Alternator Rectifier Diode Short Fault Detection via Field Winding Ripple
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Solution Overview
Problem
Existing systems fail to reliably detect alternator rectifier diode shorts during normal operations of electric vehicles, leading to potential secondary damage due to undetected AC fault currents, as customary fault detection methods are disabled during transients, resulting in missed fault detections.
Innovation Solution
A method and apparatus that sample the field winding signal of an alternator, determine a fault ripple period, and detect a short fault by comparing it to the armature period, using band pass filtering and a hysteresis frequency counter to differentiate between normal and fault ripples, triggering a countdown to confirm the fault before signaling a short.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fault detection is disabled during normal operation transients to avoid false detections, then false fault detections are reduced, but the ability to detect actual diode shorts during these transients is lost
Solution Approach 1:
The patent changes the detection parameter from monitoring AC ripple current (which varies during transients) to monitoring field winding voltage ripple frequency. By using a frequency counter to detect the specific frequency signature of rectifier diode faults in the field winding voltage, the system can reliably detect faults during all operating conditions including transients, without suffering from false detections caused by transient conditions.
2Reliability
If AC ripple monitoring is used to detect diode faults, then fault detection capability is provided, but false detections occur during normal transients such as regenerative braking and speed changes
Solution Approach 1:
The patent introduces an intermediary measurement approach by monitoring the field winding voltage ripple frequency as an intermediate indicator of rectifier diode health. Instead of directly monitoring the AC ripple current at the rectifier output (which is affected by many transient conditions), the system uses the field winding voltage as an intermediary signal that carries fault information while being less susceptible to false transient effects. The frequency counter serves as the intermediary device that extracts the diagnostic information.
Data Source
AI summary
Methods for detecting a short fault of an alternator rectifier electronic component include sampling a field winding voltage or current signal of an alternator, during operation of the alternator, and determining a fault ripple period at which the alternator field winding signal exceeds a fault threshold. A short fault of an electronic component of a rectifier coupled to the alternator is detected in the event that the fault ripple period closely matches an alternator armature period. Alternatively or additionally, the sampled field winding signal is band pass filtered, and a short fault is detected in the event that an amplitude of the band pass filtered field winding signal exceeds a fault threshold. The methods can be implemented, for example, by an apparatus that includes a hysteresis frequency counter, a frequency comparator, and a countdown timer.