Vacuum relays

Jennings vacuum relays are widely used in airborne, mobile and marine communications equipment. Typical applications include antenna coupling, tap changing on radio frequency coils, transmit and receive switching to an antenna, switching in pulse-forming networks and heavy duty power supplies.

Jennings vacuum relays are available in SPST normally open (N/O) and normally closed (N/C) models, as well as SPDT configurations. Latching relays are available in some models.

Vacuum as a dielectric

Vacuum is the ideal dielectric for high voltage relay switching. It has extremely high voltage breakdown characteristics, a fast recovery rate (up to 10 kV per millisecond) and it provides an absolutely inert and non-reactive environment for switching contacts. Since there is no oxygen in a vacuum, contacts remain oxidation free. The high dielectric strength of the vacuum permits close contact spacing, on the order of 1000 V per mil. The small movement required to operate a vacuum relay permits the use of small, low mass actuators, allowing high operating speeds. Use of refractory metal contacts provides exceptional interrupting ability and ensures long contact life.

If a load is switched, an arc will form. At the point where the contacts are getting very close and the current density is getting higher and higher, a breakdown occurs. This arc will have a very low voltage of 18–23 V and be quite stable in comparison to an arc in air, which is another advantage of vacuum. The vacuum relay constant arc voltage acts as a current limiter and, when considered in combination with the inherent short arc time, offers a technology that generally wears less than other types of relays, providing stable performance over the life of the relay

Jennings vacuum relays product selection

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