US2883487A

US2883487A - Electromagnetic device

Info

Publication number: US2883487A
Application number: US637384A
Authority: US
Inventors: Charles W Spaulding; Robert A Pelz
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-01-31
Filing date: 1957-01-31
Publication date: 1959-04-21
Anticipated expiration: 1976-04-21

Description

ober% ATTORNEY 2 Sheets-Sheet 1 ELECTROMAGNETIC DEVICE c. w SPAULDING ET AL April 21, 1959 Filed Jan. 51, 1957 v w Lg INVENTORS Charles W.Spcu'|ding 8 I WITNESSES: U 25% A ril 21, 1959 c.-w. SPAULDING ET AL 3,

ELECTROMAGNETIC DEVICE I Filed Jan. 31, 1957 2 Sheets-Sheet 2 Fig.2.

United States Patent Q ELECTROMAGNETIC DEVICE Charles W. Spaulding and Robert A. Pelz, Beaver, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 31, 1957, Serial No. 637,384

7 Claims. (Cl. 200-87) Our invention relates, generally, to electromagnetic devices and, more particularly, to electromagnetic relays,

and contactors which are utilized as motor starters.

Heretofore, motor starters have been so constructed that the contact members of a starter are opened as a result of a drop in the line voltage. In the interest of safety it is the usual practice to connect a motor starter for non-automatic or manual reclosing. Therefore, when a starter drops open, power to the machine or machines controlled by the starter is interrupted until the starter is reclosed manually. In some cases, the reclosing of starters is the duty of people other than the machine op erators, which results in a considerable loss of productron.

An object of our invention is to provide a means for holding an electromagnetic device closed during momentary dips in the control voltage.

Another object of our invention is to provide a low voltage holding attachment for an electromagnetic device which may be readily installed on the device when desired.

A further object of our invention is to provide for adjusting the dropout voltage of an electromagnetic contactor or relay.

Other objects of our invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of our invention, a permanent magnet, which is clamped between two pole pieces, is mounted on the stationary base for the arc box of an electromagnetic contactor or starting relay for a motor. An armature for the magnet is attached to the cross bar or member of the starter which carries the movable contact members of the starter. When the contact members are closed, the armature is brought into contact with the pole pieces of the permanent magnet. The additional holding force provided by the permanent magnet causes the main contact members to remain closed at a relatively low voltage on the operating coil of the starter, thereby preventing the motor controlled by the starter from being disconnected during momentary dips in the line voltage. The dropout voltage may be adjusted by means of shunting screws which vary the reluctance of the magnetic path of the permanent magnet.

For a better understanding of the nature and objects of the invention, reference may behad to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a view, in side elevation, of an electromagnetic contactor embodying the principal features of the invention;

Fig. 2 is a view, in section, of a portion of the contactor shown in Fig. 1;

Fig. 3 is a view partly in plan and partly in section, showing the permanent magnet mounted on the contactor;

Fig. 4 is a view, in elevation, of the base for the permanent magnet;

2,883,487 I a-tented Apr. 21, 1959 Fig. 5 is a view, in elevation, of the permanent magnet, and

Fig. 6 is a view, in elevation, of one of the pole pieces for the permanent magnet.

Referring to the drawings and particularly to Figs. 1 and 2, the motor starter or contactor shown therein is of the electromagnetic type and comprises an electromagnet 10, an armature 11, a contact carrier or cross bar 12, an arc box 13, an insulating base 14, and a sheet metal pan or base 15. The pan 15 may be mounted on any suitable supporting structure such as a switchboard panel or it may be mounted in an enclosing cabinet. The electromagnet 10 is mounted on a base 16 which is attached to the pan 15 by means of

brackets

17 and 18.

A coil 19, which may be energized from a suitable power source of a predetermined voltage, is provided for the electromagnet 10. The armature 11 is pivotally mounted on the bracket 18 which functions as a bearing member for the armature 11. A kickout spring 21 biases the armature 11 to the open position when the coil 19 is deenergized. When the coil is energized, the armature 11 is actuated to the closed position, thereby causing a bridging contact member 22, which is carried by the cross bar or carrier 12, to engage

stationary contact members

23 and 24. As shown more clearly in Fig. 2, the stationary contact member 23 is attached to a terminal member 25. The stationary contact member 24 is attached to a terminal member 26. The

terminal members

25 and 26 are mounted on the insulating base 14 which is attached to the supporting pan 15.

As shown in Fig. 2, the bridging contact member 22 is mounted in a yoke or saddle 27 which is attached to the cross bar or carrier 12. A spring 28 is mounted in the saddle 27 to maintain a predetermined contact pressure between the bridging contact member 22 and the

stationary contact members

23 and 24 when the contact members are closed. The cross bar 12 is preferably composed of insulating material. Likewise, the arc box 13 is composed of an insulating material. As shown, the arc box 13 may be provided with a plurality of spaced metal plates 29 which assist in a manner well known in the art in interrupting the are drawn between the contact members when opened.

As explained hereinbefore, the contact members of a contactor or motor starter of the type previously constructed have been opened during momentary dips in the voltage of the power source which energizes the coil 19. Heretofore the contact members have been opened when the control voltage is reduced to approximately 50% of the normal rated voltage. As also explained hereinbefore, it is customary to so connect motor starters that they must be reclosed manually after having been opened by a reduction in voltage. This is done for safety reasons in order to protect personnel who are Working around the apparatus driven by the motors controlled by the motor starters. The time required to reclose the starters results in a needless loss in production in case the dip in voltage is of a short duration which would not affect the operation of the motors.

In order to prevent the starter from being opened by a momentary dip in the operating voltage, we have provided a holding attachment for retaining the contact members of the starter closed at a still lower momentary reduction in the applied voltage. As shown in Figs. 1 and 3, a permanent magnet assembly 31 is attached to the base 14 at one side of the arc box 13. An armature 32 is attached to an extension 33 on the carrier 12. The magnet assembly 31 comprises a permanent magnet 34 which is clamped between two pole pieces 35 by means of screws 36. The pole pieces 35 may be soldered or otherwise secured to a base 37. The base 37 is attached 3 to the insulating base 14 of the contactor by means of screws 33. The pole pieces 35 are composed of a magnetic material and the base 37 is preferably composed of a non-magnetic material.

As shown more clearly in Fig. 1, the armature 32 is of a .i-shape. The short leg of the J is attached tothe extension 33 of the cross bar 12 by means of screws 39. Thus, the armature 32 is of a spring-like construction and the long leg of the armature may deflect slightly when it is actuated into engagement with the pole pieces 35 of the magnet assembly 31. In this manner, the armature 32 does not interfere with the closing of the main contact members of the starter by the operation of the cross bar 12 which is attached to the armature 11 of the electromagnet 10. When the armature 32 engages the polepieces 35 the added force provided by the attraction of the armature, 32 to the permanent magnet assembly 31 enables the main contact members. of the starter to remain closed during momentary dips in the operating voltage.

In order to provide for adjusting the voltage at which the contacts of the starter will open, part or all of the screws 36 may be composed of magnetic material. By making the screws magnetic and then removing or replacing part of them with non-magnetic screws the re luctance of the magnetic path of the. permanent magnet may be varied, thereby providing for adjustment of the dropout voltage. The utilization of a holding attachment of the present type enables the dropout voltage to be reduced to zero if desired. As previously explained, the

dropout voltage may be adjusted by means of the shunting screws 36 which function as a magnetic bridge between the magnetic pole pieces 35 of the magnet assembly. The number of the screws which are of magnetic material may be varied to adjust the dropout voltage to approximately any value between zero and the dropout voltage that would be normal Without permanent magnet attachment.

From the foregoing description, it is apparent that we have provided a relatively simple and inexpensive attachment for electromagnetic contactors and motor starters which provides a means for holding the electro-magnetic device closed during momentary. dips in the operating voltage, thereby avoiding costly and unnecessary interruptions in the operation of the machines driven by the motors controlled by motor starters. The holding device is so constructed that it may be readily attached to an electromagnetic contactor when the contactor is manufactured or after it is installed in service.

Since numerous changes may be made in the above described constructon and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the foregoing description or shown in the ac-- companying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In an electromagnetic device, in combination, a base, a stationary contact member supported by the base, a movable contact member for engaging the stationary contact member, a carrier for the movable contact member, an electromagnet having an armature for actuating the carrier to close said contact members to conduct current therethrough, a permanent magnet mounted on the base, an armature for the permanent magnet, said armature being separate from the armature for the electro magnet and actuated by said carrier to a position. in which the attraction of the permanent magnet for its armature assists the electromagnet in holding-the contact members closed. after they have been closed. by the electromagnet, and said permanent magnet functioning independently of the current flowinglthrough said contact members.

2. In an electromagnetic device, in combination, a

4 base, a stationary contact member supported by the base, a movable contact member for engaging the stationary contact member, an arc box attached to said base and substantially enclosing said contact members, a carrier for the movable contact member, an electromagnet having an armature for actuating the carrier to close said contact members to conduct current therethrough, a permanent magnet mounted on the base externally of said arc box, an armature for the permanent magnet, said armature being separate from the armature for the electromagnet and attached to the carrier and actuated by said carrier to a position in which the attraction of the permanent magnet for its armature assists the electromagnet in holding the contact members closed after they have been closed by the electromagnet, and said permanent magnet being disposed to function independently of the current flowing through said contact members.

3. In an electromagnetic device, in combination, a base, a stationary contact member supported by'the base, a movable contact member for engaging the stationary contact member, a carrier for the movable contact memher, an electromagnet having an armature for actuating the carrier to close said contact members to conduct current therethrough, a permanent magnet mounted on the base, a spring type armature for the permanent magnet, said armature being separate from the armature for the electromagnet and actuated by saidcarrier to engage the permanent magnet whereby the attraction of the permanent magnet for its armature assists the electromagnet in holding the contact members closed after they have been closed by the electromagnet, and said permanent magnet being disposed to function independently of the current flowing through said contactmembers.

4. In an electromagnetic device, in combination, a base, a stationary contact member supported by the base, a movable contact member for engaging the stationary contact member, a carrier for the movable contact member, an electromagnet having a magnetic circuit and an armature for actuating the carrier to close said contact members to conduct current therethrough, a permanent magnet disposed between two spaced pole pieces mounted on the base, said pole pieces'providing a magnetic circuit separate from the magnetic circuit. for the electromagnet, a spring: type armature for the permanent magnet, said armature for the permanent magnet being actuated. by said carrier to engage-the pole pieces whereby the attraction of the permanentimagnetfor the armature assists the electromagnet in holding the contact members closed after they have been closed by the electromagnet, and said. permanent magnet being disposed to function independently of they current flowing. through said contact members.

5. In an electromagnetic device, in. combination, a base, a stationary contact member supported by the base, a movable contact member for engaging the stationary contact member, a carrier for the movable contact memher, an electromagnet having a. magnetic circuit and an armature for actuating. the carrier to close said contact members, a permanent magnet disposed between two spaced-pole pieces mounted on the base, said pole pieces providinga magnetic circuit separate from the magnetic circuit for the electromagnet, a spring type armature for the permanent magnet, said armature, for the permanent magnet being actuated by said carrier to engage the pole pieces whereby the attraction of the permanent magnet for the armatureassists the electromagnet in holdingthe contact members closed after they have been closed by the electromagnet, and magnetic material; means bridging said pole pieces to adjust the attraction of the permanent magnet for said armature.

6. In an electromagnetic device, in combination, a base, a stationary contact member supported by the base, a movable contact member for engaging th tionary contact member, a carrier for the movable contact member, an electromagnet having a magnetic circuit and an armature for actuating the carrier to close said contact members, a permanent magnet disposed between two spaced pole pieces mounted on the base, said pole pieces providing a magnetic circuit separate from the magnetic circuit for the electromagnet, a spring type armature for the permanent magnet, said armature for the permanent magnet being actuated by said carrier to engage the pole pieces whereby the attraction of the permanent magnet for the armature assists the electromagnet in holding the contact members closed after they have been closed by the electromagnet, and screws for clamping the pole pieces against the permanent magnet, the number of said screws being variable to vary the reluctance of the magnetic path of the magnet thereby adjusting the attractive force on the armature.

7. In an electromagnetic device, in combination, an insulating base, a stationary contact member supported by the base, a movable contact member for engaging the stationary contact member, a carrier for the movable contact member, an electromagnet having a magnetic circuit and an armature for actuating the carrier to close said contact members when the electromagnet is energized by a predetermined voltage, a permanent magnet .6 disposed between two spaced pole pieces mounted on the base, said pole pieces providing a magnetic circuit separate from the magnetic circuit for the electromagnet, a J-shaped armature for the permanent magnet, the short leg of the J-shaped armature being attached to said carrier and the long leg of the armature being actuated into engagement with said pole pieces when the contact members are closed, whereby the permanent magnet assists the electromagnet in holding the contact members closed during momentary dips in the voltage on the electromagnet.

References Cited in the file of this patent UNITED STATES PATENTS 1,298,746 Lum Apr. 1, 1919 1,918,232 Baker et a1. July 11, 1933 2,432,899 lmrnel Dec. 16, 1947 2,467,720 Austin Apr. 19, 1949 2,539,547 Mossman et a1 Jail. 30, 1951 2,542,835 Pierce Feb. 20, 1951 2,550,110 Ellis Apr. 24, 1951 2,594,088 Sonnemann et al. Apr. 22, 1952 2,679,561 Thompson May 25, 1954