TD12-40.5/1250A Vacuum Interrupter, 35KV Vacuum Tube

ZN12, ZW7 and ZN23 vacuum interrupters, also known as vacuum switch tubes, are core components of medium and high voltage power switchgear. Their main function is to use a high-insulation medium in a vacuum environment to achieve the make and break of circuits, and quickly extinguish the arc when the current passes through zero, so as to safely and reliably cut off power lines.

I. Basic Structure and Components

A vacuum interrupter is a sealed electro-vacuum device, and its typical structure mainly includes the following systems:

Airtight insulating housing: Usually made of glass or ceramic, it is used to maintain the high vacuum state inside (the degree of vacuum is usually below 10 Pa) and provide main insulation.

Conductive system: Consists of a static conductive rod, a static contact, a moving contact, a moving conductive rod, etc. The moving contact is connected to the external operating mechanism through the moving conductive rod to realize the opening and closing operations.

Contact system: It is the key part for generating and extinguishing arcs. The contact material of vacuum interrupters for circuit breakers usually uses copper-chromium alloy (copper and chromium each account for about 50%). This material has high breaking capacity, high electrical corrosion resistance and good anti-welding performance. The early contact structure was a simple cylindrical shape, and modern ones generally adopt a longitudinal magnetic field cup-shaped structure to improve the ability to break large currents.

Shield system: Mainly composed of a shield (cylinder) surrounding the contacts. Its functions include: preventing the metal vapor generated by arcing from polluting the inner wall of the insulating housing; improving the electric field distribution inside the interrupter; absorbing part of the arc energy and helping to condense the arc products, thereby increasing the breaking capacity.

Bellows: A thin-walled elastic element made of stainless steel, welded between the moving conductive rod and the housing. Its core function is to maintain the vacuum seal inside the interrupter while allowing the moving contact to move linearly during the opening and closing processes, which is a key component for achieving high mechanical life.

II. Working Principle

The working principle of a vacuum interrupter is based on the excellent insulation and arc-extinguishing performance of high-vacuum medium:

Circuit closing: The operating mechanism pushes the moving conductive rod to close the moving and static contacts, making the circuit conductive.

Arc generation: When the charged contacts separate, the contact point shrinks rapidly, the current density increases sharply, causing the metal material to melt and evaporate into metal vapor. Under the action of a strong electric field, the metal vapor is ionized to form a vacuum arc.

Arc extinction: The vacuum arc is maintained by the metal vapor evaporated from the contact material. When the AC current naturally passes through zero, the arc is temporarily extinguished, and the metal vapor particles diffuse rapidly and condense on the shield. At the same time, the contact gap increases, and the dielectric strength of the gap recovers quickly, preventing the arc from reigniting and completely disconnecting the circuit.

III. Main Features and Advantages

Vacuum interrupter technology has the following remarkable advantages:

Safety and environmental protection: Using vacuum as the arc-extinguishing medium, there is no risk of fire or explosion, and no toxic or harmful gases are produced, resulting in no pollution during operation.

Excellent performance: Fast arc-extinguishing speed, strong breaking capacity, long electrical life and mechanical life.

Simple maintenance: Small size, light weight, compact structure, basically maintenance-free, and reliable operation.

Energy and material saving: Low energy consumption, small required operating energy, and less material consumption.

IV. Application Fields

As a core component, vacuum interrupters are widely used in the following fields:

Power system: Mainly used in vacuum circuit breakers for substations and power grid facilities, as well as vacuum load switches for power grid end users, covering voltage levels of 10kV, 35kV and even higher.

Industrial field: Widely used in power distribution systems and motor control equipment in industries such as metallurgy, mining, petroleum, chemical industry, and railways.