Design and Customization of High Voltage Relay for operating at RF Frequencies
The challenge was to solve difficulties with isolation of high voltage components in use in the Eurofighter at high altitude
It was discovered that the High Voltage Relays used for the Electronics Warfare Suite in the Eurofighter were arcing along the casing at High Altitude.
In order to supply the Electronics Warfare Suite for the Eurofighter, a High Voltage Relay was required for operating at RF Frequencies and capable of carrying several amps and have an Isolation Voltage of 7kV dc (at sea level).
Typical PASCHEN curve from spherical electrodes spaced at 1cm (393 inches)
Due to the shock/vibration and other mechanical requirements the RJ1D Vacuum Relay was selected as being small, compact, light and robust and offering the necessary electrical characteristics. This relay (3 per System), was designed in and tested in the Laboratory, where the unit was found to function satisfactorily. During simulated tests at high altitude, it was discovered that the relay was mysteriously breaking down.
After further testing it was discovered that the relay was breaking down across the glazed ceramic surface from High Voltage terminal to the coil casing. Although the creepage distances were adequate, no reasonable solution was found.
We were able to inform the customer that the breakdown was being caused due to the reduced isolation characteristics of air at high altitude. We supplied the customer with the paschen curve, denoting the isolation of air at different pressures. This was translated into the air pressure at particular altitudes above sea level and was found to be the reason why the system was failing. We were able to inform the customer what was causing these issues and also recommend potting materials that could be used to encase the relays and therefore eradicate the mode of failure. The customer encased the relays and the programme was brought to a successful conclusion
Due to our extensive knowledge and experience in the field of RF Transmission and high voltage systems, we were able to quickly deduce the cause of the problems and recommend a quick and easy solution to solve the problem and help to bring the development within the parameters required.
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