VB5 (ZN21B) -12 Vacuum Circuit Breaker Product Structure and Working Principle
November 06 , 2020

1. Electrical Structure (see Figure 1)

VB5 VCB Structure

Figure 1 Schematic diagram of solid-sealed pole structure

The electrical main circuit part of VB5 (ZN21B) adopts advanced epoxy resin casting technology, and the vacuum interrupter is directly sealed in epoxy resin, and there is a silicone rubber buffer layer between the two, which becomes a casting type circuit breaker pole. column. This process makes the conductive circuit not affected by the external environment (such as dust, moisture), and greatly improves the insulation level of the vacuum interrupter, reduces the insulation distance between the vacuum circuit breakers, and reduces the volume of the vacuum circuit breaker. Be maintenance-free. The cylindrical poles are arranged vertically and horizontally, the electric field distribution is excellent and the dust is not easy to gather. The upper and lower outlet arms are the intermediate links between the circuit breaker and the external primary circuit, and also play a role in transmitting and dissipating the internal heat of the circuit breaker. The vacuum interrupter is the heart of the circuit breaker, and the primary circuit is disconnected and connected. All are done in this part. The movable conductive part of the arc extinguishing chamber is connected with the lower outlet arm through a soft connection. The function of the circuit breaker is that the operating mechanism transmits the kinetic energy to the movable conductive rod by driving the insulating transmission member.

2. Working principle of vacuum interrupter (see Figure 2)

Working principle of vacuum interrupter

Figure 2  Cross-section drawn of vacuum fire extinguishing chamber

VB5 Vacuum Circuit Breakers use specially designed contacts to close and separate in a highly vacuum arc extinguishing chamber to achieve the purpose of closing and breaking the line current. Due to the high degree of vacuum with extremely high insulation strength, in the opening position, only a small contact distance can meet the insulation requirements. When the circuit breaker receives the closing signal under the action of the operating mechanism, the moving contact The head moves upward and contacts the static contact, completing the closing process. When the circuit of the ASHARE good quality circuit breaker is energized, when the opening signal is received, under the action of the operating mechanism, the moving contact moves downwards and leaves the static contact. The moving and static contacts separate instantly and an arc is generated. At the same time, the arc current flowing through the special structure of the contact produces a longitudinal magnetic field, which interacts with the arc, and the charged particles are rotated and diffused by the Lorentz force and move at high speed along the arc. Therefore, the burning damage to the contact surface by the arc is not concentrated in a small range, and the burning damage on the contact surface is lighter and uniform. When the arc current naturally crosses zero for the first time, it is extinguished. The residual ions, electrons and metal vapor can recombine or condense on the contact surface and the shield in a fraction of a millisecond. Therefore, the vacuum medium After the arc, the insulation strength recovers extremely quickly. Under a certain contact distance, the AC arc is extinguished to achieve the purpose of breaking the current.

3. Introduction of CRR1000 operating mechanism transmission (see Figure 3)

 VB5 Circuit Breaker mechanical transmission

Figure 3 Schematic diagram of mechanical transmission

As shown in Figure 3: The box is used as a shell to install and support various parts of the operating mechanism. The energy storage system consists of an energy storage motor with a transmission (items 4, 28), a secondary chain drive (item 29), a triangle arm (item 3), a traction chain (item 2), a guide sprocket (item 37), The closing spring (item 1), limit switch S1 (item 21), drive arm (item 26), energy storage shaft and clutch arm (item 20) are composed.

The cam transmission system consists of a cam (item 9), a transmission plate (item 11), a roller (item 10), an ejector rod (item 13), a main shaft (item 14), a contact pressure spring (item 18), and a main arm (item 18) Item 15), opening spring (item 17), and oil buffer (item 23). The closing and opening holding and releasing devices are each composed of a secondary holding crank arm (item 6, item 27, item 30, and item 31), a small crank arm (item 12) and a closing and opening operating handle.

The secondary control system consists of auxiliary switch QF (item 19), limit switch S1 (item 21), closing and opening coils HQ, TQ (item 8, item 22).

4. Energy storage system

The energy storage shaft is operated by the manual energy storage handle, or the motor and the reducer rotate the arm to rotate, so that the chain generates traction and the closing spring is compressed to complete the energy storage process and store 1000 joules of energy.

5. Closing operation

After the spring is charged, the crank arm deviates from the dead center by some angle, the closing spring will make the crank arm continue its stroke, but the crank arm of the closing interlock prevents the continued stroke of the crank arm. In this case, the clockwise rotation of the knob or the pulse jump of the trip coil keeps the closing interlocking arm ineffective. Then the crank arm is released, driving the cam to cause the crank arm to rotate. The main operating shaft is driven to rotate counterclockwise through the connecting rod, the contact pressure spring is pressed down, the main turning arm rotates clockwise, and the movable contact of the conductive rod in the vacuum arc extinguishing air moves upward through the insulator, so that the circuit breaker is closed. The auxiliary switches act at the same time, and the closing state is maintained by the closing arm. The rotation of the crank arm causes the clutch on the motor and reducer to operate and the limit switch contact rod to reverse. The limit switch can control the stored energy of the motor and indicate the state of the closing spring.

6. Opening operation

The opening spring and the contact pressure spring have stored energy during the closing process and are held by the arm. The opening coil is energized or the closing and opening knob is manually turned counterclockwise to make the arm invalid and cause the arm to rotate counterwise. , The opening spring and contact pressure spring are released, and the circuit breaker is opened. Near the final position of opening, the oil buffer starts to act and absorb the remaining kinetic energy of opening.

7. Automatic reclosing

When the Circuit Breaker is closed, the closing spring automatically recharges energy, which is accomplished by re-energizing the motor by closing the limit and closing contacts. Or use the handle to operate the shaft manually. Thus, the operating mechanism can prepare for automatic reclosing operation of the circuit breaker. In the event of a wrong closing command operation, the anti-trip relay can prevent the automatic reclosing of the circuit breaker. When the circuit breaker is closed, the roller of the turning arm can be closed and interlocked, which can prevent the opening of the circuit breaker and the false release of the closing spring.

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