Contactors are the heart of motor starters and many other important electrical installations and panels. They make or break the connections after receiving signals from either Over-Load Relays or any other mechanism. Being capable of performing millions of operations they have Silver Alloys as contacts and the outer body is heat resistant. They consist of a Solenoid Coil, a Core (set) and Contacts.
The technical and commercial potential for vacuum contactors is evident. Advances in the science of vacuum-sealing techniques and contact metallurgy have provided reliable high-performance products. This opportunity for vacuum control in mining and pumping applications is mainly due to the voltage utilization level. Vacuum contactors are inherently better suited for switching voltages above 600 V. In addition, the product's smaller size and competitive price at higher voltage proves vacuum to be an effective alternative to the air-break devices in these and other process industries. The issue, however, is not nearly as clear on applications involving voltage levels of 600 V and less. Air-break and vacuum devices have their own place at these voltage levels, and the optimum choice in a given situation is dependent on several factors, not the least of which are the application and the horsepower of the motor being switched.
Now in the case of vacuum contactors versus air break contactors, several factors should be considered.
|Contact Welding Risk||Low||High|
Arcing Time and Temperature
Contained inside a vacuum bottle, the vacuum contactor’s contacts generate very little temperature or arcing thus increasing life span of contacts almost unlimited. The air-break has much longer arc time and high arc temperature. This degrades the contacts resulting in frequent replacement and maintenance.
Contact Welding Risk and Oxidation
With the increased arc time & temperature mentioned above, the risk of contact welding and oxidations increases in air-break contactors. This raises the resistance at low currents, presents a voltage drop that could affect your application.
Electrical and Mechanic Life
Since the contacts are in a vacuum bottle the electrical life is unlimited and a robust interrupter & cold system provides the vacuum contactor with 1 million+ mechanical cycles.
Due to the arcing & contact degradation of an air break contactor, a maintenance regime will be needed. Personnel, time, material adds operating costs versus that of a maintenance free vacuum contactor.
Even at 480V, a vacuum contactor should be considered for long life, low maintenance and reliable operation when comparing an air-break contactor. While the initial cost is higher, the longer life of the vacuum contactor warrants a cost analysis.