Motor Power Cable Disconnection Detection via Common-Mode Removal
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Solution Overview
Problem
The disconnection of a power cable in a motor system can lead to overcurrent, overvoltage, and damage to the inverter and motor, and existing methods lack accuracy in detecting such disconnections, particularly in open-end mode operations.
Innovation Solution
A system that includes current sensors to detect currents in motor windings, removes common mode currents, and uses a cable disconnection index to accurately identify phase disconnections by determining correction current values in a stationary reference frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power cable disconnection is not detected accurately, then motor system continues operating with faulty cable, but this causes overcurrent, overvoltage, and damage to inverter and motor
Solution Approach 1:
The patent extracts and removes the common mode current component from the sensing current values to isolate the actual phase current information. By separating the common mode current (which is present in all phases during open-end mode) from the phase-specific currents, the system achieves accurate disconnection detection without false positives caused by common mode interference.
Solution Approach 2:
The patent introduces a cable disconnection index as an intermediary parameter that processes the correction current values. This index serves as a mediator between the raw current measurements and the final disconnection detection decision, enabling accurate identification of cable disconnections by analyzing the relationship between correction currents across different phases.
2Measurement precision
If common mode current is not removed from sensing current values, then all current measurements include interference, but removing it requires additional signal processing steps
Solution Approach 1:
The patent extracts and removes the common mode current component from the sensing current values to isolate the actual phase current information. By separating the common mode current (which is present in all phases during open-end mode) from the phase-specific currents, the system achieves accurate disconnection detection without false positives caused by common mode interference.
Solution Approach 2:
The system uses the existing current sensors and processor to perform common mode current removal and disconnection detection functions. The same hardware components that measure phase currents also compute the common mode current and generate disconnection indices, eliminating the need for additional dedicated hardware and reducing overall system complexity.
3Measurement precision
If traditional disconnection detection methods are used, then detection is simple, but accuracy is insufficient particularly in open-end mode operations
Solution Approach 1:
The patent introduces a cable disconnection index as an intermediary parameter that processes the correction current values. This index serves as a mediator between the raw current measurements and the final disconnection detection decision, enabling accurate identification of cable disconnections by analyzing the relationship between correction currents across different phases.
Solution Approach 2:
The patent transforms the detection approach by changing from direct current value comparison to using derived parameters (common mode current removal and cable disconnection index calculation). This parameter transformation enables the system to distinguish between normal operating conditions and actual cable disconnections, significantly improving detection accuracy in open-end mode.
Data Source
AI summary
An apparatus for detecting disconnection of a power cable of a motor may include a computing device including a processor and a storage medium on which one or more programs configured to be executable by the processor are recorded, wherein the one or more programs may include: obtaining a plurality of sensing current values from a plurality of current sensors respectively sensing currents flowing in a plurality of windings of the motor corresponding to a plurality of phases of the motor; determining a plurality of correction current values by removing a common mode current from each of the sensing current values; and detecting disconnection in each of the phases based on a cable disconnection index based on the plurality of correction current values.