GB2507638A - Rotary actuator for electricity meter contactor - Google Patents

Abstract

An H-armature rotary actuator 500 is suitable for use in a two-pole contactor and comprises a coil 504 wound on a magnetic core 508, two vertical magnetic upstands 510a, 510b coupled to the core, and an H-armature 514 that is situated vertically above the coil. The magnetic upstands pass perpendicularly between the two pole pieces 514a, 514b of the H-armature, and the armature is configured to pivot, in a horizontal plane vertically above the coil, to switch between a first latched state, in which it is magnetically latched with the upstands, and a second latched state, in which it is magnetically latched with the upstands. Armature 514 pivots in a plane that is spaced apart from coil 504 in a direction that is perpendicular to the plane. Armature 514 can have magnet 512 between pole pieces 514a,514b and pivot on a spigot 516 attached to a bobbin on which the coil is wound. The actuator can be used to drive a two-pole contactor (fig 6) for an electricity meter.

Description

Improved Rotary Actuators

Background and prior art

There are numerous actuating and switching applications which employ what is generally referred to as a bi-stable H-armature rotary actuator, which has two defined magnet-latching states, relating to the angular rotation of the actuator part -the stroke -when driven electrically to perform the desired two-way actuating function.

The actuating function may be a basic latching mechanical drive, or suitably linked via a sliding mechanism or pivoting lever arrangement to actuate the contacted blade(s) of a disconnect switch, at low DC voltage or AC mains voltage, thus achieving a safe isolated switching function. The size and strength of the actuator drive and switch elements determine the capability of the load's switching function.

As shown in Figure 1, the bi-stable H-armature rotary actuator 100 comprises two distinct half sub-assemblies:-The first part of the rotary actuator is a coil assembly, comprising generally a plastics bobbin (not shown) wound either with a single coil or a twin coil 104 whose DC resistance and number of energisable turns of a particular gauge of copper winding wire filling the space, which is determined for a certain drive voltage relating to the particular application.

The single coil version is generally driven reversibly through a so-called I-I-bridge -comprising four diagonal transistors -to achieve the desired two-way latching functions, whereas the twin coil ends can be driven by a voltage, taken negatively (to the 0 V common supply line) via two separate conducting transistors, with-respect-to the central +ve Common supply connection, for Operate and Release functions.

Two overlapping ferrous field-pieces 1 08a, 1 08b are assembled through the bobbin and coil sub-assembly. They are formed as a C-shape in such a way that their other wider open ends are spaced apart vertically on the same axis, a certain distance from and parallel with the bobbin axis, to accept the second half part of the latching rotary actuator.

The second part of the rotary actuator comprises a permanent magnet 112 placed centrally between two identical ferrous pole-pieces 11 4a, 11 4b -distanced apart by the magnet thickness -all generally moulded together with small pivot bosses above and below the central vertical axis, which locate in suitable pivot sockets, also centrally and on axis, between the vertical flat ends of the C-shaped field-pieces of the coil assembly. The magnet and pole-piece sub-assembly resembles the letter H, hence it is referred to as the H-armature actuator, the central bridge of the H being the permanent magnet.

The inner faces of the outer ends of the parallel ferrous pole-pieces are coined" or angled slightly such that they are intimate with the mating field-piece faces, at each rotated latched end. The type and size of magnet used, and the intimacy of the rotating pole-pieces on the field-piece faces determines the strength of the magnetic Hold at each rotated latched end, and enhances the coil-driven translated attraction.

The operation of the H-armature actuator will now be described with reference to Figure 2. As shown in Figure 2(a), when the coil is pulse driven, the initial function of the magnetic flux generated in the field-pieces is to partially de-magnetise the magnet between the latched pole-pieces ("Demag" arrows) breaking their Hold, at the same time channelling the rest of the available flux across the open pole-piece gaps (Attrn" arrows) attracting and causing rotation to the other latched state, and at the same time performing the mechanical drive function (via the ball-ended actuator shown).

This de-magnetisation of Hold, attraction translation, and rotational latching across, is usually aided by the nature of the load, whether it being a sprung mechanical actuator, or a relay blade assembly with developed over-travel contact forces. As can be seen in Figure 2(b), the balanced H-armature drive requires assistance through the relatively weak mid stroke, to tip the armature through to near the opposite latching position as shown in Figure 2(c), where the magnetic forces of the magnet and the coil attract and latch the armature in the fully latched position as shown in Figure 2 (d), the driving force being strongest only near the latching end-stroke points (see drive curve in Figure 3). Once pivoted to an end of travel position, the armature is held in the latched state by the magnet until the coil is energised to change states.

All current applications employing the bi-stable H-armature actuator have the two halt assemblies -the coil and field pieces, and the magnet and pole-pieces -both lying on the same horizontal plane. adiacent to each other as shown in Figure 1, for convenience, on a base structure, or within the casing of a switch assembly, pivoting freely to achieve the latching actuating function and translated drive. This tends to cause a non-symmetric assembly -the H-armature assembly being on one side, and the load or actuated mechanism, or switch assembly being on the other side.

One of the earliest patent ideas identified for an H-armature actuator relates to a prominent relay manufacturer Hengstler GmbH of Wehingen, West Germany, their published patent application being US 4,623,863 filed on 2 July 1984, based on an earlier German application DE 3,324,246 dated 6 July 1983.

The rotary actuator of the Hengstler patent is illustrated in Figure 4, in a partially exploded state. It clearly comprises both related parts of the actuator as already described -the coil assembly with ferrous field-pieces, and the H-armature rotary part with pole-pieces and magnet between -all assembled together on the same horizontal plane, adiacent to each other, to create the rotary drive, with the switch assembly on the other side.

One extended arm of the moulded H-armature part is slidably linked with a changeover switch arrangement, the actuator and switch assembly being conveniently integrated together, alongside each other, in a relatively small plastics housing, comprising a base moulding for the various parts, and a snap-on protective lid. The housing is not shown in the Figures.

Although the rotary magnetic-latching H-armature principle was well known prior to this time, the strength of the Hengstler patent related to its unique application as an actuator for a small switching relay.

This well-known H-armature principle was adopted by many relay companies who began to use it in their switch and contactor designs.

Prolific use of the rotary H-armature actuator principle: At the same time as the Hengstler patent application described above, another German Company, Bach GmbH Company lodged a similar patent application DE 3,624,783 Al with a priority date of 22 July 1986. This document features a larger H-armature rotary actuator connected to a contacted power-switch blade for connecting and disconnecting single-phase AC loads, all assembled together on the same horizontal plane, adiacent to each other, to create the rotary drive, with the switch assembly set apart on the other side.

More recent patent applications using the H-armature actuator and power switch are listed below, some for AC single-phase connect and disconnect, others for two-phase switching, as is standard in North America, all assembled together on the same horizontal plane, adiacent to each other, to create the rotary drive, with the switch assembly set apart on the other side.

US 6,046661 Gruner AG 4 April 2000 US 2009/0033446 Al Coldi LLC 5 February 2009 US 2009/0033447 Al Clodi LLC 6 February 2009 Inadequacies of current H-armature configurations: Up to the present time, all H-armature actuators had been configured in the same way, comprising a coil/field-piece sub-assembly and magnetlpole-piece sub-assembly -all assembled together on the same horizontal plane, adiacent to each other, to create the rotary drive, with the switch assembly on the other side.

This is generally acceptable and convenient for simple arrangements, for example, the types of single-phase switch as that featuring in some of the cited designs above, such as US 4,623,661 of Hengstler GmbH, DE 3,624,783 Al of Bach GmbH Co, and US 2009/0033447 Al of Clodi LLC.

For other two-phase switches using the H-armature actuator drive, the configuration is similar as that for the single-phase applications, except that the two isolated switches together are on one side of the actuator assembly -all assembled together on the same horizontal plane, adjacent to each other. Typical examples already listed above are US 6,046,661 of Gruner AG and US 2009/0033446 Al of Coldi [C.

These two-phase disconnect switches are specifically configured for North American metering applications, with standard plug-in terminals, or stabs", suitably cased and fitting within a standard meter base moulding. The stab" terminals plug into sprung jaws in the meter-box which are connected to heavy-duty cables, feeding the two-phase input supplies and the load out connections, for the domestic premises.

As configured and cased, they are fundamentally non-symmetric, in that the H-armature actuator is set apart from the various heavy-duty copper runs of both switches, being routed closely together while exiting to the related "stab" connections.

In the related North American ANSI C12.1 specification for electric meters containing disconnect switches, the two switches not only have to comply with fairly arduous switching Endurance at nominal 200 Amp current, but also have to withstand large short-circuit fault conditions up to 12,000 Amps rms, safely. At this level, very strong magnetic fields are generated in the two switches and the heavy-duty copper runs, which could easily interfere with, and disturb, the latched condition of the H-armature actuator, particularly as the overall configuration is very non-symmetric.

The worst, undesirable result would be if the disturbed H-armature actually caused the switches to lose contact pressure, open, arc and create a destructive explosion, at the very high shod-circuit current levels concerned.

It is particularly desirable therefore that the H-armature actuator should be placed in the centre of the cased switch arrangement, with the two switches and the related heavy-duty copper runs carefully routed either side, for the best symmetric layout possible, thus minimising the possible interference from the very strong magnetic fields generated by the short-circuit currents flowing in the closed switches.

Ideally, the H-armature actuator's magnetic axis should be central to, and parallel with the axes of the two switches, providing cancellation of the strong magnetic fields, with virtually no interference of the latched state of the actuator.

This is not possible with all of the existing known configurations, for single-switch or double-switch arrangements using an H-armature actuator -as they are all assembled tociether on the same horizontal plane, adiacent to each other, with the rotary drive set apart from the switch (or switches) on the other side.

Summary of the Invention: The "vertical" H-armature The following description, with reference to Figures 5 and 6, is of a novel, modified version of the standard H-armature actuator-the vertical" H-armature, specifically aimed at a symmetric two-pole switch to satisfy the North American ANSI C12.1 meter specification, at the ultimate short-circuit fault level of 12,000 Amps rms.

A top view of one example 500 of a "vertical" H-armature actuator according to the present invention is shown in Figure 5(a). Figure 5(b) is a side view of the actuator of Figure 5(a). The first part is a coil assembly as before, comprising generally a longer plastics bobbin 502 wound either with a single coil or a twin coil 504 whose DC resistance and number of energisable turns of a particular gauge of copper winding wire in the space, which is determined for a certain drive voltage relating to the particular application. The central bobbin cheek has a vertical plastic spigot 506 for freely pivoting the "vertical" H-armature sub-assembly mounted centrally above on the same longitudinal axis This pivot spigot may be a separate metal rod inserted tightly in the central bobbin cheek.

A rectangular-section ferrous strip core 508 is assembled through the bobbin and coil sub-assembly with ferrous vertical up-stands 510a, SlOb riveted at the two ends on the same longitudinal axis, supported in the bobbin end cheeks, in order to accept the vertical" H-armature sub-assembly of the latching rotary actuator mounted centrally above.

The "vertical" H-armature sub-assembly comprises two permanent magnets 512a, 512b placed centrally between two longer identical ferrous pole-pieces 514a, 514b -distanced apart by the magnet thicknesses -all generally moulded or clipped together, which locates and rotates freely on the central bobbin pivot spigot on axis. The magnet and pole-piece sub-assembly rotates about the ferrous up-stands at the ends of the central ferrous core, and sized for a certain rotational stroke, for the balanced drive.

The result is a novel "vertical" H-armature actuator, located above the coil assembly on the same longitudinal axis, which can now be placed on the same central axis as the two separate disconnect switches, but each being symmetrically displaced, either side of, and parallel with the central actuator.

Specific embodiment of a "vertical" H-armature actuator and a symmetric two-pole switch comprising the actuator: With reference to Figure 6, a vertical" assembly according to an embodiment of the invention comprises a bobbin and coils with central ferrous core and up-stands below on axis plus the symmetric "Vertical" H-armature including pole-pieces and magnets rotating on central spigot, all aligned on the longitudinal axis together.

Figure 6 also shows it in a notional, balanced, symmetric 2-pole contactor. Figure 6a shows an exemplary two-pole symmetric switch 600 with the "vertical" H-armature actuator in an open position, while Figure 6b shows the two-pole symmetric switch 600 in a closed position (transparent view for clarity).

As can be seen, switch blade magnetic fields (N, S) due to the short-circuit current cancelling out leaving the "vertical" H-armature undisturbed on the neutral symmetric axis between the switches. Transparent view for clarity.

These are the attributes and advantages of the proposed improved "vertical" H- armature actuator according to the present invention:-a * The "vertical" H-armature actuator is a novel improvement on the conventional H-armature actuator -with the coil sub-assembly, and the magnet and pole-pieces sub-assembly -laying one above the other on the same longitudinal axis and vertical plane, not adjacent to each other, as is common in all existing H-armature actuators, * The coil sub-assembly: comprises a plastics bobbin with one or two windings, a central pivot spigot, a rectangular ferrous core extending through the bobbin, with vertical ferrous upstands at each end, for accepting the rotating magnet and pole-pieces sub-assembly above (H-armature), all mounted on the same longitudinal and vertical axis, * The rotating magnet and pole-pieces sub-assembly: comprises two permanent magnets placed centrally between two longer identical pole-pieces -distanced apart by the magnet thicknesses -all generally moulded or clipped together tightly, which locates and rotates freely on the central bobbin spigot on axis being suitably sized for a defined rotational stroke, * The bobbin coil(s) are determined for their DC resistance, number of energisable wire turns, wattage, and drive voltage for the application concerned, and mechanical performance required for the rotary drive actuation, * When the coil(s) are energised, initially the latched magnet is partially de-magnetised to de-latch the Hold, the remaining flux attracting and translating the pole-pieces sub-assembly through the rotational stroke, mechanically driving a load, or actuating switch blade(s) for an Open/Close switching function, * The "vertical" H-armature actuator is intended to be placed centrally and symmetrically between two (offset) switches of a two-pole contactor, each side of it, the large short-circuit magnetic fields generated in each cancelling along the main axis, thus not affecting the latched status of the actuator, and maintaining the switches Open (if already Open) or Closed (if already Closed), * In the two-pole switch version illustrated, during coil energisation for Closure, the two moving switch blades are pre-formed and configured such that after contact closure, their tang ends deflect further for over-travel, developing a defined pressure force while the H-armature latches, * When the coil is reverse driven to Open the switch, the magnets are partially de-magnetised to de-latch the Hold, the build-up over-travel pressure force on Closure is then released, helping to translate the H-armature rotationally to latch Open both switches together.

List of Figures Figure 1 Conventional H-armature actuator Figure 2 Operation of a conventional H-armature actuator Figure 3 Drive curve

Figure 4 Prior art rotary actuator

Figure 5(a) "Vertical" H-armature actuator of the present invention (top view) Figure 5(b) "Vertical" H-armature actuator of the present invention (side view) Figure 6(a) Two-pole symmetric switch with "vertical" H-armature actuator (open) Figure 6(b) Two-pole symmetric switch with "vertical" H-armature actuator (closed) Reference signs list Conventional H-armature actuator 104 Coil 108, 508 Ferrous core 112, 512 Permanent magnet 114, 514, Ferrous pole pieces 500 "Vertical" H-armature actuator 502 Bobbin 504 Coil 506 Bobbin spigot 510 Ferrous upstands 600 Two-pole symmetric switch with "vertical" H-armature 602 Contacted switch 604 Axis of symmetry 606 "Stab" terminal 608 External load 610 Short circuit

Claims (5)

1. CLAIMS1. A rotary actuator comprising a coil and an armature driven by the coil, wherein the armature is spaced from the coil in a first direction and is configured to pivot in a plane perpendicular to the first direction.
2. 2. A rotary actuator according to claim 1 further comprising a magnetic core assembled through the coil and two magnetic members coupled to the core proximate its ends and extending in the first direction, wherein the armature is configured to pivot between a first state of magnetic latching with the magnetic members and a second state of magnetic latching with the magnetic members.
3. 3. A rotary actuator according to claim 1 or claim 2 wherein the armature comprises a magnet arranged between two magnetic pole pieces.
4. 4. A rotary actuator according to any preceding claim wherein the coil is
5. 5. A rotary actuator according to claim 4 further comprising a spigot coupled to the bobbin intermediate its two ends and extending in the first direction between the magnetic pole pieces of the armature and wherein the armature is configured to pivot about the spigot.6 A rotary actuator substantially as described herein with reference to Figures 5 and 6 of the accompanying drawings.7. A two-pole contactor comprising a rotary actuator according to any preceding claim.