X-ray generator discharge identification via transformer isolation
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Solution Overview
Problem
Existing X-ray generators in helical scan CT apparatuses face challenges in identifying discharging parts within high-voltage units, leading to potential damage and reduced throughput due to large and heavy resistors required for high-voltage insulation and the difficulty in distinguishing discharges within the X-ray tube from other components.
Innovation Solution
The X-ray generator employs a direct-current power source, an inverter circuit, a high-voltage transformer, and a symmetric Cockcroft-Walton circuit to generate X-rays, with discharge current suppressing resistors and tube voltage dividing resistors to accurately detect discharges by monitoring voltage and current changes, allowing for precise identification of discharge locations within the high-voltage generating unit and X-ray tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage insulation resistors are used to withstand 50kV-150kV direct current, then the resistors can avoid damage from high voltage, but the resistors become very large in size and heavy in weight
Solution Approach 1:
The patent introduces a potential isolating transformer as an intermediary component between the high-voltage circuit and the detection circuit. The transformer's secondary side provides electrical isolation, allowing detection resistors to operate at low voltage while still detecting high-voltage discharge conditions. This mediator enables the use of small, lightweight resistors instead of large high-voltage insulation resistors.
Solution Approach 2:
The patent replaces the direct electrical connection system (where resistors must physically withstand high voltage) with a magnetic coupling system through the transformer. The detection is achieved through electromagnetic induction on the secondary side, substituting direct electrical measurement with indirect magnetic field-based measurement, thereby eliminating the need for heavy high-voltage rated resistors.
2Measurement precision
If detection resistors are placed directly in the high-voltage circuit, then discharge locations can be identified, but the resistors must withstand large short-circuit currents and become very large in size
Solution Approach 1:
The potential isolating transformer acts as an intermediary that transfers discharge information from the high-voltage primary circuit to the low-voltage secondary circuit through electromagnetic coupling. This allows detection resistors on the secondary side to measure discharge conditions without being exposed to high voltage or large short-circuit currents, significantly reducing their required size.
Solution Approach 2:
The patent segments the detection system into two independent parts: the high-voltage primary circuit containing the X-ray tube and high-voltage generating device, and the low-voltage secondary circuit containing the detection resistors and measurement instruments. This segmentation allows each part to be optimized independently, with small resistors in the secondary circuit sufficient for accurate discharge location identification.
3Power
If the anode becomes high potential with respect to earth potential, then the X-ray tube can operate, but the detection circuit becomes inoperative and discharge identification becomes difficult
Solution Approach 1:
The patent creates an equipotential reference system on the secondary side of the transformer, where the detection circuit operates at earth potential regardless of the primary side voltage conditions. The transformer isolates the detection circuit from potential fluctuations on the primary side, ensuring the detection circuit remains operational and easy to use even when the anode is at high potential.
Solution Approach 2:
The potential isolating transformer serves as a mediator that decouples the detection circuit from the high-voltage potential variations. By transferring signals through magnetic coupling rather than direct electrical connection, the transformer ensures the detection circuit operates independently of anode potential changes, maintaining ease of operation throughout.
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
This solution enables accurate identification of discharging parts, reducing the need for large resistors, minimizing size and weight, and preventing unnecessary X-ray tube replacements, thus enhancing the reliability and efficiency of the X-ray generator.
Implementation Method 1
a symmetric Cockcroft-Walton circuit (4) for transforming voltage of the high-voltage transformer (3) into direct current voltage by further stepping up the voltage four times
Implementation Method 2
an anode-earthed type X-ray tube (5) for generating X-rays by applying output voltage of the symmetric Cockcroft-Walton circuit (4) between an anode (5a) and a cathode (5b)
Implementation Method 3
tube voltage dividing resistors (Rvdet_H, Rvdet_L) connected between the cathode (5b) of the X-ray tube (5) and the earth, for dividing the tube voltage of the X-ray tube (5) to detect voltage commensurate with a divided voltage
Data Source
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AI summary
A discharging part of an X-ray generator using a one-side earthed X-ray tube, i.e., the anode or cathode is earthed is identified on the basis of the tube voltage detected value and the tube current detected value. For the identification, the X-ray generator comprises a device comprising tube voltage decrease slope calculating means (S4) for calculating the slope of decrease with time of the tube voltage detected value, tube current increase calculating means (S4) for calculating the increase of the tube current detected value in a predetermined time, first judging means (S5) for judging whether or not the slope of the tube voltage decrease calculated in the tube voltage decrease slope calculating means exceeds its acceptable value, second judging means (S6) for judging whether or not the increase of the tube current calculated in the tube current increase calculating means exceeds its acceptable value, and discharge portion identifying means (S7, S8) for identifying the discharging part which is in the X-ray tube or a high-voltage generating unit on the basis of the results of the judgments made by the first and second judging means. The identified discharging part is displayed on display means (S9). Therefore, provided is a small-sized high-reliable X-ray generator having a function of identifying a discharging part with high accuracy.