Patent Application
20220208489
The present disclosure relates to switch mechanisms for medium voltage electric equipment.
Medium voltage circuit breakers used in industrial and commercial applications, may have a rated maximum voltage of, for example, from 5 to 15 kV, a rated continuous current of, for example, from 1200 to 2000 Amperes, and a rated power frequency of, for example, 60 Hz. Medium voltage circuit breakers typically handle three-phase voltage systems and have line and load primary disconnects for each phase, which are heavy duty electrical connectors.
Medium voltage circuit breakers are designed to limit the peak magnitude of fault current that flows through them by opening within a AC first half-cycle after fault initiation, before the fault current has a chance to reach its peak value. This helps provide a degree of protection for downstream equipment that could otherwise be damaged by the magnetic or thermal effects produced by the high-level faults. When a fault is detected, the trip mechanism in the circuit breaker immediately releases spring energy of the main current carrying contacts of the circuit breaker to rapidly move apart, interrupting the main current.
To reduce the destructive effects of arcing on the main contacts, medium voltage circuit breakers are designed to rapidly close the main contacts by means of a closing spring that is compressed by a charging motor or manual charge handle to store mechanical energy. When the closing spring has been compressed to the charged position, a closing latch holds the closing spring in a fully compressed position. When a close button is pressed or a close coil is energized, the close latch is removed and the closing spring engages the closing linkage to abruptly force the contact arm to drive the main contacts together.
Auxiliary switches in the circuit breaker are mechanically coupled to the main contacts and change state when the main contacts change, to pass an indication of the state of the main contacts as being open or closed. In order to ensure that the electrical indication does not itself fail due to the interruption of the main current, the open/closed state of the main current carrying contacts is mechanically signaled to the auxiliary switches by a mechanical linkage to the main current carrying contacts.
In the previous designs, the force of rapidly opening and closing the main contacts would push directly into the auxiliary switch, which could cause damage to the switch.
What is needed is a mechanical mechanism for signaling the open or closed state of the main current carrying contacts to the auxiliary switches, which reduces the forces transmitted to the auxiliary switch.
In accordance with one example embodiment described herein, a crank arm of an auxiliary rotary switch in a circuit breaker changes electrical connections of contacts in the auxiliary rotary switch when the crank-arm is rotated about its axis. An auxiliary switch actuator decouples abrupt forces from being applied to the crank arm resulting from closing the main contacts of the circuit breaker. In response to the main contacts starting to close, the crank arm is set into rotation by motion of a connection-state link that is coupled to the main contacts. The rotation of the crank arm continues up to a point at which the rotation is stopped, while the connection-state link continues its motion without being connected to the crank arm. In this manner, the connection-state link is decoupled from the crank arm, to relieve the crank arm from receiving the abrupt forces conducted by the connection-state link resulting from the main circuit breaker contacts closing.
A return spring in the circuit breaker is connected to the connection-state link to apply a second force to the connection-state link. When the main circuit breaker contacts are opening, the edge of the aperture of the connection-state link comes into contact with the crank pin and applies the second force to the crank pin. This imparts a rotary motion to the crank arm about the axis in a second rotary direction opposite to the first rotary direction, to rotate the auxiliary rotary switch corresponding to the opening of the main circuit breaker contacts.
In accordance with one example embodiment described herein, an auxiliary switch actuator for a circuit breaker, comprises:
In accordance with the example embodiment described herein, a return spring in the circuit breaker connected to the connection-state link, the return spring having a spring bias configured to apply a second force to the connection-state link;
In accordance with the example embodiment described herein, wherein, the drive link is configured to not contact the connection-state link in response to opening of the main circuit breaker contacts, and the second force of the return spring on the connection-state link is configured to cause the edge of the aperture of the connection-state link to force the crank pin to impart a rotary motion to the crank arm about the axis in a second rotary direction opposite to the first rotary direction to rotate the auxiliary rotary switch corresponding to the opening of the main circuit breaker contacts.
In accordance with the example embodiment described herein, wherein, the return spring and weight of the connection-state link have a combined force that is applied by the upper edge of the aperture of the connection-state link to the crank pin, which is greater than the force of the crank spring applied to the crank pin, to impart the rotary motion to the crank arm about the axis in the second rotary direction corresponding to the opening of the main circuit breaker contacts.
In accordance with an example embodiment described herein, wherein while the main contacts are closed, a holding link coupled to the main contacts is configured to support the connection-state link against the force of the return spring;
In accordance with an example embodiment described herein, wherein when the main circuit breaker contacts open, the upper edge of the aperture of the connection-state link pushes against the crank pin of the crank arm as it moves in the second rotary direction;
In accordance with one example embodiment described herein, an auxiliary switch actuator for a circuit breaker, comprises:
In accordance with the example embodiment described herein, a return spring in the circuit breaker is connected to the connection-state link, the return spring having a spring bias configured to apply a downward directed force to the connection-state link;
In accordance with the example embodiment described herein, wherein, the downward directed force of the return spring on the connection-state link is configured to maintain the connection-state link in contact with the upward directed force of the drive link on the connection-state link in response to closure of the main circuit breaker contacts.
In accordance with the example embodiment described herein, wherein, the drive link is configured to not apply the upward directed force to the connection-state link in response to opening of the main circuit breaker contacts, and the downward directed force of the return spring on the connection-state link is configured to cause the upper edge of the aperture of the connection-state link to apply a downward directed force on the crank pin to impart a rotary motion to the crank arm about the axis in a second rotary direction opposite to the first rotary direction to rotate the auxiliary rotary switch corresponding to the opening of the main circuit breaker contacts.
In accordance with the example embodiment described herein, wherein, the return spring and weight of the connection-state link have a combined downward directed force applied by the upper edge of the aperture of the connection-state link on the crank pin, which is greater than the upward directed force of the crank spring on the crank pin, to impart the rotary motion to the crank arm about the axis in the second rotary direction corresponding to the opening of the main circuit breaker contacts.
In accordance with one example embodiment described herein, a circuit breaker, comprises:
In accordance with the example embodiment described herein, a return spring in the circuit breaker connected to the connection-state link, the return spring having a spring bias configured to apply a second force to the connection-state link;
In accordance with the example embodiment described herein, wherein, the drive link is configured to not contact the connection-state link in response to opening of the main circuit breaker contacts, and the second force of the return spring on the connection-state link is configured to cause the edge of the aperture of the connection-state link to force the crank pin to impart a rotary motion to the crank arm about the axis in a second rotary direction opposite to the first rotary direction to rotate the auxiliary rotary switch corresponding to the opening of the main circuit breaker contacts.
In accordance with the example embodiment described herein, wherein, the return spring and weight of the connection-state link have a combined force that is applied by the upper edge of the aperture of the connection-state link to the crank pin, which is greater than the force of the crank spring applied to the crank pin, to impart the rotary motion to the crank arm about the axis in the second rotary direction corresponding to the opening of the main circuit breaker contacts.
The resulting apparatus provides a mechanical mechanism for signaling the open or closed state of the main current carrying contacts to the auxiliary switches, which reduces the forces transmitted to the auxiliary switch.
A more detailed description of the disclosure, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. While the appended drawings illustrate select embodiments of this disclosure, these drawings are not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
Identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. However, elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Generally, medium voltage circuit breakers have a rated maximum voltage of from 5 to 15 kV, a rated continuous current of from 1200 to 2000 Amperes, at a rated power frequency of 60 Hz. A racking mechanism is used to insert or rack the breaker into a metal-enclosed switchgear cabinet having line and load primary buses accessible at the back of the cabinet. When the line and load primary disconnects of the breaker are initially connected to the primary buses, the main contacts of the breaker remain open in what is referred to as the disconnected position. While in the disconnected position with the main contacts open, secondary power may be connected to the breaker to enable testing. For each phase, the breaker has a moving contact arm with one end pivotally connected to a corresponding phase load-side primary connector or bushing. The bushing is connected to a corresponding phase load-side disconnect, and the moving contact arm has a main contact on the other end. For each phase, the breaker has a stationary contact connected to a corresponding phase line-side primary connector or bushing connected to a corresponding phase line-side disconnect. For each contact arm, an insulated link connects the moving arm to contact closing linkage and contact opening linkage that open or close the main contacts of the breaker.
To reduce the destructive effects of arcing on the main contacts, medium voltage circuit breakers are designed to rapidly close the main contacts by means of a closing spring that is compressed by a charging motor or manual charge handle to store mechanical energy. When the closing spring has been compressed to the charged position, a closing latch holds the closing spring in a fully compressed position. When a close button is pressed or a close coil is energized, the close latch is removed and the closing spring engages the closing linkage to abruptly force the contact arm to drive the main contacts together. When the main contacts close, the contact opening linkage latches the contacts in the closed position with a trip latch, to allow the closing spring to return to its originally decompressed state, enabling it to be recharged.
Medium voltage circuit breakers are designed to rapidly open the main contacts by means of an opening spring during a trip event, to limit the peak magnitude of fault current that flows through the main contacts to within a AC first half-cycle after fault initiation, before the fault current has a chance to reach its peak value. The opening spring is compressed during the close operation and its energy is stored until a trip event occurs, or until an open button is pressed or an open coil is energized. When the main contacts are in the closed position, the trip latch is in position to hold the contacts closed. For the circuit breaker to remain in the closed position, the main contacts have to be held in the closed position by the trip latch. To trip the circuit breaker, either by a trip event or by pressing the open button or energizing the open coil, the trip latch is removed and the opening spring engages the opening linkage to force the contact arm to drive the main contacts apart.
Medium voltage circuit breakers are designed with an auxiliary switch that is mechanically coupled so as to respond to the opening or closing of the main contacts, so that auxiliary contacts change state when the main contacts change. The auxiliary switch passes data on the state of the contacts to a logic controller, which in turn gives instructions to linked devices about whether to turn on or off. An auxiliary circuit is designed to control, measure, signal and regulate other parts of the breaker, other than the main breaker current.
The circuit breaker 100 may be a three phase unit in which each phase has a moving contact arm 106 with one end pivotally connected to a corresponding phase load-side primary connector or bushing 102. The moving contact arm 106 has a main moving contact 108 on the other end. For each phase, the breaker 100 has a stationary contact 110 connected to a corresponding phase line-side primary connector or bushing 104.
Each contact arm 106 connects to a contact closing linkage 204, via the linkage functional interface 200, to close the main contacts 108 and 110 when the close button is pressed or close coil is energized 216, which removes the close latch 214 so that the closing linkage 204 forces the contact arm 106 to drive the main contacts 108 and 110 together. An example of the structure and operation of the linkage functional interface 200, contact closing linkage 204, close latch 214, close coil 216, and closing spring 215 to close the main contacts 108 and 110 is disclosed in U.S. Pat. No. 3,773,995 to Davies, entitled “Motor Advanced Spring Charging Pawl and Ratchet Mechanism with Spring Assist”, issued Nov. 20, 1973, which disclosure is incorporated herein by reference.
Each contact arm 106 connects to a contact opening linkage 202, via the linkage functional interface 200, to open the main contacts 108 and 110, either when a trip event occurs or when the open button is pressed or open coil is energized 212, which removes the trip latch 210 so that the opening linkage 202 forces the contact arm 106 to drive the main contacts 108 and 110 apart. When the trip latch 210 is removed, the opening spring 211 engages the contact opening linkage 202 to force the contact arm 106 to drive the main contacts apart. An example of the structure and operation of the contact opening linkage 202, trip event detection, trip latch 210, and opening spring 211 to force the main contacts apart is disclosed in the U.S. Pat. No. 3,773,995 to Davies, entitled “Motor Advanced Spring Charging Pawl and Ratchet Mechanism with Spring Assist”, issued Nov. 20, 1973, which disclosure is incorporated herein by reference.
The auxiliary switch actuator 101 includes a crank arm 152 of the auxiliary rotary switch 150 in the circuit breaker 100, which changes electrical connections of contacts in the auxiliary rotary switch when the crank-arm 152 is rotated about its axis. The auxiliary switch actuator 101 includes mechanism 160 configured to move the crank arm 152 in two different resting positions 164 (
A connection-state link 170 is coupled to the main contacts 108 and 110 of the circuit breaker 100, by means of the contact closing linkage 204 and the contact opening linkage 202. In
The crank arm 152 of the auxiliary rotary switch 150 is configured to change electrical connections of contacts in the auxiliary rotary switch 150 when the crank arm 152 is rotated about its axis. The rotation of the crank arm 152 about its axis in a first or clockwise rotary direction is limited to a rotation limit by a limit pin 180 or limit stop.
The crank spring 168 connected to the crank arm 152 at an end opposite to the axis of the crank arm 152, has a spring bias configured to apply an upward directed force to the crank arm 152 to impart a rotary motion to the crank arm 152 about the axis in the first rotary or clockwise direction to rotate the auxiliary rotary switch 150.
The connection-state link 170 in the circuit breaker 100, has an aperture 173 with an upper edge 177 configured to contact the crank pin 176 mounted on the crank arm 152 at the end opposite to the axis of the crank arm 152. The crank pin 176 is configured to apply an upward directed force on the upper edge 177 of the aperture 173 of the connection-state link 170 in response to the spring bias of the crank spring 168.
The connection-state link 170 is contacted by the drive link 208 coupled to the main contacts 108/110 of the circuit breaker 100. The drive link is configured to apply an upward directed force to the connection-state link 170 in response to closure of the main circuit breaker contacts 108/110 to move the connection-state link 170 in the upward direction. This action thereby reduces the upward directed force by the crank pin 176 on the upper edge 177 of the aperture 173 of the connection-state link 170 and enables the crank arm 152 to impart the rotary motion to the crank arm 152 about the axis in the first or clockwise rotary direction to rotate the auxiliary rotary switch 150 corresponding to the closure of the main circuit breaker contacts.
The limit pin 180 (
The drive link 208 provides support to the connection-state link 170 against the downward spring force of the return spring 172. This support ends when the contact closing linkage 204 drops or withdraws the drive link 208 (
Each contact arm 106 connects to an opening linkage 202, via the linkage functional interface 200, to open the main contacts 108 and 110, either when a trip event occurs or when the open button is press or the open coil is energized 212, which removes the trip latch 210 so that the opening linkage 202 forces the contact arm 106 to drive the main contacts 108 and 110 apart.
In the auxiliary switch actuator 101, when the main contacts begin opening (
The resulting apparatus provides a mechanical mechanism in the circuit breaker, for signaling the open or closed state of the main current carrying contacts to the auxiliary switches, which reduces the forces transmitted to the auxiliary switch.
In the preceding, reference is made to various embodiments. However, the scope of the present disclosure is not limited to the specific described embodiments. Instead, any combination of the described features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the preceding aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementation examples are apparent upon reading and understanding the above description. Although the disclosure describes specific examples, it is recognized that the systems and methods of the disclosure are not limited to the examples described herein but may be practiced with modifications within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
This application claims the benefit of and priority to U.S. Provisional Application No. 63/131,396, filed on Dec. 29, 2020 under 35 U.S.C. 119(e), which application is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63131396 | Dec 2020 | US |
