15 kV @ 30 mA Floating-Output AC or DC High-Voltage Power Supply

Posted on Feb 6, 2014

Transformers made for powering large neon signs are inexpensive and very reliable. Most commonly, the secondary is center-tapped, which prevents the use of its full peak-to-peak output in applications where one of the terminals needs to be grounded. In the power supply described in this post, I took out the high-voltage transformer out of its metal

15 kV @ 30 mA Floating-Output AC or DC High-Voltage Power Supply
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lic enclosure to isolate the center tap from ground. This requires very careful application of a thick insulated layer to the transformer. I used a full can of Shellac to patiently coat and re-coat the transformer. I built a thick Delrin insulating bracket for the modifiedtransformer, and placed it inside a grounded metallic enclosure. I wired it using high-voltage cable that is further insulated by thick silicone tubing. Iliberally use high-voltage putty (GC ELECTRONICS # 10-8882) for insulation. I purchased the high-voltage connectors at Surplus Sales of Nebraska. To obtain a variable AC output, I use a 500 W variac. It must be remembered that neon-tube transformers are commonly designed to first produce a voltage spike to start discharge in the gas, and then enter constant-current mode. As such, the voltage will vary quite a bit depending on the load. A one-to-one voltagerelationship between the variac`s output (the input to the neon transformer) and the neon transformer`s output is only possible for very light loads. Floating DC output is generated by full-wave rectification and filtering of the neon transformer`s output. I used eight NTE542 high voltage diodes (commonly used in small microwave ovens) to build a full-wave-bridge rectifier as shown in the schematic diagram above. Twenty 0. 01 uF @ 10 kV capacitors are used to filter the rectified voltage. I used asurplus panel meter (labeled in kV, probably from an X-ray...

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