Tuesday, March 13, 2012

High Voltage TWT Power Supply Guidelines

I was doing a little research on design considerations for TWT power supplies, and came across this report from NASA.

This is an analysis of an 11kV High Voltage Power Supply that apparently exhibited evidence of a corona-induced short in the high voltage connector. 

Figure 2 - High Voltage Compartment Construction - NASA PD-ED-1202
Included in the report is a photo of a partially de-encapsulated unit.  It's hard to say for sure, but it looks like they used epoxy diodes?! 

You know how the internet is....down the rabbit hole I went, and, well, one thing let to another, and before I knew it, I came across even more design practices from NASA.

As for researching TWT power supplies, I was looking to confirm guidelines for specifying high voltage diodes.  I seem to recall hearing that diodes are susceptible to damage on the high voltage end of the multiplier because of arcs from the tube.  TWT PS typically run hot and fast, and unless a diode has sufficient reverse power capabilities, it could spell trouble. 

Comments anyone?

2 comments:

  1. Hello, I appreciate the author as this post presents the design issues and challenges in the realization of high performance Traveling Wave Tube (TWT) based Transmitter for Weapon Locating Radar for the detection of targets having very small RCS viz. mortar shell, gun shells etc and to locate the origin of the weapon. I hope to keep it up. Thanks, @Kingkinu from Ac Dc Adapter for you

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  2. Hi, I like to add a little bit. If you are using a tube outside its 'official' frequency range, and if the helix overcurrent problem persists for all helix voltages and beam currents, while you are increasing the drive, it could be that the output matching structure is not matched at your frequency. You can check this by connecting the output terminal of the cold tube (no DC power applied) to a network analyzer (a directional coupler with a detector will do also). If the return loss at your desired frequency is less than 10 dB, then this is very probably the problem. Try using an external tuning circuit to make at least a narrow 'hole' at your desired frequency. Try at least for 15db, 20 or more is best. I have had this problem, but was lucky because the tube had waveguide output with tuning screws. thanks!
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