Electromagnetic contactor with algorithm controlled closing system

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CROSS REFERENCE TO RELATED APPLICATIONS

The inventions taught herein are related to concurrently filed commonly assigned copending applications as follows:

Application Ser. No. 016,425 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH ENERGY BALANCED CLOSING SYSTEM" (W. E. Case 53,124) by J. A. Bauer.

Application Ser. No. 016,423 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH CURRENT REGULATED ELECTROMAGNETIC COIL FOR HOLDING THE CONTACTS CLOSED" (W. E. Case 53,662) by G. F. Saletta et al.

Application Ser. No. 016,419 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH CONTROL CIRCUIT FOR PROVIDING ACCELERATION, COAST AND GRAB FUNCTIONS" (W. E. Case 53,125) by J. A. Bauer.

Application Ser. No. 016,426 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH DISCRIMINATOR FOR DETERMINING WHEN AN INPUT CONTROL SIGNAL IS TRUE OR FALSE AND METHOD" (W. E. Case 53,663) by J. C. Engel.

Application Ser. No. 016,422 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH LIGHTWEIGHT WIDE RANGE CURRENT TRANSDUCER" (W. E. Case 53,126) by J. A. Bauer.

Application Ser. No. 016,420 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH LIGHTWEIGHT WIDE RANGE CURRENT TRANSDUCER WITH SINTERED POWDERED METAL CORE" (W. E. Case 53,664) by J. C. Engel.

Application Ser. No. 016,424 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH UNIVERSAL CONTROL" (W. E. Case 53,665) by J. C. Engel.

Application Ser. No. 016,421 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH WIDE RANGE OVERLOAD CURRENT RELAY BOARD UTILIZING LEFT SHIFTING AND METHOD" (W. E. Case 53,666) by G. F. Saletta et al.

Application Ser. No. 016,417 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH CIRCUIT BOARD SUPPORT SYSTEM" (W. E. Case 53,702) by D. W. Cole and G. E. Pruitt II.

Application Ser. No. 016,415 filed concurrently herewith entitled "ELECTROMAGNETIC CONTACTOR WITH REDUCED NOISE MAGNETIC ARMATURE" (W. E. Case 53,703) by R. A. Hurley and B. L. DeVault.

Application Ser. No. 725,179 entitled "ANALOG SIGNAL PROCESSING CIRCUIT", filed Apr. 19, 1985 by J. C. Engel.

Application Ser. No. 725,050 entitled "A SUPERVISORY CIRCUIT FOR A PROGRAMMED PROCESSING UNIT," filed Apr. 19, 1985 by J. C. Engel.

Application Ser. No. 868,834 (W. E. Case 53,378) entitled "MASTER METERING MODULE WITH VOLTAGE SELECTOR" by D. P. Orange, J. C. Engel, G. F. Saletta, D. A. Mueller and R. T. Elms.

Application Ser. No. 868,833 (W. E. Case 53,061) entitled "MASTER METERING MODULE WITH DIGITAL SATURATION ADJUSTER AND METHOD FOR USE THEREOF" by D. P. Orange, J. C. Engel, G. F. Saletta and D. A. Mueller.

Application Ser. No. 868,832 (W. E. Case 53,364) entitled "PROCESS FOR MANUFACTURING ELECTRICAL EQUIPMENT UTILIZING PRINTED CIRCUIT BOARDS" by S. L. Glover.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject matter of this invention is related generally to electromagnetic contactors and more specifically to apparatus for controlling an electromagnetic contactor.

2. Description of the Prior Art

Electromagnetic contactors are well known in the art. A typical example may be found in U.S. Pat. No. 3,339,161 issued Aug. 29, 1967 to J. P. Conner et al. entitled "Electromagnetic Contactor" and assigned to the assignee of the present invention. Electromagnetic contactors are switch devices which are especially useful in motor-starting, lighting, switching and similar applications. A motor-starting contactor with an overload relay system is called a motor controller. A contactor usually has a magnetic circuit which includes a fixed magnet and a movable magnet or armature with an air gap therebetween when the contactor is opened. An electromagnetic coil is controllable upon command to interact with a source of voltage which may be interconnected with the main contacts of the contactor for electromagnetically accelerating the armature towards the fixed magnet, thus reducing the air gap. Disposed on the armature is a set of bridging contacts, the complements of which are fixedly disposed within the contactor case for being engaged thereby as the magnetic circuit is energized and the armature is moved. The load and voltage source therefor are usually interconnected with the fixed contacts and become interconnected with each other as the bridging contacts make with the fixed contacts. Generally, as the armature is accelerated towards the magnet, it must overcome two spring forces. The first spring force is provided by a kickout spring which is subsequently utilized to disengage the contacts by moving the armature in the opposite direction when the power applied to the coil has been removed. This occurs as the contacts are opened. The other spring force is provided by a contact spring which begins to compress as the bridging contacts abut the fixed contacts, but while the armature continues to move towards the fixed magnet as the air gap is reduced to zero. The force of the contact spring determines the amount of electrical current which can be carried by the closed contacts, and furthermore determines how much contact wear is tolerable as repeated operation of the contactor occurs. It is usually desirous for the contact spring to be as forceful as possible, thus increasing the current-carrying capability of the contactor and increasing the capability to adapt for contact wear. However, since this force must be overcome by the energy provided to the electromagnet during the closing operation, more closing energy will generally be required for relatively stiffer contact springs than for less stiff contact springs. Many electromagnets in contactors are powered by alternating current. However, no teaching has been found in the prior art for controlling the alternating current in a logical way to obtain predictable results. It would be desirable to control the alternating current in such a manner.

SUMMARY OF THE INVENTION

In accordance with the invention an electrical contactor or controller is taught which includes a first contact means and a second contact means for being moved into disposition of electrical continuity with the first contact means. An electromagnet means with a movable armature means is provided which is mechanically interlocked with the second contact means for moving that second contact means into the disposition of electrical continuity with the first contact means in response to the algorithm controlled flow of electrical current through a winding of the electromagnet means by way of a controlled voltage pulse the voltage amplitude of which is free to vary within limits. Spring means are provided for resisting the movement of the armature means. In one embodiment of the invention a microprocessor implements the algorithm.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be had to the preferred embodiments thereof, shown in the accompanying drawings in which:

FIG. 1 shows an isometric view of an electromagnetic contactor embodying teachings of the present invention;

FIG. 2 shows a cutaway elevation of the contactor of FIG. 1 at section II--II thereof;

FIG. 3 shows force and armature velocity curves for a prior art contactor with electromagnetic armature accelerating coil, kickout spring and contact spring;

FIG. 4 shows a set of curves similar to those shown in FIG. 3 but for one embodiment of the present invention;

FIG. 5 shows a set of curves similar to those shown in FIG. 3 and FIG. 4 but for another embodiment of the invention;

FIG. 6 shows still another set of curves for the apparatus of FIGS. 4 and 5 for voltage and current waveshapes;

FIGS. 7A through 7D show a schematic circuit diagram partially in block diagram form for an electrical control system for the contactor of FIGS. 1 and 2;

FIG. 8 shows a plan view of a printed circuit board which includes the circuit elements of FIG. 7 as well as the contactor coil, current transducers and voltage transformers of FIG. 2;

FIG. 9 shows an elevation of the circuit board of FIG. 8;

FIG. 10 shows the circuit board of FIGS. 8 and 9 in isometric view in a disposition for mounting in the contactor of FIG. 2;

FIG. 11 shows a circuit diagram and wiring schematic partially in block diagram form for the contactor of FIGS. 2 and 7 as utilized in conjunction with a motor controlled thereby;

FIG. 12 shows a schematic arrangement of a current-to-voltage transducer for utilization in an embodiment of the present invention;

FIG. 13 shows a schematic arrangement of the transformer of FIG. 12 with an integrator circuit;

FIG. 14 shows a plot of air gap length versus the voltage-to-current ratio for the transducer arrangements of FIGS. 12 and 13;

FIG. 15 shows an embodiment of a current-to-voltage transducer utilizing a magnetic shim;

FIG. 16 shows an embodiment of a current-to-voltage transducer using an adjustable protrusion member;

FIG. 17 shows an embodiment of a current-to-voltage transducer utilizing a movable core portion;

FIG. 18 shows an embodiment of a current-to-voltage transducer utilizing a powdered metal core;

FIG. 19 shows an algorithm, READSWITCHES, in block diagram form for utilization by a microprocessor for reading switches and discharging capacitors for the input circuitry of the coil control board of FIG. 7;

FIG. 20 shows an algorithm, READVOLTS, in block diagram form for reading line voltage for the coil control board of FIG. 7;

FIG. 21 shows an algorithm, CHOLD, in block diagram form for reading the coil current for the coil control circuit of FIG. 7;

FIG. 22 shows an alogithm, RANGE, in block diagram form for reading line current as determined by the overload relay board of FIG. 7;

FIG. 23 shows a schematic representation of an A-to-D converter and storage locations associated with determining line current as found in the microprocessor of the coil control board of the present invention;

FIG. 24 shows an algorithm, FIRE TRIAC, in block diagram form for utilization by a microprocessor for firing the coil controlling triac for the coil control board of FIG. 7;

FIG. 25A shows a plot of the derivatives of the line current shown in FIG. 25A;

FIG. 25B shows a plot of one-half per unit, a one per unit and a two per unit sinusoidal representation of a line current for the apparatus controlled by the present invention;

FIG. 25C shows a plot of resultant analog-to-digital converter input voltage versus half-cycle sampling intervals (time) for three examples of line current magnitude of FIG. 25A;

FIG. 26 shows a representation of the binary numbers stored in storage locations in the microprocessor of FIG. 23 for Example 1 of an analog-to-digital conversion for six sampling times in the RANGE sampling routine of FIG. 22 for the one-half per unit line cycle;

FIG. 27 shows a representation of the binary numbers stored in storage locations in the microprocessor of FIG. 23 for Example 2 of an analog-to-digital conversion for six sampling times in the RANGE sampling routine of FIG. 22 for the one per unit line cycle;

FIG. 28 shows a representation of the binary numbers stored in storage locations in the microprocessor of FIG. 23 for Example 3 of an analog-to-digital conversion for six sampling times in the RANGE sampling routine of FIG. 22 for the two per unit line cycle;

FIG. 29 shows plots of VLINE, VRUN(T), and VRUN(F) at the input of the microprocessor;

FIG. 30 shows a plan view of a printed circuit board similar to that shown in FIGS. 8 and 9 for utilization in another embodiment of the invention;

FIG. 31 shows a cutaway elevation of a contactor similar to that shown in FIGS. 1 and 2 for another embodiment of the invention; and

FIG. 32 shows a sectional view of the contactor of FIG. 31 along the section lines XXXII--XXXII.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a three phase electrical contactor or controller 10 is shown. For the purpose of simplicity of illustration the construction features of only one of the three poles will be described it being understood that the other two poles are the same. Contactor 10 comprises a housing 12 made of suitable electrical insulating material such as glass/nylon composition upon which are disposed electrical load terminals 14 and 16 for interconnection with an electrical apparatus, a circuit or a system to be serviced or controlled by the contactor 10. Such a system is shown schematically in FIG. 11, for example. Terminals 14 and 16 may each form part of a set of three phase electrical terminals as mentioned previously. Terminals 14 and 16 are spaced apart and interconnected internally with conductors 20 and 24, respectively, which extend into the central region of the housing 12. There, conductors 20 and 24 are terminated by appropriate fixed contacts 22 and 26, respectively. Interconnection of contacts 22 and 26 will establish circuit continuity between terminals 14 and 16 and render the contactor 10 effective for conducting electrical current therethrough. A separately manufactured coil control board 28 (as shown hereinafter in FIGS. 8, 9 and 10) may be securely disposed within housing 12 in a manner to be described hereinafter. Disposed on the coil control board 28 is a coil or solenoid assembly 30 which may include an electrical coil or solenoid 31 disposed as part thereof. Spaced away from the coil control board 28 and forming one end of the coil assembly 30 is a spring seat 32 upon which is securely disposed one end of a kickout spring 34. The other end of the kickout spring 32 resides against portion 12A of base 12 until movement of carrier 42 in a manner to be described hereinafter causes bottom portion 42A thereof to pick up spring 34 and compress it against seat 32. This occurs in a plane outside of the plane of FIG. 2. Spring 34 encircles armature 40. It is picked up by bottom portion 42A where they intersect. The dimension of member 42 into the plane of FIG. 2 is larger than the diameter of the spring 34. A fixed magnet or slug of magnetizable material 36 is strategically disposed within a channel 38 radially aligned with the solenoid or coil 31 of the coil assembly 30. Axially displaced from the fixed magnet 36 and disposed in the same channel 38 is a magnetic armature or magnetic flux conductive member 40 which is longtiduinally (axially) movable in the channel 38 relative to the fixed magnet 36. At the end of the armature 40 and spaced away from the fixed magnet 36 is the longitudinally extending electrically insulating contact carrier 42 upon which is disposed an electrically conducting contact bridge 44. On one radial arm of contact bridge 44 is disposed a contact 46, and on another radial arm of contact bridge 44 is disposed a contact 48. Of course, it is to be remembered that the contacts are in triplicate for a 3 pole contactor. Contact 46 abuts contact 22 (22-46), and contact 48 abuts contact 26 (26-48) when a circuit is internally completed between the terminal 14 and terminal 16 as the contactor 10 closes. On the other hand, when the contact 22 is spaced apart from the contact 46 and the contact 26 is spaced apart from contact 48, the internal circuit between the terminals 14 and 16 is open. The open circuit position is shown in FIG. 2. There is provided an arc box 50 which is disposed to enclose the contact bridge 44 and the terminals 22, 26, 46 and 48, to thus provide a partially enclosed volume in which electrical current flowing internally between the terminals 14 and 16 may be interrupted safely. There is provided centrally in the arc box 50 a recess 52 into which the crossbar 54 of the carrier 42 is disposed and constrained from moving transversely (radially) as shown in FIG. 2, but is free to move or slide longitudinally (axially) of the center line 38A of the aforementioned channel 38. Contact bridge 44 is maintained in carrier 42 with the help of a contact spring 56. The contact spring 56 compresses to allow continued movement of the carrier 42 towards slug 36 even after the contacts 22-46 and 26-48 have abutted or "made". Further compression of contact spring 56 greatly increases the pressure on the closed contacts 42-46 and 26-48 to increase the current-carrying capability of the internal circuit between the terminals 14 and 16 and to provide an automatic adjustment feature for allowing the contacts to attain an abutted or "made" position even after significant contact wear has occurred. The longitudinal region between the magnet 36 and the movable armature 40 comprises an air gap 58 in which magnetic flux exists when the coil 31 is electrically energized.

Externally accessible terminals on a terminal block J1 may be disposed upon the coil control board 28 for interconnection with the coil or solenoid 31, among other things, by way of printed circuit paths or other conductors on the control board 28. Another terminal block JX (shown in FIG. 32) may also be disposed on printed circuit board 28 for other useful purposes. Electrical energization of the coil or solenoid 31 by electrical power provided at the externally accessible terminals on terminal block J1 and in response to a contact closing signal available at externally accessible terminal block J1 for example, generates a magnetic flux path through fixed magnet or slug 36, the air gap 58 and the armature 40. As is well known, such a condition causes the armature 40 to longitudinally move within the channel 38 in an attempt to shorten or eliminate the air gap 58 and to eventually abut magnet or slug 36. This movement is in opposition to, or is resisted by, the force of compression of the kickout spring 34 in initial stages of movement and is further resisted by the force of compression of the contact spring 56 after the contacts 22- 46 and 26-48 have abutted at a later portion of the movement stroke of the armature 40.

There may also be provided within the housing 12 of the contactor 10 an overload relay printed circuit board or card 60 (also shown in FIGS. 8, 9 and 10) upon which are disposed current-to-voltage transducers or transformers 62 (only one of which 62B is shown in FIG. 2). In those embodiments of the invention in which the overload relay board 60 is utilized, the conductor 24 may extend through the toroidal opening 62T of the current-to-voltage transformer or transducer 62B so that current flowing in the conductor 24 is sensed by the current-to-voltage transformer or transducer 62B. The information thus sensed is utilized advantageously in a manner to be described hereinafter for providing useful circuit information for the contactor 10.

There may be also provided at one end of the overload relay board 60, selector switches 64, which may be accessible from a region external of the housing 12. Another embodiment of the invention is depicted on FIG. 30 and FIG. 31 the description of which and operation of which will be provided hereinafter.

Referring now to FIG. 2 and FIG. 3, four superimposed curves are shown for the purpose of depicting the state or the art prior to the present invention. In particular, plots of force versus distance for a magnetic solenoid such as 31 in FIG. 2, a kickout spring such as 34 shown in FIG. 2, and a contact spring such as 56 shown in FIG. 2, are depicted. In addition, a superimposed plot 92 of instantaneous velocity versus distance is depicted for an armature such as 40 shown in FIG. 2. Although the independent variable in each case is distance, it could just as well be time as the two variables are closely related for the curves shown in FIG. 3. It is to be understood that the reference to component parts of the contactor 10 of FIG. 2 is made for the purpose of simplifying the illustration; it is not to be presumed that the elements shown in FIG. 2, when taken together as a whole, are covered by the prior art. There is shown a first curve 70 which depicts force versus distance (time could be utilized) for a kickout spring (such as 34) as the spring is compressed starting at point 72. The spring 34 offers initial force 74. The spring 34 gradually resists compression with greater and greater force until point 78 is reached on the distance axis. The area enclosed by the lines interconnecting point 72, point 74, the curve 70, point 76, point 78 and point 72 once again represents the total amount of energy that is necessary to compress a kickout spring by the movement of the armature 40 as it is accelerated to close the air gap 58 between it and the fixed magnet 36. This force resists the movement of the armature 40. At point 80 on the distance axis, the contacts 22-42 and 26-48, for example of FIG. 2, abut, and continued movement of the armature 40 causes compression of the contact spring 56 which operates to place increasing force on the now abutted contacts for reasons described previously. Curve 79 represents the total force which the moving armature 40 works against as it is accelerated to close the air gap 58. A step function increase in force between point 81 and point 82 occurs as the contacts 22-42 and 26-48 touch. This force grows increasingly larger until at point 78 the moving armature 40 experiences the maximum force applied by the combination of the kickout spring 34 and contact spring 56. That amount of additional energy which the moving armature must supply to overcome the resistance of the contact spring 56 is represented by the area enclosed by the lines which interconnect the points 81 and 82, curve 79, points 84 and 76, curve 76A and point 81 once again. Consequently, as the armature 40 is accelerated from its position of rest at 72 to its position of abutment against the magnet 36 at 78 the coil or solenoid 31 must supply at least the amount of energy represented by the lines which connect the points 72, 74, 81, 82, 84, 78 and 72 once again. The positive slope of curve 70 is purposely kept as small as possible consistent with allowing the armature 40 to be driven in the reverse direction when the coil energy is removed so that the contactor may reopen. The initial force required to be overcome by the armature 40 in its first instant of movement is the threshold value of force represented by the difference between the points 72 and 74. Consequently, the armature must supply at least that much force at that instant of time. For purposes of simplicity of illustration, therefore, in an illustrative sense, it will be presumed that the electromagnetic coil 31 provides the force represented at point 88 in FIG. 3 for the armature 40 at 72. It is also necessary that the amount of force provided by the coil or solenoid 31 at the instant that the contacts 22-42 and 26-48 touch and the contact spring 56 is engaged at 80 be greater than the amount of force represented by the distance between the points 80 and 82 in FIG. 3, otherwise, the accelerating armature 40 will stalll in midstroke, thus providing a very weak abutment of contacts 22-46 and 26-48. This is an undesirable situation as the tendency for the contacts to weld shunt is greatly increased under this condition. Consequently, the force supplied by the coil 31 in accelerating the armature 40 must be greater at point 80 than the force represented at poing 82. A magnetic pull curve for solenoids and their associated movable armatures follows relatively predictable configurations which are a function of many things including the weight of the armature, the strength of the magnetic field, the size of the air gap, etc. Such a curve is shown at 86 in FIG. 3. With the relative shape of the curve 86 and the previous conditions of constraint associated with the value of the force required of the coil 31 at points 72 and 80 on the distance axis of FIG. 3, the entire profile for the magnet pull curve for the armature 40 and coil 31 of FIG. 2 is fixed. It ends with a force value 90. It is to be understood that it is a characteristic of magnetic pull curves that the magnetic force increases appreciably as the air gap 58 narrows as the moving armature 40 approaches the stationary magnet 36. Consequently, at point 78, the force 90 exists. It is at this point that the armature 40 first abuts or touches the fixed magnet 36. This unfortunately creates two undesirable situations: First, it can be easily seen that the total energy supplied to the magnetic system by way of the coil 31, as represented by the lines which interconnect the points 72, 88, curve 86, points 90, 78 and point 72 once again, is significantly greater than the amount of energy needed to overcome the various spring resistances. The difference in energy is represented by the area enclosed by the lines which connect the points 74, 88, curve 86, points 90, 84, 82, 81 and 74 once again. This energy is wasted or unnecessary energy, and it would be very desirable not to have to produce this energy. The second undesirable characteristic or situation is the fact that the armature 80 is accelerating at its maximum and producing its most force of kinetic energy at the instant immediately before it makes abutting contact with the permanent magnet 36. A velocity curve 92 which starts at point 72 and ends at point 94 as shown in FIG. 3, represent the velocity of the armature 40 as it accelerates along its axial motion path. Note the change in shape at 80 as the kickout spring 34 is engaged. At the time immediately before the armature 40 touches the permanent magnet 36, the velocity V1 is maximum. This has the very undesirable characteristic of transferring high kinetic energy due to high velocity at the instant of impact or abutment between the armature 40 and the permanent magnet 36. This energy must be instantaneously dissipated or absorbed by other elements of the system. Typically, the reduction of the armature velocity to zero instantaneously at 78 requires the energy to be instantaneously reduced. This kinetic energy is converted to the sound of abutment, to heat, "bounce", to vibration, and mechanical wear, among other things. If the armature 40 bounces, since it is loosely interconnected with the contacts 46-48 on the contact bridge 44 by way of the contact spring 56, there is a high likelihood that the mechanical system represented thereby will oscillate or vibrate in such a manner that the contact arrangements 22-42 and 26-48 will rapidly and repeatedly make and break. This is a very undesirable characteristic in an electrical circuit. It would therefore be desirable to utilize the contactor 10 of FIG. 2 in such a manner that the energy which is supplied to the coil 31 is carefully monitored and chosen so that only the exact amount of energy (or an energy value close to that amount) which is necessary to overcome the resistance of the kickout spring 34 and the contact spring 56 is provided. Furthermore, it would be desirable if the velocity of the moving armature 40 is significantly reduced as the armature abuts against the permanent magnet 36 so that the likelihood of "bounce" is correspondingly reduced. The solution of the aforementioned problems is accomplished by the present invention as shown graphically in FIGS. 4, 5 and 6, for example.

Referring now to FIG. 2, FIG. 3 and FIG. 4, a series of curves similar to those shown in FIG. 3 is depicted in FIG. 4 for the present invention. In this case, the spring force curves 70 and 79 for the kickout spring 34 and contact spring 56 respectively are the same as those shown in FIG. 3. However, the energy represented by the contact spring and kickout spring are designated X and Y respectively. In this embodiment of the invention, the magnet pull curve 86' representing the force applied by the coil 31 starts at point or force level 95 in order to overcome the kickout spring threshold force as described previously and continues on to point or force level 97 which occurs at distance 96. It will be noted that the electrical energy supplied to the armature 40 by the coil 31 ceases at distance 96 corresponding to force level 97. This occurs before the armature 40 has completed its movement to the position of abutment with fixed magnet 36. It will be noted at this time that the maximum velocity V.sub.m attained by the armature 40 is indicated at point 98 on the velocity curve 92'. This is the maximum velocity that the armature will attain during its movement to the position of abutment with the magnet 36. Said in another way, this means that once the electrical energy has been removed from the coil 31, the armature will cease accelerating and begin to decelerate. The deceleration curve is shown at 100 in FIG. 4 and it ranges from point 98 to point 78 with a slope change where the kickout spring is engaged. This is accomplished by prematurely interrupting the flow of electrical energy to the coil 31 at the time distance 96 is achieved. Prior to the armature 40 completing its movement to the position of abutment with fixed magnet 36, only that amount of energy necessary to overcome the spring forces need be applied, thus providing for an energy-efficient system. At the time the electrical energy is removed from the solenoid 31, the energy necessary to complete the movement of the armature to its resting position of abutment with magnet 26, is represented by the area enclosed by the lines interconnecting the points 96, 99, curve 70, points 81, 82, curve 79, points 84, 78 and 96 once again. This energy is supplied during that portion of time that electrical energy is being supplied to the armature coil 31 which is represented by the area Z (not necessarily to scale) enclosed by the lines interconnecting the points 74, 95, curve 86', points 97, 99 and point 74 once again. The latter-mentioned energy balance is chosen in some convenient way which may include empirical analysis in which the energy levels are determined experimentally. The energy represented by area Z' is utilized to compress the kickout spring 34 during initial movement of the armature and is not available for utilization later in the travel stroke. As will be described hereinafter, a microprocessor may be utilized to determine the amount of energy to be supplied. The continued motion of the armature 40 during the deceleration phase depicted by curve 100 is a function of the kinetic energy level E attained by the armature 40 at point 96 as the electrical energy is removed from coil 31. This energy E is equal to one-half the mass (M) of the armature times the velocity (V.sub.m) it achieves at point 98 squared. In a perfectly energy-balanced system, the decelerating armature 40 strikes the permanent magnet 36 with zero velocity at 78, thus eliminating bounce and the need to absorb excessive energy in the form of noise, wear, heat, etc. It is to be understood, of course, that the attainment of the ideal as shown in FIG. 4 is difficult and is, in fact, not necessary for a highly efficient system to be nevertheless produced. Consequently, FIG. 4 should be viewed as depicting an ideal system which is provided to illustrate the teachings of the present invention. It may become very difficult to have the armature 40 impact the permanent magnet 36 with exactly zero velocity at 78. A small residual veocity is tolerable, especially when compared with the velocity 94 which is attained in the prior system as shown in FIG. 3.

Referring now to FIG. 2, FIG. 4 and FIG. 5, a collection of curves similar to that shown in FIG. 4, is depicted for a system in which the contact spring 56 is stiffer and thus offers more force against which the moving armature 40 must work. In addition to the foregoing, other illustrative features are depicted; for example, the electrical power is applied to the coil for a longer period of time, thus allowing the velocity of the moving armature 40 to attain a higher value. The higher value of velocity is necessary because increased kinetic energy is necessary to overcome the increased spring force of the contact spring 56. With regard to the comparison of FIGS. 4 and 5, like reference symbols represent like points on the curves of the two figures. In the embodiment of the invention of FIG. 5, the total energy necessary to compress the kickout and contact springs 34 and 56, respectively, is increased by an amount U represented by the area enclosed by the curves or lines connecting the points 82, 102, curve 79', points 104, 84, curve 79 and point 82 once again. The remaining area, i.e., the area enclosed by the lines interconnecting the points 72, 74, curve 70, points 81, 82, curve 79, points 84, 78, and 72 once again, is the same as that shown in FIG. 4. In order to provide the increased energy U, a different magnet pull curve 86" is generated. This magnetic pull curve has a slightly higher average slope and continues for a time period represented by the distance difference between point 96 and point 100 thus generating an incremental increase in energy U. The new magnetic pull curve 86" starts at point 95, which may the same as that shown in FIG. 4, and ends at point 97' at time represented by distance 100. This in turn generates a steeper and longer velocity curve 92" for the moving armature 40. The peak velocity V.sub.2 is attained at point 98' on velocity curve 92". At this time, the kinetic energy (E.sub.2) of the armature 40 is equal to one-half MV.sub.2 squared. The instantaneous velocity then decreases, following curve 100' with a definite breakpoint at velocity V.sub.1. This breakpoint represents the armature initially abutting against the contact spring 56. A portion of the increased velocity V.sub.2 and thus increased energy E.sub.2 is quickly absorbed by the previously described increase in energy provided by the stiffened or more resistive contact spring such that the curve 100' theoretically reaches zero at the point 78 which corresponds to the moving armature 40 abutting the fixed magnet 36.

Referring now to FIGS. 2, 4 and 6, voltage and current curves for the coil 31 and their relationship to force curves of FIG. 4 are shown and described. In a preferred embodiment of the invention, the coil current and voltage are controlled in a manner described with respect to the embodiment of FIG. 7 in a four-stage operation: (1) the ACCELERATION stage, for accelerating the armature 40, (2) the COAST stage, for adjusting the speed of the armature later in the armature movement operation prior to abutment of the armature 40 with the fixed magnetic 36, (3) the GRAB stage, for sealing of the armature 40 against the fixed magnet 36 near or immediately after abutment to dampen oscillation or bounce, if any, and (4) the HOLD stage, for armature hold-in. Reference may be had to Table 1 to help understand the foregoing and that which follows. Information from cable 1 is disposed as a menu in memory in a microprocessor as will be described hereinafter. Electrical energy is supplied to the coil or solenoid 31 at a time 72' which is related to point 72 on the distance axis of FIG. 4 and ending at a time 96' which is related to point 96 on the distance axis of FIG. 4 for the ACCELERATION stage. The energy represented by areas Z and Z' in FIG. 4 is provided by judicious choice of the electrical voltage across the terminals of coil 31 and the electrical current flowing therethrough.

TABLE 1 __________________________________________________________________________ CLOSING PROFILE ACCELERATION COAST GRAB HOLD Percent Percent Percent Percent Conduction Conduction Conduction Conduction Control of TRIAC Q1 of TRIAC Q1 of TRIAC of TRIAC Q1 Voltage Number of Pulses FOR Number of Pulses FOR Number of Pulses FOR FOR 106 of .beta..sub.1, .beta..sub.2 of .beta..sub.3 of .beta..sub.4, .beta..sub.5, .beta..sub.7, .beta..sub.8 . . . etc (VOLTS) Coil Current 108 (%) Coil Current 108 (%) Coil Current 108 (%) (%) __________________________________________________________________________ Below 78 None -- None --