Thyratron under load

Submitted by Ed_B on Thu, 10/21/2010 - 22:38

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A thyratron is a type of electron tube used for controlling large amounts of AC power in motor drives and simlar applications. I have a small collection of thyratrons. This one is medium size. It can switch up to about 1000 volts and about 1.5 amps.  The load it's carrying is a 40 watt 120 volt light bulb (out of the image frame). (Click READ MORE to see the whole post.)

The purple glow is exaggerated by the camera. It's from the controlled mercury-vapor  arc that the tube uses to pass current to the load. This circuit isn't doing anything useful. It's a first test of a first step along the road to thyratron bliss.

The filament is the electron-emitting cathode in this tube. As the hot filament brings the tube up to operating temperature a small amount of the liquid mercury in the tube vaporizes. The process is rather pretty. I'll make photos of it later. Here is the cold tube at rest. The plate cap is the silver button on top of the tube. It's the anode connection terminal.

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This shows some of the condensed mercury in the bottom of the cold tube.