Parallel Stator Winding Fault Mitigation via Phase Current Imbalance Detection
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Solution Overview
Problem
In electric powertrain systems with polyphase/alternating current (AC) rotary electric machines having parallel stator windings, phase current imbalances due to aged or degraded windings lead to increased electrical losses and accelerated aging, as the system continues to function in a partially degraded state, necessitating real-time detection and mitigation of these faults.
Innovation Solution
A controller, in communication with current sensors and a traction power inverter module (TPIM), detects phase current imbalances by measuring phase currents and executing thermodynamic control actions, such as adjusting temperature and output state, and records diagnostic codes to manage fault severity, including increasing coolant pump speed or derating the electric machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel stator windings are used in the electric machine, then hardware redundancy and high-frequency performance are improved, but phase current imbalance faults occur due to aged or degraded windings leading to increased electrical losses
Solution Approach 1:
The controller continuously monitors phase currents through current sensors and compares measured currents against expected values. When an imbalance is detected (indicating a fault in one of the parallel windings), the controller provides feedback to adjust the switching signals to the TPIM, redistributing current to maintain balanced operation and minimize electrical losses while preserving the redundancy benefit
Solution Approach 2:
The system dynamically changes operating parameters by adjusting the switching signals to the TPIM based on detected phase current imbalances. This allows the controller to modify current distribution in real-time, compensating for degraded windings and maintaining optimal electrical efficiency despite the presence of aging components
2Duration of action of moving object
If the system continues to function with degraded windings, then operational continuity is maintained, but accelerated aging occurs due to extra current load on remaining windings
Solution Approach 1:
The controller implements continuous feedback monitoring of phase currents to detect imbalances caused by degraded windings. Upon detection, the controller adjusts switching signals to redistribute current loading, preventing excessive current concentration on remaining healthy windings and thereby slowing their degradation rate while maintaining continuous operation
Solution Approach 2:
The system proactively compensates for winding degradation by detecting imbalances early and adjusting current distribution before excessive stress accumulates on remaining windings. This cushioning effect prevents accelerated aging and extends the operational life of the stator windings while maintaining system functionality
3Reliability
If real-time detection and mitigation of phase current imbalances is implemented, then electrical losses are reduced and system life is prolonged, but device complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The controller performs multiple functions using the same hardware resources: it controls the TPIM switching signals for motor operation, monitors phase currents through existing current sensors, detects imbalances, and executes mitigation strategies. This multi-functionality reduces the need for separate dedicated components and minimizes overall system complexity while achieving real-time detection and mitigation
Data Source
AI summary
An electric powertrain system includes an electric machine having a rotor and stator. The stator has multiple phase legs, each respective one of which includes a single phase lead connected to two or more parallel stator windings. The stator thus has multiple phase leads collectively conducting phase currents. A rotary output member is connected to the rotor and connectable to a load. A traction power inverter module (TPIM) is electrically connected to the phase legs. Current sensors collectively measure the phase currents. Each respective current sensor is connected to a different phase lead. A controller in communication with the current sensors and the TPIM, in response to a commanded current and the measured phase currents, detects a threshold variation in the measured phase currents indicative of a phase current imbalance fault, and selectively changes a thermodynamic state of the electrified powertrain in response to the fault.