RELAY AND CONTACTOR DIELECTRIC MATERIALS

GIGAVAC is the established leader in the design and manufacture of sealed relays and contactors. Sealing is critical in preventing contamination from polluting the internal parts of any component. GIGAVAC has developed and uses several sealing technologies to accomplish this task for our products.  More important is that these sealing technologies allow GIGAVAC to precisely control the internal switch environment by providing a variety of dielectric medium.  This has led to several innovations including special liquid filled relays. 

The choice of dielectric is based on product design and the intended primary function of the product. For instance, High Voltage Relays are designed to isolate voltage in the smallest space possible and switch small current levels under load.  These products generally use vacuum as the dielectric. While there have been many design modifications that allow High Voltage Relays to switch larger loads, including the use of various gases as the dielectric, their load switching capability remains limited. GIGAVAC Contactors, and many of our other Power Products, are designed to switch loads at various voltage and higher current combinations. 

The two dielectric materials used throughout the GIGAVAC product offering today are vacuum and gas. 
 

Vacuum as a dielectric

The styles of High Voltage Relays manufactured by GIGAVAC were initially intended for use in high power RF circuits.  The relays were to be as small as possible, have low RF losses, have good dielectric isolation at the rated RF voltage, and be able to operate at various altitudes and in harsh environments. The dielectric strength of vacuum is about 8 times greater than air. And because there is no oxidation in a vacuum, low resistance copper contacts can be used allowing the relay to carry significantly more current than traditional open-air relays.

These small vacuum relays quickly gained acceptance and new applications. Many of these applications required additional load switching capability. In order to accommodate the larger loads relay designs were changed to include versions with harder contact materials such as molybdenum and tungsten.
 

Gas as a dielectric

As High Voltage Relays became more popular, other applications developed which took advantage of the hard contact materials. These applications include high in-rush capacitive make and capacitive discharge such as those found in ESD test equipment, cable test equipment, heart defibrillators, and for applications where no high voltage is applied for long periods of time where low and or stable leakage current is needed. In High Voltage Relays a mixture of sulfur hexafluoride, SF6, and nitrogen is used primarily because of the way the gas performs during switching. SF6 is an excellent insulator but once the switch is closed if the relay bounces the SF6 becomes easily ionized and carries the arc current. This makes the relay electronically ‘bounceless’ and dramatically reduces contact wear.

Contactors are by definition designed to switch larger amounts of power versus relays. As with relays there are several aspects of contactor design and application requirements that facilitate the use of a particular gas. GIGAVAC EPIC® sealed contactors use a ceramic to metal seal which allows the use of virtually any gas as a dielectric. Standard GX EPIC® contactors use hydrogen as a dielectric. While providing an excellent medium for the power switching requirements of the GX contactors hydrogen allows higher voltage ratings versus other gases. Standard MX EPIC® contactors use nitrogen as a dielectric. While nitrogen does not allow for the higher voltage ratings it does allow for higher inrush and overload currents at the lower voltages.

GIGAVAC also provides custom gas mixes for special applications. Just contact any of our applications experts. They are there to help you in selecting the right switching product for your circuit.