Integrated precharge contactor

Abstract

Embodiments in accordance with the present disclosure are directed to apparatuses, systems, and methods for an integrated precharge contactor. A particular embodiment is directed to an integrated precharge contactor assembly that includes a plurality of stationary main contacts, a plurality of stationary auxiliary contacts, and a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact. The integrated precharge contactor assembly also includes an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of stationary main contacts and the plurality of stationary auxiliary contacts.

Description

INTEGRATED PRECHARGE CONTACTORBACKGROUND

[0001] Electromechanical switching devices, such as contactors and relays, are designed to carry a certain amount of electrical current for certain periods of time. Such devices are particularly important in electric vehicles. Typically, electric vehicles include one or more high voltage batteries connected, via a main contactor, to a vehicle power distribution system for powering an electric motor. The main contactor is typically an electromechanical switch that opens or closes high current paths between the battery packs and the vehicle power distribution system. To facilitate switching in a high voltage system, a precharge circuit is used to charge an output capacitor to the battery voltage before connecting the high voltage system to the high voltage battery pack.SUMMARY

[0002] Embodiments in accordance with the present disclosure are directed to apparatuses, systems, and methods for operating an integrated precharge contactor. In some examples, an integrated precharge contactor integrates precharge relay functionality into the main contactor by combining a precharge contactor and a main contactor with an intermittent auxiliary switch. This eliminates the need for separate switching components for the precharge and main contactors and also reduces component count and complexity. The integrated precharge contactor reduces the space consumed by the main contactor and precharge contactor through integration in the same assembly and further reduces the connections and control logic by utilizing the same coil connection for both the main contactor and the precharge contactor.

[0003] A particular embodiment is directed to an integrated precharge contactor assembly that includes a plurality of stationary main contacts, a plurality of stationary auxiliary’ contacts, and a moveable contact assembly that includes a moveable main contact and a moveable auxiliary' contact. The integrated precharge contactor assembly also includes an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of stationary main contacts and the plurality of stationary auxiliary contacts.

[0004] Another embodiment is directed to an integrated precharge contactor system including a high voltage battery', a capacitive circuit, a precharge circuit configured to charge the capacitive circuit, a main circuit coupled to the high voltage battery and the capacitive circuit in parallel with the precharge circuit, and an integrated precharge contactor coupled to theprecharge circuit and the main circuit, where the integrated precharge contactor implements a first switch for the precharge circuit and a second switch for the main circuit.

[0005] Yet another embodiment is directed to a method of operating an integrated precharge contactor that includes coupling the integrated precharge contactor to a precharge circuit and a main circuit. The method also includes applying a first voltage to a magnetic coil of the integrated precharge contactor, where the integrated precharge contactor closes the precharge circuit in response to the first voltage. The method also includes applying a second voltage to the magnetic coil of the integrated precharge contactor, where the integrated precharge contactor closes the main circuit in response to the second voltage.

[0006] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 shows a side view of an example integrated precharge contactor assembly in accordance with at least one embodiment of the present disclosure.

[0008] FIG. 2 shows an isometric top view of the example integrated precharge contactor assembly of FIG. 1.

[0009] FIG. 3 shows an isometric bottom view of the example integrated precharge contactor assembly of FIG. 1.

[0010] FIG. 4 is a block diagram of an example integrated precharge contactor system in accordance with at least one embodiment of the present disclosure.

[0011] FIG. 5 sets forth a flow chart of an example method of operating an integrated precharge contactor assembly in accordance with at least one embodiment of the present disclosure.DETAILED DESCRIPTION

[0012] The terminology7used herein for the purpose of describing particular examples is not intended to be limiting for further examples. Whenever a singular form such as ’’a". “an” and “the” is used and using only a single element is neither explicitly or implicitly defined as being mandatory, further examples may also use plural elements to implement the same functionality. Likewise, when a functionality is subsequently described as being implemented using multiple elements, further examples may implement the same functionality using a single element or processing entity. It will be further understood that the terms “comprises”, “comprising”, ’‘includes” and / or “including”, when used, specify thepresence of the stated features, integers, steps, operations, processes, acts, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, processes, acts, elements, components and / or any group thereof.

[0013] It will be understood that when an element is referred to as being ‘‘connected” or “coupled” to another element, the elements may be directly connected or coupled via one or more intervening elements. If two elements A and B are combined using an “or”, this is to be understood to disclose all possible combinations, i.e., only A. only B. as well as A and B. An alternative wording for the same combinations is “at least one of A and B”. The same applies for combinations of more than two elements.

[0014] Accordingly, while further examples are capable of various modifications and alternative forms, some particular examples thereof are shown in the figures and will subsequently be described in detail. However, this detailed description does not limit further examples to the particular forms described. Further examples may cover all modifications, equivalents, and alternatives falling within the scope of the disclosure. Like numbers refer to like or similar elements throughout the description of the figures, which may be implemented identically or in modified form when compared to one another while providing for the same or a similar functionality.

[0015] A methodology7for precharge is to charge a DC link capacitor via a separate circuit typically comprised of a resistor and a discrete precharge relay. Alternative approaches are bidirectional DC-DC converters to convert the low voltage from the system’s auxiliary battery to high voltage to charge the DC link capacitor, or active precharge which is similar to the aforementioned approach with discrete componentry but utilizes an inductor rather than a resistor. The need to precharge the DC link capacitor before closing the main contactor drives additional components and connections when using conventional or active precharge and drives implementation cost when carried out in the form of a bidirectional DC-DC converter.

[0016] Embodiments in accordance with the present disclosure provide an integrated precharge contactor in which a set of auxiliary contacts support the functionality of a precharge contactor in the same assembly as the main contactor. The auxiliary contacts on the integrated precharge contactor are intermittently connected at a specific voltage to provide the same function as a discrete precharge relay. The precharge contactor and the main contactor are controlled by the same coil circuit and the precharge is performed through the auxiliary contacts. By combining the precharge relay into the main contactor, the function of a conventional precharge contactor is achieved while minimizing the size of thecomponents by combining the main contactor and precharge function into one component. This further minimizes connections and control logic by utilizing the same coil connection as the main contactor.

[0017] Exemplary methods and apparatuses for an integrated precharge contactor in accordance with the present disclosure are described with reference to the accompanying drawings, beginning with FIG. 1. For further explanation, FIG. 1 sets forth a side view of an example integrated precharge contactor assembly 100 in accordance with at least one embodiment of the present disclosure. FIG. 2 show s an isometric top view of the example integrated precharge contactor assembly 100 of FIG. 1. FIG. 3 show s an isometric bottom view of the example integrated precharge contactor assembly 100 of FIG. 1. In FIGS. 1-3. certain elements of the example integrated precharge contactor assembly 100 are omitted for clarity, including the housing, internal support structures, and actuating solenoid or magnetic coil. The arrangement of these features will be understood by those of ordinary skill in the art.

[0018] The example integrated precharge contactor assembly 100 of FIGS. 1-3 includes a pair of stationary main contacts 102. 104 respectively coupled to or integrated with a pair of main terminals 103, 105 that are supported by a housing portion 110. The example integrated precharge contactor assembly 100 further includes a moveable contact assembly 190 coupled to an actuator shaft 118 and supported by a spring 116. The moveable contact assembly 190 includes a moveable main contact 106.

[0019] When an actuating solenoid (not shown) is energized, the actuator shaft 1 18 is driven upward by magnetic flux thus moving the moveable main contact into contact with the stationary main contacts 102, 104, thereby closing a main contactor circuit. When the actuating solenoid (not shown) is deenergized, the moveable contact 106 is pulled out of contact with the stationary main contacts 102, 104 by the spring 116, thereby opening the main contactor circuit.

[0020] The example integrated precharge contactor assembly 100 of FIGS. 1-3 also includes a pair of stationary auxiliary contacts 114. 115 respectively coupled to or integrated with a pair of stationary auxiliary terminals 1 12, 113 by a housing portion 110. The stationary auxiliary terminals may be connected to a precharge circuit (not shown) that includes a DC link capacitor. In the example integrated precharge contactor assembly 100, the moveable contact assembly further includes a moveable auxiliary contact 107 coupled to the actuator shaft 118 and / or the moveable main contact 106. When an actuating solenoid (not shown) is energized, the actuator shaft 118 is driven upward by magnetic flux thus moving themoveable auxiliary contact 107 into contact with the stationary auxiliary contacts 114, 115, thereby closing a precharge contactor circuit. When the actuating solenoid (not shown) is deenergized, the moveable auxiliary contact 107 is pulled out of contact with the stationary auxiliary contacts 114, 115 by the spring 116, thereby opening the precharge contactor circuit. Thus, as the auxiliary7moveable contact is mounted above the moveable main contact, the auxiliary contacts are closed before and without closing the main contacts.

[0021] As will be explained further below, a controller may be configured to control the integrated precharge contactor 100 by controlling a voltage applied to the actuating solenoid surrounding the actuator shaft 118. Changing the voltage of the solenoid may change the position of the actuation shaft and the position of the moveable contact assembly relative to the stationary7contacts. In a particular embodiment, the actuator shaft is configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of stationary main contacts and the plurality of stationary auxiliary contacts. In the pre-charge position, the moveable auxiliary contact is in contact with the plurality of stationary auxiliary contacts and the moveable main contact is separated from the plurality of stationary main contacts. In the closed position, the moveable auxiliary contact is in contact with the plurality of stationary auxiliary contacts and the moveable main contact is in contact with the plurality of stationary7main contacts. In the open position, the moveable auxiliary contact is separated from the plurality of stationary auxiliary contacts and the moveable main contact is separated from with the plurality of stationary main contacts. In a particular embodiment, the moveable contact assembly may move sequentially from the open position to a precharge position to the closed position.

[0022] For further explanation, FIG. 4 depicts a block diagram of an example integrated precharge contactor system 400 in accordance with at least one embodiment of the present disclosure. The integrated precharge contactor system 400 includes an integrated precharge contactor 402 (e.g., comprising the integrated precharge contactor assembly 100 of FIGS. 1- 3), a main circuit 404, a precharge circuit 406, and a controller 408. In the example system 400 of FIG. 4, a power source (battery 410) is coupled to a set of contacts of the actuating solenoid of the integrated precharge contactor. The controller 408 controls a voltage / current applied by the pow er source to the actuating solenoid of the integrated precharge contactor 402. When a first voltage / current level is applied, the actuator assembly in the integrated precharge contactor 402 moves the moveable auxiliary contact into contact with the stationary auxiliary contacts, thus closing the precharge circuit 406. When a second voltage / current level that is higher than the first voltage / current level is applied, the actuatorassembly in the integrated precharge contactor 402 moves the moveable main contact into contact with the stationary main contacts, thus closing the main circuit 404. Accordingly, the same controller 408 controls both the precharge contactor and the main contactor of the integrated precharge contactor 402 through power that is applied to the integrated precharge contactor 402. As such, the auxiliary contacts of the integrated precharge contactor 402 maybe intermittently connected at a specific voltage, which serv es the same function as a discrete precharge relay, thus facilitating a precharge of the DC hnk capacitor before closing the main contactor.

[0023] In an implementation, the example integrated precharge contactor system 400 of FIG. 4 includes a high voltage battery 410 and a capacitive circuit (not shown), and the precharge circuit 406 is configured to charge the capacitive circuit. The main circuit 404 is coupled to the high voltage battery 410 and the capacitive circuit in parallel with the precharge circuit 406. The integrated precharge contactor 402 is coupled to the precharge circuit 406 and the main circuit 404 such that the integrated precharge contactor implements a first switch for the precharge circuit 406 and a second switch for the main circuit 404. For example, the integrated precharge contactor system 400 may be implemented with a high voltage battery of an electric vehicle.

[0024] For further explanation, FIG. 5 sets forth a flow chart of an example method of operating an integrated precharge contactor system in accordance with at least one embodiment of the present disclosure. The method includes coupling 502 the integrated precharge contactor to a precharge circuit and a main circuit. For example, the precharge circuit may be used to precharge a capacitive circuit that is connected in parallel with a main circuit of a high voltage battery-. The integrated precharge contactor may implement a first switch for the precharge circuit and a second switch for the main circuit.

[0025] The method of FIG. 5 also includes applying 504 a first voltage to a magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the precharge circuit in response to the first voltage. In some examples, applying 504 the first voltage causes an actuator of the integrated precharge contactor to move a moveable auxiliary contact into contact with a pair of stationary auxiliary contacts to close the precharge circuit. The first voltage causes the magnetic coil to apply a first amount of magnetic flux to drive an actuator shaft into a first position that closes the precharge circuit.

[0026] The method of FIG. 5 also includes applying 506 a second voltage to the magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the main circuit in response to the second voltage. In some examples, applying 506 thesecond voltage causes an actuator of the integrated precharge contactor to move a moveable main contact into contact with a pair of stationary main contacts to close the main circuit. The second voltage causes the magnetic coil to apply a second amount of magnetic flux to drive the actuator shaft into a second position that closes the main circuit.

[0027] In view of the foregoing, it will be appreciated that an integrated precharge contactor in accordance with the present disclosure provides a number of advantages, including but not limited to:• integrates precharge relay functionality into the main contactor by combining the functionality of a precharge contactor into a main contactor with an intermittent auxiliary switch;• eliminates the need for separate switching components for precharge and main contactors;• reduces component count and complexity;• reduces the space consumed by the main contactor and precharge contactor through integration in the same assembly; and• reduces connections and control logic by utilizing the same coil connection for both the main contactor and the precharge contactor.

[0028] Advantages and features of the present disclosure can be further described by the following statements:

[0029] 1. An integrated precharge contactor assembly comprising: a plurality' of stationary' main contacts; a plurality' of stationary auxiliary contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact; and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly7between an open position, a pre-charge position, and a closed position relative to the plurality7of stationary' main contacts and the plurality7of stationary7auxiliary7contacts.

[0030] 2. The integrated precharge contactor assembly of statement 1, wherein in the precharge position, the moveable auxiliary contact is in contact with the plurality of stationary- auxiliary contacts and the moveable main contact is separated from the plurality of stationary main contacts.

[0031] 3. The integrated precharge contactor assembly of statements 1 or 2, wherein in the closed position, the moveable auxiliary contact is in contact with the plurality of stationary auxiliary contacts and the moveable main contact is in contact with the plurality of stationary main contacts.

[0032] 4. The integrated precharge contactor assembly of any of statements 1-3, wherein in the open position, the moveable auxiliary contact is separated from the plurality of stationary auxiliary contacts and the moveable main contact is separated from with the plurality of stationary main contacts.

[0033] 5. The integrated precharge contactor assembly of any of statements 1-4, wherein actuation of the actuator shaft causes the moveable auxiliary contact to move into contact with the plurality of auxiliary contacts before the moveable main contact is moved into contact with the plurality of stationary main contacts.

[0034] 6. The integrated precharge contactor assembly of any of statements 1-5, wherein the plurality of stationary auxiliary contacts and the moveable auxiliary contact implement a precharge contactor, and wherein the plurality of stationary main contacts and the moveable main contact implement a main contactor.

[0035] 7. The integrated precharge contactor assembly of any of statements 1-6 further comprising a magnetic coil configured to apply a first amount of magnetic force to the actuator shaft in response to a first voltage and a second amount of magnetic force to the actuator shaft in response to a second voltage.

[0036] 8. The integrated precharge contactor assembly of any of statements 1-7, wherein the moveable contact assembly is moved into the precharge position in response to application of the first amount of magnetic force and the moveable contact assembly is moved into the closed position in response to application of the second amount of magnetic force.

[0037] 9. An integrated precharge contactor system comprising: a high voltage battery; a capacitive circuit; a precharge circuit configured to charge the capacitive circuit; a main circuit coupled to the high voltage battery and the capacitive circuit in parallel with the precharge circuit; and an integrated precharge contactor coupled to the precharge circuit and the main circuit, wherein the integrated precharge contactor implements a first switch for the precharge circuit and a second switch for the main circuit.

[0038] 10. The integrated precharge contactor system of statement 9, wherein integrated precharge contactor comprises: a plurality of stationary main contacts; a plurality of stationary auxiliary contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact; and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of main contacts and the plurality of stationary auxiliary contacts.

[0039] 11. The integrated precharge contactor system of statement 9 or 10, wherein actuation of the actuator shaft causes the moveable auxiliary contact to move into contact with the plurality of auxiliary contacts before the moveable main contact is moved into contact with the plurality of stationary main contacts.

[0040] 12. The integrated precharge contactor system of any of statements 9-11, wherein the plurality of stationary auxiliary’ contacts and the moveable auxiliary contact implement the first switch for the precharge circuit, and wherein the plurality of stationary main contacts and the moveable main contact implement the second switch for the main circuit.

[0041] 13. The integrated precharge contactor system any of statements 9-12 further comprising a magnetic coil configured to apply a first amount of magnetic force to the actuator shaft in response to a first voltage and a second amount of magnetic force to the actuator shaft in response to a second voltage.

[0042] 14. The integrated precharge contactor system any of statements 9-13 further comprising a controller configured to control application of the first voltage and the second voltage to the magnetic coil.

[0043] 15. A method of operating an integrated precharge contactor, the method comprising: coupling the integrated precharge contactor to a precharge circuit and a main circuit; applying a first voltage to a magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the precharge circuit in response to the first voltage; and applying a second voltage to the magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the main circuit in response to the second voltage.

[0044] 16. The method of statement 15, wherein integrated precharge contactor comprises: a plurality of stationary' main contacts; a plurality of stationary auxiliary' contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact; and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality’ of main contacts and the plurality of stationary auxiliarycontacts.

[0045] 17. The method of statements 15 or 16, wherein actuation of the actuator shaft causes the moveable auxiliary' contact to move into contact with the plurality of stationary' auxiliary contacts before the moveable main contact is moved into contact with the plurality’ of stationary' main contacts.

[0046] 18. The method of any of statements 15-17, wherein the plurality of stationary auxiliary contacts and the moveable auxiliary contact implement a first switch for theprecharge circuit, and wherein the plurality of stationary main contacts and the moveable main contact implement a second switch for the main circuit.

[0047] 19. The method of any of statements 15-18, wherein a first amount of magnetic force is applied to the actuator shaft in response to the first voltage and a second amount of magnetic force is applied to the actuator shaft in response to the second voltage.

[0048] 20. The method of any of statements 15-19, wherein the moveable contact assembly is moved into the precharge position in response to application of the first amount of magnetic force and the moveable contact assembly is moved into the closed position in response to application of the second amount of magnetic force.

[0049] It will be understood from the foregoing description that modifications and changes may be made in various embodiments of the present disclosure without departing from its true spirit. The descriptions in this specification are for purposes of illustration only and are not to be construed in a limiting sense. The scope of the present disclosure is limited only by the language of the following claims.

Claims

CLAIMSWhat is claimed is:

1. An integrated precharge contactor assembly comprising: a plurality of stationary main contacts; a plurality' of stationary auxiliary contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact: and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of stationary main contacts and the plurality of stationary auxiliary contacts.

2. The integrated precharge contactor assembly of claim 1 , wherein in the pre-charge position, the moveable auxiliary contact is in contact with the plurality of stationary auxiliary contacts and the moveable main contact is separated from the plurality' of stationary main contacts.

3. The integrated precharge contactor assembly of claim 1. wherein in the closed position, the moveable auxiliary contact is in contact with the plurality of stationary auxiliary contacts and the moveable main contact is in contact with the plurality' of stationary main contacts.

4. The integrated precharge contactor assembly’ of claim 1, wherein in the open position, the moveable auxiliary contact is separated from the plurality of stationary auxiliary contacts and the moveable main contact is separated from with the plurality' of stationary main contacts.

5. The integrated precharge contactor assembly of claim 1, wherein actuation of the actuator shaft causes the moveable auxiliary contact to move into contact with the plurality of auxiliary contacts before the moveable main contact is moved into contact with the plurality of stationary main contacts.

6. The integrated precharge contactor assembly of claim 1 , wherein the plurality of stationary auxiliary contacts and the moveable auxiliary contact implement a precharge contactor, and wherein the plurality of stationary main contacts and the moveable main contact implement a main contactor.

7. The integrated precharge contactor assembly of claim 1 further comprising a magnetic coil configured to apply a first amount of magnetic force to the actuator shaft inresponse to a first voltage and a second amount of magnetic force to the actuator shaft in response to a second voltage.

8. The integrated precharge contactor assembly of claim 7, wherein the moveable contact assembly is moved into the precharge position in response to application of the first amount of magnetic force and the moveable contact assembly is moved into the closed position in response to application of the second amount of magnetic force.

9. An integrated precharge contactor system comprising: a high voltage battery; a capacitive circuit; a precharge circuit configured to charge the capacitive circuit; a main circuit coupled to the high voltage battery and the capacitive circuit in parallel with the precharge circuit; and an integrated precharge contactor coupled to the precharge circuit and the main circuit, wherein the integrated precharge contactor implements a first switch for the precharge circuit and a second switch for the main circuit.

10. The integrated precharge contactor system of claim 9. wherein integrated precharge contactor comprises: a plurality' of stationary main contacts; a plurality of stationary auxiliary contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact; and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of main contacts and the plurality of stationary auxiliary contacts.

11. The integrated precharge contactor system of claim 10, wherein actuation of the actuator shaft causes the moveable auxiliary contact to move into contact with the plurality of auxiliary contacts before the moveable main contact is moved into contact with the plurality of stationary main contacts.

12. The integrated precharge contactor system of claim 10, wherein the plurality of stationary auxiliary' contacts and the moveable auxiliary' contact implement the first switch for the precharge circuit, and wherein the plurality of stationary main contacts and the moveable main contact implement the second switch for the main circuit.

13. The integrated precharge contactor system of claim 10 further comprising a magnetic coil configured to apply a first amount of magnetic force to the actuator shaft in response to a first voltage and a second amount of magnetic force to the actuator shaft in response to a second voltage.

14. The integrated precharge contactor system of claim 13 further comprising a controller configured to control application of the first voltage and the second voltage to the magnetic coil.

15. A method of operating an integrated precharge contactor, the method comprising: coupling the integrated precharge contactor to a precharge circuit and a main circuit; applying a first voltage to a magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the precharge circuit in response to the first voltage; and applying a second voltage to the magnetic coil of the integrated precharge contactor, wherein the integrated precharge contactor closes the main circuit in response to the second voltage.

16. The method of claim 15. wherein integrated precharge contactor comprises: a plurality of stationary main contacts; a plurality' of stationary auxiliary' contacts; a moveable contact assembly that includes a moveable main contact and a moveable auxiliary contact: and an actuation shaft coupled to the moveable contact assembly and configured to move the moveable contact assembly between an open position, a pre-charge position, and a closed position relative to the plurality of main contacts and the plurality of stationary' auxiliary contacts.

17. The method of claim 16, wherein actuation of the actuator shaft causes the moveable auxiliary contact to move into contact with the plurality' of stationary auxiliary contacts before the moveable main contact is moved into contact with the plurality of stationary main contacts.

18. The method of claim 16. wherein the plurality of stationary auxiliary contacts and the moveable auxiliary' contact implement a first switch for the precharge circuit, and wherein the plurality' of stationary' main contacts and the moveable main contact implement a second switch for the main circuit.

19. The method of claim 16, wherein a first amount of magnetic force is applied to the actuator shaft in response to the first voltage and a second amount of magnetic force is applied to the actuator shaft in response to the second voltage.

20. The method of claim 19, wherein the moveable contact assembly is moved into the precharge position in response to application of the first amount of magnetic force and the moveable contact assembly is moved into the closed position in response to application of the second amount of magnetic force.

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