Motor Drive Current Sensor Fault Detection via Normalized Negative Sequence
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Solution Overview
Problem
Existing motor drive systems fail to accurately distinguish between normal operating errors and current sensor faults, leading to potential damage to the system and safety hazards.
Innovation Solution
A method and apparatus for detecting phase current sensor faults by calculating a normalized negative sequence current from sensed phase currents and comparing it to a threshold value, with remedial actions such as setting a fault flag, reducing drive voltage or current, and executing a soft or hard shut-down to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sensors are used to monitor motor phase currents, then the control system can monitor and control current flowing to each phase, but the sensor accuracy may change with time and faults cannot be distinguished from normal operating errors
Solution Approach 1:
The system continuously monitors phase currents through sensors and feeds this information back to the controller, which compares actual currents with commanded currents. This closed-loop feedback mechanism enables real-time detection of sensor faults by identifying discrepancies between expected and measured values, thereby maintaining measurement precision and reliability over time.
Solution Approach 2:
The patent introduces an intermediate diagnostic layer that acts as a mediator between the current sensors and the control system. This intermediary component analyzes sensor outputs, distinguishes between normal operating variations and actual sensor faults, and provides fault information to the controller without interfering with normal current control operations.
2Device complexity
If no fault detection system is implemented, then the system remains simple, but undetected sensor errors may cause damage to the motor drive system and safety hazards
Solution Approach 1:
The system performs preliminary fault detection and diagnosis before actual damage can occur. By continuously monitoring current sensor outputs and comparing them with expected values, the system identifies potential sensor faults early in their development, allowing for preventive action before the faults cause motor drive system damage or safety hazards.
Solution Approach 2:
The patent implements a protective diagnostic layer that cushions against potential harm by detecting sensor faults before they can propagate through the system and cause damage. This beforehand protection mechanism isolates potential fault sources and prevents them from affecting the motor drive system or creating safety hazards.
3Productivity
If sensor faults go undetected, then the system operates continuously, but the system controller and propulsion motor may be damaged and users exposed to hazards
Solution Approach 1:
The continuous feedback mechanism monitors sensor outputs in real-time, enabling the system to detect faults while maintaining operation. When faults are detected, the feedback loop triggers appropriate responses such as fault flags or controlled shutdowns, balancing continuous productivity with system safety and component protection.
Solution Approach 2:
The system dynamically adjusts its operation based on sensor fault detection. Rather than operating rigidly, the control system can transition between normal operation, fault-warning modes, and protective shutdown states depending on the severity and nature of detected sensor issues, thereby maintaining productivity when safe and protecting the system when necessary.
Data Source
AI summary
Methods and apparatus are provided for detecting a phase current sensor fault in a multi-phase electrical motor. The method comprises, receiving an input torque command T* and measuring a set of feedback signals of the motor including a phase current Ix for each of the phases of the motor, generating direct and quadrature command phase currents Id*, Iq* for the motor corresponding to a value of the input torque command T*, determining a total command current Is=[(Iq*)2+(Id*)2]½, generating a negative sequence current Ineg, where for three phases Ineg=(⅓)[Ia+(α2)Ib+(α)Ic], where α=ej2π/3, combining Ineg and Is to provide a normalized negative sequence current Inn=Ineg/Is, comparing the normalized negative sequence current Inn to a predetermined threshold value INN* to determine the presence of a phase current sensor fault, and executing a control action when Inn>INN*.