Fuel Cell Air Compressor Demagnetization Detection by Motor Current
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Solution Overview
Problem
Existing methods for diagnosing permanent magnet demagnetization in air-compressor motors for fuel cell vehicles are inaccurate due to measurement errors and design deviations, leading to insufficient air supply and power fluctuations, which can cause fuel cell system failures.
Innovation Solution
A system and method that calculates the estimated consumption current of the air-compressor motor through a relationship between applied voltage and rotation speed, comparing it with the actual consumption current to determine demagnetization, using a correction coefficient derived from the relationship between power and rotation speed, and accounting for the opening degree of the air control valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the back EMF constant is calculated using the three-phase voltage equation, then the demagnetization can be diagnosed, but measurement errors and design deviations cause calculation errors that deteriorate diagnosis accuracy
Solution Approach 1:
The patent introduces an intermediary diagnostic approach by using consumption current as a mediator variable. Instead of directly measuring the back EMF constant which is prone to errors, the system calculates estimated consumption current based on voltage and rotation speed, then compares it with actual consumption current. This intermediary method bypasses the measurement errors inherent in direct back EMF constant calculation while still enabling accurate demagnetization diagnosis.
Solution Approach 2:
The patent replaces the electrical measurement system (direct back EMF constant measurement via three-phase voltage equation) with an alternative diagnostic system based on power consumption analysis. By substituting the measurement approach from direct electrical parameter measurement to power consumption-based inference, the system eliminates the measurement errors associated with the original electrical measurement method.
2Ease of operation
If the motor is not operating at maximum power section, then the back EMF generated is small, but it becomes difficult to clearly determine demagnetization when comparing design value with calculated value
Solution Approach 1:
The patent changes the diagnostic parameter from back EMF constant (which varies with operating conditions) to consumption current characteristics. By using consumption current calculated from voltage and rotation speed relationships, the diagnostic method becomes independent of the motor's operating power section. This parameter change allows consistent and clear demagnetization determination regardless of whether the motor is operating at maximum power or other operating points.
3Device complexity
If demagnetization is diagnosed using only variables in the air compressor, then the diagnosis is simple, but the influence of fuel cell system changes is not taken into account
Solution Approach 1:
The patent creates a universal diagnostic method that can account for both air compressor variables and fuel cell system influences. By using consumption current as the diagnostic parameter, the system naturally incorporates the effects of the entire fuel cell system since consumption current reflects the overall system operating conditions. This multi-functional approach maintains diagnostic simplicity while improving reliability by considering system-wide influences.
Data Source
AI summary
A system and a method of inspecting an air compressor for a fuel cell are proposed. The inspection system includes a fuel cell; an air compressor provided on an inlet side of a cathode of the fuel cell and provided with a motor; and a controller configured to calculate an estimated consumption current of the air-compressor motor through a relationship between an applied voltage and a rotation speed of the air-compressor motor and configured to compare the calculated estimated consumption current with a measured actual consumption current to determine whether a permanent magnet of the air-compressor motor is demagnetized.