Electromagnetic operator for an electrical contactor and method for controlling same

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrical contactors and similar devices for completing and interrupting electrical current-carrying paths between a source of electrical energy and a load. More particularly, the invention relates to a coil assembly and actuator for such a device which facilitates assembly and installation, and which provides improved electrical, magnetic and thermal performance during transient and steady state phases of operation.

2. Description Of The Related Art

A great variety of devices have been designed for completing and interrupting current-carrying paths between an electrical source and an electrical load. In one type of device, commonly referred to as a contactor, a set of movable contacts is displaced relative to a set of stationary contacts, so as to selectively complete a conductive path between the stationary contacts. In remote-controllable contactors of this type, an actuating assembly is provided to cause the movable contacts to shift between their open and closed positions. Such actuating assemblies typically include a coil forming an electromagnet, and a core to intensify a magnetic field generated around the coil when an actuating current is passed therethrough. The magnetic field attracts a movable armature which is coupled to the movable contacts within the device, thereby displacing the movable contacts and thus making electrical contact or closing the electrical circuit. When the actuating current is removed, biasing members return the movable assembly back to its normal position thus breaking the electrical connection or opening the electrical circuit.

Contactors of the type described above are commonly available with either alternating current or direct current actuating coil assemblies. The selection of either an alternating current assembly or a direct current assembly typically depends upon the type of electrical power available in the application. However, advantages and disadvantages are associated with each type of assembly. For example, direct current coils can be associated with simple solid core structures which do not need to minimize heating from circulating eddy currents found in alternating current coils. Also, direct current coils tend to have a higher force to power ratio because the current is steady and does not pass through zero with each half cycle as is the case with alternating current, and therefore require lower currents to obtain a desired armature pull-in or contact retaining force. Moreover, direct current assemblies do not require shading coils as are typically provided in alternating current assemblies, and therefore are quieter in operation and experience lower wear. On the other hand, alternating current power sources are very widespread and are favored in many cases due to their availability.

Coil assemblies for contactors have also been constructed with multiple coils, including coaxially aligned pickup coils and holding coils. Because a greater coil MMF is often required to close the contactor than is required during steady-state operation (i.e., after closure), both the pickup and holding coils are energized during closure, and with the pickup coil being deenergized following closure. The pickup coil is designed to have a significantly higher MMF and power than the hold coil. Turning off the pickup coil minimizes heating and reduces the power required once the armature has closed (i.e. steady state operation). Timing for deenergization of the pickup coil is typically fixed, and is set so as to provide sufficient force and time for displacement of the movable contact assembly to a closed position. However, if the time or force varies, as is sometimes the case, such arrangements may either provide insufficient or excessive periods of energization of the pickup coil. Also, such devices typically employ mechanical switches to release the pickup coil, or to switch the pickup coil in series with the holding coil following the initial closure period.

In addition to the foregoing drawbacks, where conventional coil assemblies are associated with control circuits supported on conventional circuit boards, these must often be supported by additional structures in the coil assembly or in the housing adjacent to the coil assembly. These structures add further to the cost of the device, and require additional labor for installation. Moreover, in multiple-coil actuating assemblies, care must be taken to ensure that proper polarity of the pickup and holding coils during electrical connection to the control circuit. Again, this can add to the cost of the device, and, in the event of an error in the polarity of the connections, can result in malfunction or the need to rework the assembly.

There is a need, therefore, for improved operator structures for contactors and similar electrical devices. In particular, there is a need for an actuating coil assembly in which multiple coils can be provided to reduce the power to the device during steady-state operation, but in which a pickup coil is energized for sufficient time to ensure adequate movement of the movable contact assembly. There is also a need for an improved coil structure which facilitates mounting of control circuit components and wiring of coil leads, thereby facilitating manufacturing of the overall assembly.

SUMMARY OF THE INVENTION

The invention provides a novel approach to the design of contactor actuating coil assemblies and the control of assemblies designed to respond to these needs. The technique employs a dual-coil assembly including a pickup coil and a holding coil. Both coils may be energized for actuation of the device. The pickup coil is then de-energized based upon an input signal which is derived from a sensed parameter of the energization signal, such as voltage. The pickup coil is thus energized for a sufficient time to ensure closure of the movable elements in the device. The holding coil may be powered by direct current which is produced by a rectifying circuit when the incoming power to the device is an AC wave form. The holding coil current is rapidly dissipated by control circuit upon deenergization of the main coil terminals, thereby avoiding the creation of induced currents and associated magnetic fields upon release of the device. The coil may then benefit from all of the advantages from a DC coil structure, while offering the advantage of being powered by an AC power source. The coil structure also provides a simple and convenient arrangement for supporting a control circuit board on a coil subassembly. The coil subassembly also facilitates proper wiring of the pickup and holding coils to the control circuit board. In a preferred configuration, common leads are brought from the coil assembly in a central location, thereby facilitating identification of the leads for electrical connection to a circuit board.

Thus, in accordance with a first aspect of the invention, an electromagnetic operator is provided for an electrical contactor. The operator includes a coil assembly, including a first coil and a second coil. A first switching circuit is coupled to the first coil and is configured to apply energizing current to the first coil in response to a control signal. A second switching circuit is coupled to the second coil and is configured to apply energizing current to the second coil in response to the control signal for a variable duration which is a function of a parameter of the control signal. The second switching circuit may apply the energizing current to the second coil for a duration which is based upon the voltage of the control signal. Moreover, the second switching circuit may include an analog timing circuit which interrupts power to the second coil after the variable duration.

A common support may be provided for both coils, and the coils may be wound coaxially on the support. Flanges extending from the support may serve to mechanically support the first and second switching circuits. Leads directed to the switching circuits may be channeled through guides in the support. Moreover, the coil assembly may include a magnetic base support defining a core or armature of the assembly.

In accordance with another aspect of the invention, a control circuit is provided for an electromagnetic operator. The operator includes first and second coils for generating actuating fields in response to energizing signals. The control circuit includes a first switching circuit coupled to the first coil and configured to apply a first energizing signal to the first coil. A second switching circuit is coupled to the second coil and is configured to apply a second energizing signal to the second coil for a variable duration after application of the first energizing signal to the first coil. The second switching circuit may include a timing circuit wherein the variable duration of application of the second energizing signal is determined by the configuration of the timing circuit. The first and second switching circuits may be coupled across a common direct current bus, and the first and second energizing signals may be applied by the direct current bus.

In accordance with a further aspect of the invention, a coil assembly is provided for an electromagnetic operator. The coil assembly includes a coil support having first and second annular recesses defined between upper and lower flanges, and separated from one another by a central flange. First and second lead guides are defined in the central flange. A first coil is wound in the first annular recess and has a first lead disposed in the first lead guide. A second coil is wound in the second annular recess and has a second coil disposed in the second lead guide. A control circuit board may be supported on the coil support and coupled to the leads.

In accordance with a further aspect of the invention, a method is provided for actuating an electrical contactor. A contactor includes an electromagnetic operator, a carrier displaceable under the influence of the operator, stationary contacts, and movable contacts, movable by the carrier to selectively contact the stationary contacts. In the method, an energizing signal is first applied to the first and second coils in the operator to energize the first and second coils. The energizing signal is then removed from the second coil a variable period of time after application of the energizing signal to the second coil. In a particularly preferred embodiment, the variable period of time is a function of a parameter of the energizing signal, such as voltage.

In accordance with a further aspect of the invention, a flat plate armature is utilized to provide reduced mass and lower return spring force resulting in low magnetic pickup force requirements and hence low coil power requirements. Furthermore, the armature has a thin cross section which saturates at small air gaps thereby reducing velocity and impact force upon closure. Additionally, this construction facilitates greater acceleration upon opening due to the decreased mass of the armature.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:

FIG. 1

is a perspective view of a three-phase contactor incorporating certain features of the present invention;

FIG. 2

is a perspective view of the contactor of

FIG. 1

, in which operative components of the contactor have been removed from the contactor housing to illustrate the various components and subassemblies;

FIG. 3

is an exploded perspective view of certain of the subassemblies illustrated in

FIG. 2

, including movable and stationary contact structures, a movable contact carrier assembly, and a magnetic operator coil assembly;

FIG. 4

is a perspective view of a stationary contact structure in accordance with one presently preferred embodiment, for use in a contactor subassembly of the type shown in

FIG. 3

;

FIG. 5

is a top plan view of the stationary contact structure of

FIG. 4

, illustrating the position of contact pads and other elements of the stationary contact structure;

FIG. 6

is a sectional view of the contact structure of

FIG. 5

along line

6

—

6

, illustrating current flow paths defined during operation of the stationary contact;

FIG. 7

is a perspective view of an alternative stationary contact structure for use in a contactor in accordance with the present techniques;

FIG. 8

is a top plan view of the contact structure of

FIG. 7

;

FIG. 9

is a sectional view of the stationary contact structure of

FIG. 8

, along line

9

—

9

, illustrating current flow paths defined during operation of the stationary contact structure;

FIG. 10

is a sectional view of a pair of stationary contact structures of the type shown in

FIGS. 7

,

8

and

9

, disposed as they would be in an assembled contactor;

FIG. 11

is a perspective view of a movable contact module for use in a contactor of the type shown in

FIG. 1

;

FIG. 12

is an exploded view of the movable contact module of

FIG. 11

, illustrating in greater detail the various components of the module;

FIG. 13

is a partial sectional view of a contact structure of the type shown in

FIG. 11

, along line

13

—

13

, illustrating the position of the various components as they would be installed in a contactor of the type shown in

FIG. 1

;

FIG. 14

is a transverse section of the contact module of

FIG. 11

, along line

14

—

14

, also shown in its installed position within a contactor of the type shown in

FIG. 1

;

FIG. 15

is a perspective view of an alternative configuration for modular movable contact structures positioned in a three-phase carrier assembly;

FIG. 16

is a perspective view of an alternative arrangement for stationary contact structures of the type shown in

FIG. 15

, including multiple current-carrying elements for each power phase;

FIG. 17

is a sectional view of one of the movable contact structures of

FIG. 16

, along line

17

—

17

;

FIG. 18

is a transverse section of the movable contact arrangements of

FIG. 17

;

FIG. 19

is a sectional view of the housing of

FIG. 2

, along line

19

—

19

, illustrating internal partitions dividing a contact portion of the housing from an operator portion;

FIG. 20

is a sectional view of the housing of

FIG. 2

, along line

20

—

20

, illustrating an internal partition between power phase sections of the housing;

FIG. 21

is a sectional view, along line

21

—

21

, of the housing of

FIG. 2

, illustrating the orientation of internal partitions for separating the contactor and operator structures from one another, and the power phase sections from one another;

FIG. 22

is a partially broken bottom perspective view of the housing of

FIG. 2

, illustrating internal features of the housing and side walls thereof;

FIG. 23

is a perspective view of an alternative housing configuration, including partitions for separating power phase sections from one another on an external wall of the housing;

FIG. 24

is a perspective view of a magnetic operator assembly of the type shown in

FIGS. 2 and 3

, illustrating in greater detail the components of the operator;

FIG. 25

is a sectional view of the coil assembly of the operator of

FIG. 24

, illustrating a structure for routing coil wires of the operator to a control circuit board;

FIG. 26

is a perspective view of a coil assembly and circuit board support for use in the operator of

FIG. 24

;

FIG. 27

is a diagrammatical view of the armature and base plate of the operator assembly shown in

FIG. 24

, illustrating flow of magnetic flux during energization of the operator coils; and

FIG. 28

is a diagram of an exemplary circuit for use in controlling the operator of

FIG. 24

, permitting the use of both alternating current and direct current power, and for allowing rapid and high efficiency operation of the coil assembly.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Turning now to the drawings, and referring first to

FIG. 1

, an electrical contactor

10

is illustrated in the form of a three-phase contactor for completing electrical current carrying paths for three separate phases of electrical power. Contactor

10

includes a housing

12

from which input or line terminals

14

and output or load terminals

16

extend. Contactor

10

is divided into three separate phase sections

18

, with a pair of input and output terminals being associated with each phase section. Housing

12

includes end panels

20

and side walls

22

enclosing internal components as described more fully below. Input and output terminals

14

and

16

extend from end panels

20

for connection to power supply and load circuitry. Housing

12

further includes a lower securement flange

24

having apertures

26

formed therein for securing the contactor to a support base, such as in a conventional industrial enclosure (not shown). Ribs

28

are formed on end panels

20

to aid in electrically isolating phase sections

18

from one another, as more fully described below. A cover

30

extends over an upper region of housing

12

to cover internal components of the contactor. Cover

30

is held in place by fasteners (not visible in

FIG. 1

) lodged within fastener apertures

32

of cover

30

. In the contactor illustrated in

FIG. 1

, wire lugs

36

are secured to both input and output terminals

14

and

16

for receiving and completing an electrical connection with current-carrying wires or cables of a conventional design.

FIG. 2

illustrates the housing, cover and internal operational components of the contactor of

FIG. 1

, separated for explanatory purposes. As indicated above, phase sections

18

of contactor

10

are divided within housing

12

. Internal phase partitions

38

are provided as integral members of housing

12

for physically and electrically isolating the sections from one another. Also, as described below with particular reference to

FIGS. 19 through 22

, housing

12

preferably provides internal contact partitions

40

, contiguous with phase partitions

38

, for subdividing the internal volume of housing

12

into separate regions for contact subassemblies, and a lower region for housing an operator structure. Slots

42

are formed in end panels

20

, permitting terminals

14

and

16

to extend from individual phase sections

18

lodged within housing

12

for conducting power to and from the contact assemblies.

In its various embodiments described herein, contactor

10

generally includes a series of subassemblies which cooperate to complete and interrupt current-carrying paths through the contactor. As shown in

FIG. 2

, the subassemblies include an operator assembly

44

, movable contact assemblies

46

, a carrier assembly

48

, stationary contact assemblies

50

, and splitter plate assemblies

52

. Operator assembly

44

, which is lodged in a lower region of housing

12

when assembled therein, serves to generate a controlled magnetic field for opening and closing the current-carrying paths through the contactor. The movable contact assemblies

46

are supported on carrier assembly

48

and move with carrier assembly

48

in response to the establishment and the interruption of magnetic fields generated by the operator assembly. The stationary contact assemblies

50

, each coupled to input and output terminals

14

and

16

, contact components of the movable contact assemblies

46

to establish and interrupt the current-carrying paths through the contactor. Finally, splitter plate assemblies

52

, positioned about movable contact assemblies

46

, serve to dissipate and extinguish arcs resulting from opening and closing of the contactor, and dissipate heat generated by the arcs.

The foregoing subassemblies are illustrated in an exploded perspective view in FIG.

3

. Referring more particularly to the illustrated arrangement of operator assembly

44

, in a presently preferred embodiment operator assembly

44

is capable of opening and closing the contactor by movement of carrier assembly

48

and movable contact assemblies

46

under the influence of either alternating or direct current control signals. Operator assembly

44

, thus, includes a base or mounting plate

54

on which an yoke

56

and coil assembly

58

are secured. While yoke

56

may take various forms, in a presently preferred configuration, it includes a unitary shell formed of a ferromagnetic material, such as steel, providing both mechanical support for coil assembly

58

as well as magnetic field enhancement for facilitating actuation of the contactor with reduced energy input as compared to conventional devices.

Coil assembly

58

is formed on a unitary bobbin

60

made of a molded plastic material having an upper flange

62

, a lower flange

64

, and an intermediate flange

66

. Bobbin

60

supports, between the upper, lower and intermediate flanges, a pair of electromagnetic coils, including a holding coil

68

and a pickup coil

70

. As described more fully below, a preferred configuration of coil assembly

58

facilitates winding and electrical connection of the coils in the assembly. Also as described below, in a presently preferred configuration, the holding and pickup coils may be powered with either alternating current or direct current energy, and are energized and de-energized in novel manners to reduce the energy necessary for actuation of the contactor, and to provide a fast-acting device. Coil assembly

58

also supports a control circuit

72

which provides the desired energization and de-energization functions for the holding and pickup coils.

Yoke

56

forms integral side flanges

74

which extend upwardly adjacent to coil assembly

58

to channel magnetic flux produced during energization of coils

68

and

70

during operation. Moreover, in the illustrated embodiment, a central core

76

is secured to yoke

56

and extends through the center of bobbin

60

. As will be appreciated by those skilled in the art, side flanges

74

and core

76

thus form a flux-channeling, U-shaped yoke which also serves as a mechanical support for the coil assembly, and interfaces the coil structure in a subassembly with base plate

54

. As described more fully below, operator assembly

44

may be energized and de-energized to cause movement of movable contact assemblies

46

through the intermediary of carrier assembly

48

.

As best illustrated in

FIG. 3

, biasing springs

78

are supported by spring guide posts

80

of operator assembly

44

to bias carrier assembly

48

is an upward direction. Carrier assembly

48

includes a unitary carrier piece

82

which spans operator assembly

44

when assembled in the contactor. Carrier piece

82

includes linear bearing members

84

at either end thereof Linear bearing numbers

84

contact and bear against slots formed in the contactor housing, as described in greater detail below, to maintain alignment of the carrier piece in its translational movement during actuation of the contactor. Carrier piece

82

also includes a series of mounting features

86

for receiving and supporting movable contact assemblies

46

. At a base of mounting features

86

, carrier piece

82

forms a movable armature support to which a ferromagnetic armature

90

is secured via fasteners

92

. Armature

90

serves to draw carrier assembly

48

toward operator assembly

44

during operation, thereby displacing movable contact assemblies

46

. A rubber cushion piece

88

is disposed between carrier piece

82

and armature

90

to cushion impact between the components resulting from rapid movement of the carrier assembly and armature during operation.

As discussed throughout the following description, in the presently preferred embodiments, the mass of the various movable components of the contactor is reduced as compared to conventional contactor designs of similar current and voltage ratings. In particular, a low mass movable armature

90

is preferably used to draw the carrier assembly toward the operator assembly during actuation of the device, providing increased speed of response due to the reduced inertia. Also, the use of a lighter movable armature permits the use of springs

78

which urge the carrier assembly towards a normal or biased position, of a smaller spring constant, thereby reducing the force required of the operator assembly for displacement of the carrier assembly and actuation of the device.

As illustrated in

FIG. 3

, stationary contact assemblies

50

are disposed on either side of carrier assembly

48

. A pair of such stationary contact assemblies is associated with each power phase of the contactor. Moreover, each stationary contact assembly includes a stationary contact structure

94

, preferred configurations of which are described in greater detail below. Stationary contacts

94

are coupled to input and output terminals

14

and

16

, and serve to complete current-carrying paths through the contactor upon closure with movable contact assemblies

46

.

In the present embodiment illustrated in

FIG. 3

, movable contact assemblies

46

each comprise modular assemblies which can be easily installed into the contactor, and removed from the contactor for replacement or servicing. Accordingly, a modular movable contact assembly

46

is provided for each power phase, and functions with a corresponding pair of stationary contact assemblies

50

. Each modular movable contact assembly

46

includes movable contacts

96

supported in a modular housing

98

. The preferred arrangement of movable contact assemblies

46

both facilitates assembly of the components thereof, as well as protects internal components, such as biasing members from arcing and material debris which may be released during opening and closing of the contactor. Splitter plate assemblies

52

are assembled as modular components positioned on either side of movable contact assemblies

46

. Each splitter plate assembly

52

includes a series of splitter plates

110

assembled in vertical parallel arrangement supported by lateral plate supports

102

. Above each pair of splitter plate assemblies

52

, a shunt plate

104

is provided for each power phase section. Shunt plates

104

serve to complete temporary current-carrying paths upon opening and closing of the contactor in a manner generally known in the art.

STATIONARY CONTACT ASSEMBLIES

Referring more particularly now to preferred embodiments of stationary contact assemblies

50

, a first preferred embodiment for each such assembly is illustrated in

FIGS. 4

,

5

and

6

. As shown in

FIG. 4

, each stationary contact assembly

50

includes a base component

106

integrally forming certain desired features for conducting electrical current both during steady-state operation and during transient operation (i.e., during opening and closing of the contactor). Thus, base

106

in

FIG. 4

forms a terminal attachment section

108

and a current-carrying extension

110

generally in line with terminal attachment section

108

. Current-carrying contacts

112

are disposed on an upper surface of current-carrying extension

110

for conducting current into or out of the base

106

during steady-state operation. Base

106

also forms a riser portion

114

which extends generally perpendicularly to a terminal attachment section

108

and current-carrying extension

110

. At an upper end of riser of portion

114

, a turnback

116

is formed. In the presently preferred embodiment illustrated, riser portion

114

is generally perpendicular to both a turnback portion

116

and to the current-carrying flow path defined by terminal attachment section

108

and current-carrying extension

110

. An arc guide

118

is secured to an upper face of turnback portion

116

to lead arcs which may be generated during opening and closing of the contactor in a direction toward splitter plate assemblies

52

(see FIG.

3

). Arc guide

118

extends around an arc contact

120

which also is secured to the upper face of turnback portion

116

over riser portion

114

.

As best illustrated in

FIG. 6

, the foregoing arrangement of base

106

, including terminal attachment section

108

, current-carrying extension

110

, riser

114

and turnback portion

116

, permits current-carrying paths to be defined within each stationary contact assembly

50

which provide enhanced performance as compared to conventional structures. Particularly, a generally linear current carrying path

122

is defined between terminal attachment section

108

and current-carrying contacts

112

supported on extension

110

. In

FIG. 6

, this current-carrying path is illustrated as bi-directional. However, in practice, the direction of a current flow will generally be defined by the orientation of the stationary contact in the contactor (i.e., coupled to the source or load).

During opening and closing of the contactor, a different current-carrying path is defined as illustrated by reference numeral

124

. This current-carrying path extends at an angle from path

122

. Moreover, path

124

terminates in arc contact

120

which overlies riser

114

. Thus, immediately following opening of the contactor (i.e., movement of the movable contact elements away from the stationary contacts), the steady state path

122

is interrupted, and current flows along path

124

. Arcs developed by separation of movable contact elements from the stationary arc contact

120

initially extend directly above riser

114

, and thereafter are forced to migrate onto turnback portion

116

and then onto arc guide

118

, expanding the arcs and dissipating them through the adjacent splitter plates. Any residual current flow is then channeled along the splitter plate stack to the shunt plates

104

(see, e.g.,

FIG. 3

) positioned above the splitter plates.

It has been found that this current-carrying path

122

established during transient phase of operation results in substantially reduced magnetic fields within the stationary contact opposing closing movement of the carrier assembly and movable contacts. As will be appreciated by those skilled in the art, conventional stationary contact structures, wherein steady-state or arc contacts are provided in a turnback region, or wherein contacts are provided on a bent or curved turnback/riser arrangement, magnetic fields can be developed which can significantly oppose the contact spring force and movement of the movable contact assemblies and associated armature. By virtue of the provision of riser

114

and the location of arc contact

120

substantially above the riser, thus defining path

124

, it has been found that the force, and thereby the energy, required to close the contactor is substantially reduced.

To facilitate formation of the desired features of the stationary contact assembly

50

, and particularly of base

106

, base

106

is preferably formed as an extruded component having a profile as shown in FIG.

6

. As will be appreciated by those skilled in the art, such extrusion processes facilitate the formation of terminal attachment section

108

, extension

110

, riser

114

and turnback

116

, and permit a recess

126

to be formed beneath the turnback

116

. The extrusion may be made of any suitable material, such as high-grade copper. Alternatively, casting processes may be used to form a similar base of structure. Following formation of base

106

(e.g., by cutting a desired width of material from an extruded bar), contacts

112

and

120

are bonded to base

106

. In a presently preferred arrangement, contacts

112

are made of silver or a silver alloy, while contact

120

is made of a conductive yet durable material such as a copper-tungsten alloy. Arc guide

118

is also bonded to base

106

and is made of any suitable conductive material such as steel. The resulting structure is then silver plated to cover conductive surfaces by a thin layer of silver. As best illustrated in

FIGS. 4 and 5

, prior to such assembly, apertures

128

are formed in base

106

, and apertures

130

are formed in arc guide

118

, to facilitate placement of fasteners (not shown) for securing the stationary contact assembly in this housing and for securing terminal conductors to the stationary contact assemblies during assembly of the contactor.

An alternative configuration for a stationary contact assembly in accordance with certain aspects of the present technique is illustrated in

FIGS. 7

,

8

and

9

. The arrangement of

FIGS. 7

,

8

and

9

is particularly well suited to smaller-size contactors, having lower current-carrying or power ratings. In this embodiment, each stationary contact assembly

50

includes a base

132

forming a current-carrying extension

134

designed to be secured to a terminal conductor. Accordingly, current-carrying extension

134

includes an aperture

136

for receiving a fastener (not shown) for this purpose. A turnback portion

138

is formed at least partially over a current-carrying extension

134

, and is integral with extension

134

through the intermediary of a riser

140

. Riser

140

forms an angle with extension

134

, preferably extending generally perpendicular to the extension. Directly above riser

140

, a contact

142

is provided. From the location of contact

142

, turnback portion

138

forms a descending extension

144

which curves downwardly toward current carrying extension

134

(see, e.g., FIG.

9

). A shunt plate

146

is bonded to extension

134

below extension

144

, and includes a fastener aperture

136

generally in line with the corresponding aperture of base

132

. Finally, a pair of fastener receiving recesses or bores

148

are formed in a lower face of base

132

for facilitating of mounting and alignment of the base in the contactor.

The foregoing structure of stationary contact assembly

50

offers several advantages over heretofore existing structures. For example, as in the case of both embodiments described above, a current-carrying path is defined in the assembly base which substantially reduces the force required for actuation and holding of the contactor. As shown in

FIG. 9

, this current-carrying path, designated by reference numeral

150

, extends through current-carrying extension

134

, riser

140

, and directly through contact

142

. Forces resulting from electromagnetic fields generated during opening and closing of the contactor, which attempt to oppose movement of the movable armature and movable contact structures in conventional devices or which oppose current flow through the stationary contacts, are substantially reduced by positioning of contact

142

over riser

140

.

Moreover, in the embodiment of

FIGS. 7

,

8

and

9

, the provision of a descending extension

144

on turnback

138

permits arcs to be channeled to splitter plates

100

at a substantially lower location along the stack of splitter plates than in conventional devices, as indicated by reference number

152

in FIG.

10

. As in the foregoing embodiment, arcs generated during opening and closing of the device are initially channeled generally upwardly above riser

140

. The arcs subsequently migrate along turnback

138

toward splitter plates

100

, where they are dissipated and conveyed upwardly to a shunt plate positioned above the stack.

In a presently preferred embodiment illustrated, arcs generated during opening and closing of the contactor are channeled to the fourth or fifth splitter plate from a bottom-most plate, dissipating the arcs in the lower splitter plates in the stack, adjacent to or slightly above the level of contact

142

, and forcing rapid extinction of the arcs by introduction at a lower location and into multiple plates in the stack. Also shown in

FIG. 10

, the preferred configuration for base

132

facilitates positioning of the stationary contacts in close proximity to one another, as indicated by reference numeral

154

in FIG.

10

. Those skilled in the art will recognize that this is in contact to arrangements obtainable through the use of heretofore known contact structures wherein a turnback portion was formed by bending a single piece of metallic conductor. Again, the reduction in spacing between the stationary contact structures substantially helps to reduce the force and thereby the power required to close the device and maintain it in a closed position. Also shown in

FIG. 10

, the foregoing structure facilitates mounting of the stationary contacts by means of fasteners

156

extending through apertures

136

.

As noted above with respect to the embodiment of

FIGS. 4

,

5

and

6

, the embodiment of

FIGS. 7

,

8

,

9

and

10

is preferably formed by an extrusion process, thereby facilitating formation of descending extension

144

and risers

140

. Shunt plate

146

maybe made of any suitable material, such as a steel plate. Plate

146

provides a short circuit path for flux generated during passage of current through current carrying extension

134

, thereby reducing field interaction between extension

134

and turnback portion

138

. It should also be noted that in the embodiment illustrated in

FIGS. 7

,

8

,

9

and

10

, turnback

138

is of a substantially reduced thickness as compared to current carrying extension

134

and riser

140

. Because the turnback is subjected to high transient temperatures during opening and closing of the contactor, the reduced thickness permits rapid cooling of the turnback. Similarly, the enhanced thickness of extension

132

and riser

140

aids in drawing thermal energy away from contact pad

142

. Again, the formation of the reduced thickness turnback

138

is facilitated by extrusion of base

132

.

MOVABLE CONTACT ASSEMBLIES

Presently preferred configurations for movable assemblies

46

are illustrated in

FIGS. 11-18

. In a first preferred embodiment for these structures, shown in

FIGS. 11

,

12

,

13

and

14

, the movable contact assemblies each include separate movable structures for completing current-carrying paths during transient operation of the contactor, and during steady-state operation. In particular, as shown in

FIG. 11

, an arc carrying spanner assembly

158

is provided for initially completing a contact between pairs of stationary contact assemblies for each phase section during closure of the device. Separate current carrying contact spanner assemblies

160

are provided for carrying electrical current during steady-state operation. Upon opening of the contactor, current-carrying contact spanner assemblies

160

undergo an initial movement, followed by movement of arc contact spanner assemblies

158

, thereby forcing any arcing during opening or closure of the device between the arc contact spanner assemblies

158

and corresponding structures of the stationary contact assemblies.

As best illustrated in

FIGS. 11 and 12

, each movable contact assembly

46

in this embodiment includes a housing base

162

designed to receive and to interface with a housing cover

164

. The housing base and cover enclose internal components, including central regions of arc contact spanner assembly

158

and current-carrying contact spanner assemblies

160

, these assemblies extending from the housing to face portions of the stationary contact assemblies. An interface portion

166

extends from each housing base

162

and is configured to be securely seated within a mounting feature

86

(see

FIG. 3

) of carrier piece

82

. Moreover, fasteners

168

extend through both housing base

162

and housing cover

164

, protruding from interface portion

166

to secure the assembled movable contact module to the carrier piece as described more fully below.

Housing base

162

and cover

164

are configured to support the contact spanner assemblies

158

and

160

, while allowing movement of the contact assemblies during operation. Accordingly, a lower face of housing base

162

is open, permitting current-carrying contact assemblies

162

to extend therethrough, as shown in FIG.

11

. Furthermore, recesses

170

are formed in lateral end walls of housing base

162

for receiving a lower face of arc contact spanner assembly

158

. Slots

172

are formed above recess

170

, in housing cover

164

. In the illustrated embodiment arc contact spanner assembly

158

forms a hollow spanner

174

having side walls

176

which engage slots

172

when assembled in the housing. Slots

172

engage these side walls to aid in guiding the contact spanner assembly

158

in translation upwardly and downwardly as contact is made with stationary contact pads as described below. At ends of spanner

174

, arc contact spanner assembly

158

forms arc guides

178

which extend upwardly and aid in drawing arcs toward splitter plates in the assembled device. Adjacent to arc guides

178

, spanner

174

carries a pair of contact pads

180

. Below arc contact spanner assembly

158

in housing base

162

, each current-carrying contact spanner assembly

160

includes a spanner

182

formed of a conductive metal such as copper. Each spanner terminates in a pair of contact pads

184

. Apertures

186

are formed in each spanner

182

to permit passage of fasteners

168

therethrough.

Contact spanner assemblies

158

and

160

are held in biased positions by biasing components which are shrouded from heat and debris within the contactor by the modular housing structure. As best illustrated in

FIG. 12

, a pair of compression springs

188

are provided for urging arc contact spanner assembly

158

in a downward orientation in the illustrated embodiment. Springs

188

bear against housing cover

164

, but permit vertical translation of arc contact spanner assembly

158

during operation. Another pair of biasing springs

190

are provided for each current carrying contact spanner assembly

160

. These springs also bear against housing cover

164

, and urge spanners

182

to a lower biased position. In the illustrated embodiment, springs

190

are aligned with apertures

192

formed in housing cover

164

, and fit loosely around fasteners

168

when installed in the movable contact assembly, as best shown in

FIG. 14. A

pair of threaded apertures

194

are provided in carrier piece

82

to receive fasteners

168

for securement of each movable contact assembly in the carrier. Threaded inserts may be provided at the base of each aperture for interfacing with the fasteners.

As best illustrated in

FIGS. 13 and 14

, in this embodiment, each movable contact assembly

46

is received within a corresponding mounting feature

86

of carrier piece

82

. The entire carrier assembly, including the movable contact assemblies, is biased in an upward direction by springs

78

disposed adjacent to yoke

56

in the operator portion of the contactor. To permit the arc contact spanner assemblies

158

to complete the current-carrying paths through the contactor prior to the current-carrying contact assemblies, and to interrupt the current-carrying path after movement of the current carrying contact assemblies, contact pads

180

are spaced from stationary contacts

120

by a distance as indicated by reference number

196

in FIG.

13

. The contact pads provided on spanners

182

of the current-carrying contact assemblies are spaced from stationary contacts

112

by a greater distance as indicated by reference numeral

198

. Thus, arcs produced during opening and closing of the contactor will primarily occur between contacts

180

and

120

, and will be led away from contacts

180

and

120

by the arc guiding structures of the stationary contact assemblies and by arc guides

178

of the arc contact assemblies. It should be noted that the internal components of the movable contact assemblies, particularly springs

188

and

190

, are shielded from such arcs, and from debris which may result from opening and closing of the contactor, by the housing provided around each movable contact assembly. In addition, the movable contact assemblies are independently removable and replaceable by simply removing fasteners

168

, and lifting the modular assembly from mounting feature

86

within carrier piece

82

. Thus, replacement of one or more of the assemblies, or of all or a portion of each movable contact assembly does not require disassembly of the entire contactor, or removal of the stationary contact assemblies.

A second preferred configuration for the movable contact assemblies is illustrated in

FIGS. 15

,

16

,

17

and

18

. As shown in

FIG. 15

, in this embodiment the carrier piece

82

may include a series of risers

200

which extend. A slot

202

is formed in each riser for receiving a modular movable contact assembly. Thus, at an upper end of each riser

200

, a housing

204

is formed against which the movable contact assembly bears during operation. In a presently preferred configuration, a slip or press-in-insert

206

is provided around an inner periphery of each housing

204

to facilitate insertion of the movable contact assembly and to bear against portions of the assembly during operation. A spanner

208

is provided within each housing

204

and carries a pair of contacts

210

. Adjacent to each contact pad, arc guides

212

are formed to lead arcs created during opening and closing of the contactor toward splitter plate assemblies as described above.

As in the foregoing embodiment, forces created for biasing of the movable contact assemblies illustrated in

FIGS. 15-18

are preferably compressive forces which are opposed by the modular housing structure. Accordingly, as best illustrated in

FIGS. 15

,

17

and

18

, housing

204

forms an upper wall

114

and a lower wall

116

against which such compressive forces are exerted. Above upper wall

114

of a center housing, an auxiliary switch interface

118

is formed for receiving a modular auxiliary contact structure (not shown). A spring

190

is disposed between each spanner

208

and upper wall

214

of each housing

204

. This compression spring exerts a biasing force against the spanner to urge it into contact with lower wall

116

. The springs then permit movement of the spanners within the housings to maintain adequate contact between the contact pads carried by each spanner and stationary contact assemblies of the type described above with reference to

FIGS. 7

,

8

,

9

and

10

during operation. As shown in

FIGS. 17 and 18

, projections

220

and

222

are provided on a lower face of upper wall

214

, and on spanner

208

, respectively, to aid in locating spring

190

there between, and for maintaining alignment of the spanner within the respective housing. Again, as in the case of the foregoing embodiment, springs

190

are thus shielded from arcs by the modular housing structure, and are easily installed without the need for additional tension members other than housing

204

.

As illustrated in

FIG. 16

, the foregoing arrangement may be adapted to provide a plurality of spanners and associated contact pads for each phase section of the contactor. In particular, in the embodiment of

FIG. 16

, two spanners

208

are provided within risers for each power phase section. Each riser is, in turn, divided into housings

204

supporting each individual spanner. As described above, the spanners are associated with biasing springs

190

, protected by housings

204

, for urging the spanners toward a lower or biased position. Moreover, each spanner is associated with a pair of stationary contacts

50

, for completing current-carrying paths between pairs of stationary contacts upon closure of the contactor.

As best illustrated in

FIG. 17

, in the assembled contactor, each spanner

208

is positioned above the stationary contact assemblies described with reference to

FIGS. 7-10

. Upon movement of the carrier assembly in a downward direction, contacts

210

are brought into contact with the stationary contacts, thereby completing the current-carrying path therethrough. Upon opening of the contactor, these contact pads separate from the stationary contacts, with arcs being drawn from the opening surfaces as described above.

CONTACTOR HOUSING

As mentioned above, housing

12

is configured with integral partitions to divide the areas occupied by the operator assembly and contact assemblies from one another. Presently configurations of housing

12

are illustrated in greater detail in

FIGS. 19-23

. As shown in

FIGS. 19 and 20

, housing

12

includes end panels

20

and side walls

22

extending there between. Housing

12

is preferably a unitary structure molded of a thermoplastic material with good mechanical strength, high deflection temperature and flame retardancy, such as a glass filled thermoplastic polyphthalamide (PPA) commercially available from Amoco under the designation Amodel. Due to the arc management, thermal management and power reduction afforded by the stationary and movable contact structures described above, and by the operator assembly and control technique described below, it has been found that a unitary thermoplastic housing is capable of withstanding temperatures generated during operation of the contactor. Thus, in contrast to heretofore known contactor structures, housing

12

may include contiguous side walls and partitions which effectively isolate regions of the internal volume from one another, thereby reducing the potential for discharges and transfer of plasma between the operational components of the contactor, particularly between power phases. In particular, it has been found that the unitary housing configuration made of a thermoplastic as described herein is now viable in larger contactor sizes and ratings.

As best illustrated in

FIGS. 19

,

20

and

21

, these partitions include both vertically oriented phase partitions

38

which extend in an upper part of the housing between end panels

20

. Contact partitions

40

divide the housing into upper and lower volumes. The partitions effectively define a series of upper contact compartments

224

and a lower operator compartment

226

. The contact compartments

224

are separated from one another by integral phase partitions

38

, and the contact compartments are separated from the operator compartment by contact partitions

40

. In the illustrated embodiment, contact partitions

40

form a floor-like structure which is integral with end panels

20

(see, e.g., FIGS.

19

and

20

), side walls

22

(see, e.g., FIG.

21

), and with the phase partitions

38

. Likewise, phase partitions

38

are integral with end panels

20

(see, e.g., FIG.

20

).

Housing

12

includes features for accommodating the carrier assembly described above. In particular, a series of carrier slots

228

(see

FIGS. 19 and 22

) are formed through contact partitions

40

to permit the carrier piece to extend from the operator compartment

226

to the contact compartments

224

. As noted above, the carrier piece supports a movable armature on its lower side, and movable contact assemblies on its upper extremities. A guide slot

230

is formed in each side wall

22

for guiding the carrier assembly in its translational movement. As best illustrated in

FIG. 14

, the carrier assembly includes guide extensions

232

which engage slots

230

to maintain alignment of the carrier assembly throughout its movement. As shown in

FIGS. 19 and 22

, housing

12

includes a series of lower ribs

34

integrally formed with contact partitions

40

. Ribs

234

serve to define an internal air cushioning volume in which air within the operator compartment is compressed during rapid movement of the carrier assembly. Thus, ribs

234

serve to cushion the carrier assembly as it approaches the end of its movement upwardly upon release of the operator and upward movement of the carrier.

FIG. 23

illustrates an alternative configuration for housing

12

, including the foregoing features, as well as external dividers for further isolating the phase sections of the contactor from one another. As shown in

FIG. 23

, housing

12

may be provided with a plurality of side ribs

236

extending in pairs vertically along end panels

20

, between terminal slots

42

. Each pair of side ribs

236

defines a vertical space

238

there between. Dividing panels

240

may be installed in the ribs, and each includes a longitudinal bead

242

which is slideable within a space

238

defined by the ribs. Thus, dividing panels

240

may be installed between terminals extending from slots

242

to further separate the phase sections from one another.

During operation, the foregoing housing structure contains plasmas, gases and material vapors within the individual compartments defined therein. For example, within each phase section, plasma created during opening of the contactor is restricted from flowing into neighboring phase sections by contiguous partitions

38

and

40

. The plasma is similarly restrained from flowing outwardly from the housing by partition

40

, which is contiguous with panels

20

and side walls

22

. Resistance to hot plasmas and arcs is aided during operation by splitter plate supports

102

(see, e.g., FIG.

2

), which at least partially shield portions of the housing in the vicinity of the splitter plates.

OPERATOR ASSEMBLY

FIGS. 24

,

25

and

26

illustrate presently preferred configurations for the operator assembly

44

discussed above. As mentioned above, operator assembly

44

includes a base plate

54

which serves as a support for the components of the assembly. A unitary yoke

56

is mounted to base plate

54

and a coil assembly

58

is supported thereon. Yoke

56

may be formed of a bent ferromagnetic plate, such as steel, to define side flanges

74

extending around coil assembly

58

. A core

76

is provided integral with yoke

56

to further enhance the magnetic field generated during energization of the coil assembly.

Coil assembly

58

includes a pair of coils which may be powered by either alternating current or direct current power. As described below, by virtue of the preferred control circuitry, the coils take the general configuration of DC coils independent of the type of power applied to the operator assembly. Thus, in the illustrated embodiment, a holding coil

68

is provided in a lower position on bobbin

60

, while a pick up coil

70

is provided in an upper position. Coils

68

and

70

are wound in the same direction and are co-axial with one another, such that both coils may be energized to provide a maximum pickup force, and subsequently pickup coil

70

may be de-energized to reduce the power consumption of the contactor. As described below, in a preferred embodiment, pickup

70

is de-energized following a prescribed time period which is a function of a parameter of the control signal applied to the operator assembly, such as voltage.

In the illustrated embodiment, bobbin

60

also serves to support a control circuit board

244

on which control circuit

72

is mounted. Surface components

246

defining control circuit

72

are supported on board

244

. Support extensions

248

are formed integrally with upper and lower flanges

62

and

64

of bobbin

60

, to hold board

244

in a desired position adjacent to the coils. In the illustrated embodiment, tabs

250

formed on board

244

are lodged within apertures provided in support extensions

248

to maintain the board in the desired position. As will be appreciated by those skilled in the art, leads extending from coils

68

and

70

are routed to board

244

, and interconnected with control circuitry as described more fully below. Operator terminals

252

are supported on base plate

54

, and are electrically coupled to board

44

via terminal leads

254

. In an alternative configuration illustrated in

FIG. 25

, hold down tabs

256

may be provided at diametrically opposed locations on either side of coil assembly

58

.

In both the embodiment of FIG.

24

and that of

FIG. 25

, bobbin

60

is preferably configured to facilitate the wiring of coils

68

and

70

and a connection of the coils to the control circuitry. In particular,

FIG. 26

shows a sectional view of bobbin

60

through intermediate flange

66

. As shown in

FIG. 26

, a lead groove

258

is formed in intermediate flange

66

to permit an inner end of one of the coils to be routed directly to board

244

. Thus, in manufacturing of the coil assembly, both coils may be wound about bobbin

60

, and leads routed directly outwardly from the bobbin at upper, lower and intermediate locations for connection to board

244

. Subsequently, board

244

may be installed in support extensions

248

and interconnected with terminals

252

or

254

, according to the particular embodiment desired. The provision of routing groove

258

also facilitates control of the polarity of the coils, permitting the incoming and outgoing leads of each coil to be easily identified by their relative position exiting from the bobbin.

It should be noted that alternative configurations may be envisaged for disposing the pickup and holding coils of assembly

58

. In the illustrated embodiment, these coils are disposed coaxially in separate annular grooves within bobbin

60

, and are wound electrically in parallel with one another. Alternatively, one of the coils may be wound on top of the other, such as within a single annular groove of a modified bobbin. Also, in appropriate systems, the coils may be electrically coupled in series with one another during certain phases of their operation.

As best illustrated in

FIG. 27

, the foregoing arrangement of yoke

56

and a ferromagnetic base plate

54

enhances the flow of flux within the operator during operation. In particular, when one or both of the coils of the operator are energized, lines of flux are channeled through the central core

76

of the armature, through the body of the armature, and through the side flanges

74

. Base plate

54

aids in channeling the flux between these regions of the armature, as indicated by lines F in FIG.

27

. By virtue of the combination of the armature and base plate, the primary body of the armature may be made of a constant thickness plate which is bent to form the side flanges illustrated, providing a simple and cost effective assembly.

CONTROL CIRCUIT

As mentioned above, control circuitry for commanding actuation of the contactor facilitates the use of either alternating or direct current power. Moreover, by virtue of the preferred configurations of the stationary and movable contact structures described above, it has been found that significantly lower power levels may be employed by the operator both during transient and steady-state operation. Power consumption is further reduced by the use of two separate coils, both of which are powered during initial actuation of the contactor, and only one of which is powered during steady-state operation. The pickup coil has a significantly higher MMF and power than the hold coil. A presently preferred embodiment for such control circuitry is illustrated in FIG.

28

.

As shown in

FIG. 28

, control circuit

72

includes a pair of input terminals

268

for receiving either AC or DC power. Holding coil terminals

270

, and pickup coil terminals

272

are provided for coupling to holding coil

68

and pickup coil

70

, respectively. A metal oxide varister (MOV)

274

or other transient circuit protector extends between terminals

268

to limit incoming power peaks in a manner generally known in the art.

Downstream of MOV

274

circuit

72

includes a rectifier bridge

276

for converting AC power to DC power when the device is to be actuated by such AC control signals. As mentioned above, although DC power may be applied to terminals

268

, when AC power is applied, such AC power is converted to a rectified DC waveform by bridge circuit

276

. Bridge rectifier

276

applies the DC waveform to a DC bus as defined by lines

278

and

280

in FIG.

28

. When DC power is to be used for actuating the contactor, bridge circuit

276

transmits the DC power directly to high and low sides

278

and

280

of the DC bus while maintaining proper polarity. As described in greater below, power applied to the high and low sides of the DC bus is selectively channeled through the coils coupled to terminals

270

and

272

to energize and de-energized the operator assembly. Moreover, the preferred configuration of circuit

72

permits release of pickup coil

70

following an initial actuation phase, thereby reducing the energy consumption of the operator assembly. The circuitry also facilitates rapid release of the holding coil, and interruption of any induced current that would be allowed to recirculate through the coil by the presence of rectifier circuit

276

.

As illustrated in

FIG. 28

, control circuit

72

includes a field effect transistor (FET)

282

for controlling energization of holding coil

68

. Additional components, described in greater detail below, provide for latching of FET

282

upon application of voltage to the DC bus. The circuitry also provides for rapidly interrupting a current carrying path through the FET, and hence through coil

68

upon removal of the energizing power. By virtue of the removal of this current carrying path, induced current through the coil is interrupted, permitting rapid opening of the contactor. Circuit

72

also includes an FET

294

for selectively energizing pickup coil

70

. Clamping circuitry is provided for maintaining FET

294

closed and a timing circuit is included for opening FET

294

after an initial energization phase as described below.

FET

282

is disposed in series with coil

68

between high and low sides

278

and

280

of the DC bus. In parallel with these components, a pair of 100KΩ resistors

284

and

286

are provided, as well as a 21.5KΩ at resistor

288

. In parallel with resistor

288

, a 0.22 microF capacitor

290

is coupled to low side

280

of the DC bus. The gate of FET

282

is coupled to a node point between resistors

286

and resistor

288

. A pair of Zener diodes

292

are provided in parallel with FET

282

, extending from a node point between the drain of the FET and low side

280

of the DC bus. The operation of the foregoing components is described in greater detail below.

Operative circuitry for controlling the energization of pickup coil

70

includes a pair of 43.2KΩ resistors

296

and

298

coupled in series with a diode

300

. Diode

300

is, in turn, coupled to a node point to which the drain of FET

294

is coupled. A timing circuit, represented generally by the reference numeral

302

, provides for de-energizing coil

70

after an initial engagement period. Also, a clamping circuit

304

is provided for facilitating such initial energization of the pickup coil. In the illustrated embodiment, timing circuit

302

includes a pair of 43.2KΩ resistors

306

and

308

coupled in a series with a 10 microF capacitor

310

between high and low sides

278

and

280

of the DC bus. A programmable uni-junction transistor (PUT)

312

is coupled to a node point between resistor

308

and capacitor

310

. PUT

312

is also coupled to the gate node point of FET

294

through a 511KΩ resistor

314

. Output from PUT

312

is coupled to the base of an n-p-n transistor

316

, the collector of which is coupled to the node point of the gate of FET

294

, and the emitter of which is coupled to low side

280

of the DC bus. In parallel with transistor

316

, a Zener diode

318

is provided. Finally, in parallel with FET

294

, a pair of Zener diodes

320

are coupled between coil

70

and the low side of the DC bus.

The foregoing control circuitry operates to provide initial energization of both the pickup and holding coils, dropping out the pickup coil after an initial engagement phase, and interrupting an induced current path through the holding coil upon de-energization of the circuit. In particular, upon application of power to terminals

268

, a potential difference is established between DC bus sides

278

and

280

. This potential difference causes FET

282

to be closed, and to remain closed so long as the voltage is applied to the bus. At the same time, PUT

312

serves to compare a voltage established at capacitor

310

to a reference voltage from Zener diode

318

. During an initial phase of operation, the output from PUT

310

will maintain transistor

316

in a non-conducting state, thereby closing FET

294

and energizing pickup coil

70

. However, as the voltages input to PUT

312

approach one another, as determined by the time constant established by resistors

306

and

308

in combination with capacitor

310

, transistor

316

will be switched to a conducting state, thereby causing FET

294

to turn of dropping out pickup coil

70

. Voltage spikes from the pickup coil are suppressed by Zener diodes

320

. As will be appreciated by those skilled in the art, the duration of energization of pickup coil

70

will depend upon the selection of resistors

306

and

308

, and of capacitor

310

, as well as the voltage applied to the circuit. Thus, pickup coil

70

is energized for a duration proportional to the actuation voltage applied to the control circuit.

Following the initial actuation phase of operation, holding coil

68

alone suffices to maintain the contactor in its actuated position. In particular, during the initial phase of operation, electromagnetic fields generated by both pickup coil

70

and holding coil

68

are enhanced and directed by yoke

56

to attract movable armature

90

supported on the carrier assembly (see, e.g.,

FIGS. 2

,

3

,

14

and

24

). This initial magnetic field causes the carrier assembly to be drawn towards the electromagnet, dosing the current-carrying paths established between the movable and stationary contact assemblies described above. The initial energization phase, after which pickup coil

70

is de-energized by control circuit

72

, preferably lasts a sufficient duration to permit full movement and engagement of the carrier assembly and the movable contacts. Thereafter, to reduce the energy consumption of the contactor, only holding coil

68

remains energized.

As mentioned above, so long as voltage is maintained on the DC bus of the control circuit, holding coil

68

will remain energized. Once actuation voltage is removed from the circuit, the drain of FET

282

assumes a logical low voltage, opening the current carrying path through the FET. Residual energy stored within the holding coil is dissipated through Zener diodes

292

. As will be appreciated by those skilled in the art, the removal of the current-carrying path established by FET

282

permits for rapid opening of the contactor under the influence of springs

78

,

188

and

190

(see, e.g.,

FIGS. 2

,

3

and

14

). Thus, when power is removed, magnetic lines of flux established by coil

68

begin to collapse and springs

78

begin to displace the carrier assembly within the contactor. Opening of FET

282

effectively removes the current-carrying path that would otherwise be established through bridge rectifier

276

. Such current-carrying paths can cause an increase in the coil current under the influence of induced currents during displacement of the movable armature, retarding the opening of the device. By removal of this conductive path, the electromagnet is fully released, and such induced currents are minimized, enhancing the transient response of the device.

As will be appreciated by those skilled in the art, various alternative arrangements may be envisaged for the foregoing structures of control circuit

72

. In particular, while analog circuitry is provided for de-energizing pickup coil

70

after the initial engagement phase of operation, other circuit configurations may be used to perform this function, including digital circuitry. Similarly, while in the present embodiment the period for the initial energization of pickup coil

70

is determined by an RC time constant and the voltage applied to the components defining this time constant, the time period for energization of the pickup coil could be based upon other operational parameters of the control circuitry or control signal. Moreover, while the circuitry described in presently preferred for interruption of a current-carrying path through rectifier

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, various alternative configurations may be envisaged for this function. Furthermore, the particular component values described above have been found suitable for a 120 volt contactor. Depending upon the device rating, the other components may be selected accordingly.

As will be appreciated by those skilled in the art, considerable advantages flow from the use of the dual coil operator assembly described above in connection with control circuit

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. In particular, the use of DC coils offers the significant advantages of such coil designs, eliminating vibration or buzzing typical in AC coils, the need for shading coils, and other disadvantages of conventional AC coils. Also, the use of such coils in combination with a rectifier circuit facilitates the use of a single assembly for both AC and DC powered applications creating a more universally applicable contactor. Furthermore, by providing both holding and pickup coils, and releasing the pickup coil after initial movement of the carrier assembly, energy consumption, and thereby thermal energy dissipation, is significantly reduced during steady-state operation of the contactor. Such reduction in thermal energy permits the use of such materials as thermoplastics for the construction of the contactor housing. Moreover, by interrupting a current path between holding coil

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and rectifier

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upon release of the contactor, opening times for the contactor are significantly reduced.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. For example, those skilled in the art will readily recognize that the foregoing innovations may be incorporated into switching devices of various types and configurations. Similarly, certain of the present teachings may be used in single-phase devices as well as multi-phase devices, and in devices having different numbers of poles, including, for example, 4 and 5 pole contactors.

Number	Name	Date	Kind
3761730	Wright	Sep 1973
5303012	Hortlacher et al.	Apr 1994

Electromagnetic operator for an electrical contactor and method for controlling same

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