Field-Winding Rotating Electrical Machine Dynamic Current Control
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Solution Overview
Problem
Conventional methods for preventing temperature-related failures in rotating electrical machines for vehicles, such as limiting field current, often result in reduced output, particularly during engine restarts, necessitating the use of temperature sensors and increasing costs.
Innovation Solution
A field-winding rotating electrical machine with a field current detecting and controlling system that limits and releases field current based on predetermined thresholds and times without the need for a temperature sensor, ensuring normal output during critical vehicle operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field current is limited to prevent temperature increase, then temperature-related failure is prevented, but output capability is reduced
Solution Approach 1:
The patent implements dynamic field current control by switching between normal operation mode and limitation mode based on accumulated field current values. The system dynamically adjusts the field current threshold based on operating conditions (power generation vs. motor drive), allowing full output capability when safe and enforced limitation when temperature risk exists, thus resolving the contradiction between reliability and power output
Solution Approach 2:
The system changes the parameter of field current threshold dynamically based on accumulated usage and operating mode. By integrating field current over time and comparing against thresholds, the system adapts the safe operating parameters in real-time, enabling full power when conditions permit and enforced limitation when temperature accumulation risk is detected
2Measurement precision
If temperature sensor is added to detect temperature, then temperature monitoring accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The system uses existing field current detection and control circuits to infer temperature conditions without requiring external temperature sensors. By monitoring accumulated field current and operating mode, the system self-determines when temperature-related limitations are necessary, achieving temperature monitoring functionality using only components already present in the field current control system
Solution Approach 2:
The patent introduces an accumulated field current value as an intermediary parameter that correlates with temperature rise. Instead of directly measuring temperature, the system uses the integrated field current history as a proxy indicator, which can be calculated from existing electrical measurements and accurately reflects thermal accumulation without requiring physical temperature sensing
3Temperature
If field current limitation time is extended to ensure cooling, then temperature control is improved, but output availability time is reduced
Solution Approach 1:
The limitation release timing is dynamically determined based on the duration of field current limitation that was enforced. The system calculates the appropriate release time based on how long the limitation mode was active and the specific operating conditions, allowing the field current to be restored as soon as sufficient cooling has occurred, thus minimizing unnecessary output unavailability while ensuring adequate temperature control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses temperature increases in the machine while maintaining normal output capabilities, even during engine restarts, thereby minimizing the impact on vehicle behavior without the need for additional temperature sensing equipment.
Implementation Method 1
a field current detecting section for detecting field current flowing in the field winding
Implementation Method 2
a motor generator having a field winding
Data Source
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AI summary
[Object] To provide a field-winding rotating electrical machine capable of, even when field current is limited, releasing the limitation of field current within a predetermined range of time in the case where a vehicle needs a normal output. [Solution] A field current limiting section 140 includes a field current limitation instructing section 143 for, when a field current limitation determining section 142 determines that a determination value has reached a predetermined determination threshold value, generating a field current limiting instruction to a field current control section 110 so as to limit field current to be equal to or smaller than a predetermined permissible value during a predetermined field current limitation time Tlim. A field current limitation releasing section 150 outputs a field current limitation releasing instruction to the field current limiting section so as to release limitation of the field current during a predetermined field current limitation release time Tc. When having received the field current limitation releasing instruction from the field current limitation releasing section, the field current limiting section releases limitation of the field current during the predetermined field current limitation release time.