X-ray High Voltage Apparatus Power Factor Corrector Choke Coil Design
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Solution Overview
Problem
Conventional power factor correction circuits for large output power supplies in X-ray diagnostic and CT apparatuses result in large currents at commercial frequencies, leading to increased size and weight of choke coils due to magnetic saturation, making it difficult to mount these systems in limited spaces like rotating units of X-ray CT apparatuses.
Innovation Solution
The X-ray high voltage apparatus employs a power factor corrector with interleaving operation of high-frequency converter circuits and choke coils featuring a main winding and two correction windings, which cancel magnetic flux generated by commercial frequency currents, reducing the size and weight of the choke coil and improving power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional PFC circuit is applied to a large output power supply, then the power factor can be improved by reducing the harmonic current, but a large current of commercial frequency flows through the choke coil, requiring a large sectional area of the iron core to avoid magnetic saturation, which makes the choke coil large and difficult to mount in limited spaces
Solution Approach 1:
The patent divides the single choke coil into multiple choke coils (one per phase), and further segments the correction function by adding separate correction windings to each choke coil. This segmentation allows the magnetic flux from each phase to be independently corrected, enabling the use of smaller iron cores that avoid magnetic saturation while maintaining compact size for mounting in limited spaces.
Solution Approach 2:
The patent introduces correction windings as intermediary elements on the choke coils. These correction windings generate counteracting magnetic flux that cancels the magnetic saturation effect caused by commercial frequency current. By using these intermediary correction windings, the system achieves power factor correction without requiring oversized iron cores, thus solving the contradiction between reducing harmonic current and maintaining compact choke coil size.
2Reliability
If the iron core of the choke coil is designed to have a large sectional area to avoid magnetic saturation, then magnetic saturation is prevented, but the choke coil becomes large and cannot be mounted in limited mounting space such as a rotating unit of an X-ray CT apparatus
Solution Approach 1:
The patent segments the correction function by providing separate correction windings on each phase choke coil. This allows the magnetic flux to be corrected phase-by-phase, preventing magnetic saturation in each individual choke coil with a smaller, more compact iron core design that fits within limited mounting spaces like rotating units.
Solution Approach 2:
The correction windings act as intermediaries that generate opposing magnetic flux to cancel the saturation-causing flux from the main windings. This intermediary mechanism enables reliable operation without magnetic saturation while using compact iron cores with smaller sectional areas that can be mounted in space-constrained environments.
3Volume of moving object
If a capacitor input type AC/DC converter is used, then the size of the power supply is reduced, but a large harmonic current flows in the power supply, which adversely affects the system
Solution Approach 1:
The patent introduces correction windings on the choke coils as intermediary elements that generate counteracting magnetic flux. This intermediary mechanism corrects the power factor by canceling harmonic currents while maintaining the compact size of the capacitor input type AC/DC converter, thus solving the contradiction between small size and harmonic current reduction.
Solution Approach 2:
The patent changes the magnetic flux parameters by introducing correction windings that generate opposing flux. This parameter change (magnetic flux cancellation) reduces harmonic currents in the power supply while maintaining the compact physical dimensions of the power supply unit, resolving the contradiction between size and harmonic current levels.
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 significantly reduces the size and weight of the choke coil, enabling the power factor correction circuit to be mounted in limited spaces while maintaining high power output and reducing harmonic currents, thus improving the power factor and peak power handling capabilities.
Implementation Method 1
Each of currents flowing through the respective two correction windings... flows so as to cancel a magnetic flux generated in the main winding
Data Source
AI summary
According to one embodiment, the X-ray high voltage apparatus includes a plurality of converters and control circuitry. The plurality of converters converts AC power to DC power. Each converter includes choke coils and three-phase rectifier circuits. Each choke coil has a main winding and is provided on each phase line of three-phase AC power supply lines. Each three-phase rectifier circuit includes a switching device. The control circuitry is configured to interleave the plurality of converters. Each choke coil of the each converter has the single main winding and two correction windings of a first correction winding and a second correction winding. Each of currents flowing through the respective two correction windings is a sum of currents flowing through the plurality of converters performing interleaving operation, and flows so as to cancel a magnetic flux generated in the main winding.