Patent Description:
A major goal of a power distribution company is to have a continuous supply of power to the end customer, be it residential loads or industrial. A circuit breaker that is used in a starting point of a distribution system is a low voltage vacuum interrupter.

A primary purpose of a circuit breaker is to protect downstream devices from a surge of current arising from a fault. This is accomplished by interrupting a fault current as quickly as possible in order to reduce the energy provided to the downstream devices. A vacuum bottle of a vacuum interrupter may have to undergo maintenance or replacement depending on how many faults it has seen. During this period maintenance or replacement, there will be a shutdown of power which is not desirable for the utility as it will have certain amount of monetary impact. Hence the fault current has to be commutated to a system which can sustain high fault current and interrupts quickly.

Power electronic breakers, such as solid-state circuit breakers, are particularly good at fast interruptions with low amounts of energy being let through. Unfortunately, these power electronic devices have high operational resistances that cause high power losses when they carry the breaker's load current. These high losses make them unsuitable for many applications.

One potential solution is to develop a hybrid breaker having both a vacuum interrupter and a power electronic interrupter in the form of a solid-state interrupter, where the solid-state interrupter only carries current during a fault. The vacuum interrupter is a more conventional path that carries the current during ordinary operation. The faster the fault current can be commutated from the conventional path to the power electronic path, the sooner the power electronics can interrupt the fault current, and the lower the amount of energy that is let through. Fast commutation is achieved by rapid opening of a mechanical switch.

A challenge in a hybrid circuit breaker is to provide a fast mechanism to open the VI contacts, so that the current can commutate to the semiconductor branch within a small span of time, before it crosses the maximum current handling capability of the semiconductor switches.

In <CIT> there is disclosed an actuator as it is defined in the preamble of claim <NUM>.

In a conventional Thomson coil actuator, a Thomson plate will be connected to a moving component and a Thomson coil will be situated adjacent the Thomson plate. The nature of force is a sudden impulse in this actuator. The total moving mass has a big impact on the travel that can be achieved by this type of actuator. As the mass of the Thomson plate increases, a higher amount of energy from the capacitor bank that excites the Thomson coil is required. With increased mass of the Thomsen plate, opening velocity can reduced, and the time required for moving the Thomsen plate between positions is increased. There is thus room for improvements in switching apparatuses.

These needs and others are met by a number of embodiments of the invention, which are directed to an improved actuator and combination. As employed herein, the expression "a number of" shall refer broadly to any non-zero quantity, including a quantity of one.

In one embodiment the present invention provides an actuator which comprises a support, an armature that is rotatable with respect to the support about an axis of rotation, and a plurality of Thomson coils that are each spaced from the axis of rotation. The armature comprises a hub and a plurality of Thomson plates, the plurality of Thomson plates each being electrically conductive and extending from the hub. Each Thomson plate of the plurality of Thomson plates is situated adjacent a corresponding Thomson coil of the plurality of Thomson coils when the plurality of Thomson coils are in a non-energized state, and the armature further comprises an output shaft connected with the hub and structured to rotate a rotational distance responsive to the Thomson coils being energized.

In another embodiment the present invention provides a combination comprising a first circuit interrupter, a second circuit interrupter, and an actuator as defined in the above embodiment that is structured to switch a current path that includes a protected portion of a circuit between the first interrupter and the second interrupter.

A full understanding of the present invention can be gained from the following Description when read in conjunction with the accompanying drawings in which:.

Similar numerals refer to similar parts throughout the Specification.

An improved actuator <NUM> in accordance with an embodiment of the present invention is depicted in a schematic fashion in <FIG> as being a part of an improved combination <NUM> that is likewise in accordance with an embodiment of the present invention. The combination <NUM> further includes a first circuit interrupter <NUM> that is in the exemplary form of a vacuum interrupter and a second circuit interrupter <NUM> that is in the exemplary form of a solid-state circuit interrupter. The combination <NUM> is connected with a protected portion of a circuit <NUM>, and the actuator <NUM> is advantageously operable to rapidly commutate the current in the circuit <NUM> between the first circuit interrupter <NUM> and the second circuit interrupter <NUM> in, for example, a fault condition or other appropriate condition.

The actuator <NUM> is further depicted in <FIG> and is depicted in part in <FIG>. The actuator <NUM> can be said to include a support <NUM> upon which are situated an armature <NUM> and a Thomson coil apparatus <NUM>. The armature <NUM> is rotatable about an axis of rotation <NUM> in response to the Thomson coil apparatus <NUM> being energized by, for example, a capacitor bank.

The armature <NUM> is formed of a conductive material such as copper or aluminum and includes a tubular hub <NUM> and a plurality of Thomson plates that are generally indicated at the numeral <NUM>. The Thomson plates <NUM> are, in the depicted exemplary embodiment, four in quantity and thus can be referred to with the numerals 40A, 40B, 40C, and 40D. The Thomson plates <NUM> each extend radially outwardly from the hub <NUM> in a direction generally away from the axis of rotation <NUM> and are equally circumferentially spaced ninety degrees apart from one another.

The armature <NUM> further includes an output shaft <NUM> that includes a cam <NUM> that rotates with the output shaft <NUM>. The armature <NUM> additionally includes a follower <NUM> that is cooperable with the cam <NUM>. When the Thomson coil apparatus <NUM> is energized in a fashion that is set forth in greater detail elsewhere herein, the armature <NUM> is caused to responsively rotate a rotational distance, such as is depicted generally in the positional difference between <FIG>. Such rotation of the armature <NUM> the rotational distance about the axis of rotation <NUM> causes the follower <NUM> to responsively translate a linear distance along a translation axis <NUM> that is coaxial with the axis of rotation <NUM>.

The follower <NUM> is movably situated in an opening <NUM> that is formed in the support <NUM>, but the follower <NUM> is advantageously constrained to move only via translation, i.e., linear motion, and along the translation axis <NUM>. That is, the follower <NUM> is advantageously resisted from rotating with respect to the support <NUM>, and this is accomplished by providing a pair of tabs <NUM> on the follower <NUM> that function as a first guide portion <NUM> and by providing a pair of corresponding slots <NUM> that are formed on the support <NUM> within the opening <NUM> and that function as a second guide portion <NUM>. The first and second guide portions <NUM> and <NUM> cooperate to restrain the motion of the follower <NUM> with respect to the support <NUM> to be merely translational motion of the follower <NUM>, i.e., motion along a straight line, along the translation axis <NUM>. In this regard, the tabs <NUM> are slidably received in the slots <NUM>.

The actuator <NUM> further includes a shank <NUM> upon which the armature <NUM> is rotatably situated and that is mechanically connected with a set of separable contacts <NUM> of the first circuit interrupter <NUM>. When the Thomson coil apparatus <NUM> is in a non-energized state, such as is depicted generally in <FIG> and <FIG>, the set of separable contacts <NUM> are in a closed state, meaning that the set of separable contacts <NUM> are electrically connected with one another. However, when the Thomson coil apparatus <NUM> is energized and the armature <NUM> is caused to thereby rotate the cam <NUM> the rotational distance about the axis of rotation <NUM> and to thereby cause the follower <NUM> to responsively move the linear distance along the translation axis <NUM>, the follower <NUM> pulls the shank <NUM> along the translation axis <NUM> to cause the set of separable contacts <NUM> to be in an open state, such as is generally in <FIG>. In so doing, the current that had been flowing through the first circuit interrupter <NUM> is commutated to instead flow through the second circuit interrupter <NUM>, which is operable to interrupt current flowing therethrough in an understood fashion.

The Thomson coil apparatus <NUM> can be said to include a plurality of Thomson coils that are indicated generally at the <NUM>. The Thomson coils <NUM> are four in quantity and can also be referred to with the numerals 88A, 88B, 88C, and 88D. In the depicted exemplary embodiment, the four Thomson coils <NUM> are positioned to be axisymmetric with respect to the axis of rotation <NUM> and, in the depicted exemplary embodiment, are circumferentially positioned ninety degrees apart from one another. It is noted, for instance, that the Thomson coils 88A and 88C are diametrically opposed to one another, and that the Thomson coils 88B and 88D are likewise diametrically opposed to one another, with respect to the hub <NUM>. In this regard, it is noted that the Thomson coils 88A and 88C could be diametrically opposed to one another, and that the Thomson coils 88B and 88D could be likewise diametrically opposed to one another, and the Thomson coils <NUM> could still be axisymmetric with respect to the axis of rotation <NUM> even if the Thomson coils <NUM> are not necessarily positioned ninety degrees apart from one another. For instance, the Thomson coil 88A might be <NUM> degrees apart from the Thomson coil 88B but might be only <NUM> degrees apart from the Thomson coil 88D. It is also noted that the Thomson coils <NUM> need not necessarily be axisymmetric with respect to the axis of rotation <NUM> and can still be within the scope of the present invention. For instance, a plurality of the Thomson coils <NUM> might be situated along only one-half the circumference of the armature <NUM> and could still be within the scope of the present invention.

The Thomson coils <NUM> are advantageously electrically connected with one another in parallel, which advantageously reduces the effective inductance of the Thomson coil apparatus <NUM> combined with the set of Thomson plates <NUM>. This advantageously achieves a quick rise time, which is the time required to reach peak force between the Thomson coil apparatus <NUM> and the armature <NUM>. When the Thomson coils <NUM> are in a non-energized state, each of the Thomson coils 88A, 88B, 88C, and 88D, is situated adjacent a corresponding Thomson plate 40A, 40B, 40C, and 40D. When the Thomson coils <NUM> are energized, the magnetic fields that are formed in the Thomson coils <NUM> induce in the corresponding Thomson plates <NUM> currents that form equal and opposite magnetic fields that result in magnetic repulsion between the Thomson coils <NUM> and the Thomson plates <NUM>. Since the Thomson coils <NUM> are affixed to the support <NUM>, and inasmuch as the armature <NUM> is rotatably situated on the support <NUM>, energizing the Thomson coils <NUM> results in the armature <NUM> rapidly rotating about the axis of rotation <NUM>.

It is also noted that the follower <NUM> has a reaction surface <NUM> that is oriented at a particular angle with respect to the translation axis <NUM>. When the angle is <NUM> degrees, rotation of the cam <NUM> and corresponding translation of the follower <NUM> can be said to be <NUM>:<NUM>. However, if the angle is adjusted to instead be, for instance, a much steeper <NUM> degrees, the cam <NUM> and the follower <NUM> can together amplify the translation of the follower <NUM> with respect to the rotation of the cam <NUM> in, for instance, a <NUM>:<NUM> ratio. This would assist with rapid translation of the follower <NUM> along the translation axis <NUM> in response to a relatively modest rotation of the cam <NUM> about the axis of rotation <NUM>. The angle of the reaction surface <NUM> and of the corresponding driving surface of the cam <NUM> can be tuned to achieve a desired translational distance along the translation axis <NUM> in response to a given rotation of the armature <NUM> about the axis of rotation <NUM>.

It is also noted that the actuator <NUM> can be configured to perform other functions that are merely rotational in nature and thus can be configured to not include the cam <NUM> and the follower <NUM>. For instance, the actuator <NUM> can be a part of a rotational actuator wherein the Thomson coil apparatus <NUM>, when energized, causes rotation of the armature <NUM> to rotate a rotatable component of the rotational actuator. Other variations and benefits will be apparent.

Claim 1:
An actuator (<NUM>) comprising:
a support (<NUM>);
an armature (<NUM>) that is rotatable with respect to the support (<NUM>) about an axis of rotation (<NUM>); and
a plurality of Thomson coils (<NUM>) that are each spaced from the axis of rotation (<NUM>);
the armature (<NUM>) comprising a hub (<NUM>) and a plurality of Thomson plates (<NUM>), the plurality of Thomson plates each being electrically conductive and extending from the hub,
characterized in that
each Thomson plate (<NUM>) of the plurality of Thomson plates is situated adjacent a corresponding Thomson coil (<NUM>) of the plurality of Thomson coils when the plurality of Thomson coils are in a non-energized state; and
the armature (<NUM>) further comprises an output shaft (<NUM>) connected with the hub (<NUM>) and structured to rotate a rotational distance responsive to the Thomson coils (<NUM>) being energized.