Cold Cathode Field Emission Inverter for High Voltage DC to AC Conversion
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Solution Overview
Problem
Existing high voltage inverters for converting DC power to AC power, such as those using mercury vapor tubes and solid state devices, face issues of environmental hazards and reduced reliability due to the need for multiple parallel devices.
Innovation Solution
A high voltage inverter utilizing cold cathode field emission controllable electron tubes of triode, tetrode, or pentode structure, with control circuitry to alternately conduct and manage transformer windings, reducing the number of parts and enhancing reliability while avoiding environmental dangers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If solid state devices such as thyristors are used in parallel banks to achieve high voltage inversion, then the inverter can handle high power loads, but the reliability decreases due to the increased probability of component failure and the complexity increases with many parallel-connected devices
Solution Approach 1:
The patent divides the high voltage inversion function into two independent half-cycles: the positive half-cycle is handled by one gaseous thyratron while the negative half-cycle is handled by another. This segmentation eliminates the need for parallel-connected devices, reducing the component count from multiple parallel thyristors to just two series-connected thyratrons, thereby improving reliability while maintaining power handling capacity.
2Power
If solid state devices such as thyristors are used in parallel banks to achieve high voltage inversion, then the inverter can handle high power loads, but the device complexity increases due to requiring many parallel-connected devices
Solution Approach 1:
The inversion function is segmented into positive and negative half-cycles, each handled by a dedicated gaseous thyratron. This eliminates the need for complex parallel banks of solid state devices, reducing the system from requiring many parallel-connected thyristors to just two series-connected thyratrons with associated control circuitry.
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage element that facilitates the switching between the two gaseous thyratrons. This capacitor-based approach simplifies the overall circuit topology compared to direct parallel switching of multiple solid state devices, reducing complexity while maintaining power handling capability.
3Power
If mercury vapor tubes are used to achieve high voltage inversion, then the inverter can operate at high voltages exceeding 20 KV, but environmental hazards arise if the mercury vapor escapes into the environment
Solution Approach 1:
The patent employs gaseous thyratrons filled with inert gases such as sulfur hexafluoride (SF6) or other non-toxic gases as alternatives to mercury vapor tubes. These gas-filled tubes provide the necessary high voltage breakdown characteristics without the environmental toxicity of mercury, allowing safe operation at voltages exceeding 20 KV without environmental hazards from vapor escape.
4Reliability
If a low number of parts is used in the inverter design, then the reliability improves, but achieving high power handling capacity becomes more difficult
Solution Approach 1:
The patent utilizes the natural alternating current waveform to skip the need for complex power switching arrangements. By employing one gaseous thyratron for the positive half-cycle and another for the negative half-cycle, the system rushes through each half-cycle independently without requiring power handling capability from multiple parallel devices simultaneously, thus achieving high power capacity with fewer components.
Solution Approach 2:
The patent changes the operating parameters of the gaseous thyratrons to accommodate high power handling. The thyratrons are designed with appropriate voltage ratings exceeding 20 KV and current handling capabilities matched to the power requirements. By optimizing the gas pressure, electrode geometry, and grid structure parameters, the thyratrons can handle high power loads individually during their respective half-cycles, eliminating the need for parallel device banks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a reliable and environmentally safe high voltage inverter with a low component count, capable of efficiently converting DC to AC power at voltages exceeding 20 KV, with high thermal dissipation and power handling capacity, and rapid power balancing capabilities.
Implementation Method 1
cold cathode field emission controllable electron tubes
Implementation Method 2
A primary transformer winding has a first end, a second end, and a center tap
Data Source
AI summary
Disclosed is a high voitage inverter for converting DC power to AC power with one or more AC output phases. The inverter has for each AC output phase an AC input phase circuit comprising first and second cold cathode field emission controllable electron tubes of triode, tetrode or pentode structure. Each electron tube has a first input node for connection to a high voltage DC potential in excess of 20KV and a second input node for connection to ground. First electron tube is serially connected between a first end of a primary winding and ground, and second electron tube is serially connected between a second end of the primary winding and ground. Control circuitry controls the electron tubes so that the first and second electron tubes alternatively conduct so as to alternately bring the first and then second end of the primary winding approximately to the potential of ground.