Encoder Cable Shield Current Detection in Motor Drive Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting disconnection in shielded cables require additional components such as transformers, DC power sources, resistors, photocouplers, or conduction sensing electric paths, and often necessitate a disconnection sensing line, which complicates the setup and increases costs.
Innovation Solution
A power conversion device that includes a power conversion circuit, an encoder circuit, a control circuit, a shield terminal connected to the ground line, and a determination circuitry to detect current flowing through the shield of the signal transmission cable, allowing for disconnection detection without the need for additional power sources or sensing lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components (transformer, DC power source, resistor, photocoupler, or conduction sensing electric path) are added to detect shield disconnection, then disconnection detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The ground line is made to serve dual purposes: its original function as a safety ground reference and an additional function as a sensing path for detecting shield disconnection. By detecting current flow through the ground line that connects to the shield, the system can identify shield disconnection without requiring separate sensing components.
Solution Approach 2:
The existing ground line and power conversion circuitry are utilized to perform the detection function. The power conversion circuit naturally generates current flow through connected ground paths, and this existing current is monitored to detect shield status, allowing the system to self-diagnose without external assistance.
2Measurement precision
If a disconnection sensing line is added to detect shield disconnection, then detection accuracy is improved, but ease of installation and device complexity worsen
Solution Approach 1:
The ground line is repurposed to serve both its traditional grounding function and as a sensing conductor for detecting shield disconnection. This eliminates the need for separate sensing lines while maintaining detection accuracy through monitoring current flow patterns in the existing ground path.
3Reliability
If additional power sources are added to enable shield disconnection detection, then detection capability is improved, but use of energy and device complexity increase
Solution Approach 1:
The power conversion circuit's existing operational current is utilized for detection purposes. The circuit monitors current flow through the ground line that naturally occurs during normal power conversion operation, eliminating the need for separate power sources dedicated to detection functions.
Solution Approach 2:
The power conversion circuit serves dual functions: performing its primary power conversion task and simultaneously providing the current flow necessary for shield disconnection detection through the ground line, thereby eliminating dedicated detection power sources.
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
Enables accurate disconnection detection of the signal transmission cable's shield without adding new power sources or sensing lines, preventing signal loss and equipment downtime by identifying potential disconnections early.
Implementation Method 1
determination circuitry to detect a current input to the shield terminal and flowing through the shield of the signal transmission cable
Data Source
AI summary
A power conversion device includes: a power conversion circuit that outputs power to a power output terminals to which electric cables of a power cable for supplying AC power to a motor is connected; an encoder circuit that outputs encoder information on the basis of angle information input to an information input terminal and supplied from signal lines of a signal transmission cable; a control unit that outputs a control signal that controls the power conversion circuit on the basis of the encoder information supplied from the encoder circuit; a shield terminal connected to a shield of the signal transmission cable which is electrically connected to a ground line of a power cable on the motor side; and a determination unit that detects a current input to the shield terminal and flowing through the shield of the signal transmission cable, and outputs disconnection detection information for disconnection in the shield.