Cathode drop test in compact fluorescent lamps

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Supervisor:
Dr. Csubák Tibor
Department of Control Engineering and Information Technology

There is a significant difference between the operation of the incandescent bulb and fluorescent lamp. Incandescent bulbs will phased out from the market gradually, operates with phase-cutted dimmer very well. Nevertheless, fluorescent lamps operate with fluorescent lamps not well.

The purpose of my thesis is the investigation of cathode fall in compact fluorescent lamps, that plays a very important role in the determination of lamp life. Near electrodes the electromagnetic field is higher than in the positive column, this is the cathode fall. By dimming lamps cathode fall depends especially on the dimming level and the auxiliary heating. The cathode fall increases by dimming in such fluorescent lamps due to reducing the discharge current, so auxiliary heating must be provided to the electrodes. My own work was implementing a software for measuring the cathode fall, demonstrating the results, and drawing the conclusions.

In the first section, I present the physical ground and the build-up of the fluorescent lamps. I review here the function of the ballasts and their types. I fully explain the operation and the build-up of the electronic ballasts and the phase-cutted dimmers that plays a very important role in reducing the discharge current.

In the third section readers get know of the opportunities of measuring the cathode fall. In the second part of this section, I demonstrate here my practical work, the measuring method, parts of the software and the results.

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