CT20 spring operating mechanism principle--about High Voltage SF6 Circuit Breaker

CT20 series spring operating mechanisms are widely used in domestic substations. It is impossible for any mechanism to be perfect, because the production of high-power operating mechanisms is a manual job, and there are problems in the entire process from production to operation. Various possible influencing factors.

When a defect or failure occurs in the operating mechanism, the cause must be analyzed. First, we must have a very clear understanding of the operating principle of the operating mechanism of the structure. This is very important to accurately grasp the cause of defects and formulate elimination plans.

This article explains the principle of the operating mechanism of this structure. Figures a, b and c in the article respectively correspond to the different states of this type of mechanism (closing & closing has stored energy, opening & closing spring has stored energy, closing The gate & closing spring is not charged & the opening spring is charged):

In the mechanism schematic diagram in Figure a above, the mechanism is in the closing position and the closing spring has stored energy. The solid black circles and solid black hexagons in the picture are the shafts on the transmission chain. These shafts are carried through bearings or directly by the aluminum alloy base of the operating mechanism. These shafts can only rotate, or they cannot rotate, but the bearings transmitted to the shaft rotate to realize their functions. The X and Y coordinate positions of these shafts in the above figure will not change.

The upper end of the "lever arm 18" in the picture a above is connected to the sliding tray of the "opening spring 2" through a shaft pin (used to compress the opening spring 2, see the yellow rectangle on the left end of the opening spring, also refer to the picture c below ; But "arm 18" is two parts).

In the closed state:

At this time, the energy in the opening spring will push the yellow sliding spring plate on its left side to move to the left, and the pull rod fixed on this plate will further push the "lever arm 18" to rotate counterclockwise. "Arm 18" and "Arm 14" are connected through the hexagonal axis in the middle. The counterclockwise rotation of "Arm 18" will drive the arm 14 to rotate counterclockwise. The "pin A" at the lower end of the "lever arm 14" pushes the "closing holding latch 13" to rotate clockwise. The red circle on the "closing holding pawl 13" is the cylindrical pin or bearing fixed with it. At this time, since the "closing holding pawl 13" has a tendency to rotate clockwise, the red pin will press the opening On the pawl 12, there is a tendency for the "opening pawl 12" to rotate counterclockwise (as can be seen from Figure a-2 below, due to the design direction of the arc surface at the top of the opening pawl, the force is Obliquely downward direction, and this force can be decomposed into a downward force along the radius of the opening pawl's rotation axis and a force in the tangential direction to the left along the top of the opening pawl. It is this component force that causes the opening pawl. There is a tendency to turn counterclockwise). As can be seen from Figure a-2 below, the "opening detent return spring" on the upper right is a compression spring, pushing the "opening detent 12" to rotate counterclockwise. However, there is a limited shaft pin on the left side above the opening pawl (not shown in the picture), which restricts the opening pawl from continuing to rotate counterclockwise as shown in Figure a.

In this way, the circuit breaker mechanism remains in the closed state.

It should be noted that there is no gap between the opening electromagnet push rod and the opening latch in the schematic diagram of Figure a and Figure a-2, but in fact there is a gap. The size is about 0.8~1.2mm. Ensure that the electromagnet The iron core push rod has a certain initial velocity before hitting the opening detent.

Opening of Operating Mechanism:

The opening process is from the picture a above (Figure a-2 is a partial enlargement of picture a) to the picture b below. In the picture b below, the mechanism is already in the opening state (you can see that the opening spring is a compression spring. Compared with Figure a, its length has been longer and the energy in the compression spring has been released).

When the "opening coil 10" in Figure a is operated remotely, locally, or manually, its electromagnet core (see "Opening electromagnet core 11" in the figure above) will move to the left, pushing the The "opening latch 12" in a rotates clockwise (compressing the return spring B on the upper left side). After it rotates, the limit of the "closing holding latch 13" no longer exists, and the "closing latch" The holding latch 13" will rotate clockwise, and its rotation will cause the "lever arm 14" and "lever arm 18" to rotate counterclockwise along the hexagonal axis at the center of the "lever arm 14". After the rotation, the energy of the opening spring is released, and the operating mechanism drives the arc extinguishing chamber of the circuit breaker to complete the opening operation. The opening state of the mechanism (the closing spring still stores energy) is shown in Figure b below:

Operating Mechanism closing:

Based on the opening status of the mechanism in Figure b above, let’s analyze the closing process of the mechanism. At this time, the closing spring of the mechanism is still compressed and is in an energy-stored state. Since the closing spring in the picture is compressed, its reaction force will push the yellow sliding plate on the right side of the spring to move to the right, and the left end of the metal connecting rod that passes through the central axis of the closing spring and is connected to the sliding plate is in contact with "ratchet 3" The fixed yellow shaft pin is connected to the top. At this time, the vector direction of the force on the shaft pin is to the right. Since the yellow shaft pin is at the lower left of "ratchet shaft 4" (black solid hexagonal shaft), after decomposing the force, its There will be a component force along the tangential direction of "ratchet shaft 4" that causes the shaft to rotate counterclockwise.

The partial enlargement of Figure b is shown in Figure b-2. The "ratchet pin" on "ratchet 3" presses on the "energy storage holding detent" shown in Figure b, so that it has a black solid axis around its right side. The trend is to move counterclockwise. The red cylindrical pin (or bearing) on the "energy storage holding latch" presses the "closing latch 6", making it tend to rotate counterclockwise along its circular black solid axis (the principle of component force and the principle of component force) The brake lever is the same).

When the mechanism receives the closing command, the closing electromagnet is energized, and the electromagnet core push rod moves to the left, pushing the "closing detent 6" to rotate clockwise, thus releasing the "energy storage holding detent shown in Figure b ”, the “energy storage holding detent” rotates counterclockwise.

The counterclockwise rotation of the "energy storage holding detent" releases the limit of the "ratchet pin" on the "ratchet 3", thereby causing the "ratchet 3" to move with its center under the force of the closing spring. The hexagonal solid shaft serves as the axis for counterclockwise rotation. The blue "cam" that shares the same rotation axis as "ratchet 3" also rotates counterclockwise. The involute surface on the cam presses on the yellow metal pin (or bearing) on the right side of the "lever arm" in Figure b, so that the "lever arm 14" and "lever arm 18" shown in Figure a are along its The black circular rotating shaft in the center rotates clockwise. Thus completing the closing operation. Since the top of the "lever arm 18" shown in Figure a is connected to the opening spring pull rod, the energy storage of the opening spring is completed during the closing process.

The relative position diagram of each component of the mechanism in the closing state (opening spring is charged & closing spring is not charged) is shown in Figure c below:

Operating mechanism recharge:

After completing the closing operation, if the motor power supply is normal, the motor begins to store energy in the closing spring. When storing energy, the blue cam "ratchet 3" as shown above will rotate counterclockwise along the hexagonal solid axis in its center. Until it reaches the state as shown in Figure a, the limit switch (travel switch) will cut off the motor circuit, and the energy storage of the operating mechanism is completed.

The above is the principle description of the CT20 series operating mechanism, for reference only.

Note: The pictures in this article are all from the Internet.