Custom high voltage power supply for Chinese scientific research
08 February 2012
Leading edge scientific research in China is being aided by a customised high voltage power supply developed by HiTek Power for the Institute of Applied Electronics at the China Academy of Engineering Physics.
The HiTek Power supply is being used in a terahertz free electron laser (FEL) driven by an accelerator and provides power for an electron gun. The terahertz FEL light source is a very good tool for basic science research within the fields of physics, chemistry, life sciences and medical imaging. However, the demanding requirements for the quality of electron beam, such as very small energy spread, require very high stability from the power supply. Large peak power is required for the study of new non-linear phenomena in advanced materials and devices and a large average power was specified to allow "full field" real-time image capture - in effect, terahertz movies.
The customer's requirement was for a 10kW, 400kV power supply that met its specific need for very high stability. Although the converter unit would be housed in a 3U 19-inch rack-mountable chassis, the modular high voltage unit, using 20 HV discs, had to fit inside a sealed chamber. This would then be filled with SF6 insulating gas to a pressure of up to approximately 10 Bar. This presented a number of mechanical design challenges in addition to the need to meet a demanding electrical specification. The electrical and mechanical design teams at HiTek Power worked closely together in conjunction with China Academy to develop this custom system.
The power supply is based on HiTek Power's established and highly successful 10kW Series OL10K range. It is a high-stability, negative polarity supply with industry-leading levels of line and load regulation and ripple. It incorporates HiTek Power's proprietary Arc Count and Extinguish (ACE) arc management system, which continuously monitors the output of the supply and can be programmed to perform a number of different actions if one or more arcs are detected. This dramatically improves the reliability of the entire system in which it is installed.
A new resistance divider column was designed in two 200kV sections to meet tooling, pressure chamber and oven restrictions and a design was developed to mechanically and electrically couple the two dividers. In addition a new RS232 interface unit was designed to provide the required control functionality for the converter unit.
Using its finite elemnet analysis software, HiTek Power carried out a detailed voltage stress analysis of the HV unit mounted within the pressure vessel, to minimise voltage stress within the system.
The mechanical design team worked on a number of special fittings, mainly to accommodate the requirements of the high pressure chamber. New electrical feedthroughs were designed to be pressure-sealed to the electrical insulators with O-rings. A new reinforced electrical insulator plate was designed to withstand the forces caused by the pressure and the weight of the equipment. A new reinforced circular base plate was designed to be pressure-sealed to the electrical insulator with O-rings. Features for sealing the base plate to the pressure chamber were designed to meet customer specifications. A detailed analysis was then carried out to ensure that all mechanical elements met the demanding system specifications.
Commenting on the HiTek Power system, the China Academy said that it was "satisfied with this power supply's high precision and low ripple, which meet the technical requirements". The breadth of research planned for the Terahertz FEL should produce valuable results across many fields of science.
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