Triaxial cable transformer
The present invention relates to an isolation transformer suitable for use in a modulator for generating high voltage pulses for supply across a high voltage load having a thermionic cathode such as a magnetron, the isolation transformer comprising a primary winding formed from a triaxial cable where the triaxial cable comprises a core conductor surrounded by a dielectric insulator, in turn surrounded by a screening conductor, with an outer insulating jacket.
1. An isolation transformer suitable for use in a modulator system for generating high voltage pulses for supply across a high voltage load having a thermionic cathode, the isolation transformer comprising a primary winding formed from a triaxial cable where the primary winding comprises:
a core conductor surrounded by a dielectric insulator; and
a screening conductor in turn surrounding the dielectric insulator, with an outer insulating jacket, wherein the screening conductor is formed from two layers of close mesh braid each connected to a safety earth.
2. The isolation transformer as claimed in claim 1 wherein each layer has greater than 80% coverage.
3. The isolation transformer as claimed in claim 1 wherein the two layers of braid in the screen conductor are in direct contact with each other.
4. The isolation transformer as claimed in claim 1 comprising a ferrite core.
5. The isolation transformer as claimed in claim 4 wherein the core is formed of high-frequency Nickel-Zinc ferrite.
6. The isolation transformer as claimed in claim 4 wherein the core is formed of a ferrite having at least one of: a permeability of greater than 1500, a saturation flux density of greater than 3000 Gauss; and a volumetric resistivity of between 2.5×109 Ohm cm and 0.5×108 Ohm cm.
7. The isolation transformer as claimed in claim 4 comprising a core of material type CMD5005, CMD908 or N16.
8. The isolation transformer as claimed in claim 1 comprising a toroidal core.
9. The isolation transformer as claimed in claim 1 wherein the transformer is an oil-filled transformer.
10. The isolation transformer as claimed in claim 1 wherein the load is a magnetron.
11. A modulator system including the isolation transformer as claimed in claim 1 .
12. A combination including the modulator system of claim 11 and a high voltage load.
13. The combination as claimed in claim 12 wherein the high voltage load is a magnetron.