Inductive Rotary Joint Secondary Safety Circuit
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Solution Overview
Problem
Inductive power couplers in CT scanners face safety issues due to short circuits between the rotating power channel and protective earth, leading to excessive voltages at the rotating part, and existing solutions fail to detect such faults without communication from the rotating side.
Innovation Solution
A low-impedance galvanic connection between the DC output and the mechanical base, along with a control unit at the primary side to measure current anomalies, allows for detection of short circuits and emergency shutdown, preventing excessive voltages and ensuring safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a galvanic connection is provided between the rotating and stationary parts for safety grounding, then safety against short circuits is improved, but wear and corrosion of the connection occurs due to current flow
Solution Approach 1:
The patent employs two galvanic connections with dynamically switching roles: during normal operation, the first connection (slip ring) carries no current while the second connection (bearing) provides grounding; during fault conditions, the current path switches to the first connection. This dynamic role assignment eliminates wear during normal operation and provides backup safety during faults.
Solution Approach 2:
The grounding function is segmented into two separate galvanic connections: a slip ring connection and a bearing connection. Each connection serves specific functions at different times, with the bearing providing continuous mechanical support and occasional electrical grounding, while the slip ring provides dedicated electrical connection when needed. This segmentation allows each component to be optimized for its specific role.
2Measurement precision
If communication from the rotating side is used to detect faults, then detection capability is improved, but system complexity increases due to feedback link requirements
Solution Approach 1:
The patent uses the galvanic ground connection itself as an intermediary for fault detection. By measuring the current through this connection at the stationary side, the system can detect short circuit faults without requiring communication from the rotating side. The ground connection serves dual purposes: safety grounding and fault detection signaling.
Solution Approach 2:
The system implements feedback by continuously monitoring the current through the galvanic ground connection. When a short circuit occurs, the abnormal current flow is detected by the control unit, which then triggers an emergency shutdown. This closed-loop feedback mechanism enables automatic fault detection and response without complex communication systems.
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 significantly enhances safety and reliability by preventing electrical shocks and component failures due to short circuits, allowing for timely power shutdown and reducing wear and corrosion in the galvanic connection.
Implementation Method 1
a rotating transformer having a primary winding and a secondary winding for inductively coupling electrical signals from the primary side to the secondary side
Implementation Method 2
The voltage output of the secondary winding is provided at secondary winding contacts, which are connected to a rectifier
Implementation Method 3
followed by a filtering capacitor to generate a smooth DC voltage
Data Source
AI summary
An inductive rotating power transfer circuit, preferably for transferring electrical power from the stationary part to the rotating part of a CT scanner comprises an inductive power transformer having a stationary primary side and a rotating secondary side. The secondary side is connected via a rectifier to a filtering capacitor, delivering electrical power to a load. One of the output pins of the filtering capacitor is connected to a secondary ground at the rotating part which is further connected to a stationary protective ground via a galvanic slip ring. In the case of a short circuit between a secondary transformer winding and the secondary ground, the secondary winding is partially short-circuited by one of the rectifier diodes. This causes an asymmetric current load at the primary side and a current flowing through the slip ring. Both currents may be used to detect a failure of the secondary winding.