Circuit interrupters with masses in contact spring assemblies

Devices and assemblies are provided for operating circuit interrupters. A circuit interrupter assembly includes a circuit interrupter and a contact spring assembly. The circuit interrupter is located within the housing and includes a moving contact and a stationary contact. Contact spring assembly includes a mass, a plunger, a ferrule, a spring, and a dielectric drive rod. The mass defines an inner bore with a first diameter at a first portion of the mass and a second diameter that is larger than the first diameter at a second portion of the mass. The plunger has a flange portion and a body portion. The flange portion is located within the inner bore at the second portion and has a flange diameter that is larger than the first diameter. The spring is disposed within the inner bore between the plunger and the ferrule.

TECHNICAL FIELD

This disclosure generally relates to circuit interrupters, and more particularly relates to circuit interrupters in power distribution switchgear that have contact spring assemblies with masses.

BACKGROUND

Circuit interrupting devices function to isolate a fault condition in a power distribution system. Upon clearing of the fault condition certain types of these devices may be manually or automatically reclosed to restore the circuit. Faults in a power distribution system can occur for any number of reasons and are typically transient. Reclosing after the fault is cleared provides for quick service restoration.

A typical circuit interrupting device may include a vacuum interrupter having a stationary contact and a moving contact. During opening operations and closing operations of such vacuum interrupters, arcing and current flow through a partially opened vacuum interrupter may cause the stationary and moving contacts to weld together. Such welding increases the force required to subsequently open the vacuum interrupter. A typical circuit interrupting device may increase a mass of an insulating actuator rod or increase a spring constant of a contact spring within an actuation assembly to assist with opening such welded contacts. Although these typical circuit interrupting devices are suitable for their intended purpose, there is a need for circuit interrupters with improved performance.

Accordingly, it is desirable to provide a circuit interrupter device with a configuration designed for opening welded or partially welded vacuum interrupters. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.

DETAILED DESCRIPTION

Circuit interrupting devices, circuit interrupting assemblies, and contact spring assemblies are provided. In one embodiment, a circuit interrupting device includes a circuit interrupter and a contact spring assembly. The circuit interrupter has a moving contact and a stationary contact. The circuit interrupter includes a closed position in which the stationary contact and the moving contact are in contact at an interface. The contact spring assembly includes a dielectric drive rod, a mass, and a plunger. The mass is attached to the dielectric drive rod and a distance between the mass and the interface is less than the drive rod length. The plunger is attached to the moving contact and engages with the mass in response to actuation of the dielectric drive rod.

In another embodiment, a circuit interrupter assembly includes a solid insulation housing, a first conductor, a second conductor, a vacuum interrupter, a mass, a plunger, a ferrule, a spring, and a dielectric drive rod. The solid insulation housing defines a first cavity. The first conductor is disposed in the solid insulation housing and has a first external coupling. The second conductor is disposed in the solid insulation housing and has a second external coupling. The vacuum interrupter is disposed within the first cavity and includes a moving contact and a stationary contact. The moving contact is electrically coupled with the first conductor and the stationary contact is in selectable electrical communication with the second conductor. The mass is disposed within the first cavity and has an annular shape that defines an inner bore. The inner bore has a first diameter at a first portion of the mass and a second diameter that is larger than the first diameter at a second portion of the mass. The plunger has a flange portion and a body portion. The flange portion is disposed within the inner bore at the second portion and has a flange diameter that is larger than the first diameter. The body portion is received for translation through the inner bore at the first portion and is attached to the moving contact of the vacuum interrupter. The ferrule is fastened to the inner bore of the mass and the dielectric drive rod is fastened to the ferrule. The spring is disposed within the inner bore between the plunger and the ferrule.

In another embodiment, a contact spring assembly for a circuit interrupting device includes a mass, a ferrule, a plunger, and a spring. The mass defines an inner bore. The inner bore has a first diameter at a first portion of the mass and a second diameter that is larger than the first diameter at a second portion of the mass. The ferrule is fixed to the inner bore of the mass and is configured to receive a dielectric drive rod. The plunger has a flange portion and a body portion. The flange portion is disposed within the inner bore at the second portion and has a flange diameter that is larger than the first diameter. The body portion is received for translation through the inner bore at the first portion and is configured to attach to a moving contact of the circuit interrupting device. The spring is disposed within the inner bore between the plunger and the ferrule.

Example embodiments will now be described more fully with reference to the accompanying drawings. There is no intention to be bound by any principle presented in the preceding background or the following detailed description.

FIGS. 1-2illustrate an embodiment of a pole unit circuit interrupting device100typically used as switchgear in a power distribution system. In the example provided, circuit interrupting device100provides fault interruption for a single phase in power distribution switchgear. It is understood that additional devices would be included for three-phase power distribution. Circuit interrupting device100includes a solid insulation housing102, a fast acting interrupter such as a vacuum interrupter104, a contact spring assembly106, a slow acting disconnect108, a first external conductor110, a flexible conductor112, an internal conductor114, and a second external conductor116.

Solid insulation housing102is a molded electrically insulating material, such as plastic. Solid insulation housing102is molded with a first cavity120and a second cavity122. First cavity120extends inward from an external opening123to a first conical portion124, a second conical portion126, and a cylindrical portion128. First and second conical portions124and126surround contact spring assembly106. In the example provided, second conical portion126is lined by an insulating epoxy material. First cavity120encloses vacuum interrupter104and the associated mechanical and electrical coupling components. Solid insulation housing102may have any suitable shape, such as cylindrical, rectangular box, or an irregular shape.

Vacuum interrupter104is electrically coupled between first external conductor110and internal conductor114to selectively disconnect electrical current through circuit interrupting device100. Vacuum interrupter104may be secured within cylindrical portion128of first cavity120by a potting material, such as silicone or another suitable material. Vacuum interrupter104includes a stationary contact130and a moving contact132.

Stationary contact130is electrically coupled with internal conductor114, moving contact132is electrically coupled with flexible conductor112, and flexible conductor112is electrically coupled with first external conductor110. As will be appreciated by those with skill in the art, current flows through vacuum interrupter104when vacuum interrupter is in a closed position in which moving contact132is in contact with stationary contact130at an interface134, as illustrated. Conversely, current flow through circuit interrupting device100is interrupted when vacuum interrupter104is in an open position with moving contact132separated from stationary contact130. Other fault interrupters capable of interrupting the current path within a sealed enclosure and providing arc control and/or arc suppression may be used without departing from the scope of the present disclosure.

Conductors110,112,114,116, vacuum interrupter104, and disconnect108define a current path through circuit interrupting device100, as will be appreciated by those with skill in the art. In the example provided, first external conductor110is a conductive rod including a first tap136for coupling externally of the solid insulation housing102and a second tap138for fastening to flexible coupling112. Internal conductor114is a conductive rod that includes a first tap140for fastening to stationary contact130and a second tap142for fastening to slow acting disconnect108. Internal conductor114is selectively electrically coupled with first external conductor110by vacuum interrupter104. Internal conductor114is further selectively electrically coupled with second external conductor116by slow acting disconnect108. Second external conductor116is a conductive rod that includes a first tap144for coupling externally of solid insulation housing102. In the example provided, first tap136and first tap144are threaded external couplings.

Disconnect108includes a stationary contact150, a moving contact152, and an actuation rod154. Stationary contact150is fastened to internal conductor114at second tap142with a suitable fastener, such as a threaded fastener. Moving contact152is attached to actuation rod154and is in sliding engagement and is electrically coupled with second external conductor116. Actuation rod154may be any insulating rod, such as a fiberglass rod. It should be appreciated that other types of slow acting disconnects108may be used.

Referring now toFIGS. 3-5, details of contact spring assembly106are illustrated in various views. Contact spring assembly106includes an annular mass160, a threaded rod162, a plunger163, a contact spring164, a ferrule166, and a dielectric drive rod168.

Annular mass160is a rigid mass with an annular shape that defines an inner bore170. A metal alloy or other material may be used as the rigid material of annular mass160. The rigid material resists deformation to quickly accelerate upon actuation of dielectric drive rod168. The rigid material further resists reduction of impact forces due to deformation when annular mass160strikes plunger163during an opening operation of vacuum interrupter104, as will be described below. Annular mass has a first portion172, a second portion174, and a third portion176. Counter bore170extends through mass160and has a first diameter at first portion172, a second diameter at second portion174, and a third diameter at third portion176. The third diameter is larger than the second diameter, which is larger than the first diameter. Portions172,174, and176are each cylindrical in shape and circumscribe at least portions of the other components of contact spring assembly106. First portion172defines a striking surface177at the transition between the first diameter and the second diameter of bore170for impacting plunger163during opening operations of vacuum interrupter104. In the example provided, striking surface177is an annulus. It should be appreciated that other shapes, such as a conical surface, may be used without departing from the scope of the present disclosure.

Annular mass160has a generally cylindrical outer surface180with rounded outer edges182. Cylindrical outer surface180has an extended diameter to increase the inertial mass of annular mass160. As used herein, an “extended diameter” means that the diameter is larger than any diameter needed for structural support of components in contact spring assembly106. The added inertial mass from the extended diameter improves the hammer-blow effect when annular mass160impacts plunger163to assist with opening welded contacts within vacuum interrupter104, and limits the severity of contact welding during closing operations, as will be appreciated by those with skill in the art.

Rounded outer edges182reduce electrical stresses that occur between components of contact spring assembly106that are at high voltage differential with respect to the insulating material of the dielectric drive rod168and housing102. Because annular mass160may be at high voltage, rounded edges provide reduced concentrations of electric charge when compared with sharp edges. Therefore, rounded outer edges182reduce chances of dielectric breakdown of the air and arcing within first cavity120towards materials located outside of first cavity120.

Annular mass160is disposed proximate to vacuum interrupter104. As used herein, annular mass160being “proximate to” vacuum interrupter104means that annular mass160is located as close as the various connections allow to an interface between stationary contact130and moving contact132. In the example provided, annular mass160is located closer to interface134than to external opening123of first cavity120. Such proximity provides a beneficial mass ratio between moving contact132and the effective mass acting to pull open moving contact132.

By having an enlarged and rigid amount of mass proximate to moving contact132, impact losses may be reduced when compared to systems where masses are farther away from a moving contact. Impact losses during the opening operation can occur through a number of factors; the accumulation of joints (e.g., pin slop), the strain of its components (e.g., stretch and flexing), and the inefficient distribution of effective mass, whether rotational or linear motion. The proximity also increases the natural frequency of vibration of the components between the mass160and the contact interface134, and reduces the duration of contact bounce upon closing vacuum interrupter104. Limiting the duration of contact bounce lessens arc duration and contact separation, which leads to smaller welds with less mechanical strength. Such improved weld breaking and reduced contact bounce also permits low spring contact forces and pressures as necessary for current carrying purposes. Lower contact pressure leads to a reduction in the force a drive mechanism needs to exert on dielectric drive rod168to close vacuum interrupter104. This reduction in force improves the drive mechanism reliability, reduces the ‘hold close’ latching force, and reduces the amount of energy needed to drive or charge the energy storage elements, as will be appreciated by those with skill in the art.

Threaded rod162threads into moving contact132and plunger163. Flexible coupling112is fastened to threaded rod162to keep threaded rod162electrically coupled with first external conductor110during opening and closing of vacuum interrupter104. Annular mass160is disposed proximate to vacuum interrupter104in part due to a length of threaded rod162. In the example provided, the length of threaded rod162is defined by a size of flexible conductor112and any associated fasteners, as well as an amount of threaded rod162that will extend into moving contact132and plunger163when fastened. In the example provided, threaded rod162is received for sliding translation in ferrule166.

Plunger163has a flange portion184and a body portion186. Body portion186is attached to threaded rod162, such as by receiving threaded rod162with complementary threads. Flange portion184is disposed within inner bore170at second portion174and has a flange diameter that is larger than the first diameter at first portion172. Body portion186is received for translation through inner bore170at first portion172. In the closed position of vacuum interrupter104, flange portion184is separated from striking surface177of first portion172by a “lost motion” distance188. Lost motion distance188is selected in part based on a spring constant of contact spring164, and may be on the order of several millimeters. In the example provided, lost motion distance188is four millimeters.

Contact spring164is disposed within second portion174of inner bore170between plunger163and ferrule166. When vacuum interrupter104is in the closed position, contact spring164is compressed by the lost motion distance188to bias moving contact132with a contact pressure. Contact pressure maintains low contact resistance and prevents contacts from separating due to the blow-off effect while accommodating high electrical current, as will be appreciated by those with skill in the art.

Ferrule166is fastened within inner bore170at third portion176and is configured to receive dielectric drive rod168. For example, ferrule166may be threaded into third portion176and may receive dielectric drive rod168with a threaded connection.

Dielectric drive rod168is threaded at a first end into ferrule166. Dielectric drive rod extends through first cavity120and external opening123to a second end on which a drive mechanism coupler190is attached for actuation of contact spring assembly106. For example, drive mechanism coupler190may be configured to attach to a mechanical, electrical, or pneumatic actuator that is operable to pull dielectric drive rod168and open vacuum interrupter104, as will be described below. In the example provided, dielectric drive rod168has a drive rod length that is longer than a distance between annular mass160and interface134. Accordingly, dielectric drive rod168accommodates the location of annular mass160proximate to vacuum interrupter104.

It should be appreciated that in alternative embodiments, contact spring assembly106may be located in other electrical contact assemblies (e.g., contactors, relays, switches) that perform closing under load duties. In other alternative embodiments, contact spring assembly106may be utilized in actuation of high pressure fluid valves or in work hardening presses.

During opening of vacuum interrupter104, a drive mechanism pulls drive mechanism coupler190away from solid insulation housing102. Dielectric drive rod168transmits the driving force from the drive mechanism to ferrule166, which transmits the driving force to annular mass160. Annular mass160accelerates away from vacuum interrupter104based on the driving force and a force from contact spring164and builds inertia as annular mass160travels over lost motion distance188. When annular mass160has traveled lost motion distance188, striking surface177of annular mass160impacts flange portion184of plunger163. The impact provides a hammer-blow effect to plunger163, which provides the impact force to threaded rod162, which provides the impact force to moving contact132. The impact force provided to moving contact132breaks the weld at interface134to open vacuum interrupter104.