Arc Flash Control with New RVI-43A Vacuum Interrupter

Vacuum Interrupters has released the RVI-43A, a circuit interrupter that enhances industrial safety and equipment surety. The RVI-43A keeps employees safe from high currents, as well as arc flash hazard during operation by disconnecting the circuit in a small vacuum chamber, instead of allowing arcing to occur in the open. This interrupter is designed to replace several common interrupters, including the General Electric (GE) Power/Vac VB, VB1H, PVDB1, VVC, and PV-VL vacuum circuit breakers, and catalog numbers 0282A2751G047 and 0282A2751G062.

 

Vacuum Interrupters’ new line of RVI-43A vacuum devices. Image used courtesy of Vacuum Interrupters

 

What are Vacuum Interrupters?

Although the manufacturer is named Vacuum Interrupters, this is also the label for a category of industrial devices. A vacuum interrupter is a mid-to-high range current limiting device, a circuit breaker used for industrial circuits. When an overcurrent condition is detected, the contacts pull apart inside the vacuum housing. The contact breaks, disconnecting the circuit and thus limiting the potential for electrical shock or fire. Vacuum interrupters are used on power generation switchgear, arc furnaces for melting steel, railways, manufacturing plants, refineries, and many other high-voltage applications. 

A good vacuum interrupter will act quickly, breaking the circuit and withstanding high voltage between the contacts. Because a true vacuum is a good insulator, the broken circuit cannot arc across it, and the circuit is shut down. The interrupter itself must maintain a good vacuum seal, or else the vacuum will be backfilled by air, moisture, and dust, and will not function properly. The body of the interrupter must also withstand brief high temperatures and debris from an arc flash.

 

The Bulwark arc flash suit. This and other kinds of flash suits protect workers from injury while dealing with broken circuits. Image used courtesy of Model Apparel

 

What is Arc Flash?

Arc flash is present any time a circuit is physically broken. As the conductors spread apart, the air between them temporarily breaks down, just like with a static shock from rubbing feet on the carpet and touching a doorknob. However, unlike the low current static shock, high currents arc across the gap, melting and even vaporizing metal. The violent process often launches sparks and metal shrapnel in all directions. A good vacuum interrupter surrounds this disconnection, catching the sparks, shrapnel, and debris, preventing injury and fire.

 

Vacuum Interrupters’ RVI-43A. Image used courtesy of Vacuum Interrupters

 

The RVI-43A

This vacuum interrupter was designed as a replacement for several common or obsolete interrupters, such as the General Electric (GE) Power/Vac VB, PVDB1, VVC, and many others. The RVI-43A is designed to meet ANSI C37, the standard to test conformance of circuit breakers on electrical switchgear, for both impulse and AC threats. While ruggedly built for the industrial sector, they are also small and lightweight, making them easier to handle and replace as necessary. Besides ANSI C37, the vacuum interrupters are subjected to stringent testing requirements to ensure proper disconnection during an overcurrent event.

The case is made from fine-grained alumina (aluminum oxide) for its favorable electrical properties, low porosity, resistance to chemical attack, and strength. As machined, it can also form a tight seal, which will maintain the vacuum chamber. The contacts inside are made from copper and chromium, and have an internal torsion control to keep torque on the power line from twisting the contacts apart. This is especially useful for outdoor installations, such as electrical switchgear, where wind loading generates torsional forces on the line.

 

Bottom Line

The Vacuum Interrupter RVI-43A is a replacement for several existing interrupters, made from high-quality materials, and passing through rigorous testing. The installation of a vacuum interrupter will improve the safety of any mid to high voltage application, where overcurrent is possible, without increasing the arc flash hazard.