .coilcjurrent is OB. CF::closing force opposed to gravity and the series lockeout coil when shunt coil current is OD.

If forall'p oints such as K between D and B the corresponding closing .iorce HJ opposed to 'ravity and the-series-lock-out coil 1s sucht at HJzAEzCF exact compensation isproduced and the resultant closing Iforce opposed to gravity and the series lockout coil will be-constant for all variations of current in the closing coil for the working range 'of the contactor. This is the result which is required sothat when the lockout magnet is set to release at a particular valueof the'current, it will do, so, although the current in the closingecoil may have any value between OD and OB.

The advantages of my contactor over A thosejpreviou'sly devised will be readily understood from the following :-If the magnetic circuit of the lock-out magnet were not independent of the magnetic circuit of the closing-coil, the release current adjustment could not be made as described above, as altering the reluctance of the series lock-out magnet would at the same time affect the closin circuit and would therefore not produce thedesired efi'ect. If as an alternative the adjustmentis not madeby altering the magnetic path, but by altering the tension of a spring applied so as to oppose the force of the lock-out 'ni'agnet the "arrangement being such that the lock-out magnet has to attract its armature to it through an air gap'there is a possibility of the contactor closing while the current in the series coil is higher than the desired value. The reason for this is that with such an arrangement a higherivalue of current is required in the series coil to attract the armature through the air gap, than to retain it in a position closer to the coil. For the same reason, such an arrangement cannot be set so that a miniinumlock-out value of the current is as close to the corresponding maximum value of the series current at which the contactor will close, as the contactor we have described in which the armature of the lock-out magnet when in the open position is brought by gravi ty to the positlon where it is retained v by thelock-out magnet.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to v represent thebest embodimentthereo f, but

'I desire tohave it understood that the apparatus shown is only illustrative and that I the invention can be carried out by other posing magnet drops to a predetermined value.

out typehaving a shunt wound closing magnet, a series lockout magnet the flux path of which is independent of that of the closing magnet, and a shunt wound compensating magnet the coil of which is in series with the closing coil and the pull of which assists the look-out magnet, so that variations in pull of the closing magnet due to voltage and temperature variations are balanced by corresponding variations in the pull of the compensating magnet. 1

.3. An electromagnetic switch having a single movable pivoted switch lever, a shunt wound closing magnet for actuating the switch, a series lock-out magnet and a shunt wound compensating magnet the coil of which is in series with the closing coil and the'pull of which assists the-lock-out magnet, the flux paths of the series lock-out magnet and the shuntavound compensating magnet being independent of other 2. An electromagnetic switch of the lockand inde' pendent of that of the closing magnet, whereby variations in the closing force due to variations in the current in the shunt wound closing magnet are balanced by corresponding variations in the pull of the compensating magnet so that the switch will be actuated when the current in the opposing magnet drops to a predetermined value.

4. An electromagnet switch having a single movable pivoted switch lever, a shunt wound closing magnet on one side of the fulcrum of said lever, a series lock-out magnet and a shunt wound compensating magnet the coil of which is in series with the closing coil and the pull of which assists the lock-out magnet, on the other side of the fulcrum of said lever, the flux paths of the series lockout magnet and the shunt wound compensating magnet being independent of each other and independent of that of the closing magnet, whereby variations in the closing force due to variations in the current in the shunt Wound closing magnet are balanced by corresponding variations in the pull of the compensating magnet so that the switch will be actuated when the current in the opposing magnet drops to a predetermined value.

In witness whereof, I have hereunto set my hand this 13th day of June 1919.

HAMMOND CHARLES HASTINGS.

Witnesses:

JOHN HALFORD, DOROTHY WHITE.

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