Current Sensor Insulation Layout for Partial Discharge Suppression
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Solution Overview
Problem
Existing electrosurgical devices face issues with inaccurate current measurement due to partial discharges between high-frequency current-carrying conductors under adverse conditions, leading to electromagnetic interference and erroneous readings, especially at high altitudes and high humidity.
Innovation Solution
A current sensor with an insulating body positioned between conductors to maximize the distance between them, using non-polar materials like PE, PP, or PTFE to reduce capacitive leakage and partial discharges, and a conductive layer to symmetrize the electric field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulation thickness of conductors is increased to prevent partial discharges, then reliability improves, but the available space in the current sensor is limited, making it impossible to accommodate thicker insulation
Solution Approach 1:
An insulating body is introduced as an intermediary element positioned between the two conductors in the current sensor. This mediator provides additional insulation and increases the distance between conductors, preventing partial discharges without requiring thicker conductor insulation, thus resolving the space constraint while improving reliability
Solution Approach 2:
Instead of increasing insulation thickness in the radial dimension of conductors, the solution adds insulation in the axial dimension by positioning an insulating body between conductors along their length. This dimensional shift allows sufficient insulation distance within the limited sensor volume
2Measurement precision
If the distance between conductors is increased to reduce partial discharges, then measurement precision improves, but the limited space in the current sensor prevents adequate separation
Solution Approach 1:
The insulating body serves as a spacer and mediator that physically separates the two conductors within the limited opening space. This intermediary element ensures adequate distance between conductors to prevent partial discharges and reduce capacitive coupling, thereby improving measurement precision without requiring more sensor volume
Solution Approach 2:
The insulating body changes the physical parameters of the conductor arrangement by increasing the distance between conductors and modifying the electric field distribution. This parameter change reduces capacitive leakage current and partial discharge effects, improving measurement accuracy within constrained space
3Measurement precision
If non-polar insulating materials are used to reduce capacitive leakage current, then measurement precision improves, but the selection of suitable materials with high dielectric strength and low loss is more restrictive
Solution Approach 1:
The solution changes the material parameter by selecting non-polar insulating materials (such as PTFE, PE, or PP) with specific dielectric properties. These materials have low dielectric loss and high insulation resistance, which reduce capacitive leakage current and improve temporal resolution of measurements, though they impose stricter material selection criteria
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
Enhances the precision and reliability of current measurement by minimizing partial discharges, improving temporal resolution and reducing measurement noise, ensuring accurate detection even under adverse conditions.
Implementation Method 1
The additional insulating element positioned between the leads in the central opening of the current sensor increases the distance between the two leads, particularly the distance between their conductors, thus reducing both capacitive leakage current and any partial discharges.
Implementation Method 2
A current sensor is known in practice that incorporates a magnetic circuit through which both the leads leading to the instrument and those leading back from the instrument or patient are routed. A sensor coil also integrated into the magnetic circuit, or other means for detecting a magnetic field, provides a signal that indicates the measured current.
Data Source
Figure 1~3
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AI summary
According to the invention, a ring-shaped magnetic circuit (25) is provided for a current sensor (23) of a device (10) for supplying an instrument (11, 11'), through which two conductors (19, 21) supplying the instrument (11) and a neutral electrode (15) or the instrument (11') are guided. The sheaths (28, 30) of the two conductors (19, 21) have a sufficient thickness in terms of their dielectric strength relative to the voltage load of the conductors (19, 21). However, this thickness is limited to such an extent that an insulating body (31) can still be inserted between the two conductors (19, 21), which, like the sheaths (28, 30), consists of a non-polar, highly insulating insulator material, for example, a plastic with a low loss angle. The insulating body (31, 31a) to (31d) reduces partial discharges in the area of the current sensor (23), which could otherwise lead to electromagnetic emissions and thus to interference with the signal (24) generated by the current sensor (23).