Field Winding Rotary Machine Thermal Protection Without Sensors
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Solution Overview
Problem
Conventional vehicular AC generators require a temperature sensor to detect excessive heat and limit field current, leading to increased costs and structural changes to prevent thermal runaway, but this solution is not ideal as it necessitates sensor mounting and structural modifications.
Innovation Solution
A field winding type rotary electric machine that includes a field current detection unit, a field current control unit, a field current limiting determination section, and a field current limiting command section, which integrates the field current over time to determine if it exceeds a threshold, allowing for controlled reduction of field current to prevent overheating without the need for a temperature sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature sensor is mounted to detect excessive heat and limit field current, then the reliability of the rotary electric machine is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The system uses the existing field current detection capability to monitor thermal conditions and trigger protective action without requiring external temperature sensors. The control device serves itself by using its own measurement resources (field current) to detect the need for protection and execute the protection logic internally.
Solution Approach 2:
The patent uses field current as an intermediary parameter to infer temperature conditions. Instead of directly measuring temperature with a sensor, the system measures field current (which is already being monitored for other control purposes) and uses this measurement as a proxy indicator of thermal state to trigger protective action.
2Temperature
If field current is limited to prevent overheating, then the temperature rise is suppressed, but the productivity and power output decrease
Solution Approach 1:
The protection mechanism operates periodically by continuously monitoring the field current integration value and comparing it against thresholds. When the threshold is exceeded, protective action is taken temporarily, and the system can resume normal operation once the integration value decreases below the threshold, creating a periodic on-off protection pattern rather than continuous limitation.
Solution Approach 2:
The system dynamically adjusts the protection level based on real-time field current conditions. Rather than using a fixed current limit, the protection threshold is adaptive, allowing the system to maintain high power output when conditions permit while automatically reducing output only when thermal limits are approached, as indicated by the integration value.
3Measurement precision
If continuous field current monitoring and integration is performed, then the temperature control precision is improved, but the loss of energy increases
Solution Approach 1:
The system performs integration of field current over time, which accumulates thermal effect information progressively. Rather than requiring continuous high-power cooling or intervention, the integration approach partially processes the thermal information over time, triggering protection only when the accumulated value exceeds the threshold, thus reducing unnecessary energy consumption while maintaining monitoring precision.
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 solution effectively monitors and limits field current to prevent overheating in the rotary electric machine, allowing for dynamic adjustment of limiting times based on field current values, thereby reducing the need for additional sensors and structural changes, ensuring efficient operation and reduced risk of thermal damage.
Implementation Method 1
a field current detection unit which detects a field current flowing through the field winding
Implementation Method 2
a field current limiting determination section which calculates a field current integration value in which the field current detected by the field current detection unit is integrated by time
Implementation Method 3
a field current control unit which controls the field current
Data Source
AI summary
A field winding type rotary electric machine includes a motor generator; a field current detection unit; a field current control unit which controls a field current; a field current limiting determination section which calculates a field current integration value and determines whether or not the field current integration value reaches a predetermined field current integration threshold value; and a field current limiting command section which, when it is determined that the field current integration value reaches the predetermined field current integration threshold value, outputs a command which sets the field current to be lower than or equal to a predetermined field current limiting value to the field current control unit during a predetermined limiting time, and outputs a command which changes the predetermined limiting time depending on the field current. Accordingly, a temperature rise of the machine is suppressed and limiting of the field current can be released as needed.